Shanghai Daoqin Plastics Co., Ltd.

一, shrinkage rate

    effect/influence thermoplastic property plastics molding shrinkage factors lower:

    1.1 plastics product types thermoplastic property plastics molding process in due to also in crystallization 化形起 体积变化, internal stress strong/high, in parts inner residual stress large, separation orientation property strong/high and other factors, therefore and hot solid property plastics versus ratio shrinkage rate relatively large, shrinkage rate scope/range wide, direction property obvious, another molding rear shrinkage, or wet rear shrinkage rate generally ratio hot solid property plastics large.

    1.2塑 parts features molding melt material and type surface outer 层立即 cooling formed low density solid outer housing/shell. due to plastics thermally conductive property 差, make parts inner slow cooling formed shrinkage large high density solid 态层. therefore thick, cooling slow, high density thick shrinkage large. another, has parts and parts 布局, amount 都直接 effect/influence material direction, density distribution and shrinkage retardant force large small and other, therefore parts features for shrinkage large small, direction property effect/influence relatively large.

    1.3进 material 口形式, dimensions, distribution this factors effect/influence material direction, density distribution, holding pressure shrink function and molding time. 直接进 material 口, material 口截面 large （ especially relatively thick ）则 shrinkage small direction property large, material wide and long degree short direction property small. material or and material direction 平行 则 shrinkage large.

    1.4 molding conditions mold temperature degree high, melt material cooling slow, density high, shrinkage large, especially for crystallization material crystallization degree high, 体积变化 large, shrinkage more large. mold temperature distribution and parts inner outer cooling and density uniform property has 关, effect/influence to separation shrinkage amount large small and direction property. another, maintain pressure and time for shrinkage effect/influence relatively large, pressure large, time long shrinkage small direction property large. injection molding pressure high, melt material viscosity small, 层间剪切应 force small, demolding rear elastic property large, shrinkage can amount decrease small, material temperature high, shrinkage large, direction property small. therefore in molding adjustment mold temperature, pressure, injection molding speed degree and cooling time and other factors can 适当改变塑 parts shrinkage 情况.

    mold design according to various plastics shrinkage scope/range, parts thick, 形状, material 口形式 dimensions and distribution 情况, experience 确定塑 parts 各部位 shrinkage rate, again type dimensions. for high degree parts and difficult 以掌握 shrinkage rate 时, generally use lower methods design mold:

    ① for parts outer relatively small shrinkage rate, inner relatively large shrinkage rate, has mold trial rear positive 余.

    ② mold trial 确定浇注 system 形式, dimensions and molding conditions.

    ③ need rear 处理 塑 parts rear 处理确定 dimensions 变化情况（测 amount must in demolding rear 24 small rear ）.

    ④按实际 shrinkage 情况修 positive mold.

    ⑤ again mold trial can 适当 改变 process conditions micro positive shrinkage value meet/satisfy parts requirements.

    二, flow property

    a) thermoplastic property plastics flow property large small, generally can from molecular weight large small, melt flow index, 阿基米德螺旋线 flow long degree, performance viscosity and flow ratio （ process/workflow long degree /塑 parts thick ） and other series 指数进行 analysis. molecular weight small, molecular weight distribution wide, separation structure property 差, melt flow index high, flow long degree long, performance viscosity small, flow ratio large flow property good, for product plastics must its 说明书判断 its flow property is suitable for injection molding. mold design requirements large can will commonly used plastics flow property separation is type:

    flow property good PA, PE, PS, PP, CA, poly （4）甲基戍烯;

    flow property in and other polystyrene (PS) series resin （如ABS, AS）, PMMA, POM, polyphenylene oxide (PPO);

    flow property 差PC, hard PVC, polyphenylene oxide (PPO), polysulfone (PSU), poly 芳砜, fluorine plastics.

    b) various plastics flow property 也因各 molding factors 而变, main/primary effect/influence factors has lower 几点:

    temperature degree material temperature high flow property increase large, different plastics has 差异, PS（ especially resistant impact type and MFR value relatively high ）, PP, PA, PMMA, modified polystyrene (PS) （如ABS, AS）, PC, CA and other plastics flow property temperature degree relatively large. for PE, POM, temperature degree increase decrease for its flow property effect/influence relatively small. therefore front in molding adjustment temperature degree control flow property.

    pressure injection molding pressure increase large melt material 受剪切 function large, flow property increase large, especially is PE, POM relatively is 敏感, therefore molding adjustment injection molding pressure control flow property.

    mold structure system 形式, dimensions, 布置, cooling system design, melt material flow retardant force （如 type light degree, material 道截面 thick degree, type 腔形状, gas system ） and other factors 都直接 effect/influence to melt material in type inner flow property, make melt material reduce temperature degree, increase flow property retardant force flow property reduce. mold design according to use plastics flow property, selection combined structure. molding 时则也 can control material temperature, mold temperature and injection molding pressure, injection molding speed degree and other factors adjustment filling 情况以 meet/satisfy molding need.

    三, crystallization property

    thermoplastic property plastics its cold 凝时无出现 crystallization phenomenon can separation is crystallization type plastics and non crystallization type （ also 称无定形） plastics large type. crystallization phenomenon is plastics melt to cold 凝时, separation 子由独立移动, full 处于无次序状态, formed separation 子停止自由运动, micro solid 定 位置, has make separation 子排列 formed is positive type toward types phenomenon. as is this type plastics appearance standards can plastics thick parts transparent property 而定, generally crystallization property material is transparent or semi transparent （如POM and other ）, 无定形 material is transparent （如PMMA and other ）. has outer 情况, poly (4)甲基戍烯 is crystallization type plastics has high transparency property, ABS is 无定形 material 但却并不 transparent. in mold design and selection injection molding machine attention/notes for crystallization type plastics has lower requirements and precautions:

    material temperature upper rise to molding temperature degree hot amount more, need use can force large equipment.

    cooling 回化时放出 hot amount large, need separation cooling.

    melt and solid specific gravity large, molding shrinkage large, easy shrink 孔, gas 孔.

    cooling fast, crystallization degree low, shrinkage small, transparent degree high. crystallization degree and parts thick has 关, thick cooling slow, crystallization degree high, shrinkage large, material property good. therefore crystallization property material requirements must control mold temperature.

    toward property significantly, internal stress large. demolding rear crystallization separation has crystallization toward, can amount balanced 状态, easy deformation, warpage.

    crystallization temperature degree scope/range narrow, easy 发生未熔 material 末注入 mold or 堵塞进 material 口.

    四, hot property plastics and easy hydrolysis plastics

    4.1 hot property certain plastics for hot relatively is 敏感, in high temperature lower hot time relatively long or material 口截面 small, function large 时, material temperature increase high easy 发生变 color, degradation, separation understanding toward, tool has this type of features plastics is hot property plastics. hard PVC, poly chlorine ethylene, acid ethylene copolymer, POM, poly fluorine chlorine ethylene and other. hot property plastics in separation understanding generate mono 体, gas 体, solid and other material, especially is has separation understanding gas for 人体, equipment, mold has 刺激, function or property. therefore, mold design, selection injection molding machine and molding 时都应 attention/notes, selection screw injection molding machine, system 截面宜 large, mold and material 筒应镀铬, has *角滞 material, must control molding temperature degree, plastics in add stabilizer, decrease low its hot property can.

    4.2 has plastics （如PC）即 make has a small amount of water separation, in high temperature, high pressure lower 也会发生 separation understanding, this type of property can is easy hydrolysis property, for must add hot drying.

    五, force cracking and melt 破裂

    5.1 has plastics for force 敏感, molding easy generate internal stress 并质脆 easy 裂, parts in outer force function lower or in solvent agent function lower 即发生 cracking phenomenon. is 此, remove in raw materials inner add additives improve/increase resistant property outer, for raw materials attention/notes drying, combined selection molding conditions, decrease/reduce internal stress and increase resistant property. selection combined 理 塑 parts 形状, 不宜设置嵌 parts and other measures amount decrease/reduce force in. mold design increase large demolding degree, selection combined 理 进 material and ejection machine 构, molding 时应适当 adjustment material temperature, mold temperature, injection molding pressure and cooling time, amount 避免塑 parts cold demolding, molding rear parts also 宜进行 rear improve/increase resistant cracking property, remove internal stress prohibited and solvent agent 接触.

    5.2当一定 melt melt flow rate polymer melt, in temperature lower through nozzle its speed ultra- certain value rear, melt surface obvious toward cracks is melt 破裂, has loss parts appearance and material property. in selection melt flow rate high polymer and other, increase large nozzle, 浇道, material 口截面, decrease/reduce injection molding speed degree, improve/increase material temperature.

    六, thermal properties and cooling speed degree

    6.1 various plastics has year-on-year hot, hot rate, heat deflection temperature (HDT) and other thermal properties. ratio hot high 塑化时 need hot amount large, selection can force large injection molding machine. heat deflection temperature (HDT) high plastics cooling time can short, demolding 早, demolding rear need anti cooling deformation. hot rate low plastics cooling speed degree slow （如离子 polymer and other cooling speed degree slow ）, must separation cooling, need add strong/high mold cooling 效果. hot mold suitable for ratio hot low, hot rate high plastics. ratio hot large, hot rate low, heat deflection temperature (HDT) low, cooling speed degree slow plastics 则不利于 high speed molding, must selection injection molding machine and add strong/high mold cooling.

    6.2 various plastics its types type features and parts 形状, requirements must maintain cooling speed degree. therefore mold must molding requirements add hot and cooling system, maintain mold temperature. material temperature make mold temperature rise high 时应予 cooling, anti parts demolding rear deformation, shrink short molding cycle, reduce crystallization degree. plastics hot 不足以 make mold maintain temperature degree 时, mold has add hot system, make mold maintain in temperature degree, control cooling speed degree, ensure flow property, improvement filling conditions or use control parts make its slow cooling, anti thick parts inner outer cooling and improve/increase crystallization degree and other. for flow property good, molding large, material temperature 不匀 则按塑 parts molding has add hot or cooling use or local add hot and cooling use. is mold has versus cooling or add hot system.

    七, wet property

    plastics in has various additives, make its for water separation has different hydrophilic hydrophobic degree, therefore plastics large can separation is wet, viscous water separation and water easy viscous water separation types, material in water amount must control in scope/range inner, in high temperature, high pressure lower water separation formed gas or hydrolysis function, make resin 起泡, flow property decline, appearance and force property can defect. therefore wet property plastics must requirements using/adopting add hot methods and specification preheating, in use anti again wet.