Plastic products are a general term for daily and industrial supplies that are made of plastic as the main raw material. Including products made from all processes such as injection molding, blow molding and blister molding using plastic as raw materials. Plastic is a type of synthetic polymer material with plasticity.
Together with synthetic rubber and synthetic fibers, it forms the three major synthetic materials that are indispensable in daily life. Specifically, plastic is a material that uses natural or synthetic resin as the main component, adds various additives, can be molded into a certain shape under certain conditions such as temperature and pressure, and maintains its shape at room temperature.
Development history
Compared with metal, stone, and wood, plastic products have the advantages of low cost and strong plasticity. They are widely used in the national economy. The plastic industry occupies an extremely important position in the world today. Over the years, the production of plastic products has developed at a high speed around the world. China’s plastic product output has always been at the forefront of the world rankings, and the output of many plastic products has ranked first in the world. China has become the world’s largest producer of plastic products. From 2001 to 2010, the average annual growth rate of China’s plastic product output remained above 15%. In 2010, China’s total plastic product output reached 58.3 million tons.
From a demand perspective, China’s per capita plastic consumption still lags far behind that of developed countries in the world. According to statistics, as an indicator of the development level of a country’s plastics industry, the plastic-to-steel ratio in our country is only 30:70, which is lower than the world average of 50:50 and far behind developed countries such as the United States (70:30) and Germany (63:37). In the future, with the technological progress and consumption upgrading of modified plastics in China, the demand for plastic products in China is expected to maintain a growth rate of more than 10%.
Plastic products are widely used, and the huge downstream industry provides strong support for the development of China’s plastic products industry. With the promulgation of the “Planning Rules for Revitalizing the Petrochemical Industry”, China’s plastic products industry is facing new development opportunities. China’s plastic products market demand is mainly concentrated in agricultural plastic products, packaging plastic products, construction plastic products, industrial transportation and engineering plastic products.
Performance characteristics
Compared with other materials, plastics have the following performance characteristics:
1. light weight
Plastic is a lighter material with a relative density ranging from 0.90 to 2.2. It is obvious whether plastic can float on the water, especially foam plastic, which has micropores and is lighter in texture, with a relative density of only 0.01. This property allows plastics to be used in the production of products that require weight reduction.
2. Excellent chemical stability
Most plastics have good corrosion resistance to chemicals such as acids and alkalis. Especially polytetrafluoroethylene (F4), commonly known as the king of plastics, its chemical stability is even better than gold, and it will not deteriorate even if it is boiled in ” Aqua Regia ” for more than ten hours. Because F4 has excellent chemical stability, it is an ideal corrosion-resistant material. For example, F4 can be used as a material for pipelines transporting corrosive and viscous liquids.
3. Excellent electrical insulation properties
Ordinary plastics are poor conductors of electricity, and their surface resistance and volume resistance are very large, which can reach 109 to 1018 ohms in numerical terms. The breakdown voltage is large and the dielectric loss tangent is very small. Therefore, plastics are widely used in the electronics and machinery industries. Such as plastic insulated control cables.
4. A poor conductor of heat, with sound-absorbing and shock-absorbing effects
Generally speaking, the thermal conductivity of plastic is relatively low, equivalent to 1/75-1/225 of steel and the micropores of foam plastic.
It contains gas, which has better heat insulation, sound insulation and shock resistance. For example, the thermal conductivity of polyvinyl chloride (PVC) is only 1/357 of steel and 1/1250 of aluminum. In terms of thermal insulation capacity, single-glass plastic windows are 40% higher than single-glass aluminum windows, and double-glass windows are 50% higher. After combining plastic windows with insulating glass, it can be used in residences, office buildings, wards, and hotels to save heating in winter and air conditioning expenses in summer. The benefits are very obvious.
5. Wide distribution of mechanical strength and high specific strength
Some plastics are as hard as stone and steel, and some are as soft as paper and leather. Judging from the mechanical properties such as hardness, tensile strength, elongation and impact strength of plastics, they are widely distributed and have a lot of room for use. Because plastic has a small specific gravity and high strength, it has a high specific strength. Compared with other materials, plastics also have obvious shortcomings, such as being easy to burn, not as stiff as metal, poor in aging resistance, and not heat-resistant.
Development trend
The development direction of plastics can be summarized in two aspects. The first is to improve performance, that is, modify existing varieties in various ways to improve their comprehensive properties; the second is to develop functions, that is, to develop polymer materials with physical functions such as light, electricity, and magnetism, so that plastics can have Photoelectric effect, thermoelectric effect, piezoelectric effect, etc.
Judging from the current development speed of the world’s plastics industry, Germany and Sweden rank first, followed by Japan and some European countries, and the United States is slower. Foreign plastic packaging shows the following development trends :
Copolymer composite packaging film
At present, some countries in Europe and the United States have invested heavily in the development of non-polar and polar ethylene copolymers, etc., which will greatly improve the tensile and co-extrusion properties of plastic films, improve transparency, sealing strength, stress resistance, crack resistance, and enhance stability properties, Improve the rheological properties of molecular weight cloth and extrusion.
Foreign experts believe that the current development focus of the world’s plastics industry lies in plastic modification, coating technology for plastic products, rapid biodegradation of waste plastics, and comprehensive plastic recycling and reuse technologies. For example, some manufacturers in Europe and the United States use linear ethylene-α-olefin copolymer and ethylene-vinyl acetate copolymer blends/PA bags, which are suitable for packaging ice cream, cream and other foods.
Multifunctional composite film
A large number of multifunctional composite films have been developed abroad to further refine their functions. For example: cold-resistant films can withstand low temperature environments of -18℃, -20℃, and -35℃; moisture-proof films made of PP with moisture-proof treatment, its series of products can be divided into moisture-proof, anti-condensation, anti-vapor and cold, and adjustable moisture Several other types; anti-corrosion film can be included Contains perishable, acidic, and sweet foods; friction film stacking is stable; special PE film is chemical-resistant and corrosion-resistant; odor-free insect repellent is added to the moth-proof film; replaced with heat-resistant film of biaxially stretched nylon 66 Biaxially stretched nylon 6 food packaging, its high temperature resistance reaches 140℃; the new special food packaging film can improve the flavor retention of food packaging; the transparency of amorphous nylon film is similar to glass; the high shielding film can maintain the stability of color, aroma, taste, nutritional indicators and taste quality; metal protective film LDPE modified film is used to package liquid products, which can be heat-sealed in low-temperature environments; PP synthetic paper is used to improve the light resistance, cold resistance, heat resistance, water resistance, moisture resistance, grease resistance, acid resistance, and alkali resistance of the packaging properties and impact resistance, etc.
Currently, plastic cups and composite cups (outer PSP, inner PP, lid PS) are popular abroad for packaging cold and hot beverages, wine, and convenience foods. France uses PE bottles to package fructose and yogurt, and Germany uses PC bottles to package milk. In China, PE bottles are used to package medicines, etc.
Plastic grade
Plastics can be seen everywhere in our lives. Plastic products are made of different materials, with different materials and different applications. The numbers on the bottom of plastic bottles represent different materials.
The number “1” represents polyethylene terephthalate, or PET. Mainly used in mineral water bottles, carbonated bottles, juice drink bottles, soy sauce and vinegar bottles, etc. PET bottles have a heat resistance of 70 degrees Celsius and are only suitable for holding warm or frozen drinks. They are easily deformed when filled with boiling water or heated, and substances harmful to the human body may also dissolve.
The number “2” represents high-density polyethylene, or HDPE. HDPE is made into composite films with other plastics and is also used in aquatic products.
The number “3” represents polyvinyl chloride, or PVC. Because of its low price, it is also used to make intravenous infusion bags and disposable sterile infusion equipment. However, long-term use can lead to the accumulation of harmful substances DEHP. Therefore, from a safety perspective, it is the future trend for the pharmaceutical industry to choose non-PVC materials.
The number “4” is low density polyethylene, or LDPE. No. 4 plastic is used extensively in packaging. LDPE is mainly used to produce food plastic wrap and plastic bags for food.
The number “5” is polypropylene, or PP. One is to make containers. PP is different from other materials. PP can be placed in plastic containers in microwave ovens, and it is a plastic container that can be used repeatedly. It can be used as a storage container to store food, oils, condiments, etc. The second type is packaging film, including unstretched and biaxially stretched. Unstretched polypropylene (CPP) is often used for packaging of snacks, bread, fruits, etc.; biaxially oriented polypropylene ( BOPP ) is a flexible packaging material comparable to cellophane.
The number “6” is polystyrene, that is, PS. PS is mainly processed into films and foam plastics for packaging. Films are used for packaging fruits and vegetables; foam plastics are mostly used in bowls of instant noodle boxes and fast food boxes. However, they are not resistant to high temperatures, so they cannot be heated directly in a microwave oven to avoid releasing toxic chemicals due to excessive temperature.
The number “7” is polycarbonate, which is PC or other plastic. Plastic containers made of PC material may release toxic bisphenol A. The higher the temperature, the more and faster the release, so do not heat it when using it, and do not expose it to direct sunlight.
Production methods
The production of plastic products generally includes the ingredients, molding, machining, joining, modification and assembly of plastics. The last four processes are carried out after the plastic has been formed into finished products or semi-finished products, also known as secondary processing of plastics.
Molding plastic processing is a key link in the production of plastic products. Plastics in various forms (powder, granules, solutions or dispersions ) are made into products or blanks of the desired shape. There are as many as thirty types of molding methods. Its choice mainly depends on the type of plastic (thermoplastic or thermoset ), the starting form, and the shape and size of the product. Commonly used methods for plastic processing of thermoplastics include extrusion, injection molding, calendering, blow molding and thermoforming. Plastic processing of thermosetting plastics generally uses molding, transfer molding, and injection molding. Lamination, molding, and thermoforming shape plastic onto a flat surface. The above plastic processing methods can all be used for rubber processing. In addition, there are also castings using liquid monomers or polymers as raw materials. Among these methods, extrusion and injection molding are the most commonly used and are also the most basic molding methods.
Mechanical processing in the production of plastic products borrows plastic processing methods such as metal and wood to manufacture plastic products with very precise dimensions or small quantities. It can also be used as an auxiliary process for molding, such as sawing of extruded profiles. Since the properties of plastic are different from those of metal and wood, plastic has poor thermal conductivity, low thermal expansion coefficient, and low elastic modulus. When the clamp or tool is pressurized too much, it is easy to cause deformation. It is easy to melt when heated during cutting, and it is easy to adhere to the tool. superior. Therefore, when plastics are machined, the tools used and the corresponding cutting speeds must be adapted to the characteristics of the plastics. Commonly used mechanical processing methods include sawing, shearing, punching, turning, planing, drilling, grinding, polishing, thread processing, etc. In addition, plastics can also be cut, drilled and welded using lasers.
Joining plastic processing in the production of plastic products The methods of joining plastic parts include welding and bonding. Welding methods include hot air welding using welding rods, hot melt welding using hot electrodes, high frequency welding, friction welding, induction welding, ultrasonic welding, etc. The bonding method can be divided into flux, resin solution and hot melt adhesive bonding according to the adhesive used.
The purpose of surface modification in the production of plastic products is to beautify the surface of plastic products, which usually includes: mechanical modification, that is, using processes such as filing, grinding, and polishing to remove burrs and burrs on the parts, as well as correct dimensions; coating, including coating the parts with paint. The surface of the product is brightened with a solvent, and the surface of the product is covered with a patterned film; color application includes painting, printing and hot stamping; metal plating includes vacuum coating, electroplating and chemical silver plating, etc. Plastic processing hot stamping is to transfer the colored aluminum foil layer (or other patterned film layer ) on the hot stamping film to the product under heat and pressure. Many household appliances, building products, daily necessities, etc. use this method to obtain patterns such as metallic luster or wood grain.
The assembly of plastic product production uses methods such as bonding, welding, and mechanical connection to assemble the finished plastic parts into complete products. For example: plastic profiles are assembled into plastic window frames and plastic doors through sawing, welding, drilling and other steps.
Composition
Some plastics themselves are pure resins, such as polyethylene, polystyrene, etc., which are called single-component plastics. In addition to synthetic resin, some plastics also contain other auxiliary materials, such as plasticizers, stabilizers, colorants, various fillers, etc., which are called multi-component plastics.
1. Synthetic resin
Synthetic resin refers to a polymer compound that uses coal, calcium carbide, petroleum, natural gas and some agricultural and sideline products as the main raw materials to first prepare low molecular compounds (monomers) with certain synthesis conditions, and then synthesize them through chemical, physical and other methods. The properties of these compounds are similar to natural resins (such as rosin, amber, shellac, etc.), but their performance is superior to natural resins. For example: synthetic resin dentures.
The content of synthetic resin accounts for 40% to 100% of all components of plastics. It plays a bonding role and determines the main properties of plastics, such as mechanical strength, hardness, aging resistance, elasticity, chemical stability, and photoelectricity. Sex etc.
2. Plastic additives
Plastic additives The main purpose of adding additives to plastics is to improve processing performance, increase efficiency and reduce costs. Additives account for a small proportion of plastic materials, but they have a great impact on the quality of plastic products. Different types of plastics require different types and amounts of additives due to different molding processing methods and usage conditions. The main additives include the following categories:
Plasticizer
Plasticizers can increase the softness, extensibility, and plasticity of plastics, reduce the flow temperature and hardness of plastics, and are beneficial to the molding of plastic products. Commonly used ones include phthalates, sebacates, chlorinated paraffins and camphor. The most common one we see is camphor.
Stabilizer
We all know that during the processing, storage and use of plastic products, under the action of light, heat and oxygen, aging phenomena such as fading, embrittlement and cracking will occur. In order to delay and prevent the occurrence of aging, stabilizers must be added. Those mainly used to prevent thermal aging are called heat stabilizers; those mainly used to prevent oxidative aging are called antioxidants; those mainly used to prevent photoaging are called light stabilizers. They are collectively called stabilizers. The most excellent plastic stabilizer today is methyl tin heat stabilizer (181 for short), which is very effective in the calendering, extrusion, injection molding and blow molding of rigid polyethylene (PVC). Because of its high safety, it is especially used in food packaging and high-definition rigid polyethylene products. At the same time, it is also widely used in plastic doors and windows, water pipes, and decorative materials to replace other highly toxic plastics. Heat stabilizer. It is widely used in the United States, Europe, and Japan. In recent years, 181 methyl tin heat stabilizer has begun to be widely used in China.
Flame retardant
Additives that can improve the flame resistance of plastics are called flame retardants. Most plastics containing flame retardants are self-extinguishing or slow down their burning rate. Commonly used flame retardants include antimony oxide, aluminum and boron compounds, halides and phosphates, tetrachlorophthalic anhydride, tetrachlorophthalic anhydride, etc.
Antistatic agent
Antistatic agents play the role of eliminating or reducing static electricity generated on the surface of plastic products. Most antistatic agents are electrolytes. Their compatibility with synthetic resins is limited, so they can migrate to the surface of the plastic to absorb moisture and eliminate static electricity.
Foaming agent
Plastic foaming agent is a low-molecular organic compound that can vaporize at a certain temperature, such as dichlorodifluoromethane; or an organic compound that decomposes into gas when heated. These gases remain in the plastic matrix to form foam plastics with many fine foam structures. Commonly used ones include azo compounds, nitroso compounds, etc.
Colorants
Colorants are used to color plastics. Mainly used for beautification and modification. About 80% of plastic products are colored and made into final products.
Lubricant
Lubricant is a substance added to improve the mold releasability of plastics during heat molding and improve the surface finish of the product. Commonly used lubricants include: stearic acid and its salts, paraffin wax, synthetic wax, etc.
Reinforcements and fillers
In many plastics, reinforced materials and fillers account for a considerable proportion, especially reinforced plastics and calcium plastic materials. The main purpose is: in order to improve the strength and rigidity of plastic products, various fiber materials or inorganic substances are generally added. The most commonly used reinforcing materials are: glass fiber, asbestos, quartz, carbon black, silicate, calcium carbonate, metal oxide, etc.
Classification
There are hundreds of types of industrially produced plastics, of which more than 60 are commonly used. The common classification methods are as follows:
According to the performance after heating
1. Thermoset plastic
The characteristic of this type of plastic is that it solidifies at a certain temperature and after heating for a certain period of time or adding a curing agent.
The cured plastic is hard and insoluble in any solvent, and it cannot be softened again by heating. It will decompose if the heating temperature is too high. Common thermosetting plastics include bakelite, electric jade, decorative boards and unsaturated polyester plastics.
2. Thermoplastic
The characteristics of this type of plastic are that it softens when heated and hardens when cooled. During processing, it generally only undergoes physical changes while maintaining its chemical nature. The resins of this type of plastic are mostly made by addition polymerization. Common thermoplastics include: nitrocellulose plastic, cellulose acetate plastic, polyethylene plastic, polypropylene plastic, polystyrene plastic, polyvinyl chloride plastic, etc. For example, our common mineral water bottles, plastic bags, etc.
According to application scope
This type of plastic mainly refers to a type of plastic with large output, wide range of uses and low price. They account for about 80% of total plastic production. The main varieties are: polyethylene, polyvinyl chloride, polypropylene, polystyrene, phenolic and amino plastics, etc.
Generally refers to plastics that can be used as structural materials in engineering technology. The distinctive features of this type of plastic are high mechanical strength, strong resistance to chemical corrosion and high temperature resistance, and can replace metal or be used for other special purposes. The main varieties are: polyamide, polycarbonate, polyformaldehyde, polysulfone, ABS, polyphenylene ether, fluoroplastics, etc.
Classified by flammability
1.Flammable plastic
This type of plastic burns violently when exposed to open flames and is difficult to extinguish. Such as nitrocellulose plastics, etc., these plastics are classified as dangerous goods.
2. flammable plastic
This type of plastic burns when exposed to an open flame and has no self-extinguishing properties, but it burns quickly. Such as polyethylene, polypropylene, etc.
3. Flame retardant plastic
This type of plastic can burn in a strong open flame and extinguish quickly after being removed from the fire. Such as phenolic plastic, cellulose acetate plastic, polyvinyl chloride plastic, etc.
Main plastic
polyethylene plastic
(1) Introduction
Polyethylene plastic (Polyethylene) is a polymer of ethylene monomer. The raw materials for production are petroleum, coke oven gas or alcohol. Industrially produced polyethylene is generally produced by dehydration of ethanol, catalytic hydrogenation of acetylene or high-temperature cracking. Its trade name is abbreviated as “E-plastic”; its English abbreviation is PE. Due to the different densities of polyethylene, it is divided into low density polyethylene. [PE(L)], medium density polyethylene [PE(M)] and high density polyethylene [PE (H)].
The molecular structural formula of polyethylene is: (— CH2 —CH2—) n. It has a linear geometric shape, theoretically has no branches, and is prone to crystallization. Generally, polyethylene macromolecules are composed of crystalline regions and amorphous regions in a highly elastic state. The crystalline regions give polyethylene plastics higher hardness, strength, chemical stability, etc.; the amorphous regions give polyethylene plastics higher softness. sex, resilience, transparency, etc. In fact, polyethylene macromolecules are not absolutely branch-free. Their crystallinity is different, their density is different, and their physical and mechanical properties are also different.
(2) Aggregation method
1.low density polyethylene
Also known as “high-pressure soft plastic “. It is formed by polymerizing ethylene monomer with trace amounts of oxygen as initiator at a pressure and a temperature of 100-300°C, using oxygen, organic peroxides or azo compounds as initiators.
2. medium density polyethylene
Medium-density polyethylene is synthesized using chromium oxide or molybdenum oxide as a catalyst at a pressure of 30-70 atmospheres and a temperature of 100-250°C. In practice, the tape is produced using the following methods:
①Made by blending low-density polyethylene and high-density polyethylene in a certain proportion;
② It is produced by copolymerizing ethylene with second monomers such as propylene and butylene using slurry method or solution method;
③Produced by high-pressure method, produced by copolymerization of ethylene with second monomers such as vinyl acetate and acrylate, or by controlling the ethylene conversion rate to a very low condition;
④Prepared by gas phase method.
3. high density polyethylene
It is polymerized using catalysts mainly aluminum alkyl and titanium tetrachloride under normal pressure of 10 atmospheres and 60-80°C.
(3) Performance
Physical and mechanical properties
PE is a milky white waxy translucent material, which is lighter than water, odorless, tasteless and non-toxic; HDPE is soft and LDPE is hard; the air permeability decreases with the increase of density, and is resistant to N2 and O2 Compared with other films, HDPE has larger CO2 air permeability, but its air permeability to water vapor is relatively small; PE’s low temperature resistance is the best among general plastics, with a brittle temperature of -70°C, but it is not resistant to water vapor. High temperature; HDPE has better strength and hardness, but poor impact strength, elasticity, and low transparency; while LDPE is the opposite.
The performance of MDPE is between the two
Chemical resistance
PE can withstand general acids, alkalis and salts at room temperature, but is not resistant to concentrated H2SO4 and HNO3. It can withstand most organic solvents below 60°C and swell in aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons.
Aging resistance
PE degrades slowly under the action of O2 in the air; it accelerates degradation under the action of heat, ultraviolet rays, and high-energy radiation.
Insulating properties
The dielectric constant is small.
Poor adhesion, printing and coloring properties.
(4) Combustion characteristics
It is flammable and continues to burn after being removed from the fire, and emits the same smell as paraffin when burning; when burning, the tip of the flame is yellow and the bottom is blue; there is little smoke; it melts, burns and drips while burning.
(5) Purpose
Low-density polyethylene has a wide range of uses. Films and hollow containers can be produced by extrusion blow molding, pipes can be produced by extrusion, composite films can be produced by extrusion calendering using kraft paper as the base, and composite films can be produced by injection. Produces various daily necessities, such as baby bottles, soap boxes, toys, cups, plastic flowers, etc.
Medium density polyethylene is mainly used to make various bottle products, hollow products, cable products and high-speed automatic packaging films.
High-density polyethylene plastic has high strength and good wear resistance, so it is mainly used to make ropes, packing straps, etc., and can also be used to make boxes, barrels, thermos bottle shells, etc.
polypropylene plastic
(1) Introduction
Polypropylene plastic (Polypropylene) is produced by polymerizing propylene under the action of aluminum methane and titanium trichloride catalysts at 20 atmospheric pressure and 50°C, using gasoline as a solvent. Its trade name is abbreviated as “propylene plastic”, and its English abbreviation is: PP.
(2) Identification characteristics
When not colored, it is a milky white translucent body with a soft texture; its relative density is smaller than that of water and can float on the horizontal surface; it does not soften significantly in boiling water and does not change shape, with a softening temperature of 110°C; it is smooth to the touch, but not greasy, and has a hard texture. toughness. When the strip was stretched, brittle fracture occurred.
(3) Combustion characteristics
It is flammable and can continue to burn after being removed from the fire, with a special smell escaping; the tip of the flame is yellow, with less smoke, and it burns, melts, and drips.
(4) Structure and performance
CH3
The structural formula of polypropylene is: [—CH2—CH—] n, which is a linear macromolecule, but the methyl side chains of polypropylene have three different arrangements, giving it a high degree of crystallinity. Due to the influence of methyl side chains, the properties of polypropylene and polyethylene plastics are different, mainly in the following aspects:
1. Better chemical stability than polyethylene
In addition to fuming nitric acid and fuming sulfuric acid, it has good resistance to other chemical corrosion. In the laboratory, 80% sulfuric acid and concentrated hydrochloric acid can reach 100°C without damaging polypropylene.
2. Outstanding heat resistance
It can be used for a long time at 100-120℃; however, the impact strength decreases sharply at low temperatures, and the impact strength at 0℃ is half of that at 20℃.
3. Air and water permeability are lower than polyethylene.
4. Rigidity and tensile strength are better than polyethylene.
5. directional stretching
The strength in the tensile direction is improved, the bending resistance is good, the flexibility is increased, and the bent area will not turn white after being bent in half for 1 million times.
6. Aging resistance is worse than polyethylene
The long chain of polypropylene contains methyl tertiary carbon atoms, which is unstable. During use, be careful to avoid long-term contact with copper to cause “copper damage”.
(5) Modification
There are certain shortcomings in the performance of polypropylene plastic, such as poor cold resistance, low impact strength, and poor aging resistance. In order to overcome these shortcomings, modification measures are often adopted.
1. Copolymerization modification
Copolymerized with monomers such as vinyl chloride and acrylic acid, it can improve the cold resistance, flammability, molding fluidity, etc. of polypropylene.
2. Blending modification
Blended with other thermoplastics and elastomers to prepare blends, it can improve the cold resistance of polypropylene.
3. Filling – enhanced modification
Filling materials and reinforcing materials are added to improve the rigidity of polypropylene at high temperatures and reduce molding shrinkage.
4. Stretch modification
By stretching, the molecules are oriented and the mechanical strength is improved. For example, after biaxial stretching of polypropylene, the strength can be increased by 3 times.
5. Cross-linking modification
The linear structure of polypropylene is cross-linked into a network structure, which can improve heat resistance and mechanical strength.
(6) Purpose
Polypropylene plastic is mainly used in films, pipes, bottles, etc. Due to its high softening point when heated, it can be used to make tableware, such as bowls, basins, cups, etc.; sterilization containers for medical devices; daily necessities such as buckets, thermos shells, etc.; can also be used to make stationery boxes, instrument boxes, etc.; and can also be used to make electrical insulation Materials and low-foaming boards that replace wood, etc. It is also suitable for making various ropes and packaging ropes.
China’s demand for polypropylene will soon surpass the United States and become the world’s largest consumer. China’s polypropylene demand is only 60% of US polypropylene demand, and this indicator has increased to 95%. The report pointed out that in the next five years, China’s demand for polypropylene will grow twice as fast as that of the United States. By 2007, China’s demand for polypropylene will be 20% higher than that of the United States.
According to industry analysis, Sinopec and PetroChina have now entered the ranks of the world’s largest polypropylene producers. Sinopec’s polypropylene production capacity ranks second in the world, and PetroChina ranks thirteenth. PetroChina has signed a licensing agreement with Basell to double its production capacity by 2007.
Although China has strong polypropylene production capacity, the annual polypropylene demand gap is still as high as 2.5 million tons. South Korea, the Middle East and India, as potential polypropylene exporters, will supplement this.
In 2002, global polypropylene demand reached 34 million tons, an increase of 7% from 2001, a net increase of 2.2 million tons. It is predicted that the world’s total demand for polypropylene will grow at a rate of 6.6% per year. By 2007, the world’s demand for polypropylene will reach more than 47 million tons.
polystyrene plastic
(1) Introduction
Polystyrene is a linear structure plastic polymerized from styrene monomer. Its commercial name is abbreviated as “styrene plastic”, and its English abbreviation is PS. Polystyrene is often synthesized by block polymerization and emulsion polymerization.
1. block polymerization
Polymerize styrene in an inert gas at a temperature of 60-90°C using dibenzoyl peroxide as a catalyst to obtain a transparent block resin. This kind of resin has higher purity, better transparency and gloss.
2. emulsion method
Under the action of a catalyst, the temperature of the aqueous emulsion of styrene monomer is controlled at 80-95°C for polymerization, and then the polymer is separated from the mother liquor and powdered resin is obtained after treatment. The heat resistance of the finished product is slightly higher than that of bulk polymer resin, but the electrical insulation and transparency are slightly worse.
(2) Identification characteristics
The surface is hard and smooth, with good transparency, strong tinting power, and bright color; the texture is brittle, the impact strength is low, and it is easy to scratch and break; the sound is crisp when struck and easily broken when bent; the relative density is greater than 1, slightly sink in the water.
(3) Combustion phenomenon
It has good combustion performance and is flammable. It will continue to burn after being removed from the fire and will emit the odor of styrene. The flame is yellow and emits black smoke; it softens and bubbles when burning.
(4) Performance
The structural formula of polystyrene is a linear structure, but there are huge phenyl groups continuously spaced on the carbon atoms of the molecular chain. This structure determines the special properties of polystyrene.
1. It has a hard texture and low impact strength; polystyrene with random configuration has good gloss, high light transmittance and good colorability.
2. The softening temperature is 80°C. Below 80°C it is a solid as hard as glass. Above 80°C it becomes a softer object with rubber-like properties. Use at high temperatures should be avoided.
3. Good molding performance, within the operating temperature range, the finished product has small shrinkage deformation and stable size; good water resistance, chemical stability decreases with the increase of temperature; it is resistant to a certain concentration of inorganic acids, organic acids, salt solutions and alkalis, alcohols, vegetable oils, etc. all have good resistance. If left in the sun for a long time, they will gradually turn yellow, lose clarity and crack.
4. Cracking, discoloration, stickiness and melting often occur when exposed to oils and insect repellents. They are prone to aging and yellowing under the action of light, oxygen and heat.
5. Easily soluble in organic solvents such as chloroform, methylene chloride, toluene, butyl acetate, etc. Avoid contact with the above solvents during storage.
(5) Modification
Polystyrene has shortcomings such as high brittleness, low softening temperature, and easy cracking, which seriously affects its use. In order to eliminate its shortcomings, modified polystyrene appeared; the approach is to copolymerize styrene monomer with other units, or to miscible polystyrene with other polymers and copolymers. Its modified varieties mainly include the following types:
1. Flexible polystyrene
In order to improve the shortcomings of polystyrene being brittle and fragile, tough modified polystyrene is made by blending it with elastomers such as rubber ( styrene-butadiene or nitrile ), which improves the impact strength of polystyrene. But it reduces the transparency and electrical properties of the product.
2. Chlorinated styrene
Two chlorine atoms are introduced into the styrene structure to produce dichlorostyrene monomer, which is then polymerized into dichlorostyrene synthetic resin. This modified polystyrene is still a transparent object, its heat resistance is greatly improved, and its impact strength is also improved.
3. Styrene and propylene copolymer ( AS )
Due to the introduction of acrylonitrile monomer, the chemical resistance, heat resistance, and mechanical strength of the material can be improved without cracks, making it an ideal material.
4. Styrene, butadiene, acrylonitrile copolymer ( ABS )
Butadiene is a good elastomer, and various monomers exert their own excellent properties in the copolymer. Therefore, ABS plastic has good comprehensive properties and is an ideal engineering plastic.
(6) Purpose
Polystyrene plastic is widely used in optical instruments, chemical industry and daily necessities. It is used to make tea trays, sugar bowls, soap boxes, cigarette cases, student rulers, combs, etc. Due to its certain air permeability, it can also be used as a good food packaging material when made into film products.
PVC plastic
(1) Introduction
PVC plastic is polymerized from vinyl chloride monomer and is one of the commonly used thermoplastics. Its trade name is abbreviated as “Chlorine Plastic”, and its English abbreviation is PVC.
Pure polyvinyl chloride resin is a hard thermoplastic substance, its decomposition temperature is very close to the plasticizing temperature, and its mechanical strength is poor. Therefore, PVC resin cannot be used to mold products. Plasticizers, stabilizers, fillers, etc. must be added to improve performance to make PVC plastic, which can then be processed into various products. Polyvinyl chloride is divided into hard polyvinyl chloride and soft polyvinyl chloride according to the amount of plasticizer added.
(2) Identification characteristics
The transparency of PVC film is higher than that of polyethylene, and the products are brightly colored, smooth to the touch, without a waxy feeling, and a special smell can often be smelled; it becomes obviously hard when exposed to cold, and the use temperature is 60°C; the relative density is greater than 1 and can sink in Under water, this is the distinguishing feature of PVC; hard products are hard and smooth, and the sound is muffled when struck; soft products are soft and elastic.
(3) Combustion performance
PVC has poor combustion performance and is extinguished immediately after leaving the fire. It is a flame-retardant plastic. When it burns, it releases the pungent smell of hydrogen chloride and softens when it burns.
(4) Performance
1. Soft polyvinyl chloride generally contains 30-50% plasticizer. Due to its soft texture and high strength, it has good air tightness and water impermeability.
2. Rigid polyvinyl chloride is made with only a small amount of plasticizer. It is characterized by hard texture, high mechanical strength and good chemical corrosion resistance. .
3. PVC plastic has poor heat resistance, and its strength is greatly affected by temperature. The strength at -20°C is 80% lower than that at 20°C. Therefore, film products are not easy to store and use at low temperatures; the use temperature of soft products does not exceed 45°C, and the use temperature of hard products does not exceed 60°C. They will age and become brittle when exposed to light for a long time.
4.When processing PVC film, in order to prevent thermal decomposition, a heat stabilizer needs to be added. Since the heat stabilizer contains lead salts, etc., it makes PVC plastic toxic and cannot be used as food packaging.
5. When PVC plastic comes into contact with organic solvents and insect repellents such as naphthalene, it will become sticky and melt, and it will easily absorb odors. Because plasticizers are highly volatile, they should not be stored for too long.
(5) Purpose
Soft polyvinyl chloride can be made into a good agricultural film, which is often used to make raincoats, tablecloths, curtains, wallets, handbags, etc. It is also widely used to make plastic shoes and artificial leather.
Rigid polyvinyl chloride can be made into transparent, translucent and pearlescent products of various colors. Commonly used to make soap boxes, combs, washboards, pencil boxes, various pipes, etc.
Its characteristics are as follows:
Light weight, easy to transport and load
PVC pipe material is very light, convenient for transportation, loading and unloading, and construction, and saves labor.
Excellent chemical resistance:
PVC pipe has excellent acid resistance, alkali resistance, and corrosion resistance, and is very suitable for use in the chemical industry.
Low flow resistance:
The wall surface of PVC pipe is smooth, the fluid resistance is small, and its roughness coefficient is only 0.009, which is lower than other pipes. Under the same flow rate, the pipe diameter can be reduced.
High mechanical strength:
PVC pipes have very high water pressure resistance, external pressure resistance, impact resistance, etc., and are suitable for piping projects under various conditions.
Good electrical insulation:
PVC pipe has excellent electrical insulation properties and is suitable for protective casing of wires and cables.
Does not affect water quality:
PVC pipes and fittings have been proven by dissolution experiments to not affect water quality and are currently the best pipe materials for tap water piping.
PVC Rongsheng refrigerator pipes
Phenolic plastic
(1) Introduction
The commercial names of phenolic plastics are ” Bakelite ” and ” Bakelite “, represented by PF. It uses phenol and aldehyde as raw materials, and is condensed into phenolic resin under the action of acid or alkaline catalyst. Plastic can be made by adding wood powder filler.
(2) Identification characteristics
The appearance of phenolic plastic is black, brown, and opaque; the surface is smooth and hard; it is brittle and fragile, with a loose cross-section structure and a wooden board sound when knocked. It is flame retardant and extinguishes immediately after leaving the fire. It is a flame retardant plastic. It emits a phenol smell when burning. The flame is yellow. The specific gravity is 1.34 to 1.45. It sinks in water.
(3) Performance
1. It has good heat resistance, is not easy to transfer heat, does not soften in boiling water, and the shape of the product is not affected by temperature changes.
2. It has good electrical insulation properties, high surface hardness, good mechanical strength, high compressive strength and bending strength, but low impact strength.
3. It has good chemical stability and is resistant to immersion in various solvents and oils. It is relatively stable in strong acids and various organic solvents, but can dissolve in alkaline solutions.
4. The product is hard and brittle, easily broken, has poor toughness, is not bright in color, has a surface gloss that is not as good as other plastics, and the resin itself is brown or black.
5. Because wood powder is used as a filler, the product is highly water-absorbent and needs to be protected from moisture and knocks during storage. Due to the varying degrees of curing, free phenol and formaldehyde are easily precipitated, so they are not suitable for use as eating utensils.
(4) Purpose
Phenolic plastics are widely used in telecommunications, electrical appliances, instruments, etc., and are also used in the manufacture of daily necessities, such as buttons, soap boxes, etc.
Urea-formaldehyde plastic
(1) Introduction
Urea-formaldehyde resin is synthesized from urea and formaldehyde. Urea-formaldehyde plastic can be made by adding pulp. Its commercial name is ” Dianyu “, and its abbreviated English name is UF.
(2) Identification characteristics
The appearance of urea-formaldehyde plastic products is mostly light-colored and translucent, which is brighter than bakelite products and bright in color; the surface is hard, brittle and brittle, and the cross-section structure is tight; it does not soften when soaked in boiling water, the relative density is 1.47 to 1.52, and it is flame retardant. It goes out when removed from the fire, and the smell of urea will escape. The tip of the flame will be light green, and the parts in contact with the flame will turn white and crack.
(3) Performance
1. The color of urea-formaldehyde plastic is lighter and can be made into light-colored products.
2. The surface of the product is hard, smooth, resistant to oil immersion, and non-mouldy.
3. Good heat resistance, heat resistance temperature above 100℃. However, when the temperature and time during molding of the product are insufficient, if the obtained product is boiled in boiling water for 10 to 15 minutes, the surface will turn white, dry quickly after cooking, and cracks will appear on the surface.
(4) Purpose
Urea-formaldehyde plastic is mainly used to make buttons, tableware, soap boxes, bottle caps, etc. It is also used in industrial and civilian electrical components and casings.
plexiglass
(1) Introduction
Plexiglass is the common name of polymethyl methacrylate. It is a linear resin polymerized from methyl methacrylate monomer. Its English abbreviation is PMMA.
(2) Identification characteristics
The product has high transparency, smooth and tough surface, light yellow color, and looks like a crystal product; there is no crisp sound when knocked, and it is tough when bent and not easy to break; when the product is rubbed with a soft object, it can produce an aromatic fruity smell; when burned, Noisy, no glue dripping.
(3) Performance
1. It has good optical properties, with a light transmittance of 92%, which allows light to travel along the curved body shape.
2. It has good dyeing performance. After adding synthetic fish scale powder, it can produce colorful pearlescent plexiglass.
3. It has good low-temperature performance and can still maintain high impact strength under the condition of -40℃.
4. It has good hygienic performance, is light in weight, is easy to be processed and formed, and can be stretched and oriented.
(4) Purpose
Plexiglas is mainly used in transparent shields and safety shields for aviation, ships, vehicles, and instruments. It is also widely used in optical industrial lenses and medical light guides. It is also used to make stationery and daily necessities, such as pen holders and T -squares., triangle ruler, cigarette case, umbrella handle, etc.
Nitrocellulose plastic
(1) Introduction
Nitrocellulose plastic is a plastic made from cotton linters or other natural cellulose from grass, wood, etc., which is esterified into nitrocellulose by nitrate camphor is added. Its commercial name is celluloid, and its English abbreviation is CN.
(2) Identification characteristics
It is translucent in nature and smells of camphor when rubbed; it easily softens and deforms when soaked in boiling water. It decomposes at a temperature of 100°C and burns at 170°C. It burns violently when exposed to an open flame and is a flammable plastic; the burning flame is yellow. It also emits a camphor smell and leaves less ash after burning.
(3) Performance
1. It is brightly dyed and can be made into opaque products by adding pigments.
2. The softening temperature is low, and when heated to 80°C, it can be processed at will, and the molding size is relatively stable.
3. It is stable to oils and easily soluble in many organic solvents, but is not affected by 5% ethanol, carbon tetrachloride and gasoline.
4. In dilute acid and alkali solutions, the surface color can be changed, and it is easy to decompose in relatively concentrated acid and alkali solutions.
5. Under the long-term action of light and heat, camphor will gradually sublimate, causing it to regain the inherent hard and brittle properties of nitrocellulose, making the product easy to break.
(4) Purpose
Celluloid is mainly used to make cultural and educational supplies, such as triangle rulers, pen holders, musical instrument casings, etc. It can also be used to make eyeglass frames, umbrella handles, etc.; it is also commonly used as toys, combs, soap boxes, etc. Because of its light weight and good elasticity, it is a good raw material for making table tennis balls.
Application plastic
(1) Foam plastics
1. Concept: Foam plastic is a plastic with countless tiny pores inside. It has properties such as softness, heat insulation, sound absorption, and buffering.
2. Classification: According to the different degrees of softness and hardness, it is divided into three types: soft, semi-rigid and rigid foam plastics; according to the bubble structure, it can be divided into open-cell foam plastics and closed-cell foam plastics. Open-cell foam plastic refers to cells that are interconnected and ventilated; it is characterized by good sound-absorbing performance and buffering performance; closed-cell plastic refers to cells that are not connected with each other and are independent of each other; it is characterized by relatively large Low thermal conductivity, low water absorption, and buoyancy.
3. Usage: Foam plastics are widely used in sound insulation, thermal insulation, thermal insulation, insulation, shockproof, filtration, packaging and other materials. Low-foaming foam plastics such as polyurethane, polystyrene, and polyvinyl chloride can be used as substitutes for wood; polyethylene, polystyrene, and polyvinyl chloride foam paper can be printed with special documents, maps, or made into cardboard. Packaging and ceiling and other building materials. In addition, composite materials of foam plastics and fibers, such as foam artificial leather, synthetic leather, etc., have a soft and plump feel and can be made into shoes, hats, boxes, bags, gloves, etc. instead of leather.
(2) Artificial leather
Artificial leather is a composite material made of fibers combined with plastic. Common artificial leather is mainly polyvinyl chloride artificial leather.
Artificial leather has the characteristics of soft texture, high elasticity, high mechanical strength, acid and alkali resistance, not easy to burn, easy to wash, bright color and various patterns, so it is particularly widely used. It is often used to make covering materials such as clothing, hats, gloves, shoes, sofas, and chairs.
(3) Synthetic leather
The surface of synthetic leather is polyurethane resin. It is a composite material formed by coating polyurethane microporous elastomer on composite fiber knitted fabric or non-woven fabric.
Synthetic leather has the characteristics of antioxidant, wear resistance, oil resistance, etc., and its mechanical strength, wear resistance, and elasticity are better than artificial leather; its air permeability and moisture vapor permeability are close to natural leather; its surface hardness is high, and it is not prone to insects, mildew, and water resistance., Good oil resistance; product size is stable, not easy to deform, and the texture is equally soft at low temperatures; product appearance is bright, beautiful, easy to maintain, strong and durable. Therefore, it has a wide range of uses and can be used as a substitute for natural leather to make various leather products such as boxes, bags, clothes, and hats. It is also widely used as a raw material for shoemaking.
Identification method
Plastics can be identified using scientific methods such as infrared spectroscopy, paramagnetic resonance and X-rays, but simpler methods can also be used. The following is a brief introduction to the simple identification method:
Sensory identification
Sensory identification (organizing students to participate in the identification of plastics)
(1) Look
First look at the color and transparency of the product.
Transparent products include: polystyrene and plexiglass.
Translucent products include: low-density polyethylene, cellulose plastic, polyvinyl chloride, polypropylene, epoxy resin, and unsaturated resin.
Opaque products include: high-density polyethylene, polyurethane and various colored plastics.
(2) Listen
When struck with hard objects, the sound is different. Polystyrene sounds like metal, while plexiglass sounds thicker and duller.
(3) Touch
If the product feels waxy when you touch it, it must be made of polyolefin. Secondly, the softness and hardness of the mold can be simply expressed as follows:
hard → soft
Polystyrene →polypropylene→polyamide→ plexiglass → high density polyethylene → rigid polyvinyl chloride → low density polyethylene → soft polyvinyl chloride
Then test the surface hardness and scratch the surface with pencils of different hardnesses to make the difference:
Line marks can be drawn on polyethylene plastic with an HB pencil;
Line marks can be drawn on polypropylene plastic with a ZH pencil.
Due to differences in people’s physiological conditions, the feelings obtained through sensory evaluation are not the same, so this method is only for reference.
Basis for identification of several easily mixed plastics
(1) Basis for identification of polyethylene and polypropylene plastics
Polyethylene and polypropylene plastics are both milky white and translucent, lightweight and can float on the water, and their combustion phenomena are basically the same. However, there are obvious differences between the two: polyethylene has a paraffin slippery feel to the hand, and its texture is soft and flexible, while polypropylene is smooth and delicate to the touch, but has no waxy slippery feel, and its texture is hard and tough; polyethylene plastic It softens significantly in boiling water, while polypropylene plastic does not soften significantly in boiling water; polyethylene plastic strips have “thin necks” when stretched, but polypropylene does not.
(2) Basis for identification of polyvinyl chloride and polyethylene plastic films
The processing methods of polyvinyl chloride and polyethylene are different: PVC is pressed into a single film by calendering method, and polyethylene is made into cylindrical double-layer bags by blow molding method; in terms of color and transparency: Polyethylene is milky white and translucent, with a bright surface, and feels waxy and smooth to the touch. When stacked in multiple layers, it still appears milky white and translucent. However, polyvinyl chloride is more transparent than polyethylene and has a slightly yellow color. They turn yellow together and are smooth to the touch, but have a sticky feeling. Upon closer inspection, there are mold fine lines; the combustion phenomena are different: polyethylene is flammable, melts and drips, and smells of paraffin, while polyvinyl chloride is refractory, the root of the flame is green, and emits the pungent smell of hydrochloric acid; polyethylene has a small specific gravity and can Floats on the water, while PVC sinks in the water.
(3) Basis for identification of phenolic and urea-formaldehyde plastics
Both are thermosetting plastics, which are hard and opaque. The main differences are as follows: phenolic plastics are generally dark brown, while urea-formaldehyde plastics are mostly light-colored and brightly colored; phenolic plastics have a loose cross-section structure, while urea-formaldehyde plastics have a loose cross-section. The structure is tight; when burning, phenolic formaldehyde releases the odor of phenol, and carbonization and cracking occur at the part in contact with the flame. Urea-formaldehyde releases the odor of urea, and whitening and cracking occur at the part in contact with the flame.
(4) Basis for identification of polystyrene, polyvinyl chloride, and polyethylene plastics
The identification of these three types of plastics is based on the following five aspects:
1. color and transparency
Polystyrene plastic has bright colors and is as transparent as glass; polyvinyl chloride plastic is worse in color and transparency than polystyrene; polyethylene plastic is translucent and looks like wax products, and dyes bleed out easily.
2. Feel
Polystyrene has a smooth feel and a hard surface, and is afraid of bumps and squeezes; polyvinyl chloride also has a smooth feel, and film products have a sticky feel; there are soft and hard products; polyethylene has a waxy and slippery feel., the product is soft and resistant to bending.
3. relative density
The relative density of polystyrene is 1.05~0.06, and it sinks slowly in water; the relative density of polyvinyl chloride soft plastic is 1.24~1.45, and the relative density of hard plastic is 1.35~1.45, so it sinks quickly in water. It sinks; the relative density of high-density polyethylene is 0.94~0.97, and the relative density of low-density polyethylene is 0.91~0.93, so it floats in water.
4. sound
When struck with a hard object, polystyrene has a crisp metallic sound, PVC is loud but not brittle, and polyethylene is dull but not brittle.
5. Flammability
Polystyrene is flammable, the flame is orange, it emits flocculent black smoke, and has a pungent and unpleasant smell of styrene monomer; PVC cannot spontaneously ignite and is extinguished when removed from the fire. The flame is yellow, the roots are green, and it emits the smell of hydrochloric acid.; Polyethylene is flammable, with a yellow flame and blue roots, emitting a small amount of black smoke, softening when burning, dripping wax tears like a candle, and emitting a paraffin smell.
Production process
Compression molding
Compression molding, also known as molding, is a molding method in which molding materials are pressurized (usually heated) in a closed mold cavity.
Laminated molding
A method of combining two or more layers of the same or different materials into a whole using heat and pressure with or without an adhesive.
Cold press molding
Cold press molding is also called cold press sintering molding. The difference from ordinary compression molding is that the material is pressurized at normal temperature to the molding point.
Transfer molding
Transfer molding is a molding method for thermosetting plastics. During molding, the molding material is first heated and softened in a heating chamber, and then pressed into the heated mold cavity to solidify.
Extrusion molding
Extrusion molding is also called extrusion molding or extrusion. It is a method in which materials are continuously passed through the die in a flowing state by heating and pressurizing the extruder.
Pultrusion
Pultrusion is one of the molding methods of thermosetting fiber-reinforced plastics. It is used to produce profiles with a fixed cross-sectional shape and unlimited length.
Injection molding
Injection molding (injection molding) is a method in which thermoplastic or thermosetting molding materials are uniformly plasticized in a heated barrel and then pushed into the cavity of a closed mold by a plunger or moving screw for molding.
Blow molding
A method in which the hot parison closed in the mold is blown by gas pressure to become a hollow product, or the tube parison is blown into a tube film without a mold.
Casting
A method of injecting liquid monomer, resin or mixtures thereof into a mold without applying pressure or with slight pressure, and turning it into a solid product.
Hand lay-up
Hand lay-up molding, also known as hand-paste molding and contact molding, is one of the methods for manufacturing reinforced plastic products.
Fiber winding molding
Under the conditions of controlled tension and predetermined line shape, continuous filaments soaked in resin glue are wound around a mandrel or mold to form reinforced plastic products.
Calendering
A molding method in which thermoplastics are passed through a series of heated pressure rollers to join them into films or sheets under the action of extrusion and stretching.
Coating
For the purpose of anti-corrosion, insulation, decoration, etc., a method of coating a thin layer of plastic (for example, less than 0.3 mm) in the form of liquid or powder on the surface of fabric, paper, metal foil or board.
Foam molding
Foam molding is the process of creating a microcellular structure in plastic. Almost all thermosetting and thermoplastic plastics can be made into foam plastics. Commonly used resins include polystyrene, polyurethane, polyvinyl chloride, polyethylene, urea-formaldehyde, phenolic formaldehyde, etc.
Overmolding
Secondary molding is one of the methods of plastic molding processing. A method that uses plastic profiles or parisons as raw materials to turn them into products of the desired shape through heating and external force.
Advantages
1. Most plastics have strong corrosion resistance and do not react with acids or alkalis.
2. Plastic is cheap to manufacture.
3. Durable, waterproof and lightweight.
4. Easily molded into different shapes.
5. Is a good insulator.
6. Plastics can be used to prepare fuel oil and fuel gas, which can reduce crude oil consumption.
Shortcoming
1. When it comes to recycling waste plastics, sorting them is difficult and uneconomical.
2. Plastic burns easily and produces toxic gases when burned. For example, when polystyrene is burned, toluene is produced. A small amount of this substance can cause blindness, vomiting and other symptoms when inhaled. PVC burning can also produce toxic gases such as hydrogen chloride. In addition to burning, high-temperature environments can cause plastics to decompose into toxic components, such as benzene rings. wait.
3. Plastics are made from products refined from petroleum, and petroleum resources are limited.
4. Plastic cannot be broken down naturally.
5. Plastics have poor heat resistance and are prone to aging.
The inability of plastic to degrade naturally has led to many animal tragedies. For example, monkeys, pelicans, dolphins and other animals in the zoo will accidentally swallow the No. 1 plastic bottles thrown away by tourists, and eventually die in pain due to indigestion; looking at the beautiful and pure sea, when you get closer, you will see that it is actually full of plastic bottles. A variety of plastic waste that cannot be accommodated by the ocean. Various types of plastic that cannot be digested have been found in the intestines of many dead seabird samples.
The most dangerous of all plastics are phthalates, which are a major cause of lower sperm counts in men. The European Union has banned the use of several phthalates in cosmetics, teething chews and children’s toys. Pregnant women are still exposed to phthalates, however, because the chemicals are often used to soften the plastic in household items such as plastic furniture, shoes, PVC flooring and shower curtains.
Phthalates can enter the human body through food and water packaged in plastic containers, such as the inner coating of food cans, recyclable milk and mineral water bottles, etc. Research shows that the higher the fat content in canned food, the more likely it is to be contaminated, such as pork, anchovies, sardines, etc. Fetuses, infants, and adolescent children are the most sensitive to it, and their health is also the most vulnerable.
In order to reduce the harm of phthalates to the human body, it is best not to use foam plastic containers to soak instant noodles, and do not use plastic containers containing polyvinyl chloride to heat food in a microwave oven. The correct approach is to heat the food in heat-resistant glass or ceramic vessels.
Industry data
The United States is still the largest export market for China’s daily plastic products, accounting for 36% of the total export share, an increase of 1.4 percentage points year-on-year. Overall, China’s status as the world’s factory has not changed, but we must also pay close attention to some current foreign-funded enterprises. The situation is shifting to Vietnam and other places and corresponding countermeasures should be taken.
As of November 2012, China’s daily plastic product output was 481,138 tons, a year-on-year increase of 31.1%. From January to November, the national output of daily plastic products totaled 4,195,220 tons, a year-on-year increase of 14.9%.
Industry development
Development of the plastics industry in 2012
China has introduced a series of economic stimulus plans and ten major industry revitalization plans, which will drive demand and consumption of plastic products and promote the development of the plastics industry. The government has successively introduced various rescue measures, including 4 trillion yuan of investment projects, and arranged and implemented ten measures to expand domestic demand, especially among them, accelerating the construction of affordable housing projects, accelerating the construction of rural infrastructure, and accelerating the construction of major infrastructure such as railways, highways, and airports. PVC plastic products will be used in major projects such as facility construction and accelerating the transformation of urban power grids. Many industries such as automobiles, electronic information, and light industry, which have already implemented adjustment and revitalization plans, are also major users and consumers of polyvinyl chloride series plastic products, and will play a role in promoting the development of the plastics industry. ( Data source : Chinese National Bureau of Statistics)
Regional distribution of China’s plastic products industry
The plastics industry has grown to varying degrees in various regions. Statistical data analysis shows that provinces with relatively weak plastic processing industries in the past, such as Hunan, Hainan, Shanxi, Inner Mongolia and other places, saw large growth in the output of plastic products in 2012, with the growth rate being More than 50%, but the uneven regional distribution pattern has not changed much. Products with high energy consumption, low processing technology content, and labor- intensive products are gradually flowing to economically underdeveloped areas.
The total plastic products in Guangdong, Zhejiang and Jiangsu provinces are 12.2133 million tons, accounting for 55.5% of the country’s total output. Guangdong still accounts for 25% of the country’s total, Zhejiang still accounts for 20%, and Jiangsu accounts for 10.5%, a slight decrease., the overall pattern has not changed; Shandong Province, which ranks fourth Accounting for 7%; the output of Hebei, Henan, and Liaoning provinces accounted for 5%, 4.7%, and 4.5% respectively, surpassing Fujian and following Shandong, ranking 5th, 6th, and 7th; Fujian, Anhui, and Shanghai accounted for 3% respectively. 93%, 3.34%, 2.82%, ranked 8th, 9th, and 10th. (Data source: National Bureau of Statistics)
The regional characteristics of various types of products are very obvious, and each province has its own emphasis on plastic products: Guangdong Province ranks first in the country in terms of output of plastic rods and pipes, plastic packaging boxes and containers, daily plastic products, and other plastic products; Zhejiang Province ranks first in the country in terms of output of plastic films and plastic products. Artificial leather ranks first in the country; Jiangsu Province’s foam plastics and plastic synthetic leather production ranks first in the country; Liaoning Province’s plastic profile production continues to rank first in the country after 2010; Shandong Province’s agricultural film and plastic woven products rank first in the country.
Zhongyan Puhua Industry Research Institute believes that plastic building materials and new packaging materials will become the main areas of plastic growth. Nowadays, chemical building materials are called the fourth generation of building materials after steel, wood and cement, and plastic building materials are the main component of chemical building materials. Plastic building materials mainly include plastic pipes, plastic doors and windows, building waterproofing materials, thermal insulation materials, decoration materials, etc. Plastic building materials are widely used in construction projects, municipal projects, and industrial construction. The real estate and construction industries are the pillar industries of China’s national economy. Although the country continues to introduce relevant macro-control policies due to the rapid rise in housing prices, the management’s attitude towards supporting the healthy development of the housing industry has not changed; as China’s economy gradually enters a comprehensively well-off society, residents’ strong demand to improve their housing conditions is still strong; the construction of the Beijing Olympics and Shanghai World Expo venues will also stimulate demand for the development of the construction industry. Under this circumstance, the National Leading Group on Chemical Building Materials has also successively formulated and issued several opinions, outlines and methods on the production, promotion and application of chemical building materials to provide policy guarantees for the stable development of plastic building materials. China’s plastic building materials products have huge market space. Taking the plastic pipe market as an example, the market share of plastic pipes in developed countriesis 50%, while China only has 25%. In the next 10 years, the domestic plastic pipe market demand will reach 800 billion yuan.
Precautions for use
Plastic cups are safer than paper cups
The plastic product code-named 5 has a temperature resistance of 130 degrees and can be filled with hot water and heated by microwaves.
The darker the straw, the less safe it is
It is not advisable to use plastic straws when drinking hot drinks
Use disposable chopsticks as little as possible
How to use plastic bowls and imitation porcelain bowls
Do not use dark-colored plastic bowls
Imitation porcelain tableware cannot contain acidic substances
Mineral water bottles and pure water buckets code number “1”
Plastic bottles can store dry items
The water bottle code-named 5 is high temperature resistant and reusable
Qualified plastic lunch boxes are marked with “5” pp and have a small ventilation hole on the lid. Since certain additives are added to plastic, the darker the color of the plastic, the more additives are added.
Related information
Plastic restriction order
The Chinese General Office of the State Council issued a notice on restricting the production, sale, and use of plastic shopping bags on December 31, 2007. This notice was called the “Plastic Restriction Order” by the masses. The reason for the introduction is that while plastic shopping bags provide convenience to consumers, they also cause serious waste of energy, resources and environmental pollution due to excessive use and insufficient recycling. As we all know, the pollution problems caused by the large volume of discarded foam plastics and the lack of clear garbage classification and recycling channels cannot be underestimated. However, due to the low cost and ease of use of foam plastic, some well-known online shopping stores continue to use it.
More environmentally friendly alternatives have appeared on the market, such as foamed polypropylene, honeycomb cardboard and pulp molded products. There is an urgent need to establish a recycling mechanism for such cushioning packaging materials, such as adding cushioning packaging materials as a recycling type in waste recycling., so that such environmentally friendly materials are vigorously promoted.
Plastic products industry profits increased by 30.86% year-on-year
Data released by the Ministry of Industry and Information Technology of China on the 19th showed that From January to August 2011, the plastic products industry achieved an industrial sales output value of 978.982 billion yuan, a cumulative year-on-year increase of 27.6%, and a cumulative production-to-sales ratio of 98.1%; realized a profit of 41.256 billion yuan, a cumulative year-on-year increase of 30.86%; and achieved an export delivery value of 1,471.51 billion, a cumulative year-on-year increase of 11.2%.
From January to August 2011, the cumulative production of plastic films was 5.3837 million tons, a year-on-year increase of 14.86%. Among them, the cumulative production of agricultural films was 912,300 tons, a year-on-year increase of 17.98%; foam plastics The cumulative production of plastic materials was 907,100 tons, a year-on-year increase of 27.18%; the cumulative production of plastic artificial leather and synthetic leather was 1.5037 million tons, a year-on-year increase of 11.42%; the cumulative production of daily plastic products was 280.03 million tons, a year-on-year increase of 11.83%.
Norway plastic ban
On March 11, 2021 local time, the Norwegian Radio and Television Corporation reported that from July 3, 2021, Norway will ban the use of disposable plastic products such as plastic straws and tableware. But the ban does not apply to medical devices.
US ban
In October 2023, the U.S. Department of the Interior announced that it would gradually ban single-use plastic products on federal lands under the jurisdiction of the Department of the Interior such as national parks.
