常用热塑性塑料的成型性能doc.docx

1、常用热塑性塑料的成型性能doc常用热塑性塑料的成型性能The commonly used thermoplastic plastic forming properties of.Txt48 smile, is a green in spring, is under the sun hungry a shade, autumn is a cool breeze, a winter campfire. Smile and face it, you will feel that life is so warm. This article is contributed by rroginDOC doc

2、uments may experience poor browsing on the WAP side. It is recommended that you first select TXT, or download the source file to the local view.1: HDPE PE1: crystalline plastics, hygroscopic; 2: good fluidity, flash gap of about 0.02mm, liquidity pressure sensitive; 3: may melt fracture, contact wit

3、h organic solvent cracking can occur: 4: long heating time is easy to decompose, burn; 5: slow cooling rate must be fully cooled, mold cooling system should be established 6:; shrinkage, shrinkage of large fluctuation, easy orientation, easily deformed, effect of cooling conditions on the crystallin

4、ity and the mold shrinkage rate is high, should control the mold temperature, ensure product cooling uniformity, stability. 7: is suitable for high pressure injection, the material temperature should be uniform, filling speed should be fast, the pressure should be fully 8. Not by the gate, or gate n

5、ear the residual stress of large, easily lead to warpage, deformation. 9: should pay attention to the choice of gate location, to prevent deformation of shrinkage, are advised to set up cold material. 10: soft easy demoulding products with shallow concave side, can be adopted Forced demoulding metho

6、dTwo: polyvinyl chloride (rigid PVC)1: non crystalline plastics, absorbing temperature of small, but in order to improve the liquidity and prevent the generation of bubbles, it is advisable to carry out drying. 2: poor mobility, strong thermal sensitivity, easy decomposition, especially in the high

7、temperature steel and copper metal contact should be decomposition, the decomposition temperature of 200 DEG C, the decomposition of produce corrosion and irritant gases. (minimally toxic) 3: forming a small temperature range, the temperature must be controlled strictly. 4: is suitable for screw inj

8、ection molding machine and through the nozzle, the nozzle diameter should be large, the need to prevent the corner lag material, must be promptly removed. 5: channel should be thick and short, the gate section should be large, the injection system there shall be no dead ends, to prevent stagnation o

9、f material, 6: cavity surface with chrome plated, there should be a mold cooling system, mold temperature control should be sensitive and accurate.Three: Polypropylene1: crystalline plastics, lower hygroscopicity, possible melt fracture, long-term contact with the hot metal was easily decomposed. 2:

10、 good fluidity, overflow the gap between 0.003mm. 3: cooling speed, cooling speed should be reasonable control of the gating system and the mold. 4: shrinkage, shrinkage wave range easy orientation. Prone to shrinkage and deformation. The attention of the 5: air depression control forming temperatur

11、e, the temperature low anisotropy significantly, especially at low temperature and high pressure is more strong, the mold temperature is lower than 50 DEG C, matte surface products, and prone to receiving the bad and flow marks, temperature higher than 90 DEG C, easy to warp 6:. Products of uniform

12、thickness, avoid gap angle, to prevent stress concentration. The 7: orientation ability, should not use the gate, or gate near the high residual stress, easy to cause the warpage.Four: polystyrene (PS)1: for non crystalline plastics, good hygroscopicity, not easy to decompose, but brittle, thermal e

13、xpansion coefficient, to produce residual stress. 2: good fluidity, flash gap of about 0.03mm. 3: thickness should be uniform, not with inserts, missing angle, angle, the surface should be smooth over even then, there must be such as insert,To insert preheating. 4: can use screw or plunger type inje

14、ction nozzle can be used straight machine, also can use self-locking. 5: should adopt modestly higher mold temperatures, and lower injection pressure, prolong the time of injection can reduce the residual stress to prevent shrinkage and deformation (especially for thick. Wall products more effective

15、), but the temperature is too high products prone to crazing, and the temperature is too low or too much amount of release agent, transparent products transparency becomes worse. 6: can be used in a variety of gates should be smooth transition between the gating system and the mold cavity, to preven

16、t damage to the gating system except products suspected of material, draft should be more than 2*, the top output should be evenly distributed, in order to avoid the occurrence of product deformation or cracking due to adverse release.Five: stupid ethylene diene acrylonitrile copolymer (ABS)1: non c

17、rystalline plastics, many varieties, mechanical properties and formability of different varieties are different, by determining the molding method and molding process conditions according to varieties. 2: is hygroscopic and molding before fully dry, require less than 0.3% moisture content of the sur

18、face gloss, high requirement, need long time preheating, drying 3: flow, overflow gap of about 4 0.04mm; molding difficult polystyrene, should adopt the modestly higher mold temperatures (for heat resistant, high impact and anti impact type, should be within the allowable range of the maximum temper

19、ature) 5: material temperature has great influence on the products the material, if the material temperature is too high, easy to melt decomposition (decomposition temperature of 250 DEG C) if the 6: products require high precision, mold temperature should be 5060*C, if the product requires surface

20、gloss or for heat resistant variety, mold temperature should be 6080 degrees. 7: injection pressure should be higher than Polystyrene Molding When was high, the plug injection machine, the temperature should be 180230 DEG C, injection pressure desirable 100140MPa, using screw injection molding machi

21、ne, the temperature of 160220 DEG C injection pressure is desirable, desirable 70100MPa 8: design should pay attention to the mold, the flow resistance of the gating system should be as small as possible, the form and position of gate should be reasonable and can to prevent or reduce the weld mark w

22、eld line number, in addition, the draft should be 2* above the top output should not be too large, otherwise, molding or molding after machining of products, product surface is easy to play, white for the products to the phenomenon of white hot water heating, to eliminate the phenomenon of white.Six

23、: styrene acrylonitrile copolymer (SAN)1; non crystalline plastics, hygroscopicity, good thermal stability, not easy to break down. 2; liquidity is better than ABS, but not prone to overflow. 3: products are prone to cracking (especially on gate) it is not easy with sharp corners and gaps, mold desi

24、gn, draft should be greater and the top output should be evenly distributed.Seven: Polycarbonate1: non crystalline plastics molding, good thermal stability, wide temperature range, the temperature above 330 DEG C to serious decomposition, gas produced in the decomposition of non-toxic, non corrosive

25、. 2: small moisture absorption, but the water sensitivity is strong, must carry out drying pretreatment before molding, the water content shall not exceed 0.2%, otherwise there will be a craze the problem, bubbles and product strength decreased significantly. 3: poor mobility, sensitive to temperatu

26、re changes, shrinkage flash gap of about 0.06mm. 4:, if reasonable molding conditions, products can be controlled in a small scale called the tolerance range, and therefore obtain products with high precision.May occur in the forming process of 5: melt fracture, and is prone to greater stress, so we

27、 should strictly control the molding condition, after molding should adopt the annealing treatment on the products, in order to eliminate the residual stress. 6: with high melting temperature, high degree of product, for the following 200 grams should adopt the screw type injection machine. The nozz

28、le should adopt the open extension nozzle, because with 7: degree, liquidity is not very sensitive to shear rate, and cooling speed, so the passage try to design the thick and short, and try to choose the direct gate area, ring gate or fan gate, but should avoid excessive stress and flow orientation

29、 large, especially large residual stress near the gate, when necessary by 8: g tab gate thickness should not be too large, and the wall thickness should be uniform, avoid sharp corners, with a notch or insert, in order to prevent stress concentration caused by crack, if it must be with The metal ins

30、ert molding before the insert preheating. 9: barrel temperature is one of the main factors to control the quality of products, the barrel temperature low temperature is low, so the product will be lack of material, surface crazing and matte defects, barrel temperature high temperature is high, it wi

31、ll cause overflow the phenomenon, and make the product appear craze, dark spots. And bubbles and other defects. 10: injection pressure should not be low, although the plastic cooling speed, but if the mold is provided with a heating device, also should ensure that products with appropriate cooling t

32、ime, 11: mold design, the draft should be larger, top output distribution uniform, and pay attention to set the cold material in the proper position, to prevent the emergence of weld defects, lack of strength, the mold cavity should adopt wear-resisting steel, and quenched. 12: mold should generally

33、 be heated, mold temperature is 70120 DEG C, effect of mold temperature on the product quality greatly, According to the wall thickness of the concrete value of thin-walled 80100 C, thick walled pieces from 80120 DEG C, the mold temperature is too high when the shrinkage value, product elongation, impact resistance, but the flexural tensile streng