Shanghai Daoqin Plastics Co., Ltd.

众 周知, injection molding machine  “ screw 塑化组 parts ” is injection molding machine main/primary core mono 元, 直接体现 injection molding machine property can excellent poor. has “心脏”之称 screw is important parts, its property can processing products quality, efficiency and other indicators high low. plastics industrial development, especially is 我国经 二十几 year development, injection molding equipment already formed 熟, as is injection molding equipment design and use 者, need understanding which screw suitable for which material material processing, especially is in material material product types 繁杂 今天, market upper screw types type day more, in use in comparison mixed 乱, use 者经常 certain screw use processing 不适宜 material features plastics. more has 一 观念误区 is: “认 is screw is can ”,   its 实不然, 借此, simple introduction types commonly used structure screw, processing products provide 一 参考.

（一）PC material （ polycarbonate (PC) ） features:
1. non crystallization property plastics, obvious melting point, 玻璃化 temperature degree 140℃-160℃,熔 melt temperature degree 215℃-225℃, molding temperature degree 230℃
-320℃;
2. viscosity large, processing temperature degree high, scope/range narrow, easy separation understanding, selection screw 时避免 hot phenomenon;
3. for water separation 敏感, high temperature lower resin easy hydrolysis, drying temperature degree 120℃-130℃, time 4 small left right.
parameters 选定:
1．L/D针 for its heat stabilized property good, viscosity large features, is improve/increase 塑化效果尽 amount large long ratio;
2． due to its melt temperature degree scope/range relatively wide, add material long, 均化段 short, pressure shrink ratio in, is increase 塑化效果 can selection type
胶头;
3．如 add flame retardant or glass fiber reinforcement PC material, can selection use corrosion resistant wear resistant excellent 质不锈工 tool material screw and small
parts.
（二）PMMA（ has machine 玻璃） features:
1.玻璃化 temperature degree 105℃, melt temperature degree large 于160℃, separation understanding temperature degree 270℃, molding temperature degree scope/range very wide 180-250℃;
2. viscosity large, flow property 差, for speed rate relatively 敏感, processing need control temperature degree;
3. material temperature degree 240℃-250℃, ultra- 260℃时滞留 time ultra- 8 separation 钟;
4.吸 water property relatively strong/high, drying temperature degree 80℃-90℃, time 3 small above.
parameters 选定:
1.L/D选取 long ratio 20-22, type screw generally 取L1=35-45%, L2=35-40%;
2. pressure shrink ratio ε generally 取2.3-2.6;
3.针 for its has hydrophilic water property, in screw front using/adopting mixing/compounding structure.
（三）PA（ polyamide (PA) ）, Common PA6（ nylon 6 ）, PA66（ nylon 66 ） features:
1. crystallization property plastics types type relatively more, types type 不一样, its melting point 也不一样, upper melting point scope/range narrow, generally PA66 its melting point 260℃-270℃;
2. viscosity low, flow property good, has comparison obvious melting point, heat stabilized property 差;
3. water absorption relatively high, drying machine temperature degree 80℃, ultra- 120℃, time 16 small 时. if raw materials 暴露于空 gas 8 small 时, need use true 空烘箱 in 105℃ left right, time 12 small 时.
parameters 选定:
1.L/D选取 long ratio 18-20 突变 type screw;
2. pressure shrink ratio generally 选取2.5-3.5, its in anti hot separation understanding h3: 0.067-0.089D;
3.因 its viscosity low, 故 胶圈 and machine 筒间隙应尽 amount small 约0.05-0.08, screw and machine 筒间隙0.08-0.12;
4.射嘴处 can elastic 簧自锁 type 射嘴.
（四）PET（ poly 脂）化 Scientific Names: terephthalic acid ester features:
1. melting point 250℃-260℃, blow molding PET molding temperature degree relatively 广, 约255℃-290℃, reinforced grade GF-PET can 达290℃-315℃ and other;
2. melting point high, viscosity low, and metal force large, easy hydrolysis;
3. hydrophilic water property, viscous material in high temperature lower for water comparison 敏感, drying temperature degree 150℃-160℃, time 4 small above.
parameters selection:
1.L/D generally 取20-22, distribution L1=50-60%, L2=20-30%;
2. using/adopting low 剪切, low pressure shrink ratio screw pressure shrink ratio ε=1.8-2.2, is hot 导致变 color or transparent h3=0.09-0.10D;
3. use recycling material （ sheet/slice material ）时, add large add material 段 输送 can force, using/adopting strong/high made material system.
（五）PVC（ polyvinyl chloride (PVC) ）
hot property material material, generally separation is hard and soft 质, its difference in raw materials in add increase agent how much, less 于10% is hard 质, more 于30% is soft 质.
features:
1.无 obvious melting point, 60℃变 soft, 100℃-150℃ viscous elastic 态, 140℃熔 melt molding temperature degree scope/range narrow, heat stabilized property 差, easy separation understanding, 170℃ separation understanding speed, soft 化点接近于 separation understanding 点, separation understanding 释放于HC1 gas 体.
2. due to UPVC melt viscosity high, heat stabilized property 差, temperature degree time 均会导致 separation understanding, for generally has function;
3. temperature degree control 严格, screw design amount need low 剪切, anti hot, runner need light slip, can has 死角, anti material separation understanding;
4. screw machine need anti 止腐蚀;
5. injection molding process 需严格 control.
parameters selection:
1.L/D=18-21, h3=0.067-0.08D,ε-1.6-2, L1=40-45%, L2=35-45%, is anti material 无 胶圈, 头部20℃-30℃, using/adopting hard screw;
2. temperature selection;
①熔胶筒 more cold plant/unit;
② low high mixing/compounding UPVC specialized screw material plant/unit.