(A) PC material (PC) features:
1. Non-crystalline plastic, no melting point, glass transition temperature of 140 ℃ -160 ℃, melting temperature of 215 ℃ -225 ℃, forming temperature 230 ℃ -320 ℃;
2. Viscosity, high-temperature processing, and narrow the scope and easy to break down and use screw to avoid overheating;
3. Sensitive to water, high temperature resin easy hydrolysis, drying temperature 120 ℃ -130 ℃, 4 hours.
Selected parameters:
1. L / D for its thermal stability, viscosity of the great features to enhance the effect of plastics as much as possible to select a large aspect ratio;
2. Because of its wide scope of the melting temperature, feeding a long paragraph, all of paragraph short, medium compression ratio, in order to increase the effectiveness of plastics may choose to use plastic barrier over-head;
3. Such as flame retardants, or to join the PC glass fiber reinforced materials, may choose to wear the use of corrosion-resistant high-quality stainless steel screw material, as well as three small pieces.
(B) PMMA (plexiglass) features:
1. Tg 105 ℃, melting temperature is greater than 160 ℃, decomposition temperature of 270 ℃, forming a wide temperature range of 180-250 ℃;
2. Viscosity, liquidity is poor, which is more sensitive to shear rate, processing, strictly control the temperature;
3. Bowl temperature of 240 ℃ -250 ℃, than 260 ℃ stranded when the time is not more than 8 minutes;
4. More absorbent, drying temperature 80 ℃ -90 ℃, 3 hours.
Selected parameters:
1.L / D select the aspect ratio 20-22, gradually taking the general screw-L1 = 35-45%, L2 = 35-40%;
2. Compression ratio ε general admission 2.3-2.6;
3. For some of its hydrophilic, the screw in the use of front-end structure of the mixing head.
(C) PA (polyamide), the common PA6 (nylon 6), PA66 (nylon 66) features:
1. Crystalline plastic more and different types, nor its melting point, melting point on the narrow scope of the general PA66 its melting point 260 ℃ -270 ℃;
2. A low viscosity, good liquidity, the more obvious point, poor thermal stability;
3. The higher water absorption, the dryer temperature 80 ℃, no more than 120 ℃, time to 16 hours. If raw materials exposed to air 8 hours, use a vacuum oven at about 105 ℃, 12-hour period.
Selected parameters:
1.L / D longer than the 18-20 select the type of mutation screw;
2. 2.5-3.5 select the compression ratio general, to prevent overheating decomposition h3 :0.067-0 .089 D;
3. Because of their low viscosity, the apron off and barrel should be a small gap of about 0.05-0.08, screw and barrel space 0.08-0.12;
4. Nozzle can be equipped with self-locking spring-mouth radio.
(D) PET (polyester) Chemical Name: PET characteristics:
1. Melting point of 250 ℃ -260 ℃, blow molding PET wider temperature, about 255 ℃ -290 ℃, enhance the level GF-PET up to 290 ℃ -315 ℃, and so on;
2. A high melting point and low viscosity, adhesion and metal, easy hydrolysis;
3. Hydrophilic, viscous material at a high temperature of the water sensitive, dry temperature 150 ℃ -160 ℃, 4 hours or more.
Preferences:
1.L / D generally take 20-22, three distribution L1 = 50-60%, L2 = 20-30%;
2. Use of low shear and low compression ratio of the screw compression ratio ε = 1.8-2.2, because the cut lead to overheating or opaque color h3 = 0.09-0.10D;
3. The use of recycling material (film material), increase the transmission capacity of the feed section, the mandatory use of plastic feed system.
(E) PVC (polyvinyl chloride)
The heat-sensitive materials are generally divided into hard and soft, the difference between the raw materials added to Plasticizers of the number, less than 10% of the rigid, more than 30% for soft.
Characteristics:
1.'s No point, 60 ℃ soften, 100 ℃ -150 ℃ viscoelastic state, 140 ℃ melt forming a narrow temperature range, poor thermal stability, easy to break down, 170 ℃ rapid decomposition, softening point close to the break point, the release of decomposition HC1 gas.
2. UPVC due to the high melt viscosity, thermal stability worse time temperature will lead to decomposition, the general corrosion of steel have effect;
3. Strict temperature control, screw design as much as possible to cut low to prevent overheating, the flow must be smooth and should not be dead, the plot is expected to prevent decomposition;
4. Screw barrel to prevent corrosion;
5. Injection process to be strictly controlled.
Preferences:
1.L / D = 18-21, h3 = 0.067-0.08D, ε = 1.6-2, L1 = 40-45%, L2 = 35-45%, to prevent the possession of material non-apron over his head 20 ℃ -30 ℃, using chrome-plated hardware of the screw;
2. The choice of temperature;
① molten plastic tube multi-unit air-cooled;
② low high-shear mixing bowl UPVC special screw device. |