Usually use plastic material performance
ABS: Acrylonitrile-butadiene-benzene polymer
1. The role of the three components Acrylonitrile (A)-make the product higher hardness, improve wear resistance and heat resistance. Butadiene (B)-Strengthen flexibility, maintain material toughness, elasticity and impact resistance. Styrene (S)-maintain good moldability (flowability and colorability) and maintain material rigidity (note that a variety of specifications and grades are derived according to different components).
2. ABS has good electroplating properties, which is the best among all plastics.
3. Compared with GPPS, the impact strength of ABS is significantly improved.
4. The ABS raw material is light yellow and opaque, and the surface of the product is good.
5. ABS has small shrinkage and stable dimensions.
6. Not resistant to organic solvents: such as soluble in ketones, aldehydes, esters, and oxidized hydrocarbons to form an opaque flow (ABS mucilage).
7. Material blending performance:
ABS+PVC~~~ Improve toughness, flame resistance and anti-aging.
ABS+PC~~~ Improve impact strength and heat resistance.
ABS molding process
1. It needs to be fully dried before molding, so that the moisture content is less than 0.1%, the drying condition temperature is 85℃, and the time is more than 3HRS.
2. ABS has good fluidity and is easy to produce beer plastic drape. The injection pressure is 70~~100MPa, not too large.
3. The temperature of the barrel cannot easily exceed 250°C. The front barrel is 160~~~210°C, the middle barrel is 170~~~190°C, and the rear barrel is 160~~~180°C. Excessive high temperature will cause the decomposition of plastic components and reduce the fluidity.
4. The mold temperature is 40~~80℃, the appearance requirements are high, and the mold temperature is also high.
5. The injection speed is mainly medium and low speed. The injection force is 80~~130MPa.
6. ABS internal stress test: the product shall be immersed in kerosene for 2 minutes without cracks.
MBS-transparent ABS, polymethacrylate-butadiene-styrene copolymer.
Main properties: transparent, good toughness, acid and alkali resistance, good fluidity, easy to shape and color, stable size.
SBS-K material (transparent). Butadiene and this ethylene polymer (KR01, KR03).
Main properties: transparent, good elasticity, easy to shape.
PS material: polystyrene (GPPS hard rubber, HIPS modified polyethylene GPPS-hard HIPS-not broken.
A) Add an appropriate amount (5~20%) of butadiene rubber to GPPS to improve the impact resistance of the hard rubber.
B) Color: GPPS-high transparency, HIPS-opaque milky white or slightly yellow.
C) HIPS and GPPS can be mixed with beer as required. The more GPPS components, the better the surface gloss and fluidity of the product. HIPS: GPPS=7:3 or 8:2 can maintain sufficient strength and surface quality.
*Polyethylene molding process
1. GPPS has a wide molding temperature range (the molding temperature is far from the degradation temperature). The heating flow and curing speed are fast, so the molding cycle is short. Under the premise that the cavity can be filled, the barrel temperature should be slightly lower, the front barrel temperature is 200 ℃, and the rear material The cylinder is 160°C.
2. GPPS has good fluidity and does not require high plastic injection pressure (70~~130PMa) during molding. Too high pressure will increase the residual internal stress of the system—especially the plastic parts are easy to crack after injection. (Modified PS or HIPS has a slightly worse fluidity than GPPS).
3. The injection speed should be higher to weaken the weld line (water trapping), but the injection speed is greatly affected by the injection pressure. Too high a speed may cause flash (floating) or chipping during mold ejection.
4. Mold temperature: 30℃~~50℃. 5. Polystyrene (GPPS) generally does not require a dry bath before molding due to its low hygroscopicity, while modified polystyrene (HIPS) must be dried at a temperature of 60°C~~80°C and a drying time of 2HRS.
Polypropylene (PP)—polypropylene, a crystalline plastic whose main properties are as follows:
1. It is translucent, light (density 0.91) and can float on water.
2. Good fluidity and moldability, surface gloss, (the colored part leaves traces on the PE).
3. The high molecular weight results in high tensile strength and high yield strength (fatigue resistance).
4. High chemical stability, insoluble in organic solvents, oil spraying, scalding, and bonding difficulties.
5. The abrasion resistance is different, and the impact resistance is good at room temperature.
6. The molding shrinkage rate is large (1.6%), the size is relatively unstable, and the plastic parts are easy to deform and shrink.
*Understanding the molding process of polypropylene (PP material)
1. Polypropylene has good fluidity, and the cavity can be filled with a lower injection pressure. If the pressure is too high, it is easy to produce flash, but if it is too low, the shrinkage will be serious. The injection pressure is generally 80~~~90MPa, the holding pressure is about 80% of the injection pressure, and a longer holding time should be used for feeding.
2. Suitable for rapid injection, in order to improve poor exhaust, the exhaust groove should be slightly deeper than 0.3mm.
3. Polypropylene has high crystallinity. The front barrel is 200~~~240°C, the middle barrel is 170~~~220°C, and the rear barrel is 160~~190°C. Because of its wide molding temperature range, it is easy to shape, but it is actually reduced Lower temperature is used for batching and shrinking.
4. Due to the large shrinkage rate of the material, in order to accurately control the size of the rubber parts, the cooling time should be appropriately extended.
5. The mold temperature is easy to choose. Low temperature (20~~~40℃). The mold temperature is too high to make the crystallinity large, the intermolecular interaction is strong, the product rigidity is good, the gloss is good, but the softness and transparency are poor, and the shrinkage is also obvious.
6. The back pressure is preferably 0.1MPa, and the dry powder coloring process should appropriately increase the back pressure to improve the mixing effect.
Polyvinyl Chloride (PVC)
Polyvinyl chloride (PVC) is a non-crystalline plastic, and the raw material is transparent.
The main performance is as follows
1. By adding plasticizers, the material has a wide range of softness and hardness.
2. Flame-retardant and self-extinguishing, poor thermal stability.
3. PVC is soluble in cycloethyl ketone, this hydrofuran, dichloroethane, and soft glue for spray water (including cycloethyl ketone).
4. PVC is mainly used for vinyl (and dolls).
*Understanding the molding process of polyvinyl chloride (PVC)
1. Soft PVC has a large shrinkage rate (1.0~~2.5%). The polar molecules of PVC are easy to absorb water and need to be dried before molding. The drying temperature is 85~95℃ for 2 hours.
2. During molding, the barrel is heated many times for a long time to decompose vinyl chloride monomer and HCL (ie degradation). Therefore, the mold cavity and internal dead corners of the machine head should be cleaned frequently.
3. Adding ABS to soft PVC can improve toughness, hardness and mechanical strength.
4. Because the PVC molding processing temperature is close to the decomposition temperature, the barrel temperature should be strictly controlled, and the molding temperature should be as low as possible. At the same time, the molding cycle should be shortened as much as possible to reduce the residence time of the melt in the barrel. The barrel temperature parameters are 160~~~170℃ Middle barrel 160~~165℃ Rear barrel 140~~150℃.
5. In view of easy decomposition and poor fluidity, the mold runner and gate should be as short as possible, thick to reduce pressure loss and fill the cavity as soon as possible. The injection pressure MPa should be high-pressure and low-temperature injection, with a back pressure of 0.5~~1.5MPa , PVC product wall The thickness should not be too thin, it should be above 1.5mm , otherwise the material flow will be difficult to fill the cavity.
6. The injection speed should not be too fast, so as to avoid the violent friction of the molten material when passing through the gate, which will increase the temperature and easily produce shrinkage marks.
7. The mold temperature is as low as possible (30~~~45℃) to shorten the molding cycle and prevent the plastic parts from being deformed (the plastic parts need to be shaped by the shaping mold when necessary).
8. In order to prevent the cold material from blocking the gate or flowing into the mold cavity, a larger cold material well should be designed to accumulate the cold material.
Polyoxymethylene (POM steel)
Polyoxymethylene (POM), commonly known as Saigang, is a crystalline plastic, and its main properties are as follows: .
1. Polyoxymethylene is a milky white glossy plastic.
2. It has comprehensive mechanical properties, high hardness and rigidity, good impact resistance and excellent wear resistance and self-lubrication.
3. Good resistance to organic solvents and stable performance.
4. After molding, the size is relatively stable, and it is less affected by the temperature environment.
*Understanding the forming process of POM polyoxymethylene
1. Polyoxymethylene has low hygroscopicity (water absorption rate <0.5%), generally, it should not be dried or dried for a short time before molding.
2. The molding temperature range is narrow, the thermal stability is poor, and the unit of formaldehyde is decomposed above 250°C (the color of the melt becomes darker), so simply increasing the temperature to improve the fluidity is harmful and ineffective. Normal beer plastics should use a lower barrel temperature and short residence time, and increasing the injection pressure can improve the fluidity of the melt and the surface quality of the product. (The fluidity of the melt is more sensitive to the shear speed). Temperature parameters: front barrel 190—210°C, middle barrel 180—205°C, rear barrel 150—170°C. Pressure parameters: injection pressure is about 100MPa, back pressure is 0.5MPa.
3. Mold temperature: 80-100 ℃ is appropriate (generally transport hot oil).
4. The cooling shrinkage rate of POM is very large (2~~2.5%), which is prone to shrinkage of beer plastics, so it is necessary to extend the holding time to compensate.
Polyethylene (PE) "Flower Material"
Polyethylene (PE) commonly known as "flower material" is a crystalline plastic, and its main properties are as follows:
1. Polyethylene is divided into high-density (HPPE) and low-degree (LPPE) two types, and the transparency decreases with the high density.
2. Polyethylene is a semi-transparent particle, and the appearance of the rubber piece is milky white.
3. Polyethylene has flexibility, impact resistance, extensibility and abrasion resistance, and good low-temperature toughness.
4. It does not melt in any flux at room temperature and has stable chemical properties. On the other hand, PE is difficult to bond.
5. The mechanical strength is not high, the heat distortion temperature is low, and the surface is easily scratched.
6. Polyethylene (PE) is often used for blow-molded products.
*Understanding the molding process of polyethylene
1. Good fluidity, wide molding temperature range and easy molding.
2. The injection pressure and holding pressure should not be too high to avoid deformation and cracking caused by large stress in the beer part. The injection pressure is 60~~70MPa.
3. No need to dry before processing.
4. Increase the barrel temperature and the appearance quality is good, but the molding shrinkage rate is large (2~~2.5%). The barrel temperature is too low, and the product is easy to deform (the use of point gates is more serious, and the use of multi-point gates to improve warpage), temperature parameters ：The front barrel is 200~220℃, the middle barrel is 180~~190°C, and the rear barrel is 160~~170°C.
5. The temperature of the front and back molds should be the same (the mold temperature is generally 20~40°C). The cooling water should not be too close to the surface of the cavity, so as to avoid the local temperature difference being too large, and the internal stress of the product will remain. Increase the mold temperature, the product gloss is good, but the molding cycle is long. Lower mold temperature, good product flexibility, high transparency, high impact strength, too low mold temperature and rapid cooling cause product deformation or molecular orientation to cause delamination. In short, the hardness and flexibility of the product can be adjusted by adjusting the mode temperature.
6. Due to its softer quality, forced demoulding can be used instead of the slide position (slider) when necessary.
Polycarbonate (PC) (the most expensive)
Polycarbonate (PC) commonly known as "bullet-proof glass glue" is a crystalline plastic whose main properties are:
1. The appearance is transparent, rigid with toughness, slow burning, slow extinguishing after leaving the fire.
2. The impact resistance of PC material is the best among plastics.
3. The molding shrinkage rate is small (0.5~~0.7%), the finished product has high precision and high dimensional stability.
4. Good chemical stability, but not resistant to organic solvents such as alkalis, ketones, and aromatic hydrocarbons.
5. Poor fatigue strength is sensitive to notches.
*Understanding of polycarbonate (PC) molding process
1. PC is very sensitive to micro-moisture. It should be fully dried before molding. The moisture content is 0.015%. The drying temperature is 110~120℃ , 12HRS.
2. The fluidity is poor and high pressure injection is required. However, if the injection pressure is too high, large internal stress will remain in the product and it will be easy to crack.
3. The viscosity of PC material is very sensitive to temperature. Increase the temperature and the viscosity will decrease. Front cylinder 240~~260℃, middle cylinder 260~~280 ℃,
The rear cylinder 220~~~230℃ does not exceed 310℃.
4. Mold design requirements The runner is thick and small, the runner is polished, and the cavity and core should be quenched or plated with hard chrome.
5. The injection speed is too fast, the solution is easy to break, the gate has sticky spots, and the exhaust is poor (trapped air), which will scorch the product.
6. Mold temperature is 80~~100℃.
7. Adopt annealing treatment, 125~~135℃ 2HRS, natural cooling to room temperature.
Polyamide (PA) nylon material
Polyamide commonly known as "nylon" (NYLON) is a crystalline plastic, and there are many kinds such as nylon 6, nylon 66, nylon 1010 and so on.
1. Nylon has good toughness, wear resistance, labor resistance, self-lubricity and self-extinguishing.
2. Good low temperature performance, high impact strength, high tensile strength and good elasticity.
3. Nylon has high water absorption, and after water absorption, the tensile strength is increased to a certain extent, but other strengths are decreased (such as stretching, stiffness) and the shrinkage rate is 0.8~~1.4%.
4. It is resistant to weak acids, weak bases and general solvents. It can be melted in phenol (phenol can be used as a binder) at room temperature and can also be dissolved in a saturated methanol solution of formic acid and calcium chloride.
*Understanding of nylon molding process
1. It needs to be fully dried before injection, the drying temperature is 80~~90℃, and the drying time is 24HRS.
2. Nylon has low viscosity, good fluidity, and is prone to cracking (flash). The pressure is not easy to be too high, generally 60~~90MPa.
3. With the change of the barrel temperature, the shrinkage rate fluctuates greatly, and the material temperature is too high, and the melting material is easy to change color, and the silver wire is brittle. Nylon materials below the melting temperature are very difficult and will damage the ring mold and screw. The temperature of the barrel is generally 220~~250℃, and should not exceed 300℃.
4. Mode temperature control: Nylon is a crystalline plastic, and the product is greatly affected by the mold temperature, so the mold temperature control requirements are higher. High mold temperature: high crystallinity, increased rigidity and wear resistance, small deformation. Low mold temperature: good flexibility, high elongation, low shrinkage, and the mold temperature is controlled at 20~~90℃.
5. High-speed injection: Nylon has a high melting point, that is, a high freezing point (rapid prototyping, high production efficiency) for smooth mold filling (without letting the melt drop to the melting point and solidify), high-speed injection must be used, which is the case for thin-walled products or long-distance products Attention should be paid to the exhaust problem caused by slow injection and high speed in the case of thick product wall thickness or overflow.
6. Annealing treatment and temperature adjustment treatment. a Annealing treatment: Annealing can increase the crystallinity, increase the rigidity, and is not easy to deform and crack , the annealing condition is 10~20℃ higher than the use temperature, and the time is 10~60 minutes. B Temperature adjustment treatment: to maintain dimensional stability, which is good for improving toughness and improving internal stress distribution. Temperature adjustment method: immersion in boiling water or potassium acetate solution. Potassium acetate: water=1.25:100 time 2~~16HRS.
Polymethacrylate (PMMA)
Commonly known as "Acrylic" or plexiglass, it is a non-crystalline plastic
1. High transparency, light weight, not easy to deform, good light guide.
2. PMMA is difficult to catch fire and can burn slowly.
3. Not resistant to alcohols, ketones and strong bases, and soluble in aromatic hydrocarbons and chlorinated hydrocarbons (trichloroethane can be used as a binder).
4. Easy to form and stable in size.
5. Impact resistance and surface hardness are slightly poor, easy to control scratches, so higher packaging requirements.
*PMM molding process understanding:
1. Acrylic has high transparency, and plastic defects such as bubbles, flow lines, impurity black spots, silver filaments, etc. are obviously exposed, so the molding difficulty is high, and the qualified rate of products is low
2. The raw materials are fully dried, and silver bubbles will occur due to insufficient drying. Drying conditions: temperature 95~~~100℃ time 6HRS The thickness of the material layer should not exceed 30mm, and the hopper should be kept warm to avoid re-blowing moisture.
3. The fluidity is poor, it is suitable for high-pressure molding, the injection pressure is 80~~100Mpa. The holding pressure is about 80% of the injection pressure, and the back pressure should not be higher to prevent early cooling of the gate runner. Properly prolong the injection time and use sufficient pressure to feed it.
4. Injection speed Injection speed has a great influence on viscosity. It should not be too fast. Too high injection speed will cause blistering, scorching, poor transparency, etc., and too low injection pressure will make the product fusion line thicker.
5. The material temperature fluidity increases with the increase of the barrel temperature, but the temperature should not be too high on the premise that the cavity can be filled to reduce discoloration, silver wire and other defects. The front barrel is 200~~~230℃, medium The barrel is 215~~235°C, and the rear barrel is 140~~~160°C.
6. The mold temperature is high, the product transparency is high, and poor welding is reduced, especially to reduce the internal stress of the product, and it is easy to fill the cavity. The mold temperature is generally 70~~90℃.
7. The design circulation of the mold should be short and smooth, and the wide gate can be formed.
8. Reduce internal stress The heat treatment temperature is 70~~80℃, and the hot air or water cooling time is generally 4HRS.
9. Reduce beer plastic black spots a ensure that the raw materials are clean (clean environment). B Clean the mold. C Machine cleaning (clean the front end of the barrel, screw and nozzle).
10. The mold surface is kept smooth, the plating is anti-corrosion, and the release agent is used as little as possible, which increases the inclination of the mold and facilitates the demolding.
