Shanghai Daoqin Plastics Co., Ltd.

         injection molding machine screw tool has 输送, melt, mixing/compounding, pressure shrink, amount and gas and other function, is effect/influence quality key/critical factors . lower to large introduction types commonly used plastics injection molding selection screw key points.

         polycarbonate (PC) PC

        PC 特 property is: non crystallization type plastics, obvious melting point, 玻璃化 temperature degree is 140~ 150℃, melt temperature degree is 215~225℃, molding temperature degree is 250~320℃. degree large, for temperature degree relatively 敏感, in positive processing temperature degree scope/range inner heat stabilized property relatively good, 300℃ lower long time basic separation understanding, ultra- 340℃开始 separation understanding, degree 受剪切 speed rate effect/influence relatively small. water property strong/high.

         injection molding PC screw attention/notes below/following key points:

        (1)针 for its heat stabilized property good, degree large features, is improve/increase 塑化效果尽 amount large long ratio, generally 取26. due to its melt temperature degree scope/range relatively wide, pressure shrink can relatively long, using/adopting type screw. L1=30%L, L2= 46%L.

        (2) pressure shrink ratio ε:渐变 degree A需 and melt speed rate versus 适应, currently melt speed rate also method fast 递精确计算 出, according to PC from 225℃熔化至320℃ between can processing features, its degree A value can versus for in and other upper value, in L2 relatively large lower, 普通渐变 type screw ε=2~3, A generally 取2.6.

        (3)因 its degree high, water property strong/high, in 均化段之 front, pressure shrink rear screw upper add mixing/compounding structure, add strong/high solid understanding 体, meanwhile, can make its in belt/tape water separation formed gas 体逸出.

        (4) other parameters 如e, s, a以 and and material 筒 间隙都 can and other screw same.

         nylon PA

        PA features lower:  crystallization type plastics, types type relatively more, types type 不一样, its melting point 也不一样, melting point scope/range narrow, generally use PA66 its melting point is 260~265°C. degree low, flow property good, has comparison obvious melting point, heat stabilized property 差. water property generally.

         injection molding PA screw attention/notes below/following key points:

        (1)选取 long ratio is 18~20 突变 type screw.

        (2) pressure shrink ratio generally 选取3~3.5, is anti hot separation understanding h3=(0.07~0.08)D.

        (3)因 its degree low, 故止逆 ring and material 筒间隙应尽 amount small, is 0.05, screw and material 筒间隙约 is 0.08, has need, its material, front can 配止逆 ring, 射嘴处应自锁.

        (4) other parameters can general purpose screw design.

         polymethyl methacrylate (PMMA) PMMA

        PMMA features lower:  玻璃化 temperature degree is 105℃, melt temperature degree large 于160℃, separation understanding temperature degree is 270℃, molding temperature degree scope/range very wide. degree large, flow property 差, heat stabilized property relatively good. water property relatively strong/high.

         injection molding PMMA screw attention/notes below/following key points:

        (1)选取 long ratio is 20~22 渐变 type screw, according to its products molding degree requirements generally L1=40%L, L2=40%L.

        (2) pressure shrink ratio ε generally 选取2.3~2.6.

        (3)针 for its has hydrophilic water property, in screw front using/adopting mixing/compounding ring structure.

        (4) other parameters generally can general purpose screw design, and material 筒间隙不 can small.

         polyester PET

        PET features lower: melting point is 250~260℃, blow molding grade PET则 molding temperature degree relatively 广一点, is 255~290℃.

         injection molding PET screw attention/notes below/following key points:

        (1)L/D generally 取20, distribution L1=(50%~55%) L, L2= 20%L.

        (2) using/adopting low 剪切, low pressure shrink ratio screw, pressure shrink ratio ε一.般取1.8~2, meanwhile is anti 止剪切 hot 导致变 color or transparent, 设置hs=0.09D.

        (3) screw front 端不设 mixing/compounding ring, anti hot, material.

        (4)因 this type of material for temperature degree relatively 敏感, generally more use recycling material, is improve/increase output/production volume, generally using/adopting is low screw, therefore can improve/increase 马达转 speed, to 目. meanwhile in use recycling material 方面(large separation is sheet/slice material), according to 实际情况, is add large add material 段 输送 can force, 也采取 add large material in material 筒里开槽 and other methods, comparison good 效果.

         polyvinyl chloride (PVC) PVC

        PVC is hot property plastics, 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.

        PVC features:无 obvious melting point, 60℃变 soft, 100~ 150℃时 is elastic 态, 140℃时熔 melt, meanwhile separation understanding, 170℃ separation understanding speed, soft 化点接近于 separation understanding 点, separation understanding 释放于HCl gas 体. disadvantages is heat stabilized property 差, flow property 差.

         injection molding PVC screw attention/notes below/following key points:

        (1) screw design amount need low 剪切, anti hot.

        (2) screw, material need anti 腐蚀.

        (3) generally 说, screw parameters is L/D=16~20, h3=0.07D, e=1.6~2, L1 = 40%L, L2= 40%L.

        (4) is anti material, 无止逆 ring, 头部锥 degree is 20°~30°, for soft relatively 适应;如 products requirements relatively high, can using/adopting amount 段, separation type screw, types screw for hard 质PVC relatively combined; but also is combined temperature 控, add material screw internal add cooling water or 油孔, material outer add cold water or 油槽, temperature degree control degree is 士2℃ left right.