ABS plastic is a ternary copolymer of acrylonitrile (A), butadiene (B) and styrene (S). The relative contents of the three monomers can be changed arbitrarily to make various resins.
ABS plastic has the common properties of three components. A makes it resistant to chemical corrosion and heat, and has a certain surface hardness. B makes it highly elastic and tough. S makes it have the processing and molding characteristics of thermoplastics and improves electrical properties. Therefore, ABS plastic is a “tough, hard, and rigid” material with easy-to-obtain raw materials, good comprehensive properties, low price, and a wide range of uses. ABS plastic has been widely used in manufacturing industries such as machinery, electrical, textiles, automobiles, aircraft, ships, and chemical industries.
Concept
ABS plastic is a terpolymer of acrylonitrile (A)-butadiene (B)-styrene (S). It combines the properties of the three components, among which acrylonitrile has high hardness and strength, heat resistance and corrosion resistance; butadiene has impact resistance and toughness; styrene has high surface gloss, easy coloring and easy processing. The characteristics of the above three components make ABS plastic a thermoplastic plastic with good comprehensive properties of “hard quality, toughness and high rigidity”. By adjusting the proportion of the three components of ABS, its properties will also change accordingly to meet the requirements of various applications, such as high-resistance ABS, heat-resistant ABS, high-gloss ABS, etc. ABS plastic has good molding and processing properties. It can be molded by injection, extrusion, thermoforming and other methods, and can be machined by sawing, drilling, filing, grinding and other mechanical processing. It can be bonded with organic solvents such as chloroform, and can also be painted, electroplated and other surface treatments. ABS plastic is also an ideal wood substitute and building material. ABS plastic has high strength, light weight, high surface hardness, very smooth, easy to clean, stable in size, good creep resistance, and is suitable for electroplating treatment materials. Its application areas are still expanding. ABS plastics are widely used in industry. ABS injection products are often used to make shells, boxes, parts, toys, etc. Extrusion products are mostly plates, rods, pipes, etc., which can be hot pressed, composited and made into models.
Molecular Structure
The structure of ABS resin includes graft copolymers with elastomer as the main chain and graft copolymers with hard ABS resin as the main chain; or a mixture of rubber elastomer and hard ABS resin. In this way, different structures show different properties. The elastomer shows the toughness of rubber, and the hard ABS resin shows rigidity. Several varieties such as high impact type, medium impact type, general impact type and special impact type can be obtained. Specifically, as the content of rubber component B (generally 5%~30%) increases, the elasticity and impact resistance of the resin will increase; but the tensile strength, fluidity, weather resistance, etc. will decrease. The content of resin component AS (generally 70%~95%) increases, which can improve the surface gloss, mechanical strength, weather resistance, heat resistance, corrosion resistance, electrical properties, processing properties, etc. However, the impact strength, etc. will decrease. The ratio of A to B in the resin component is 30%~35%/80%~65% respectively.
Key Features
Plastic ABS resin is the polymer with the largest output and the most extensive application. It organically unifies the various properties of PB, PAN and PS, and has excellent mechanical properties of toughness, hardness and rigidity. ABS is a terpolymer of acrylonitrile, butadiene and styrene, A represents acrylonitrile, B represents butadiene, and S represents styrene. It has been found in actual use that ABS plastic pipes are not resistant to sulfuric acid corrosion and will shatter when exposed to sulfuric acid.
The three components give it excellent properties; acrylonitrile gives ABS resin chemical stability, oil resistance, a certain degree of rigidity and hardness; butadiene improves its toughness, impact and cold resistance; styrene gives it good dielectric properties and good processability.
Most ABS is non-toxic, impermeable to water, but slightly permeable to water vapor, with low water absorption. The water absorption rate does not exceed 1% after being immersed in water at room temperature for one year, and the physical properties do not change. The surface of ABS resin products can be polished to obtain highly glossy products. It is 3-5 times stronger than ordinary plastics.
ABS has excellent comprehensive physical and mechanical properties, good low-temperature impact resistance. Dimensional stability. Good electrical properties, wear resistance, chemical resistance, dyeability, finished product processing and mechanical processing. ABS resin is resistant to water, inorganic salts, alkalis and acids, insoluble in most alcohols and hydrocarbon solvents, but easily soluble in aldehydes, ketones, esters and some chlorinated hydrocarbons. ABS resin has a low thermal deformation temperature and is flammable, but has poor heat resistance. The melting temperature is 217~237℃, and the thermal decomposition temperature is above 250℃. Many of the modified ABS materials on the market today are doped with nozzle materials and recycled materials. As a result, the performance of customer molded products is not very stable.
(1) Material properties
1. Good comprehensive performance, high impact strength, chemical stability and good electrical properties;
2. It has good welding property with 372 organic glass and can be made into two-color plastic parts, and the surface can be chrome plated and painted;
3. Available in high impact resistance, high heat resistance, flame retardant, enhanced, transparent and other grades;
4. The fluidity is slightly worse than HIPS, but better than PMMA, PC, etc., and has good flexibility;
5. Suitable for making general mechanical parts, wear-resistant and anti-friction parts, transmission parts and telecommunication parts.
(2) Forming performance
1. Amorphous materials have medium fluidity and high moisture absorption, so they must be fully dried. Plastic parts that require glossy surfaces must be preheated and dried at 80-90 degrees for a long time, for 3 hours;
2. High material temperature and high mold temperature are recommended, but the material temperature is too high and it is easy to decompose (the decomposition temperature is >270℃). For plastic parts with higher precision, the mold temperature should be 50-60℃, and for high gloss and heat-resistant plastic parts, the mold temperature should be 60-80℃;
3. If you need to solve the problem of water lines, you need to improve the fluidity of the material, use high material temperature, high mold temperature, or change the water level;
4. If heat-resistant or flame-retardant materials are used, plastic decomposition products will remain on the mold surface 3-7 days after production, causing the mold surface to become shiny. The mold needs to be cleaned in time, and exhaust positions need to be added to the mold surface;
5. The cooling speed is fast. The mold pouring system should be thick and short. It is advisable to set a cold material hole and the gate should be large, such as direct gate, disc gate or fan gate, etc. However, the internal stress should be prevented from increasing. If necessary, an adjustable gate can be used. The mold should be heated and wear-resistant steel should be used;
6. Material temperature has a great influence on the quality of plastic parts. If the material temperature is too low, it will cause material shortage, dull surface, disordered silver threads. If the material temperature is too high, it will easily overflow, silver threads and dark stripes will appear, and the plastic parts will change color and bubble.
7. Mold temperature has a great influence on the quality of plastic parts. When the mold temperature is low, the shrinkage rate, elongation rate, and impact strength are large, while the bending, compression, and tensile strengths are low. When the mold temperature exceeds 120°C, the plastic parts cool slowly, are easy to deform and stick to the mold, are difficult to demold, and have a long molding cycle;
8. The molding shrinkage is small, and melting cracking is prone to occur, resulting in stress concentration. Therefore, the molding conditions should be strictly controlled during molding, and the plastic parts should be annealed after molding;
9. The melting temperature is high, the viscosity is high, and it is not sensitive to shearing. For plastic parts larger than 200 grams, a screw injection machine should be used. The nozzle should be heated, and an open-type extension nozzle should be used. The injection speed should be medium to high.
(3) Adhesion problems
According to different needs, you can choose the following adhesives:
1. G-977: Single-component soft elastic shockproof adhesive that cures at room temperature, resistant to high and low temperatures, with different viscosities and bonding speeds that cure in seconds to hours;
2. KD-833: Instant adhesive, can quickly bond PC plastic in a few seconds or tens of seconds, but the adhesive layer is hard and brittle and cannot withstand immersion in hot water above 60 degrees;
3. QN-505, two-component adhesive, soft adhesive layer, suitable for large-area bonding or lamination of PC plastics. But the high temperature resistance is poor;
4. QN-906: two-component adhesive, high temperature resistant;
5. G-988: Single component room temperature vulcanized rubber, after curing, it is an elastomer with excellent waterproof and shockproof adhesive, high and low temperature resistance, 1-2mm thickness, about 10 minutes for initial curing, 5-6 hours for basic curing, with a certain strength. It takes at least 24 hours to fully cure. Single component, no need to mix, just apply after extrusion and let it stand, no need to heat.
Preparation
There are many methods for producing ABS, which can be divided into four categories: blending, grafting, combined use and grafting-blending, with about eleven preparation processes. Nowadays, the emulsion method is mostly used, and the most promising one is the emulsion grafting method. ABS can be made into various specifications of products by changing the ratio of the three monomers and using different polymerization methods. Its structure includes graft copolymers with elasticity as the main chain and graft copolymers with resin as the main chain. Generally, the ratio of the three monomers is roughly 25%~35% acrylonitrile, 25%~30% butadiene and 40%~50% styrene.
Since PC/ABS is a blend of two polymers, with PC as the main component, streaks may sometimes appear at the gate when processing products. This is usually caused by the expansion of the molten material into the mold cavity during high-speed injection. It is caused by melt fracture. From the perspective of molding process, measures such as increasing the material temperature, increasing the nozzle temperature, and slowing down the injection speed can be taken to reduce the appearance of streaks in PC/ABS products. You can also increase the mold temperature, add a surge groove, increase the gate size, and modify the gate shape to solve the problem. For example, a fan-shaped gate can be used for large thin-walled parts, or an ear-shaped gate can be used. An ear groove can be added at the gate outlet so that the injection near the gate, the material flow impact marks, and the residual stress are all concentrated in the ear groove without affecting the quality of PC/ABS parts. At the same time, weld lines will also appear when multiple gates are injected or there are many runners.
Test items
Mechanical properties: density, hardness, surface resistivity, dielectric properties, tensile properties, impact properties, tear properties, compression properties, bonding strength, wear resistance, low temperature properties, and resilience;
Aging performance: heat aging, ozone aging, UV lamp aging, salt spray aging, xenon lamp aging, carbon arc lamp aging, halogen lamp aging;
Liquid resistance: lubricating oil, gasoline, engine oil, acid, alkali, organic solvent, water;
Combustion performance: vertical combustion, alcohol torch combustion, tunnel propane combustion, smoke density, combustion rate, effective combustion calorific value, total smoke release;
Applicable performance: hydraulic resistance, pulse test, electrical conductivity, water tightness, air tightness;
Production parameters: melt index, viscosity, mold shrinkage, melt temperature, etc.
General performance
Plastic ABS is non-toxic, odorless, and has an ivory-colored translucent, or transparent granular or powdery appearance. The density is 1.05~1.18g/cm 3, the shrinkage is 0.4%~0.9%, the elastic modulus is 2Gpa, the Poisson’s ratio is 0.394, the hygroscopicity is <1%, the melting temperature is 217~237℃, and the thermal decomposition temperature is >250℃.
Mechanical properties
Plastic ABS has excellent mechanical properties, good impact strength, and can be used at extremely low temperatures; plastic ABS has excellent wear resistance, good dimensional stability, and oil resistance, and can be used for bearings under medium loads and low speeds. ABS has greater creep resistance than PSF and PC, but less than PA and POM.
Thermal properties
The heat deformation temperature of plastic ABS is 93~118℃, and the product can be increased by about 10℃ after annealing. ABS can still show a certain toughness at -40℃ and can be used in the temperature range of -40~100℃.
Electrical properties
Plastic ABS has good electrical insulation and is almost unaffected by temperature, humidity and frequency, and can be used in most environments.
Environmental performance
Plastic ABS is not affected by water, inorganic salts, alkalis and various acids, but is soluble in ketones, aldehydes and chlorinated hydrocarbons. It will produce stress cracking when corroded by glacial acetic acid, vegetable oils, etc. ABS has poor weather resistance and is easily degraded under the action of ultraviolet light; after six months outdoors, the impact strength drops by half.
Main applications
Engineering Plastics
PC/ABS recycled material is an important engineering plastic alloy, which is widely used in the fields of automobile, electronic and electrical, office and communication equipment. Nowadays, in order to meet the special requirements of fire safety in the application field (especially electronic and electrical products), the flame retardant technology of PC/ABS alloy has become a hot topic of research. However, with the advancement of science and technology, the requirements for the environmental friendliness of materials are getting higher and higher, and the harm caused by traditional halogen flame retardant is becoming increasingly obvious.
In engineering, ABS is widely used in engineering pipes. In municipal projects with relatively high material requirements, ABS pipes can generally be used for pool bottom pipes.
3D printing field
ABS plastic is one of the main materials for 3D printing. The reason why it can become a consumable material for 3D printing is determined by its characteristics. ABS plastic has the characteristics of heat resistance, impact resistance, low temperature resistance, chemical resistance, excellent electrical properties, and stable product size. ABS plastic is the most stable material among 3D printing materials.
more applications
The largest application areas of ABS resin are automobiles, electronic appliances and building materials. In the automotive field, it is used in many parts such as car dashboards, body panels, interior trim panels, steering wheels, sound insulation panels, door locks, bumpers, ventilation pipes, etc. In the electrical field, it is widely used in refrigerators, televisions, washing machines, air conditioners, computers, copiers and other electronic appliances. In the building material field, ABS pipes, ABS sanitary ware, and ABS decorative panels are widely used in the building material industry. In addition, ABS is also widely used in packaging, furniture, sports and entertainment products, machinery and instrumentation industries.
ABS resin is widely used in the automotive industry, electrical instrument industry and mechanical industry, and is often used to make gears, auto parts, fenders, handrails, refrigerator linings, blades, bearings, handles, pipes, joints, instrument housings, dashboards, basins and helmets, etc. It has a broader application prospect in household appliances and home electronic equipment, such as televisions, radio recorders, refrigerators, freezers, washing machines, air conditioners, vacuum cleaners and various small household appliances; daily necessities include shoes, bags, various travel suitcases, office equipment, toys and various containers, etc. Low-foaming ABS can replace wood and is suitable for building materials, furniture and household items.
Because ABS has good comprehensive performance and good molding processability, it has its footprint in a wide range of applications. The brief content is as follows:
1. Automobile industry
Many parts in the automobile industry are made of ABS or ABS alloys. For example, Shanghai’s Santana sedans use 11kg of ABS per car, ranking third among all plastics used in cars. The amount of ABS used in other vehicles is also quite astonishing. In 2000, the amount of ABS used in automobiles in China reached 35,000 tons. The main parts of cars that use ABS, such as the dashboard, use PC/ABS as the skeleton, and the surface is covered with a film made of PVC/ABS/BOVC. In addition, a large number of interior decorative parts use ABS, such as the glove box and the storage box assembly are made of heat-resistant ABS, the upper and lower door sill trims, and the radiator mask are made of ABS, and many other parts are made of ABS as raw materials.
2. Office machines
Because ABS has high gloss and easy formability, office equipment and machines need to have beautiful appearance and good feel. For example, telephone casings, memory casings, computers, fax machines, and copiers all use a large number of ABS parts.
3. Household appliances
Because ABS has high gloss and easy formability, it has a wide market in home appliances and small appliances. For example, ABS is widely used as a raw material in home fax machines, stereos, and VCDs. Vacuum cleaners also use many ABS parts, and kitchen utensils also use a large number of ABS parts.
The main body of plastic ABS is a blend or terpolymer of acrylonitrile, butadiene and styrene. It is a tough and rigid thermoplastic. Styrene gives ABS good moldability, gloss and rigidity; acrylonitrile gives ABS good heat resistance, chemical corrosion resistance and surface hardness; butadiene gives ABS good impact strength and low-temperature resilience. The performance of the three components varies with the proportion of the three components.
Manufacturing processes
Processability
ABS is an amorphous polymer with no obvious melting point. Due to its wide variety of grades, appropriate process parameters should be formulated according to the grades during the injection molding process. Generally, it can be molded at a temperature above 160°C and below 240°C. Because the temperature is too high, there is a tendency to destroy the rubber phase in ABS, and decomposition begins to occur above 250°C. During the molding process, ABS has good thermal stability, a wide range of options, and is not prone to degradation or decomposition. In addition, the melt viscosity of ABS is moderate, and its fluidity is better than that of polyvinyl chloride, polycarbonate, etc., and the cooling and solidification speed of the melt is relatively fast, generally within 5 to 15 seconds. The fluidity of ABS is related to both the injection temperature and the injection pressure, among which the injection pressure is slightly more sensitive. For this reason, during the molding process, the injection pressure can be used to reduce its melt viscosity and improve the filling performance. ABS has different water absorption and adhesion properties due to different components. Its surface adhesion and water absorption rate range from 0.2 to 0.5%, sometimes up to 0.3 to 0.8%. In order to obtain a more ideal product, it is dried before molding to reduce the water content to below 0.1%. Otherwise, defects such as bubbles and silver threads will appear on the surface of the product.
Molding
Plastic ABS can also be said to be a modification of polystyrene. It has higher impact strength and better mechanical strength than HIPS, and has good processing performance. It can be used for injection molding, extrusion, blow molding, calendering, lamination, foaming, thermoforming, welding, coating, electroplating and mechanical processing using plastic molding equipment such as injection molding machines and extruders. ABS has a relatively high water absorption and needs to be dried before processing. The drying temperature is 70~85℃ and the drying time is 2~6h. ABS products are prone to internal stress during processing. If the stress is too large, it will cause the product to crack. Annealing treatment should be carried out. The product should be placed in a hot air circulation drying oven at 70~80℃ for 2~4h, and then cooled to room temperature.
Extrusion process
Plastic ABS is used to produce pipes, plates, sheets, and profiles. Pipes can be used for various water pipes, air pipes, lubricating oil and fuel oil delivery pipes; plates and sheets can be used for floors, furniture, tanks, filters, wall partitions, and thermoforming or vacuum forming. The extruder screw aspect ratio is usually relatively high, with L/D between 18 and 22, and a compression ratio of (2.5 to 3.0). It is advisable to use a gradual-type torpedo head screw, and the barrel temperatures are: 150 to 160°C for the hopper, 180 to 190°C for the front of the barrel, 185 to 195°C for the die head, and 180 to 200°C for the mold. Secondly, the blow molding temperature can be controlled between 140 and 180°C.
Injection molding process
ABS resin is a terpolymer developed on the basis of modified polystyrene resin. A represents acrylonitrile, B represents butadiene, and S represents styrene. ABS resin has the comprehensive performance of three components. A can improve oil resistance and chemical corrosion resistance, thus having a certain surface hardness; B makes ABS present rubber-like toughness and improves impact toughness; S makes ABS plastic present good fluidity, giving it good performance in thermoplastic molding and processing.
ABS plastics are mainly used in China to manufacture the shells of instruments, household appliances, telephones, televisions, etc. and ABS plastics for electroplating to give them a metallic luster. ABS is used to replace metal. Among the inner tanks and various plastic products of various types of refrigerators produced by our factory, ABS injection molding products account for more than 88% of the total number of refrigerator plastic products.
Injection molding equipment
A screw injection molding machine is used to heat the plastic in the barrel through the electric heating ring and the rotating friction of the barrel screw to pre-moldify and melt it into the mold cavity, and then the product is ejected after cooling and mold opening. The plasticizing effect is good, and the molding temperature can be slightly lower than other types of equipment (such as plunger type). It avoids the damage of high temperature to the rubber phase. It should be noted that: ① The injection volume of each injection should be 50-75% of the maximum injection volume of the equipment; ② The screw should be single-headed, equidistant, gradient, full-threaded, with a check ring (the length-to-diameter ratio of the screw is L/D of 20:1, and the compression ratio is 2 or 2.5:1.3); the nozzle can choose an open-type universal nozzle or an extended nozzle (the extension length does not exceed 150min), and avoid using a self-locking nozzle to reduce the injection process or cause material discoloration. In addition, a heating and temperature control device should be provided on the nozzle.
Product mold design
1. Product wall thickness: The product wall thickness is related to the flow length of the melt, production efficiency, and usage requirements. The ratio of the maximum flow length of the ABS melt to the product wall thickness is about 190:1, and this value varies with different grades. Therefore, the wall thickness of ABS products should not be too thin. For products that need to be electroplated, the wall thickness should be slightly thicker to increase the adhesion between the coating and the product surface. For this reason, the wall thickness of the product should be selected between 1.5 and 4.5 mm.
When considering the wall thickness of the product, attention should also be paid to the uniformity of the wall thickness, and the difference should not be too large. For products that need to be electroplated, the surface should be flat and without bumps, because these parts are easy to adhere to dust due to static electricity and difficult to remove, resulting in poor fastness of the coating. In addition, sharp corners should be avoided to prevent stress concentration, so it is appropriate to use arcs for transition at corners, thick and thin joints, etc.
2. Demolding slope: The demoulding slope of the product is directly related to its shrinkage rate. Due to different grades, different product shapes and different molding conditions, the molding shrinkage rate has certain differences, generally 0.3~0.6%, sometimes up to 0.4~0.8%, so the product molding size accuracy is relatively high. For ABS products, the demoulding slope is considered to be 31° along the demoulding direction of the core part and 1°20′ along the demoulding direction of the cavity part. For products with more complex shapes or with letters and patterns, the demoulding slope should be appropriately increased.
3. Ejection requirements: Since the apparent smoothness of the product has a great influence on the electroplating performance, any tiny scratches on the surface will be clearly revealed after electroplating. Therefore, in addition to requiring that there should be no scratches on the mold cavity, it is also required that the effective ejection area should be large, the synchronization of multiple ejector pins during the ejection process should be good, and the ejection force should be uniform.
4. Exhaust: In order to prevent poor exhaust during the filling process, which may cause burns to the molten material and obvious seams, it is required to open exhaust holes or exhaust grooves with a depth of no more than 0.04mm to facilitate the discharge of gas generated by the molten material.
5. Runner and gate: In order to make the ABS melt fill all parts of the mold cavity as quickly as possible, the runner diameter is required to be no less than 5mm, the gate thickness is more than 30% of the product thickness, and the length of the straight part (the part that will enter the cavity) is about 1mm. The location of the gate should be determined according to the requirements of the product and the direction of material flow. For products that need to be electroplated, generally no margin is allowed to exist on the coating attachment surface.
Raw material preparation
Except for special grades or colored resins, most of the ABS resins used for injection molding are light ivory or porcelain white opaque particles. The water absorption of the resin is not very high. If the processing allowable value is below 0.1~0.2%, it can be molded without drying treatment if the packaging is tight, the storage is proper, and the product requirements are not too high. However, if the moisture content in the particles exceeds the specified value, they must be dried before molding. For special grades of particles or products with high requirements (such as electroplated products), they must also be dried before molding.
Molding process specifications
1. Injection temperature: including barrel temperature (which can be divided into three sections: back, middle and front), nozzle temperature and mold temperature. Although the influence of temperature on ABS melt viscosity is not as obvious as injection pressure, high temperature is beneficial for molds of thin-walled products. Theoretically, the decomposition temperature of ABS is as high as 270t. However, in the actual injection molding process, due to the influence of time and other process conditions, the resin often begins to change color at around 2501. At the same time, the rubber phase contained in ABS is not suitable for too high a temperature, otherwise it will affect the performance of the product. The molding temperature of ABS requires a slightly higher temperature (210-250℃) for heat-resistant and electroplating grades of resin to improve the difficulty of melt filling or facilitate electroplating performance. For general-purpose, flame-retardant, impact-resistant and other ABS resins, the temperature should be lower to prevent decomposition or adverse effects on its physical and mechanical properties. The temperature selected by the plunger injection machine is slightly higher than that of the screw injection machine. For general products, the plunger type selects a temperature range of 180-230°C, while the screw injection molding machine can be molded at 160-220°C. During the molding process, the general barrel temperature (rear 150-1701°C, middle 170-180°C, front 180-210°C). The nozzle temperature is generally 170-180°C. Special attention should be paid to any changes in the homogenization section and nozzle temperature, which will be reflected on the product, causing defects such as overflow, silver wire, discoloration, poor gloss, and obvious weld marks.
2. Mold temperature: Mold temperature plays an important role in the surface roughness of ABS products and reducing the internal stress of products. When the mold temperature is high, the melt is easy to fill the mold, the appearance of the product is good, the internal stress is small, and the electroplating property of the product is also improved or enhanced. However, there are also problems such as large shrinkage rate of the product molding, long molding cycle, and easy deformation after demolding. For products with general requirements, the mold temperature can be controlled at 40~50℃; for products with relatively high appearance and performance requirements, the mold temperature can be controlled at 60~70℃. In addition, the mold temperature should be uniform, and the temperature difference between the mold cavity and the mold core should not exceed 10. For deep hole products or products with more complex shapes, the mold cavity temperature is required to be slightly higher than the mold core temperature to facilitate smooth demolding of the product.
3. Injection pressure: Compared with plastics such as polyethylene, polystyrene, and nylon, ABS has slightly poor fluidity, so the required injection pressure is relatively high. However, excessive injection pressure can easily cause difficulty in demolding or demolding damage to the product, and may also cause greater internal stress to the product. In addition to the wall thickness of the product, the type of equipment, etc., the injection pressure of ABS is also related to the grade of the resin. For thin-walled, long-flow, and small-gate products, the required injection pressure is high, up to 130~150MPa, while thick-walled and large-gate products only need 100MPa. In the actual production process, the injection pressure commonly used by screw injection machines is below 100MPa (we use 50~70MPa), while the plunger injection machine is generally above 100MPa. The holding pressure should not be too high. The screw injection machine generally uses 30~50MPa, while the plunger type requires more than 60~70MPa. If the holding pressure is too high, the internal stress of the product will increase.
4. Injection speed. The injection speed has a certain effect on the change of ABS body fluidity. If the injection speed is slow, the product surface will show ripples and poor welding. If the injection speed is fast, the mold can be filled quickly, but it is easy to have poor exhaust and poor surface roughness. At the same time, it will also reduce the tensile strength and elongation of the product, and the adhesion of the coating will also be reduced due to the injection speed being too fast. For this reason, in the production process, except for the difficulty of filling the mold and the need to use a higher injection speed, it is generally appropriate to use medium or low connection speeds.
Precautions
1. Startup and shutdown There are strict requirements for flame retardant ABS to prevent the flame retardant from decomposing. When starting up, the barrel should be cleaned with general-grade ABS before processing. Before shutting down (referring to shutdown for more than 20 minutes), on the one hand, the barrel temperature must be lowered to below 100°C, and on the other hand, the material in the barrel must be emptied and the barrel must be cleaned with general-grade ABS before shutting down. The purpose is to prevent the flame retardant ABS from decomposing.
2. Utilization of recycled materials For primary or secondary clean, impurity-free, and non-decomposed ABS recycled materials, they can be crushed and used directly, or mixed with new materials. The mixing ratio is generally not more than 25% of the new materials to avoid affecting the performance. For recycled materials that have been recycled more than 5 times or have colorants added, they are generally not mixed with new materials, mainly to prevent color differences. Whether it is a single recycled material or a recycled material mixed with new materials, it must be dried according to regulations before it can be put into molding processing.
Post-processing
For ABS products with more stringent requirements, in order to eliminate or reduce internal stress, the products must be placed in a hot air circulation drying oven at a temperature of 70-80°C, treated for 2-4 hours, and then slowly cooled to room temperature. Like other plastics, ABS products also have internal stress caused by various factors (the size of which can be judged by whether the product cracks when immersed in glacial acetic acid solution and the length of time it cracks). However, under normal circumstances, stress cracking rarely occurs. For this reason, ABS products are usually put into use without post-treatment.
Performance Testing
Plastic performance testing technology services are available throughout the chemical industry, from raw material identification, chemical product formula analysis, to industrial problem diagnosis in product production, failure analysis in product application, and product reliability testing. ABS resin combines the excellent properties of three monomers, namely: styrene’s gloss, electrical properties, and moldability; acrylonitrile’s heat resistance, rigidity, and oil resistance; and butadiene’s impact resistance.
Attention should be paid to the performance testing of plastic ABS
(1) General performance
ABS is an opaque ivory-colored granular material. It is non-toxic, odorless, and has low water absorption. Its products can be dyed in various colors and have a high gloss of 90%. ABS has good bonding with other materials and is easy to print, coat, and plate. The oxygen index of ABS is 18.2. It is a flammable polymer. The flame is yellow with black smoke. It burns but does not drip, and emits a special cinnamon smell.
ABS is a resin with very good comprehensive properties. It has high impact strength and surface hardness in a relatively wide temperature range. Its heat deformation temperature is higher than that of PA and PVC, and its dimensional stability is good.
The fluidity of ABS melt is better than PVC and PC, but worse than PE, PA and PS, and similar to POM and HIPS. The flow characteristics of ABS are non-Newtonian fluids, and its melt viscosity is related to both processing temperature and shear rate, but is more sensitive to shear rate.
(2) Mechanical properties
ABS has excellent mechanical properties and good impact strength, and can be used at extremely low temperatures. Even if ABS products are damaged, they can only be tensile failures, not impact failures. ABS has excellent wear resistance, good dimensional stability, and oil resistance, and can be used for bearings under medium loads and speeds. The creep of ABS is greater than that of PSF and PC, but less than that of PA and POM. The bending strength and compression strength of ABS are relatively poor among plastics. The mechanical properties of ABS are greatly affected by temperature.
(3) Thermal properties
ABS is an amorphous polymer with no obvious melting point. It has high melt viscosity, poor fluidity, poor weather resistance, and can be discolored by ultraviolet rays. Its heat deformation temperature is 93~118℃, and the product can be increased by about 10℃ after annealing. It is sensitive to temperature and shear rate. ABS can still show a certain toughness at -40℃ and can be used in the temperature range of -40~100℃.
(4) Electrical properties
ABS has good electrical insulation and is almost unaffected by temperature, humidity and frequency, and can be used in most environments.
(5) Environmental performance
ABS is not affected by water, inorganic salts, alkali alcohols, hydrocarbon solvents and various acids, but is soluble in ketones, aldehydes and chlorinated hydrocarbons. It will cause stress cracking when corroded by glacial acetic acid, vegetable oils, etc.
Performance testing is to test the system’s various performance indicators by simulating a variety of normal, peak and abnormal load conditions through automated testing tools.
Prospects
ABS is a general-purpose thermoplastic engineering plastic developed in the 1940s. It is a plastic variety with excellent comprehensive mechanical properties. It not only has good rigidity, hardness and processing fluidity, but also has high toughness and can be injection molded, extruded or thermoformed. Most automotive parts are processed by injection molding. The advantages of ABS resin are impact resistance, sound insulation, scratch resistance, better heat resistance, and more beautiful than PP, especially in parts with strict lateral impact resistance and use temperature. ABS resin is the third largest resin used in automobiles after polyurethane and polypropylene. ABS resin can be used for the interior and exterior shells of the car, steering wheels, oil pipes, handles, buttons and other small parts, and the exterior of the car includes the front radiator grille and lampshade.
ABS resin is easy to process, has good dimensional stability and surface gloss, is easy to paint and color, and can also be subjected to secondary processing such as metal spraying, electroplating, welding and bonding. It can be widely used in the field of electronics and electrical appliances, including various office and consumer electronics/electrical appliances. Office appliances include electronic data processors and office equipment. In the electronics and electrical appliance market today, ABS resin will maintain its position in the electronics/electrical appliance market that requires flame retardancy and high heat resistance. Flame retardant and high heat resistant ABS resin has obvious advantages in the competition with engineering plastic alloys such as ABS/PC.
ABS resin has a wide range of applications in the field of daily consumer goods, such as building materials, pipes, plates or sheets, and is now partially replaced by cheaper PVC resin. ABS resin is used in construction-related fields, among which extruded sheets are used for sanitary appliances such as bath boxes, swimming pool liners, etc. In addition, injection molded pipes and pipe fittings, and a small amount of extruded telephone cable pipelines are produced.
China’s research on ABS engineering plastics began in the 1960s and has developed rapidly. According to statistics, the total consumption of plastic alloys (including modified resins) in china is about 1.2 million to 1.4 million tons, while the chinese supply is less than 600,000 tons, and the annual import volume is as high as 900,000 tons; and china’s ABS engineering plastics (mainly blended resins and modified resins) are mainly used in home appliances, electronics, automobiles and other industries. Compared with developed countries, china’s plastic alloy application market still has a lot of room for expansion.
The research and production of ABS engineering plastics in china are still in a scattered state, and have not yet formed a scale. The overall level of the industry is low, which is far from the advanced level abroad. In the chinese ABS engineering plastic production product structure, the production of high-value-added special ABS engineering plastics is almost blank, and it is basically the production of general ABS engineering plastics and modified products. In 2004, there were more than 300 ABS engineering plastics production enterprises in china. It is estimated that the production capacity of ABS engineering plastics (including modified granules) is 700,000 to 800,000 tons/year, and the output is about 600,000 tons/year. However, only 15% of them are large-scale enterprises, and the output of these 15% of enterprises accounts for more than 70% of the total output of ABS engineering plastics in the country. Most of the enterprises are processing enterprises that produce ABS engineering plastics through plastic mixing and extrusion processes. The research and development and processing technology level of ABS engineering plastics in china needs to be improved.
Development prospects of ABS plastic industry in 2023:
1. Under the background of climate change, the alternative application of ABS products in the automotive, home appliance and other industries will further promote the development of the ABS plastic industry.
As global climate change intensifies, energy-saving efficiency becomes increasingly important. Therefore, the alternative application of ABS plastics in the automotive, home appliance and other industries will further promote the development of ABS plastics. ABS plastics have good thermal stability and corrosion resistance and can be used to manufacture various automotive parts, home appliances, etc. These changes in applications will contribute to the development of the ABS plastics industry.
2. Technological innovation and application innovation will also bring new development opportunities to the ABS market.
With the continuous development of technology, more excellent products can be developed in the ABS field to protect the environment. ABS plastic can be blended with other high-performance plastics such as PE, PP and PA, which can greatly improve the performance of ABS plastic and make ABS plastic more practical, thereby promoting the development of the ABS plastic industry.
3. The development of low-carbon economy also has a certain driving effect on the ABS plastic industry.
As global climate change intensifies, the low-carbon economy is also developing. For the ABS plastics industry, the low-carbon economy can provide more development opportunities for the ABS plastics industry, making ABS plastics more market potential and also playing a positive role in promoting the development of the ABS plastics industry.
Main Origin
The world’s five largest ABS manufacturers are: Chi Mei in Taiwan, China, with a total capacity of 1.25 million tons/year, including 1 million tons/year in Tainan and 250,000 tons/year in Zhenjiang; Bayer with a total capacity of 930,000 tons/year; LG Chem with a total capacity of 700,000 tons/year; General Electric GE Plastics with a total capacity of 650,000 tons/year; and BASF with a total capacity of 560,000 tons/year. The five major companies account for 55.6% of the world’s total capacity. The five major production companies have accounted for more than half of the global ABS capacity. Because there is still a large gap in the supply of ABS in mainland China, a considerable part of the products of several major companies are exported to China. At the same time, Chi Mei and LG have successively set up factories in mainland China and have the intention to continue to expand capacity.
