Shanghai Daoqin Plastics Co., Ltd.

         polycarbonate (PC) (PC) is types property can excellent engineering plastics, not only transparent degree high, impact tough property good, but also resistant creep, property, use temperature degree scope/range wide, dimensional stability good, electrical insulation property excellent 良, weather resistance can good, therefore by widely used in device table/sheet, lighting use tool, electronics electrical equipment, use electrical appliances, packaging and other industry.

         another, polymer/macromolecule material technology 突飞猛进, its modified new product types 不断出现, large expand large it application areas. meanwhile, its processing technology 也越 越受 to 各方面 heavy 视.

        PC is separation 子主链 structure in has ring, 异丙基, 醋键 线 property polymer, this type of structure make its has rigid property also has flexibility property, and good high temperature resistance can force, meanwhile in resin melt viscosity high, for water separation and other 不足, to injection molding processing belt/tape difficult degree 川.

         its processing process features is obvious melting point, in positive processing temperature degree 即230一320℃ scope/range inner melt viscosity high, viscosity for speed rate property small for temperature degree property large, 近似于牛顿流体行 is; for water separation 敏感, high temperature lower resin easy hydrolysis; products easy generate internal stress and other. can 见, PC is types relatively difficult processing plastics.

         therefore in production process in, 我们遇 to issues relatively more. 现就几 types relatively Common products defect add analysis and discussion.

        一, products color, 出现变黑, and black spots  

         versus for 而言, PC heat resistant property relatively good, usually processing 普通PC material 时, can will its melt temperature degree setting in 240一300℃, make long time 停留, generally 也不会 separation understanding. can is what in production electrical appliances products 时, 经常会出现变 color phenomenon 呢? this is is in market competition 激烈, is reduce production cost, large more 数厂家 production in low electrical appliances products large use PC modified material or recycled material, has use add flame retardant, filling agent and other mixed material. due to this material product 流驳杂, 而塑化 requirements relatively high, process control relatively difficult, from 而出现 this that issues.

        针 for upper phenomenon, from below/following several 方面进行考虑 and solution methods:

        (1) process conditions main/primary 考虑熔 melt temperature degree, generally need reduce machine temperature degree, especially is front temperature degree, but also for different material use different temperature degree, use polyethylene (PE) (PE) modified PC production large type electrical appliances products, generally will machine temperature degree control in 230℃ left right;

         again use ABS or PS modified PC production 开关, base/seat and other small type electrical appliances parts 时, machine temperature degree generally control in 250℃ left right;而 use PBT modified PC production products machine temperature degree generally control in 280℃ left right. 当然, molding temperature degree most 终选定 also need comprehensive products 形状, dimensions, mold structure, products property can requirements and other 方面.

         its is for Raw Materials separation drying, decrease/reduce micro amount water separation for hot melt catalytic understanding can can. another, screw speed fast, back pressure high, injection speed rate fast, and nozzle 孔径, runner, gate dimensions small and other make melt generate high hot, formed PC出现 melt phenomenon, but also easy make mold cavity inner gas can and 时排出, formed products local 灼伤而变黑.

        (2) equipment due to PC melt viscosity high, flow property 差, need injection molding pressure large, and versus combined force strong/high, separation understanding material for metal has strong/high property, therefore in selection processing equipment 时, requirements selection small type or design, screw, but also system 不允许 has 死角, material, 缺口, and other 情况出现.

         generally 说, if process conditions issues, for injection 时发现熔 material has color phenomenon, this 说明塑化 system has issues, 需逐一检查塑化 system, from nozzle 开始, to nozzle method 兰, small parts, screw, machine 筒. has products 会每隔一段 time cycle property 出现两三模 large sheet/slice color 情况, this more semi and system in material has 关, PC separation understanding material ultra- 一定 amount tool has catalytic function, 引发一 large sheet/slice melt separation understanding, especially is add flame retardant plastics.

         this need 找出呆 material screw viscous material, material, machine viscous material and other, through 清洗, 修补, light add solution.

        (3) use material, as methods 方面若一开 machine 就发现 has black spots, this more semi and machine material has 关.

        故 must attention/notes as methods methods, machine front machine 筒 存 material is PC时, need use new material in molding temperature degree lower will machine 筒清洗3一4次(for injection), if material is material, especially is heat stabilized property material, 如PVC,POM and other, this requirements in machine can rise high temperature degree, but also can use PC material machine 筒, can in relatively low temperature degree lower use heat stabilized property good material 如PS,PE and other material, dry rear, again machine temperature degree rise 至PC positive processing temperature degree, rear use PC material 清洗一 lower, can processing.

         in processing process in, 如需临时 in production, will machine temperature degree drop to 160℃ below/following temperature (因PC 玻璃化 temperature degree is 160"C), time long material material separation understanding color. formed production 任务时, can use PS,PE and other heat stabilized property good material machine 筒, rear machine.

         if in production process in has color phenomenon, 就需首先检查 use material is has issues, ratio is 否掺杂 its it material and material, new material is in quality issues, gate material is combined 格, mixed material is method positive and other, troubleshooting rear, again its it causes. factors is ring 境污染 comparison heavy, gas in many 灰尘, mold by 污染, 自烘式 material 斗 滤网不起 function 而吸进 relatively more and other. this requirements processing workshop maintain dry 净, 整洁, most good use fine material gas 口, gas 口蒙住, this in processing transparent products non necessary.

        二, products 出现银纹, bubbles, true 空泡

         products 出现银纹, bubbles, true 空泡, is PC material Common products defect 之一, this defect causes relatively more complex, relatively difficult 以判断 and troubleshooting.

        银纹(or gas marks) is plastics in process in to gas dry 扰而出现 in products surface material direction upper defect. gas formed separation main/primary water 汽, gas, separation understanding gas and solvent agent gas, its in water 汽, separation understanding gas and gas is more 见.

        当 this gas ultra- 一定 限 degree 时, in injection molding rear mold cavity pressure, products surface gas 体就会冒出, material direction formed 一连串 in light lower 闪闪烁烁 large large small small 泡点, is or gas marks. upper, in injection molding process in gas 体 存 in is can 避免, but also has versus 当一部 separation also in plastics internal.

        当模 inner pressure large, gas content also ultra- 一定 限 degree 时, gas dispersion solvent understanding to plastics 里面;但当模 inner pressure large, gas content also ultra- 一定 限 degree 时, this gas from melt plastics in 纷纷释放出, to products surface formed 银纹, in thick inner formed is bubbles.

        无论 is products surface 银纹, also is products inner bubbles, can can is 由4 types gas in certain types gas is function or types gas 体共同 function 结果, it and raw materials, mold, system, process parameters adjustment, 甚至天 gas 变化(especially is wet degree 变化) and other factors has very large 关系. therefore this issues comparison complex. tube/pipe how to, issues focus/key point and solution countermeasures 应该集 in in gas upper, is how to control gas content.

        (1) water generally 说, if bubbles 不规则 dispersion in products surface, large is water 汽 引起.

        PC hot material for water separation non 常敏感, requirements water amount in 0.02% below/following. therefore need control water separation content, need for material 进行充 separation drying. generally PC material drying temperature degree in 120℃ left right, drying time 4h left right, time can long, ultra- l0h, material material easy 变质, especially is add flame retardant material more drying time long;而 drying methods remove wet drying machine is most good, for material has effect/influence. drying is good, can use for injection method, injection shot material is 否连续, light 洁且不冒白 gas.

        (2)空 gas if bubbles is fine micro 而密集, main/primary distribution in products gate 周围, formed light 芒状纹 or 扇形纹, this more semi is gas 引起.

        空 gas is: material inner belt/tape gas. gate material relatively more, pellets large small versus 差悬殊时, easy belt/tape gas. therefore use gate material 时, most good powder material 筛选出. melt back pressure low, screw speed also high, make screw fast, gas easy material 一起推 toward machine front 端, generally in cooling time inner amount long melt time, this for improve/increase quality is very has 帮助.

        若 lower material temperature degree control good, temperature degree high make separation material melt 而堵塞 空 gas lower material 口 通路;而 temperature degree low preheating 不够, make separation material 进人均化段而裹入空 gas. another, amount large 也会吸入空 gas. to upper 述情况, generally adjustment screw speed, back pressure and amount can large can solution. process in gas.

         is make melt viscosity relatively high PC material can 顺利充模, generally is improve/increase material temperature degree and increase injection molding pressure. in high temperature high pressure lower, if injection speed rate relatively fast, melt 会突然穿 狭 narrow runner and gate tool has relatively large 自由空间 mold cavity, this from melt in 释放出 gas again belt/tape runner and mold cavity inner gas formed high speed 喷射状态, in cold plastics surface 就会出现 dispersion gas 流 痕迹即 gas marks 叫.

         another, if mold cavity inner relatively more, thick thin versus large, or parts more, gate 位置不当时, melt 就会涌人 mold cavity, 激荡模 inner gas formed 涡流, in 一定 部位就会形 formed gas marks, molding electrical appliances product 开关插 base/seat sheet/plate, due to its 插口, and 开关都集 in in 一 部位, 故经常会出现 this type of 情况. solution defect method is, 一方面修改 mold, add strong/high mold gas, optimization gate 位置;另一方面 reduce speed rate, especially is has gas marks injection speed rate.

        (3) separation understanding gas due to PC material in high temperature lower molding, generate separation understanding is can 避免, how to a large amount of separation understanding and how to troubleshooting gas is value discussion.

        同 upper 述 变 color 一样, generate separation understanding gas main/primary causes is melt temperature degree high. ratio 如, machine temperature degree setting high, or machine 筒 发 hot control 失调, nozzle 开始, 逐段检查发 hot 圈, reduce machine temperature degree; melt in machine 筒里停留 time long (如 production small products use large equipment, 缓冲垫 amount large), molding cycle long, or machine inner material, 死角处存 material long time hot 而引起 separation understanding; or melt in machine 筒里受 to strong/high function, screw pressure shrink ratio large, screw speed high, back pressure large and other separation understanding.

         another, nozzle small, mold gate, runner small, type retardant force large and other can make through melt scratch formed local hot separation understanding, therefore processing PC material 时, nozzle 孔径, gate, runner dimensions relatively large, gas need deep, 且不宜 made as thin products.

         also has important causes is PC本身 quality 差, easy separation understanding, this 一点常常 by use overlook, issues to mold and processing equipment upper, from 而找不 to solution issues positive method.

        (4) solvent agent gas solvent agent gas main/primary and production in as quality has 关, machine 筒清洗不 dry 净, additives add more and other. solvent agent gas can through separation drying remove large separation, it for gas marks effect/influence is very large.

         transparent products internal in has very difficult separation is bubbles also is true 空泡. generally is, if mold opening already 发现存 in 泡点, but also 存放一段 time rear 体积没 what 变化则 is bubbles, belongs to gas dry 扰引起; if in demolding cooling process in 出现并变 large, belongs to true 空泡.

         true 空泡 形 formed is due to 充模时 material or pressure relatively low, in mold cooling function lower, and 模壁接触 熔 material surface solid 化, rear in separation material cooling shrinkage, formed shrink small formed in 空即泡点.

         its solutions is: 

        · improve/increase injection molding pressure, injection time and material amount;

        · adjustment material temperature:当 true 空泡远离 gate 位置时, improve/increase material temperature make material flow 顺畅, pressure can to gate 部位;

        · 当 true in gate 附近时 can reduce material temperature make shrinkage decrease small;

        · 适当 improve/increase mold temperature degree, especially is formed true 空泡部位 local mold temperature degree;

        · will gate in products thick 壁部位, improvement nozzle, runner and gate flow and mold gas 状况;

        · shrink short products in inner cooling time, necessary will products hot water in slow cooling;

        · use gate molding products can use slow speed, low temperature molding solution true issues, runner upper has true

        · 空泡时 can add large runner dimensions.

        · another, in production process in also 发现PC products demolding rear very fast in thick 壁部位出现鼓泡 phenomenon, this is due to cooling make PC internal gas 体膨胀造 formed.

        · generally can use long cooling time, add strong/high cooling 效果, improve/increase holding pressure pressure and time, 延缓PC separation understanding and other measures solution.

        三, products 出现“指纹” and flow marks  

         due to PC melt viscosity large, flow property relatively 差, products relatively easy 出现“指纹” and flow marks phenomenon. this types phenomenon in processing 开关插 base/seat parts and generally electrical appliances parts sheet/plate relatively is Common, this types phenomenon also due to versus 似, has very difficult separation 开. its 实, this types phenomenon formed causes same, but also its solution methods is same.

        (1)“指纹”因 its 形状像人 手指纹而 名, has also is 波纹, 震动纹 or 震纹, is its 纹路像石头掉 in water 面 形 formed 一样. its generate causes main/primary is PC melt viscosity large, injection molding pressure, injection speed rate relatively small 时, melt 便以滞流形式充模, front 端 熔 material 一接触 to cold mold surface, very fast cold shrinkage, rear hot material in pressure lower already shrinkage cold material front 进, process 交替进行, in material 流行进方 upper formed 垂直波纹线.

         its solution methods is:

         improve/increase temperature degree, main/primary is improve/increase nozzle temperature degree and machine front temperature degree and mold temperature degree, especially is generate 波纹处 temperature degree.

         this is is reduce PC melt viscosity, improve/increase melt flow property. but also if products comparison precision, for appearance requirements 严格, increase mold temperature machine, control mold temperature degree in 120℃ left right.

         increase injection speed rate and injection molding pressure, main/primary is is increase “指纹”处 melt flow rate, melt 以滞流形式 flow. if “指纹” generate in products in or gate 位置时, need using/adopting more grade injection, adjustment injection speed rate.

        修改 mold, main/primary is is decrease small melt in process in to retardant force, add large runner, gate dimensions; attention/notes for nozzle and runner light; add large gas 沟, 槽;设置镶 parts, 顶杆引 gas plant/unit; improvement mold gas 状况;设置足够 large cold material 阱, decrease small front cold material retardant function.

        (2)乱 flow marks is in PC products upper 出现以 gate is in 心 不规则 流线 phenomenon. and “指纹”线 different is, flow marks is material direction is material direction 出现. its causes can can is due to by injection to mold cavity material to large impact, from in cold upper viscous slip 致.

         its solution methods is:  

         improve/increase melt temperature degree, decrease/reduce melt cooling; improve/increase mold temperature degree, especially is 出现乱 flow marks temperature degree, anti material in mold cavity inner cooling sliding; using/adopting more grade injection, will 出现乱 flow marks injection speed rate, injection molding pressure reduce; gate 位置, 以改变熔 material flow methods; add large cold material 阱, anti cold material in inner sliding; use flow property good material, make material 充模顺畅.

        四, products cold material 斑  

         cold material is PC products gate Common defect 之一, its phenomenon is products gate belt/tape has color or color 糊斑, or gate viscous in products surface 宛若蚯蚓 bending 疤痕. its formed causes main/primary is 由进人 mold cavity material front cold material or degree holding pressure function rear mold cavity cold material formed, front material is nozzle and cold sheet/plate or runner cooling function hot amount, in mold cavity 时, also has 随之而 hot melt 推挤, is formed cold material 斑.

         cold material in relatively thin products upper will by 摊开而 formed is 烟雾状 or mixed 浊斑痕, in flow thick products upper will lower strip/profile bending toward 形如蚯蚓 疤痕. 至于由 degree holding pressure function formed cold material 斑, is holding pressure time long, in holding pressure pressure large lower will runner, gate upper cold material 继续挤进 products 致, this type of cold material 斑往往 make gate sheet/slice very small scope/range formed 圆形 亮斑.

         also has types is material fast speed small gate in gate 周围造 formed melt 破裂, or inner gas dry make gate 处出现烟云状 or light 芒状亮斑. cold material 斑不但 loss products table/sheet quality, but also effect/influence rear 续工序如 spray coating or electroplating 效果, different degree reduce products force strong/high degree.

         for defect can solution measures is:

        · 调 high machine and nozzle temperature degree, improve/increase mold temperature degree, decrease/reduce cold material effect/influence;

        · decrease slow injection speed rate, increase injection molding pressure, melt or inner gas dry 扰;

        · adjustment injection time and holding pressure time, amount 充填;

        · combined mold gate design can decrease/reduce or cold material 斑 形 formed, 传统而 has methods

        · is in runner 末端开设 cold material 阱, make front material 陷人阱 inner 而不致进人 mold cavity, has mold remove cold material outer, also need gate 形式, large small and combined property;

        · add strong/high mold gas; remove material in material, strong/high material material drying 效果, decrease/reduce or lubricant, amount less use demolding agent.

        五, transparent products internal stress  

         in production PC transparent products cationic 镜, 挡风罩, and other made parts 时, 经常会发现 products deformation, dispersion light, transparent degree good and cracking and other phenomenon, this main/primary is due to products internal in internal stress 缘故.

         its in transparent products internal in internal stress, is performance obvious 罢. internal stress is in has outer force lower, plastics internal due to molding 不当, temperature degree and other causes generate force, its essence is plastics separation high elastic deformation by in products inner formed.

         plastics products internal stress can effect/influence products force property can and use property can, generate warpage, deformation fine small 裂缝; products optical property can 变差, products 变浑浊 and other. internal stress also make injection molding products in flow direction upper 显示出 relatively high force property can, 而垂直于 flow direction strong/high degree relatively low, make products property can non-uniform, from effect/influence products use. especially is products hot or and has machine solvent agent 接触时 will accelerated products cracking.

        PC products internal stress main/primary is orientation force and temperature degree force 引起, has and demolding has 关. orientation force injection molding products internal large separation orientation rear easy generate internal stress, formed force in. in injection molding melt speed cooling, in relatively low temperature degree lower melt viscosity relatively high, orientation separation can separation 松弛, generate internal stress for products force property can and dimensional stability has effect/influence.

         therefore melt temperature degree for orientation force effect/influence most large, improve/increase melt temperature degree melt viscosity decline, 因而剪切应 force and orientation reduce. in addition, in high melt temperature degree lower orientation force 松弛程 degree relatively large, viscosity reduce 时, injection molding machine screw to mold cavity pressure increase large, can can make speed rate improve/increase, orientation force increase large. holding pressure time long, orientation force increase large; improve/increase injection molding pressure 同样会因剪切应 force and speed rate increase 而引起 orientation force increase large.

         products thick degree for internal stress has effect/influence, orientation force products thick degree increase low, is thick products cooling slow, melt in mold cavity inner cooling, time relatively long, orientation separation has time to random 状态. mold temperature degree high, melt cooling slow, can make orientation force decrease small.

        (2) temperature degree force plastics in injection molding melt temperature degree and mold temperature degree between temperature very large, this make 靠近模壁 熔 material cooling relatively is speed, generate in products inner distribution non-uniform force. due to PC specific heat capacity relatively large, thermal conductivity small, products surface ratio inner cooling fast more, products surface formed solid housing/shell retardant internal cooling 时 自由 shrinkage, its 结果引起 products internal generate tensile force in outer generate pressure shrink force.

         thermoplastic property plastics shrinkage generate force large, material in inner pressure function generate force low, holding pressure time short, holding pressure pressure low, can large large decrease small internal stress. products and dimensions for internal stress has very large effect/influence. products surface and 体积之 ratio large, surface cooling fast, orientation force, temperature degree force large. orientation force main/primary generate in products thin table/sheet inner, therefore, can is orientation force 应该随 products surface for its 体积之 ratio increase increase large. products thick degree non-uniform or products belt/tape has metal parts easy generate orientation force, therefore parts and gate 都宜设 in products thick 壁处.

         through above analysis can 知, due to plastics structure and injection molding process conditions made, need full internal stress is can can, can amount decrease small internal stress or amount make internal stress in products inner distribution uniform.

         its methods is:  

         injection temperature degree for products internal stress large small effect/influence very large, therefore need improve/increase machine temperature degree, ensure material material 塑化良 good, make separation uniform reduce shrinkage rate, decrease small internal stress; improve/increase mold temperature degree, make products cooling slow, 以松弛 orientation separation 子, reduce internal stress.

         high injection molding pressure can make plastics separation orientation function increase large generate relatively large force, make plastics separation has 序排列, products orientation force increase large, therefore, need amount using/adopting relatively low injection molding pressure;若 holding pressure time long, inner pressure due to pressure function improve/increase, material generate relatively high pressure 效应, separation orientation degree improve/increase, make products internal stress increase large, therefore holding pressure time 不宜太 long.

         injection speed rate for injection molding parts internal stress effect/influence ratio temperature degree, pressure and other factors need small more, most good using/adopting speed injection, fast speed 充模, mold cavity rear use low speed, speed injection 一方面充模 process fast, decrease/reduce 熔接痕, 另一方面 low speed holding pressure can decrease/reduce separation orientation.

         combined design gate 位置, products most good using/adopting 缝形, gate; ejection plant/unit design formed large ejection; demolding degree need large. can can use relatively good material (含杂质 less, separation quality large), use gate material.

        当 products belt/tape has metal parts 时, parts material 需预先 add hot (generally requirements 达200℃ left right), anti metal material and plastics material 线胀系数不一致而 generate internal stress. 渡处需 use 圆弧 渡.

        出模 rear can use hot methods remove internal stress. hot temperature degree is 120℃ left right, time 2h left right. its is make plastics separation in 链段, has active can force, elastic property deformation to 松弛, orientation separation to random 状态. most good use demolding agent, easy internal stress, formed products transparent, or cracking.