Plastic is a polymer compound (macromolecule) that polymerizes as a result of an addition polymerization reaction or a polycondensation reaction with a monomer as a raw material, has an average resistance to deformation and is located between fiber and rubber, reagents, stabilizers, lubricants, dyes and other additives .
The main component of plastic is resin. Resin refers to a polymer compound not mixed with various additives. The term resin was originally named after lipids secreted by animals and plants, such as rosin and shellac. Resin makes up 40% to 100% of total weight of plastic. The basic properties of plastics are mainly determined by nature of resin, but additives also play an important role. Some plastics are primarily composed of synthetic resins with no additives or with a small amount of additives such as plexiglass.1. ABS Copolymer of Acrylonitrile Butadiene Styrene Typical Applications:
Cars, televisions, refrigerators, washing machines, air conditioners and other electrical equipment.Formability:
Drying: ABS material is hygroscopic and needs to be dried before processing.
Drying conditions: 80-90℃ for 2 hours
Density: 1.05 g/cm^3
Shaping shrinkage: 0.4-0.7%
Forming temperature: 200-240℃
1. Amorphous materials, with medium fluidity and high moisture absorption, should be completely dried. Plastic parts that require a glossy surface must be preheated and dried at a temperature of 80-90 degrees for 3 hours.
2. It is desirable to use high material temperature and high mold temperature, but if material temperature is too high, it is easy to decompose (decomposition temperature > 270 degrees). -80 degrees.
3. If you need to eliminate watermark, you need to improve fluidity of material, accept high temperature of material, high temperature of mold, or change water level and other methods.
4. If heat-resistant or fire-resistant materials are molded, plastic degradation products remain on mold surface after 3-7 days of production, resulting in a glossy mold surface. The mold must be cleaned. in time, and exhaust position needs to be added to mold surface.Physical properties:
1. Good overall performance, high impact strength, chemical stability and good electrical properties.
2.Good alloy with 372 plexiglass, made of two-tone plastic parts, chrome and paintable.
3. There are grades with high impact resistance, high temperature resistance, flame retardant, reinforced, transparent and other grades.
4. The flow is slightly worse than HIPS, better than PMMA, PC, etc., and has good flexibility. It is suitable for makingmanufacturing of general mechanical parts, wear-resistant and wear-resistant parts, transmission parts and telecommunications parts.2. Typical scope of PS polystyrene:
Product packaging, household products (dishes, trays, etc.), electrical appliances (transparent containers, light source diffusers, insulating films, etc.).Formability:
Density: 1.05 g/cm^3
Shaping shrinkage: 0.6-0.8%
Forming temperature: 170-250℃
1. The amorphous material has low moisture absorption, does not need to be completely dried, does not decompose well, but has a large coefficient of thermal expansion and is subject to internal stresses, has good fluidity, and can be molded with a screw or plunger injection machine.
2. It is recommended to use high material temperature, high mold temperature and low injection pressure. Increasing injection time is useful to reduce internal stress and prevent shrinkage cavity and deformation.
3. Various gate shapes can be used, and gates are connected by arcs of plastic parts to avoid damage to plastic parts when removing gates. The demoulding slope is large and ejection is uniform. Inserts, if any, must be preheated.Physical properties:
Excellent electrical insulation (especially high frequency insulation), colorless and transparent, only pligillas light transmission, coloring, water resistance and good chemical resistance, strength is medium but brittle. Thermal insulation is easily brittle, and it is not resistant to benzene-based organic solvents such as gasoline for decorative parts such as insulating transparent parts and optical equipment for chemical equipment.3. PMMA -- acrylic -- polymethyl methacrylate Typical application range:
The common name is Plexiglas. Automotive industry (signal lighting equipment, instrument panel, etc.), pharmaceutical industry (blood storage containers, etc.), industrial applications (video disc, diffuser), FMCG (beverage glasses, stationery, etc.) d.).Formability:
Density: 1.18g/cm^3Shaping shrinkage: 0.5-0.7%Shaping temperature: 160-230℃Drying conditions: 70-90℃ for 4 hours
1. Amorphous materials, with high moisture absorption, should be dry, not easy to decompose, medium fluidity, prone to poor filling, mold sticking, shrinkage, welding marks, etc.
2. High pressure injection should be used. In defect-free state, to improve fluidity at high material temperature and high mold temperature, it is necessary to improve transparency and strength to reduce internal stresses. The surface of injection system of mold should be smooth, but in order to ensure a large dissociation gradient and uniform discharge at same time, a vent hole is provided to preventfoaming.Physical properties:
Good transparency, high strength, permanent heat and cold resistance, good corrosion resistance and insulation, overall performance is superior to PS, but quality is brittle and easily soluble in organic solvents, for example, it is a transparent material, surface hardness is slightly lower, and it is easy to be scratched . It has good complex properties, high strength and rigidity, good wear resistance, small water absorption and good dimensional stability, thermally stable, easy to burn and easy to age in atmosphere. It is suitable for making wear-resistant parts, transmission parts, chemical machines, musical instrument parts. It has good complex properties, high strength and rigidity, good wear resistance, small water absorption and good dimensional stability, thermally stable, easy to burn and easy to age in atmosphere. It is suitable for making wear-resistant parts, transmission parts, chemical machines, musical instrument parts.4. Typical application range of POM:
POM has a very low coefficient of friction and good geometrical stability, especially suitable for gears and bearings. Because it also has high temperature resistance properties, it is also used in plumbing components (pipe valves, pump housings), lawn equipment, etc.Formability:
Density: 1.41-1.43g/cm^3Shaping shrinkage: 1.2-3.0%Shaping temperature: 170-200℃Drying conditions: 80- 90℃ for 2 hours
1. Crystallization material, narrow melting range, fast melting and solidification, crystallization occurs when material temperature is slightly lower than melting point. Average mobility. Hygroscopicity is low, without drying treatment.
2. The coefficient of friction is low, elasticity is good, and surface of plastic part is prone to surface defects such as wrinkles.
3. It is very easy to decompose, and decomposition temperature is 240 degrees. Decomposition produces irritating and corrosive gases. Therefore, mold steel must be made from corrosion resistant materials.Physical properties:
It has good complex properties, high strength and rigidity, good wear resistance, low water absorption and good dimensional stability, thermally stable, easy to burn and easy to age in atmosphere. It is suitable for making wear-resistant parts, transmission parts, chemical machines, musical instrument parts. It can be used at 100 degrees for strength, hardness and heat resistance. Although it has good electrical properties and high frequency insulation, it is not affected by humidity, becomes brittle at low temperatures, is not resistant to this type, and is prone to aging.5. Typical scope of polypropylene PP:
Automotive industry (mainly using polypropylene containing metal additives: fenders, vent pipes, fans, etc.), household appliances (dishwasher door gasket, dryer vent pipe, washing machine body and cover, refrigerator door gasket etc.), consumer goods (lawn and garden equipment such as lawn mowers, sprinklers, etc.).Formability:
Density: 0.9-0.91g/cm^3Shaping shrinkage: 1.0-2.5%Shaping temperature: 160-220℃Drying conditions: -- -
1. A crystalline material with low hygroscopicity, prone to breakage when melted, and easily decomposes when in contact with hot metal for a long time. 2. The fluidity is good, but shrinkage range and shrinkage amount are large, and shrinkage hole, dent and deformation are prone to occur. 3. The cooling rate is fast, filling system and cooling system must dissipate heat slowly, and pay attention to molding temperature control. Directionality is obvious when material temperature is low. This is especially obvious at low temperature and high pressure. When mold temperature is lower than 50 degrees, plastic parts are not smooth and easy to produce. Poor welding, leaving traces, and warpage deformation easily occurs at temperatures above 90 degrees. 4. The thickness of plastic wall should be same to avoid lack of adhesive and sharp corners to prevent stress concentration.Physical properties:
It can be used at 100 degrees to ensure strength, hardness and heat resistance. Although it has good electrical properties and high frequency insulation, it is not affected by humidity, becomes brittle at low temperatures, is not resistant to this type, and is prone to aging..
Applicable to stamping general mechanical parts, corrosion resistant parts and insulating parts.6. Typical scope of PVC polyvinyl chloride:
Water pipes, household pipes, house wall panels, commercial vehicle enclosures, electronic product packaging, medical equipment, food packaging, etc.Formability:
Density: 1.38g/cm^3Shaping shrinkage: 0.6-1.5%Shaping temperature: 160-190℃Drying conditions: ---
1. Amorphous material, low moisture absorption, poor fluidity. To improve flow and prevent formation of air bubbles, plastic can be pre-dried. The sprue system of mold should be thick and short, cross section of sprue should be large, and there should be no dead corner. The mold should be cooled, surface is chrome plated.
2. It is very easy to decompose, and it is easier to decompose when it is in contact with steel and copper at a temperature of 200 degrees..
3.When using nozzle of screw injection molding machine, hole should be large to prevent material from stagnation in dead corners.It is better not to have inserts, and if there are inserts, preheat.Physical properties:
Excellent mechanical and electrical properties, high resistance to acids and alkalis, good chemical stability, but low softening point. Suitable for making thin plates, wire and cable insulation layers, seals, etc.7. Typical application range of Nylon PA:
It is widely used in structural parts due to its good mechanical strength and rigidity. Due to its good wear resistance properties, it is also used in production of bearings.Formability:
Density: PA6-1.14g/cm^3PA66-1.15g/cm^3PA1010-1.05g/cm^3Shaping shrinkage: PA6- 0.8-2.5% PA66- 1.5 -2.2%Forming temperature: 220-300℃Drying conditions: 100-110℃ for 12 hours
1. Crystallized material with higher melting point and narrow melting point range, poor thermal stability, when material temperature is over 300 degrees and residence time is over 30 minutes, it will decompose. Easily absorbs moisture and needs drying, water content should not exceed 0.3%.
2. Good fluidity, easy to overflow. Self-locking nozzles should be used and should be heated.
3. The molding shrinkage range and shrinkage rate are large, directionality is obvious, and shrinkage cavity and deformation tend to occur.
4. The mold temperature is selected according to wall thickness of plastic part in range of 20-90 degrees. The injection pressure is selected according to type of injection molding machine, material temperature, plastic shape and size. mold part and system. The molding cycle is selected according to wall thickness of plastic part. Of course. If resin viscosity is low, injection and cooling time should be longer, and vaseline oil should be used as a release agent.
5. The shape and size of mold gate system, increasing size of runner and gate can reduce shrinkage.Physical properties:
Nylon 6 is waterproof, wear-resistant, oil-resistant, water-resistant, water-absorbent, and has excellent elasticity, impact strength and large water absorption. Nylon 66 has superior performance than nylon 6, high strength and good wear resistance. Nylon 610 is similar to nylon 66 but has low water absorption and low stiffness.
Nylon 1010 has good water absorption and frost resistance, and is also translucent. It is suitable for production of general mechanical parts, wear-resistant parts, guide parts, chemicals, electrical appliances, appliances, etc.8. Typical application scope of polycarbonate PC:
Electrical and commercial equipment (computer components,connectors, etc.), household appliances (food processors, refrigerator drawers, etc.), vehicles (front and rear lights, dashboards, etc.).Formability:
Density: 1.18-1.20 g/cm^3
Shaping shrinkage: 0.5-0.8%
Forming temperature: 230-320℃
Drying conditions: 110-120℃ for 8 hours
1. Amorphous material, good thermal stability, wide molding temperature range, poor fluidity. Low moisture absorption, but sensitive to water, requires drying. The casting shrinkage rate is small, and melt cracking and stress concentration are possible, so casting conditions must be strictly controlled, and plastic parts must be annealed. 2. High melting point, high viscosity, plastic parts over 200g, heated extension nozzle is recommended.
3.The cooling rate is high.The frontal system of mold should be thick and short.It is desirable to install a cold well, gate should be large, and mold should be heated. 4. If temperature of material is too low, it will lead to a shortage of material and plastic parts will be dull. If temperature of material is too high, it will easily overflow and plastic parts will bubble. When mold temperature is low, shrinkage rate, elongation rate, and toughness are high, but bending resistance, compression resistance, and tensile strength are low. When temperature of mold exceeds 120 degrees, cooling of plastic part is slow, it is easy to deform and stick to mold.Physical properties:
It has high impact strength, high dimensional stability, colorless and transparent, good coloration, good electrical insulation, corrosion resistance and wear resistance, but poor self-lubricating properties, prone to stress cracking, easy to hydrolyze, not soluble in other substances. resins. It is suitable for manufacture of instrument parts, insulation of transparent and impact parts9, PE Polyethylene. Typical scope:
Refrigerator containers, storage containers, household kitchen utensils, sealed lids, etc. Bowls, cabinets, pipe couplingsForming properties:
Density: 0.94-0.96 g/cm^3
Shaping shrinkage: 1.5-3.6%
Forming temperature: 140-220℃
Drying conditions: ---
The crystalline material material is little hygroscopic, not completely dry, high fluidity, pressure sensitive, and requires high pressure injection during molding, uniform material temperature, high filling speed, and sufficient forced pressure. To avoid uneven shrinkage and increased internal stress, door must not be used directly. Pay attention to choice of gate position to prevent shrinkage and deformation.
2. The shrinkage range and shrinkage value are large, directionality is obvious, easy to deform and deformis being formed. The cooling rate should be slow, and mold should be equipped with a cold cavity and cooling system.
3. The heating time should not be too long, otherwise it will decompose and burn.
4. If soft plastic parts have shallow lateral grooves, they can be forced out of mold.
5. Melt degradation may occur, so it should not be in contact with organic solvents to prevent cracking.Physical properties:
Good corrosion resistance and electrical insulation (especially high frequency insulation). Chlorination, which can be modified by irradiation. Glass fiber low pressure polyethylene can be reinforced with high melting point, stiffness, hardness, strength, low water absorption, good electrical properties and radiation resistance. High pressure polyethylene has softness, plasticity, impact resistance and good magnetic permeability of UHMWPE, has high impact strength, fatigue strength and wear resistance.
LDPE is suitable for the manufacture of corrosion-resistant and insulating parts;
High density polyethylene is suitable for making films, etc.;
Ultra-high molecular weight polyethylene is suitable for shock-absorbing, wear-resistant and transmission parts.