Shanghai Daoqin Plastics Co., Ltd.

 造 type PC products quality unstable causes relatively more, effect/influence factors is more 方面, need below/following factors can make quality unstable phenomenon has obvious good 转, from made combined product.
   （1） Raw Materials. injection use PC is color transparent material, less color micro 黄, versus for separation quality is 2.3×10 四次方·3.2×10 四次方. in molding processing front 应测定PC flow property can, melt flow rate （MFR）. conditions: temperature degree is 300℃, is 1200g. tube/pipe PC吸 water property small, room temperature lower balanced water absorption is 0.3%, in molding processing in for products property can formed large effect/influence. must 经 充 separation drying, make water amount drop 至0.02% below/following, most good in 0.015% below/following, can injection molding.
   make used for PC resin drying methods has multiple, commonly used has hot ring drying, 直结式 material drying, negative pressure drying, true drying and other, its drying process methods different has 差异.
   has drying 效果 检验, can through water separation 测定仪 or pressure sheet/slice method or for slow speed injection method and other methods understanding, its in rear types methods use relatively more.
   must 指出, drying rear pellets 如若露置 in gas in, 则会因空 gas in water separation effect/influence 而导致 heavy new wet, heavy new wet rear PC for products effect/influence 情况.
   （2） process conditions and control.
    ① molding temperature degree. for/regarding large more 数PC products, material temperature degree control in 250℃·310℃. temperature degree low, degree large, material 不足, products surface shrinkage or 起皱纹, gloss, silver streaks 缭乱; temperature degree high or high 于310℃而停留 time long, formed heavy degradation, products belt/tape flash, is dark color, surface has silver streaks dark strip/profile, and 纹迹, internal has bubbles, various property can poor. specific material temperature degree 确定于 products thick and injection machine type has 关. thin 壁（2mm below/following ） products, material temperature degree high, in 285℃·305℃ is good; thick 壁（ large 于10mm） products, material temperature degree can low, 以250℃·280℃ is 宜, temperature degree ultra- 290℃, due to injection cycle long, hot separation understanding toward increase large, effect/influence products comprehensive property can.
   different type type injection machine, material temperature degree different, screw is 260℃·285℃, 柱塞式 is 270℃·310℃. therefore amount using/adopting screw injection machine, this can make plastics in relatively low material temperature degree lower uniform 塑化, from 而避免因 temperature rise high or in material in hot time long 而引起 hot separation understanding
   nozzle temperature degree 应第一点, and material front temperature degree versus and other or low 5℃·10℃. temperature degree high, easy 出现流涎 phenomenon, low 会引起 nozzle or make products in has low temperature material material formed defect. type injection machine upper nozzle add hot, temperature degree control in 260℃·310℃. add material 口一端 material temperature degree control in PC soft temperature degree above, generally requirements large 于230℃, decrease/reduce material retardant force and injection pressure loss 失.
   ② mold temperature degree. PC molding temperature degree high, cooling speed degree fast, very easy make products surface generate defect, internal formed force. is this this issues, mold temperature degree can can high. for large more products, mold temperature control in 80℃·120℃, its in thin products low （80℃·100℃）, thick products high （100℃·120℃）. mold temperature low, products can can difficult or belt/tape has shrinkage rate large, 波纹, 毛斑, dark strip/profile and other defect. more heavy is residual stress large, 往往一出模就 cracking; mold temperature high （ high 于120℃）, products can very fast cooling, molding cycle long ‘ surface gloss 差, easy 发生黏 film, demolding difficult, make products warpage deformation.
   ③ injection pressure. PC melt degree relatively high, molding thin long process/workflow or outer complex ’交汇部位 more products and using/adopting high pressure fast speed injection 不足以充满 type products, need relatively large injection pressure. other can can using/adopting low pressure slow speed, decrease/reduce products residual stress. using/adopting high pressure fast speed 时, melt flow speed degree fast, 且以不规则形式 front 进, 出现涡流, has can can mixed gas, surface generate melt cracks, internal 残留应 force large. injection pressure can low, 否则柱塞 or screw difficult 以克服 melt flow retardant force, make type inner cooling melt can to new material shrinkage, make products deformation shrinkage rate increase large. generally injection pressure is 98MPa·156MPa, screw injection machine is 78MPa·127MPa.
   injection speed degree is 8m/s·10m/s. injection speed degree fast, for stability 充模不利, products easy silver streaks 纹, 旋纹, and other defect. holding pressure time for products property can effect/influence relatively large. holding pressure time short, products shrinkage or shrinkage 空洞, true 空洞; add holding pressure time, especially is for large thick products, can increase its density, remove true 空泡, make dimensions stability. holding pressure time long, due to is strong/high 行充模, also make products generate internal stress, easy cracking, meanwhile also long molding cycle. therefore, is decrease/reduce internal stress, obtain property can good products, generally using/adopting relatively low holding pressure time and relatively short holding pressure time.
   pressure （ back pressure ） is injection pressure 10%·15%. back pressure large add long time, can 导致PC thermal degradation; small 则不利于 material material gas, material 致密以 and material temperature degree and color uniform.
   （3） precautions. PC in injection process in attention/notes lower 几点情况:
    ① demolding agent. PC is transparent property material, in molding process in generally recommendation use demolding agent, effect/influence products transparent degree, formed or cracking, for demolding has difficult, demolding agent demolding products, can use hard acid or silicon 油衍生 material as is demolding agent, its use amount need control.
    ② mold temperature degree. PC molding temperature degree high, cooling speed degree fast, very easy make products surface generate defect, internal formed force. is this issues, mold temperature degree can can high. for large more products, mold temperature control in 80℃·120℃, its in thin products low （80℃·100℃）, thick products high （100℃·120℃）. mold temperature low, products can can difficult or 一出模就 cracking; mold temperature high （ high 于120℃）, products can very fast cooling, molding cycle long, surface gloss 差, easy 发生黏 film, demolding difficult, make products warpage deformation.
   ③ injection pressure. PC melt degree relatively high, molding thin long process/workflow or outer complex, 交汇部位 more products and using/adopting high pressure fast speed injection 不足以充满 type products residual stress. using/adopting high pressure fast speed 时, melt flow speed degree fast, 切以不规则形式 front 进 出现涡流, has can can mixed gas, surface generate melt cracks, internal 残留应 force. injection pressure can low, 否则柱塞 or screw difficult 以克服 melt flow retardant force, make type inner cooling melt can to new material shrinkage, make products deformation shrinkage rate increase large. generally injection pressure is 98MPa·156MPa, screw injection machine is 78MPa·127MPa.
   injection speed degree is 8m/s·10m/s. injection speed degree fast, for stability 充模不利, products easy silver streaks 纹, 旋纹, and other defect. holding pressure time for products property can effect/influence relatively large. holding pressure time short, products shrinkage or shrinkage 空洞‘ true 空泡; add long holding pressure time, especially is for large thick products, can increase its density, remove true 空泡, make dimensions stability. holding pressure time long, due to is strong/high 行充模, also make products generate internal stress, easy cracking, meanwhile also long molding cycle. therefore, is decrease small internal stress, obtain property can good products, generally using/adopting relatively low holding pressure pressure and relatively short holding pressure time.
   pressure （ back pressure ） is injection pressure 10%·15%. back pressure large add large time, can can 导致PC thermal degradation; small 则不利于 material material gas ’熔 material 致密以 and material temperature degree and color uniform.
   （3） precautions. PC in injection process in need attention/notes lower 几点情况:
   ① demolding agent. PC is transparent property material, in molding process in generally recommendation use demolding agent, effect/influence products transparent degree, formed or cracking, for demolding has difficult, demolding agent demolding products, can use hard acid or silicon 油衍生 material as is demolding agent, its use amount need control.
   ②嵌 parts use. due to metal and plastics in thermal expansion coefficient upper relatively large, it versus interface formed very large internal stress, this in PC in performance relatively is 突出, products in use process in easy cracking phenomenon, therefore remove can can decrease/reduce metal parts use amount and for products necessary rear 处理之 outer, parts 应避免锐角 or 缺口 存 in, in molding processing in will parts preheating （ generally requirements 达200℃）, shrink small metal parts and melt between temperature 差, make parts in and resin melt 接触时, less has 120℃ above temperature degree. for parts products, its resin most good selection versus for separation quality relatively large product grade.
   ③ recycled material use. due to PC tool has relatively good stability property, for/regarding processing in gate, runner and combined products, 经破碎 rear is can heavy use. 当然, recycled material use 时, also attention/notes for products property can belt/tape effect/influence. recycled material use amount increase and recycled increase, will for PC generate effect/influence. is ensure products quality and property can stability property, requirements in material recycled 次数不 need ultra- 三次, use amount is 20% left right.
   for/regarding recycled PC, remove attention/notes anti 止污染 outer, in molding processing front, also 需经 严格 drying 处理.
   ④换 material material and machine.
   a. material 筒清洗. machine 时, material inner material material is PC时, use new material in molding temperature degree lower will material launch can （ generally 2次·3次 for injection process ）. material inner material is polyvinyl chloride (PVC), polyoxymethylene (POM) and other molding temperature degree relatively low, heat stabilized property resin 时, use PC推洗 material 筒, can rise high material temperature degree, in low temperature degree lower, use polyethylene (PE), polystyrene (PS) and other heat stabilized property relatively good resin will will material 筒清洗 dry 净. rear rise high material temperature degree 至PC processing temperature degree, use PC recycled material will material in 清洗一 lower, other resin, can use new material processing.
   b.停 machine. 临时停 machine or in production 时, requirements will material temperature degree reduce 至160℃一 lower, 以免停 machine time 久而引起 material material degradation color. processing already formed 时, can use polystyrene (PS), polyethylene (PE) and other resin material 筒, rear drop temperature machine.
   ⑤ products rear 处理. hot 处理时 is remove PC products internal stress 而采取 measures, hot 处理 介质 is gas, 甘油, liquid wax and other, its in hot gas 清洁简便, use most is 普遍. PC products hot temperature degree requirements control in its 玻璃化转变 temperature 形状, use requirements and hot 处理介质 different, can 由几十 separation to small and other.
   upper, hot methods to full remove internal stress is very difficult, can will products in force value drop to scope/range inner. therefore products in how much still 残留一定 internal stress. has internal stress can through light or property solvent agent 进行测定 understanding, its in property solvent agent method is processing 厂普遍 using/adopting types testing 手段. property solvent agent is will PC products certain solvent agent inner, according to cracking time and cracking 情况判断 its force large small and distribution 情况.