Polycarbonate (PC for short), also known as PC plastic, is a high molecular polymer containing carbonate groups in the molecular chain. According to the structure of the ester group, it can be divided into aliphatic, aromatic, aliphatic-aromatic and other types. Among them, the mechanical properties of aliphatic and aliphatic- aromatic polycarbonates are relatively low, which limits their application in engineering plastics.
Only aromatic polycarbonate has been industrialized. Due to the special structure of polycarbonate, it has become the fastest growing general engineering plastic among the five major engineering plastics.
CAS Number: 25037-45-0
Melting point: 220 to 230 °C
Water Solubility: Insoluble
Security Description: Not edible
Available temperature: −40°C to +135°C
Heat Deflection Temperature: 135 ℃
Refractive index: 1.585 ± 0.001
Light transmittance: 90% ± 1%
Thermal conductivity: 0.19 W/mK
Linear expansion rate: 3.8×10 -5 cm/cm℃
Element
Polycarbonate is a tough thermoplastic resin, and its name comes from the -OC(=O)-O- group inside it. It can be synthesized from bisphenol A and phosgene (COCl 2 ). The most commonly used method is the melt transesterification method ( bisphenol A and diphenyl carbonate are synthesized through transesterification and polycondensation ).
Nature
Chemical
Polycarbonate (PC) is a polyester of carbonic acid. Carbonic acid itself is not stable, but its derivatives (such as phosgene, urea, carbonates, and carbonate esters ) have a certain degree of stability.
According to the different alcohol structures, polycarbonates can be divided into two categories: aliphatic and aromatic.
Aliphatic polycarbonates, such as polyethylene carbonate, polytrimethylene carbonate and their copolymers, have low melting points and glass transition temperatures, poor strength and cannot be used as structural materials; however, due to their biocompatibility and biodegradability, they can be used in drug sustained-release carriers, surgical sutures, bone support materials, etc.
Polycarbonate is resistant to weak acids, weak alkalis and neutral oils.
Polycarbonate is not resistant to UV light and strong alkali.
PC is a linear carbonate polyester in which carbonate groups are arranged alternately with other groups, which can be aromatic, aliphatic, or both. Bisphenol A PC is the most important industrial product.
PC is an almost colorless glassy amorphous polymer with good optical properties. PC high molecular weight resin has high toughness, Izod notch impact strength of 600~900J/m, and heat deformation temperature of unfilled grades is about 130°C. Glass fiber reinforcement can increase this value by 10°C. The bending modulus of PC can reach more than 2400MPa, and the resin can be processed into large rigid products. When it is below 100°C, the creep rate under load is very low. PC has poor hydrolysis resistance and cannot be used for products that are repeatedly subjected to high-pressure steam.
The main performance defects of PC are that it is not stable enough in hydrolysis resistance, is sensitive to notches, has poor resistance to organic chemicals and scratches, and will turn yellow when exposed to ultraviolet rays for a long time. Like other resins, PC is easily corroded by certain organic solvents.
PC material is flame retardant and anti-oxidation.
Physics
Density: 1.18-1.22 g/cm³ Linear expansion rate: 3.8×10-5 cm /°C Heat deformation temperature: 135°C Low temperature -45°C
Polycarbonate is colorless and transparent, heat-resistant, impact-resistant, flame-retardant BI grade, and has good mechanical properties within normal use temperature. Compared with polymethyl methacrylate, which has similar performance, polycarbonate has good impact resistance, high refractive index, good processing performance, and has UL94 V-2 flame retardant performance without additives. However, polymethyl methacrylate is cheaper than polycarbonate, and large devices can be produced by bulk polymerization.
The wear resistance of materials is relative. If we compare ABS materials with PC materials, PC materials have better wear resistance. However, compared with most plastic materials, the wear resistance of polycarbonate is relatively poor, at a medium to low level, so some polycarbonate devices used for easy wear applications require special surface treatment.
Classification
Anti-static PC, conductive PC, fiber-reinforced fireproof PC, UV-resistant and weather-resistant PC, food-grade PC, and chemical-resistant PC.
Key Benefits
| Advantage | Detailed Description |
|---|---|
| Mechanical properties | It has high strength and elastic modulus , high impact strength, good fatigue resistance , good dimensional stability , small creep (very little change under high temperature conditions), high transparency and free dyeing; |
| Heat aging resistance | Wide operating temperature range, the enhanced UL temperature index reaches 120~140℃ (outdoor long-term aging resistance is also very good); |
| Solvent resistance | No stress cracking |
| Water stability | It is easy to decompose when exposed to water at high temperature (use with caution in high temperature and high humidity environment) |
| Insulation properties | Excellent (it can maintain stable electrical properties even in humidity and high temperature, and is an ideal material for manufacturing electronic and electrical parts) |
| Dielectric constant | 3.0-3.2 |
| Arc resistance | 120s |
| Forming processability | Ordinary equipment for injection molding or extrusion. |
PC plastic bonding
According to different needs, you can choose the following adhesives:
| Adhesives | Features |
|---|---|
| G-933 | One-component soft elastic shockproof adhesive that cures at room temperature, resistant to high and low temperatures, different viscosities, cures in seconds to hours |
| 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 |
| QN-505 | Two-component adhesive, soft adhesive layer, suitable for large-area bonding or lamination of PC plastics, poor high temperature resistance |
| QN-906 | Two-component adhesive, high temperature resistant |
| 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. If the thickness is 1-2mm, it will be initially cured in about 10 minutes, and basically cured in 5-6 hours, with a certain strength. It takes at least 24 hours to fully cure. Single component, no mixing is required, just apply it after extrusion and let it stand, no heating is required. |
| KD-5606 | UV curing glue can bond transparent PS sheets and plates without leaving any traces. It needs to be cured by UV light . The effect after bonding is beautiful. However, the high temperature resistance is poor. |
Applications
Development Industry
The three major application areas of PC engineering plastics are glass assembly industry, automobile industry and electronic and electrical industry, followed by industrial machinery parts, optical disks, packaging, office equipment such as computers, medical and health care, films, leisure and protective equipment, etc. PC can be used as door and window glass, and PC laminates are widely used in protective windows of banks, embassies, detention centers and public places, aircraft cabin covers, lighting equipment, industrial safety baffles and bulletproof glass.
PC sheets can be used to make various signs, such as gasoline pump dials, car dashboards, warehouse and outdoor commercial signs, point sliding indicators, PC resin is used in automotive lighting systems, instrument panel systems and interior decoration systems, used as headlight covers, front and rear fenders with reinforced ribs, reflector frames, door frame covers, operating lever covers, spoilers, PC is used as junction boxes, sockets, plugs and sleeves, gaskets, TV conversion devices, connectors for communication cables under telephone line brackets, switch boxes, telephone switchboards, switchboard components, relay housings. PC can be used as low-load parts for household appliance motors, vacuum cleaners, shampooers, coffee machines, toasters, power tool handles, various gears, worm gears, bushings, guides, and refrigerator shelves. PC is an ideal material for CD storage media.
PC bottles (containers) are transparent, lightweight, and have good impact resistance. They can withstand certain high temperatures and corrosive solution washing, and can be used as recyclable bottles (containers). PC and PC alloys can be used to make computer racks, shells, auxiliary machines, and printer parts. Modified PC is resistant to high -energy radiation sterilization, boiling and baking disinfection, and can be used for blood specimen collection instruments, blood oxygenators, surgical instruments, kidney dialyzers, etc. PC can be used to make helmets and safety helmets, protective masks, sunglasses, and sports goggles. PC films are widely used in printed charts, medical packaging, and membrane commutators.
The application development of polycarbonate is moving towards high composite, high functionality, specialization and serialization. Special grades and brands have been launched for a variety of products such as optical discs, automobiles, office equipment, boxes, packaging, medicine, lighting, films, etc.
Building materials industry
Polycarbonate sheets have good light transmittance, impact resistance, UV radiation resistance, and the dimensional stability and good molding and processing properties of their products make them have obvious technical performance advantages over the traditional inorganic glass used in the construction industry. China has built more than 20 polycarbonate hollow sheet production lines for building materials, with an annual demand of about 70,000 tons of polycarbonate, which will reach 140,000 tons by 2005.
Automotive Manufacturing
Polycarbonate has good impact resistance, heat distortion resistance, good weather resistance and high hardness, so it is suitable for the production of various parts for cars and light trucks, mainly concentrated in lighting systems, dashboards, heating plates, defrosters and bumpers made of polycarbonate alloys.
According to data from developed countries, the proportion of polycarbonate used in the electrical and electronic and automotive manufacturing industries is 40% to 50%, while China’s use of polycarbonate in this field is only about 10%. Electrical and electronic and automotive manufacturing are China’s rapidly developing pillar industries, and the demand for polycarbonate in these fields will be huge in the future. China has a large total number of cars and a large demand, so the application of polycarbonate in this field has great potential for expansion.
Medical Devices
Since polycarbonate products can withstand steam, cleaning agents, heating and high-dose radiation sterilization without yellowing or degradation of physical properties, they are widely used in artificial kidney hemodialysis equipment and other medical equipment that need to be operated under transparent and intuitive conditions and need to be repeatedly sterilized, such as the production of high-pressure syringes, surgical masks, disposable dental appliances, blood separators, etc.
Aerospace
With the rapid development of aviation and aerospace technology, the requirements for various components in aircraft and spacecraft are constantly increasing, which has led to an increasing application of PC in this field. According to statistics, there are 2,500 polycarbonate parts used in a Boeing aircraft alone, and a single aircraft consumes about 2 tons of polycarbonate. On spacecraft, hundreds of polycarbonate parts with different configurations and reinforced by glass fiber and astronauts’ protective equipment are used.
Packaging field
A new growth point in the packaging field is various types of water bottles that can be repeatedly sterilized and used. Because polycarbonate products are light, impact-resistant and transparent, and do not deform and remain transparent when washed with hot water and corrosive solutions, PC bottles have completely replaced glass bottles in some fields. It is predicted that as people pay more attention to the quality of drinking water, the growth rate of polycarbonate use in this area will remain above 10%, and it is expected to reach 60,000 tons by 2005.
Electronics Industry
Polycarbonate is an excellent insulating material because it has good and constant electrical insulation in a wide range of temperature and humidity. At the same time, its good flame retardancy and dimensional stability make it a broad application field in the electronic and electrical industry.
Polycarbonate resin is mainly used in the production of various food processing machinery, power tool housings, bodies, brackets, refrigerator freezer drawers and vacuum cleaner parts, etc. Moreover, polycarbonate materials also show extremely high use value in important parts of computers, video recorders and color TV sets that require high precision parts.
Optical lens
Polycarbonate occupies an extremely important position in this field due to its unique characteristics of high light transmittance, high refractive index, high impact resistance, dimensional stability and easy processing and molding. Optical lenses made of optical grade polycarbonate can be used not only in cameras, microscopes, telescopes and optical testing instruments, but also in movie projector lenses, copier lenses, infrared automatic focus projector lenses, laser beam printer lenses, various prisms, multi-faceted reflectors and many other office equipment and home appliances. Its application market is extremely broad.
Another important application area of polycarbonate in optical lenses is as lens material for children’s glasses, sunglasses, safety glasses and adult glasses. The annual average growth rate of polycarbonate consumption in the global eyewear industry has remained above 20%, showing great market vitality.
Optical disc manufacturing
With the rise of the information industry, optical discs made of optical grade polycarbonate are developing rapidly as a new generation of audio and video information storage media. Polycarbonate has become the main raw material for the world’s optical disc manufacturing industry due to its excellent performance characteristics. The amount of polycarbonate consumed by the world’s optical disc manufacturing industry has exceeded 20% of the overall polycarbonate consumption, and its average annual growth rate exceeds 10%. China’s optical disc production has grown rapidly. According to figures released by the China’s Administration of Press and Publication, there were 748 optical disc production lines in the country in 2002, with an annual consumption of about 80,000 tons of optical grade polycarbonate, all of which were imported. Therefore, the application prospects of polycarbonate in the field of optical disc manufacturing are extremely broad.
Use
Optical lighting
It is used to manufacture large lampshades, protective glass, left and right eyepiece tubes of optical instruments, etc. It can also be widely used as transparent materials on aircraft.
Electronics
Polycarbonate is an excellent E (120℃) grade insulating material, used to manufacture insulating connectors, coil frames, tube sockets, insulating sleeves, telephone housings and parts, battery housings for mining lamps, etc. It can also be used to make parts with high dimensional accuracy, such as CDs, telephones, computers, video recorders, telephone exchanges, signal relays and other communication equipment. Polycarbonate film is also widely used as capacitors, insulating leather bags, audio tapes, color video tapes, etc.
Mechanical Equipment
It is used to manufacture various gears, racks, worm wheels, worms, bearings, cams, bolts, levers, crankshafts, ratchets, and can also be used to make parts such as some mechanical equipment housings, covers and frames.
Medical Devices
It can be used as cups, tubes, bottles for medical purposes, as well as dental instruments, medicine containers and surgical instruments, and can even be used as artificial organs such as artificial kidneys and artificial lungs.
Other aspects
In construction, it is used as hollow rib double-wall panels, greenhouse glass, etc.; in the textile industry, it is used as textile yarn tubes, textile machine bearings, etc.; in daily use, it is used as milk bottles, tableware, toys, models, LED lamp shells and mobile phone shells, etc.
Modified use
The purpose of modifying PC is to increase toughness, improve molding and processing performance, reduce residual deformation, increase flame retardancy, etc. The specific types of PC that can be modified are:
PC/ABS can improve flexural modulus, heat resistance, electroplating performance, etc.
PC/PET and PBT processes can improve chemical resistance, solvent resistance, etc.
Adding plexiglass to PC/PMMA can enhance the pearlescent color of the appearance.
PC/PA and HIPS can improve impact toughness and surface smoothness.
PC/ HDPE can improve boiling water resistance, aging resistance, and weather resistance, while LDPE has a poorer effect.
PC is reinforced with glass fiber or carbon fiber to improve mechanical strength.
By using bromine flame retardants and antimony trioxide, flame retardant grade PC can be made.
Others can be blended and modified with polysulfone, aromatic polycarbonate, polyoxymethylene, polypropylene and polystyrene to achieve a balance between economy and performance.
Preparation
Process
The production of polycarbonate textile yarn tubes uses PC produced by the phosgene method as raw material, of which 80% is new material and 20% is recycled material. The production process is as follows:
Batching→drying→injection→trimming→ polishing → heat treatment →product.
The oven drying temperature is 115-120℃, 16-20 hours, the thickness of the material on the tray is less than 30 mm, and the moisture content of the resin is less than 0.03%.
The temperature of the three zones of the barrel is 200-220, 250-280, 260-290℃, and the nozzle temperature is slightly lower than the barrel, 5-10℃ lower. The injection pressure is 60-100MPa, the molding cycle is 25 seconds, the heat treatment temperature is 115-120℃, 1 hour, and the heat treatment should be carried out in an inverted hanging manner.
The yarn tube has a service life three times longer than that of wooden yarn tubes, is dimensionally stable, has good weather resistance, is lint-free, and has good smoothness. The yarn tubes can be provided in various colors, which facilitates the economic accounting of the team.
For the waste recycled PC materials, toughening treatment can also be carried out to replace new materials. A small amount of nylon resin or high-impact polystyrene resin can be blended into the recycled PC materials to increase the impact strength of the products by more than 1 times, and the bending strength is also improved, and the processing performance and surface finish of the resin are greatly improved.
In addition, because nylon has an extremely low viscosity when melted, it can have an excellent wetting and encapsulating effect on the pigments in the blending system, destroying the aggregation structure of the pigment particles and increasing the dispersion of the pigment, thereby reducing the amount of pigment by 20%.
Extrusion board
PC material must be dried to reduce its water content to below 0.02%. The molecular weight of PC board raw material should be 35,000.
The extruder screw has a length-to-diameter ratio of 20:1, the feeding section and metering section in the rod each account for 25% of the total length, and the screw groove depth is constant, and the compression section length is half of the total length. The screw compression ratio is 2.5-3, the screw groove depth should generally be less than 4 mm, and the mixing effect is better with a pin screw.
The over-screen mesh group can adopt 80/120/200/120/80 mesh types.
The hanger-type machine head is more commonly used, but it is more expensive.
Calendering method
The calendering methods of the sheet include horizontal extrusion calendering, inclined extrusion calendering, downward or upward extrusion calendering. However, the best one at present is the roller inclined calendering method.
Typical PC board extrusion conditions:
The temperature of the machine cylinder is 260, 280, 300℃, the temperature of the die head is 2801℃, the temperature of the calendering rollers: upper roller 121-135℃, middle roller 129-139℃, lower roller 132-150℃, the screw speed is 12-24 rpm, and the filter group is 40/60/100 mesh.
PC sheets can be used in automobiles, aircraft windshields, corrugated sheets, folding sheets, building window glass, sports facility ceiling glass, etc.
Others: PC can be blended with ABS to improve impact strength. When the ABS content is 50%, the improvement is the largest. When the ABS content is too low, such as 3%, the impact strength decreases.
PC can be blended with HDPE. When the content of HDPE is 30%, the blending effect is better, which can improve the impact strength, improve the processing flowability, and facilitate mold filling. The blending effect of LDPE is very poor, stratification occurs, and it cannot be used.
Film
PC can also be made into thin films, which have high puncture resistance and are suitable for welding and heat sealing. PC film has high surface tension and does not require corona treatment before printing, and has good electroplating performance. It can be used for medicine, food packaging, and composite decorative boards with cardboard, etc.
Main Impact
More than 100 studies have explored the ecological effects of bisphenol A leachates in polycarbonate. Howdeshell et al. found that an endocrine disruptor, Bisphenol A (C 15 H 16 O 2 ) ( bisphenol A ), appears to leach into water from polycarbonate animal cages at room temperature, and that it may be responsible for the development of reproductive organs government-funded studies tend to find significant effects.
Easy to react chemically with other substances
Sodium hydroxide and other alkaline cleaners should not be used on polycarbonate as they may result in the release of bisphenol A (C 15 H 16 O 2 ), a known endocrine disruptor (affects the reproductive system ).
Characteristic:
It is a non-crystalline thermoplastic with excellent heat resistance, good transparency, high impact strength and other physical and mechanical properties.
Features:
1. High strength and elastic coefficient, high impact strength, and wide operating temperature range;
2. High transparency and free dyeing;
3. High HDT;
4. Poor fatigue resistance;
5. Good weather resistance;
6. Excellent electrical characteristics;
7. Tasteless and odorless, harmless to human body and in compliance with hygiene and safety;
8. Low molding shrinkage and good dimensional stability.
Physical Properties
| Density | 1.18 | g/cm³ | ASTM D792, ISO 1183 |
| Melt flow rate (260°C/2.16 kg) | twenty two | g/10 min | ASTM D1238 |
| Melt Volume Rate (MVR) (260°C/2.16 kg) | 23.5 | cm³10min | ISO 1133 |
| Shrinkage – Flow | 0.40 to 0.60 | % | ASTM D955 |
| Water absorption (23°C, 24 hr) | 0.40 | % | ASTM D570 |
| – | Rating | unit | Test Method |
| proportion | 1.14 | g/cm³ | ASTM D792, ISO 1183 |
| Melt flow rate (260°C/5.0 kg) | 20 | g/10 min | ASTM D1238 |
| Melt Volume Rate (MVR) (260°C/3.8 kg) | 13.0 | cm³/10min | ISO 1133 |
Synthesis
Polycarbonate used in industry is mainly synthesized from bisphenol A and phosgene. Its main chain contains benzene ring and tetrasubstituted quaternary carbon atom, which increases rigidity and heat resistance. Tm=265-270℃, Tg=149℃, and can maintain good mechanical properties within 15-130℃. It has excellent impact resistance and transparency, stable dimensions, creep resistance, and performance better than polyester. It is an important engineering plastic. However, polycarbonate is prone to stress cracking and hydrolysis when heated, so it should be fully dried before processing.
There are two methods for preparing polycarbonate: transesterification method and direct phosgene method.
(1) Transesterification method
The principle is similar to the transesterification method for producing polyester. Bisphenol A and diphenyl carbonate are melt-condensed and transesterified, and phenol is continuously removed under high temperature and reduced pressure conditions to increase the degree of reaction and molecular weight.
The transesterification method requires a catalyst and is carried out in two stages : the first stage, the temperature is 180-200℃, the pressure is 270-400Pa, the reaction time is 1-3h, and the conversion rate is 80%-90%; the second stage, 290-300℃, below 130Pa, deepens the reaction. The initial diphenyl carbonate should be excessive, and phenol is discharged through the transesterification reaction. The amount of phenol discharged is used to adjust the ratio of the two groups and control the molecular weight.
Phenol has a high boiling point and is not easy to remove from a high-viscosity melt. Compared with polyester, the melt viscosity of polycarbonate is much higher. For example, with a molecular weight of 30,000, the viscosity at 300°C is 600 Pa·s, which places higher requirements on the stirring, mixing and heat transfer of the reaction equipment. Therefore, the molecular weight of polycarbonate produced by the transesterification process is limited and does not exceed 30,000.
(2) Phosgene direct method
Phosgene is an acyl chloride with high activity and can be directly esterified with hydroxyl compounds. The phosgene method for synthesizing polycarbonate mostly adopts interfacial polycondensation technology. Bisphenol A and sodium hydroxide are prepared into a sodium bisphenolate aqueous solution as the water phase, and an organic solution of phosgene (such as dichloromethane ) is the other phase. Amines (such as tetrabutylammonium bromide ) are used as catalysts to react at 50°C. The reaction is mainly on the water phase side, and the stirring in the reactor must ensure that the phosgene in the organic phase diffuses to the interface in time for reaction. The direct phosgene method is more economical than the ester exchange method, and the resulting molecular weight is also higher.
Interfacial polycondensation is an irreversible reaction, and it does not strictly require that the number of two groups is equal. Generally, phosgene is slightly excessive to compensate for the hydrolysis loss. A small amount of monofunctional phenol can be added to block the end groups and control the molecular weight. The purity of bisphenol A used in polycarbonate is high and has specific specifications. It is not suitable to contain monophenol and triphenol, otherwise, high molecular weight polycarbonate cannot be obtained or cross-linking will occur.
Processing methods
PC can be injection molded, extruded, molded, blow molded, thermoformed, printed, bonded, coated and machined. The most important processing method is injection molding. Pre-drying is required before molding. The moisture content should be less than 0.02%. Trace moisture processing at high temperature will cause the product to have a whitish color, silver threads and bubbles. PC has a considerable forced high elastic deformation capacity at room temperature. It has high impact toughness, so it can be cold pressed, cold drawn, cold rolled and other cold forming processes. The molecular weight of PC for extrusion should be greater than 30,000. A gradual compression screw with a length-to-diameter ratio of 1:18-24 and a compression ratio of 1:2.5 should be used. Extrusion blow molding, injection-blow molding, injection-draw-blow molding, and injection-draw-blow molding can be used to form high-quality, high-transparency bottles. There are many types of PC alloys. In order to improve the defects of high PC melt viscosity ( processability ) and easy stress cracking of products, PC forms alloys or blends with different polymers to improve material properties.
Specifically, there are PC/ABS alloys, PC/ASA alloys, PC/PBT alloys, PC/PET alloys, PC/PET/elastomer blends, PC/ MBS blends, PC/ PTFE alloys, PC/PA alloys, etc., which take advantage of the performance advantages of two materials and reduce costs. For example, in PC/ABS alloys, PC mainly contributes to high heat resistance, good toughness and impact strength, high strength and flame retardancy, while ABS can improve formability, surface quality and reduce density.
| density | 1.18~1.20 | Mold temperature | 50~80 | – | |
| Shrinkage | 0.5~0.8 | Injection pressure | 80~130 | ||
| Preheat | Temperature/°C | 110~120 | workartGinsengnumber | Injection time | 20~90 |
| Time/h | 8~10 | High pressure time | 0~5 | – | – |
| Barrel temperature/°C | Back | 210~240 | Cooling time | 20~90 | |
| Middle | 230~280 | Total cycle | 40~190 | – | |
| Front | 240~285 | Screw revolutions | 28 | ||
| Nozzle temperature | 240~250 | Type of injection machine used | Screw type | ||
1. Drying of raw materials
- Raw material drying: The temperature of the ordinary drying box is 110-130, the time is 2-4 hours, the temperature of the top hopper drying box is 100-120, and the moisture content is required to be less than 0.03%.
- Determine whether the water content is qualified: look at the material strips of empty injection. The material strips flowing out of the nozzle after plasticization should be uniform, colorless, without silver threads and bubbles; otherwise, the drying is not thorough.
2. Injection process
Adjust the molding parameters of the injection molding machine (depending on the molecular weight of the raw material):
| Barrel temperature | Front 250-310, middle 240-280, rear 230-250. |
|---|---|
| Nozzle temperature | 10 lower than the rear. |
| Mold temperature | 70-120. |
| Injection pressure | 70-140MPa. |
| Screw speed | 30-120r/min. |
| Molding cycle | Injection 1-25s, cooling 5-40s. |
3. Notes
- The injection temperature should be adjusted accordingly depending on the molecular weight of the raw material, the shape and size of the product, and the type of injection molding machine.
- It is best to adopt multi-stage injection speed, using the slow-fast-slow method.
- The injection pressure depends on the shape and size of the product. The plunger injection molding machine is generally 100-160MPa, and the screw injection molding machine is 70-140MPa.
- The molding cycle depends on the wall thickness of the product and the injection volume. Generally, the filling time is short, the holding time is long, and the cooling time is based on the principle of not causing deformation of the product during demolding.
- The mold temperature depends on the shape and thickness of the product. Properly increasing the mold temperature is conducive to demoulding and improving product quality.
- Product post-processing : For products with complex shapes, metal inserts, and extremely low or high operating temperatures, it is necessary to perform post-processing to eliminate or reduce internal stress.
Method: After the product is placed in the drying oven, the temperature begins to rise from room temperature to 100-105 and then it is kept warm for 10-20 minutes. When the temperature continues to rise to 120-125, it is kept warm for 30-40 minutes, and then it is slowly cooled to below 60 and taken out.
Bonding Problems
According to different needs, you can choose the following adhesives:
1.G-933: 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. After curing, the adhesive layer is transparent and has no traces;
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 adhesive. After curing, it is an elastomer with excellent waterproof and shockproof adhesive, high and low temperature resistance. For a thickness of 1-2mm, it takes about 15 minutes for initial curing and 5-6 hours for basic curing. It has a certain strength. It takes at least 24 hours to fully cure. Single component, no mixing required, just apply after extrusion and let it stand, no heating required.
Precautions
Molding process problems
1. Silver thread
a. Raw materials are damp — dry raw materials
b. Overheating and decomposition of resin – reduce molding temperature
c. The screw compression ratio is small and the back pressure is insufficient——Increase the back pressure
d. Mold temperature is too low——heat the mold
e. Poor exhaust — exhaust grooves are opened on the mold parting surface
2. Bubbles
a. Raw materials are damp — dry raw materials
b. Poor exhaust——Improve mold design
3. Resin discoloration and black spots
a. Material accumulation in barrel and nozzle ——Clean the barrel and nozzle
b. The molding temperature is too high————lower the molding temperature
4. The product is not full
a. The material is not plasticized enough————Increase the barrel temperature
b. The mold temperature is too low————Increase the mold temperature
c. Nozzle overflow————Adjust the mold position
d. Injection pressure is too low————Increase injection pressure
e. Too little feeding amount————adjust feeding amount
5. Shrinkage vacuum bubble
a. Insufficient pressure holding——Extend the pressure holding time
b. Mold temperature is too low————Increase mold temperature
c. Injection pressure is too low————Increase injection pressure
d. Unreasonable mold design – increase the runner and gate size
e. The molding temperature is low————Increase the barrel temperature
6. Reduced transparency
a. Raw materials are damp — dry raw materials
b. The mold temperature is too low————Increase the mold temperature
c. Overheating and decomposition of materials – lowering the molding temperature
7. Welding mark
a. Unreasonable mold design – using ring gate and multi -point gate
b. The mold temperature is too low————Increase the mold temperature
c. Too much release agent ——Reduce the amount of release agent
d. Low molding temperature————Increase barrel temperature
8. Product cracking
a. Mold temperature is too low————Increase mold temperature
b. The molding temperature is low————Increase the barrel temperature
c. The relative molecular weight of the material is too small————Reselect the material
d. The relative molecular weight drops too much during the molding process——Strictly dry and shorten the molding cycle
e. Forced demoulding——Increase the slope of the cavity and improve the mold structure
9. Difficult demoulding
a. Insufficient cooling in the mold – lower the molding temperature and extend the molding cycle
b. The slope of the cavity is too small——Increase the slope of the cavity
c. The ejector device is defective————Improve the ejector device
d. Rough mold surface——Fix the mold and use release agent
10. Warping
a. Insufficient cooling in the mold – lower the molding temperature and extend the molding cycle
b. The temperature difference between the punch and the die is large – reduce the temperature difference between the punch and the die
c. The gate position and size are unreasonable————Improve the gate structure
11. Overflow
a. The injection pressure is too high——Reduce the injection pressure
b. The molding temperature is too high————lower the barrel temperature
c. Insufficient clamping force ——Increase clamping force
d. Insufficient mold processing accuracy ————Improve mold processing accuracy
Safety controversy
Since bisphenol A needs to be added in the manufacture of polycarbonate, and bisphenol A, as a chemical raw material, has been officially identified as a toxic substance by the Canadian federal government on April 18, 2008, and is strictly prohibited from being added to food packaging, the safety of polycarbonate is a problem worthy of attention. The European Union believes that baby bottles containing bisphenol A can induce precocious puberty, and from March 2, 2011, baby bottles containing the production chemical bisphenol A (BPA) are prohibited. The Ministry of Health of China and other departments issued an announcement stating that the import and sale of polycarbonate baby bottles and other baby bottles containing bisphenol A will be prohibited from September 1, 2011, and the manufacturers or importers will be responsible for recalling them.
Packaging and transportation
Polycarbonate (PC) products are generally packed in ordinary woven bags, stored in a dry place, and transported as ordinary items.
Storage and transportation conditions
Store in a sealed, cool, ventilated and dry place and flat.
Low temperature injection molding PC plastic for IMD/ IML process
Mainly solve the following problems: 1. Ink flushing 2. Poor fluidity 3. Yellowing of products 4. Poor compatibility with sheet materials and other related problems
Low temperature injection molding PC product features: 1. Ultra-high toughness 2. High transparency 3. Ultra-high fluidity 4. Good chemical resistance 5. Good compatibility with sheet materials
Injection temperature: Low temperature injection molding PC plastic type A injection temperature is 220℃ to 240℃; low temperature injection molding PC plastic type B injection temperature is 230℃ to 260℃.
The following is a table of some physical properties of Class A PC plastics for low-temperature injection molding for IMD/IML processes.
| Performance Project | Test Method | Value/Description | unit | |
| Mechanical properties | Tensile strength (tensile strength) | ASTM D638/ISO 527 | 65 | kg/cm²(MPa)[Lb/in2] |
| Elongation at break | ASTM D638/ISO 527 | 120 | % | |
| Tensile modulus | ASTM D638/ISO 527 | 2450 | kg/cm²(MPa)[Lb/in2] | |
| Tensile elongation at yield (elongation) | ASTM D638/ISO 527 | 9 | % | |
| Tensile elongation at break (elongation) | ASTM D638/ISO 527 | 40 | % | |
| Flexural modulus (flexural elasticity) | ASTM D790/ISO 178 | 2450 | kg/cm²(MPa)[Lb/in2] | |
| Bending Strength | ASTM D790/ISO 178 | 105 | kg/cm²(MPa)[Lb/in2] | |
| Rockwell hardness | ASTM D785 | 122 | – | |
| Injection molding performance | Injection temperature | ASTM D648/ISO 75 | 270-310 | ℃ (℉) |
