Shanghai Daoqin Plastics Co., Ltd.

         mold mold trial 时, machine 构运行 basic positive 常, products comparison heavy appearance quality issues, surface generate 放射状 white 痕迹, but also this type of white 痕迹随 glass fiber (GF) content increase 趋于严 heavy, this type of phenomenon 俗称“ fiber exposure ”, is types glass fiber (GF) plastics products easy 于出现 surface defects, this for/regarding appearance requirements high automotive parts is can 接受.

         causes analysis

        “ fiber exposure ” phenomenon is glass fiber (GF) outer formed, white glass fiber (GF) in plastics melt flow process in 浮露于 outer table/sheet, cold molding rear in parts surface formed 放射状 white 痕迹, parts is black 时会因 color 泽 差异 add large more add obvious.

         its formed causes main/primary has below/following several 方面:

        1. in plastics melt flow process in, due to glass fiber (GF) and resin flow property has 差异, but also quality density different, make tool has separation trend, density small glass fiber (GF) toward surface, density large resin inner 里, is formed glass fiber (GF) outer phenomenon;

        2. due to plastics melt in flow process in to screw, nozzle, runner and gate scratch force function, formed local viscosity 差异, meanwhile also bad glass fiber (GF) surface interface 层, melt viscosity small, interface loss heavy, glass fiber (GF) and resin between adhesion force small, adhesion force small to 一定程 degree 时, glass fiber (GF) 便会摆脱 resin 基体 束缚, toward surface 累积而 outer 露;

        3. plastics melt type 腔时, formed “喷泉”效应, glass fiber (GF) internal toward outer table/sheet flow, and type surface 接触, due to mold type temperature degree relatively low, quality light cold fast glass fiber by 瞬間冻结, can and by melt separation 包围, outer 露而形 formed “ fiber exposure ”.

         therefore, “ fiber exposure ” phenomenon formed, not only and plastics material formed and features has 关, but also and molding processing process has 关, has relatively large complex property and 不确定 property.

         in production in, has various used for improvement “ fiber exposure ” phenomenon measures:

         comparison methods is in molding material in add compatibilizer, dispersant and lubricant and other additives, silicon coupling agent, maleic anhydride grafted compatibilizer, silicon ketone powder, acid type lubricant and Domestic or Imported anti glass fiber (GF) outer agent and other, through this additives glass fiber (GF) and resin between interface versus property, improve/increase dispersion versus and versus uniform property, increase interface bonding strong/high degree, decrease/reduce glass fiber (GF) and resin separation 离, from improvement glass fiber (GF) outer phenomenon;

         its in has use relatively good, is large more 价钱不菲, increase production cost, but also for material force property can has effect/influence, relatively commonly used liquid silicon coupling agent, in add rear difficult dispersion, plastics easy block formed issues, formed equipment material non-uniform, glass fiber (GF) content distribution non-uniform, 进而导致 products force property can non-uniform.

        近几 year has add short or glass beads methods, utilizing small dimensions short or glass beads tool has relatively good flow property and dispersion property, and resin between easy formed stability interface versus property features, achieve improvement “ fiber exposure ”目, especially is glass beads also can drop low shrinkage deformation rate, products rear warpage, increase material hardness and elastic property modulus, and price relatively low, 但不足之处 is make material impact resistant property can decline.

         solution methods

        1. mold system adjustment

         mold system and “ fiber exposure ” phenomenon formed related.

        针 for glass fiber reinforced plastics flow property 差, but also glass fiber (GF) and resin types separation flow property 不一致 features, its flow 距离不 can long, melt must fast speed type 腔, ensure glass fiber (GF) uniform dispersion, 不发生淤积 delamination formed “ fiber exposure ”.

         therefore system design basic is runner 截面宜 large, process/workflow 宜平直而 short. using/adopting coarse short runner, separation runner and coarse large gate, gate can is thin sheet/slice 式, and ring 形, can using/adopting more gate 形式, make material mixed 乱, glass fiber (GF) expand dispersion, decrease/reduce orientation property. but also requirements has good gas function, can and 时排出因 glass fiber (GF) surface treatment agent generate gas 体, 以免造 formed defect, material and and other defect.

         for/regarding 该 手面 cover/cap mold system, its relatively long runner process/workflow, is formed “ fiber exposure ” phenomenon heavy factors, this is mold structure need, can will its shrink short, therefore has for runner dimensions and gate and dimensions adjustment. gate is gate, gate and runner dimensions in mold trial process in add large.

         another need attention/notes is, “ fiber exposure ” easy in parts thick relatively large 部位出现, this is is melt in flow speed degree degree relatively large, melt flow its in speed degree high, 而靠近 type 腔壁面处 speed degree low, make glass fiber (GF) trend add 剧, versus for speed degree more slow, 发生滞留堆积而形 formed “ fiber exposure ”. therefore, amount make parts 各处壁 thick uniform, 并避免尖角, 缺口, ensure melt flow 顺畅.

        2. injection molding process conditions optimization

         made combined molding process conditions, for/regarding improvement “ fiber exposure ” phenomenon important. injection molding process elements for glass fiber reinforced plastics products effect/influence has different, lower 面就一 can basic separation 别进行 introduction:

         temperature degree

        ① 首先 is material temperature degree.

         due to glass fiber reinforced plastics melt flow index ratio non reinforcement plastics low 30%～70%, flow property relatively 差, therefore material temperature degree relatively generally 情况应 high 出10~30℃. improve/increase material temperature degree, can make melt viscosity reduce, improvement flow property, filling and defect, but also has add large glass fiber (GF) dispersion property and decrease small orientation property, obtain relatively low products surface coarse degree.

        但 material temperature degree is high good, temperature degree high add large nylon polymer oxidation and degradation trend, light micro 时会发生 color 变化, heavy generate 焦化发黑.

         in material temperature degree 时, make add material temperature degree ratio requirements high, low pressure shrink can, utilizing its preheating 效果, reduce screw for glass fiber (GF) generate function, decrease/reduce local viscosity and for glass fiber (GF) surface bad, ensure glass fiber (GF) and resin between adhesion strong/high degree. PA66+33%GF melt temperature degree is 275~280℃, most high temperature degree need ultra- 300℃, its material temperature degree can in scope/range inner 选取.

        ② its is mold temperature degree.

         mold and melt between temperature 差不宜太 large, anti melt 充填时 glass fiber (GF) cold in surface 淤积, formed “ fiber exposure ”, therefore using/adopting relatively high mold temperature degree, this for/regarding improve/increase melt property can, increase 熔接痕 strong/high degree, improvement products surface light degree, decrease/reduce orientation and deformation is has 利.

        但 mold temperature degree high, cooling time 愈久, molding cycle long, production rate reduce, but also molding shrinkage add large, 故也不 is high good. mold temperature degree 设置, also need resin product types, mold structure, glass fiber (GF) content and other 情况, in type complex, glass fiber (GF) content high, 充模困 difficult 时, mold temperature degree 应适当 improve/increase. for/regarding material is PA66+33%GF automotive cover/cap, selection mold temperature degree is 110℃.

         pressure

        ① injection pressure

         injection pressure for glass fiber reinforced plastics molding effect/influence very large, relatively high injection pressure has 利于充填, improve/increase glass fiber (GF) dispersion property, reduce products shrinkage rate, increase 剪切应 force and orientation, easy formed warpage deformation, demolding difficult, 甚至导致溢边 issues, therefore improvement “ fiber exposure ” phenomenon, in high non reinforcement plastics injection pressure upper, according to specific 情况适当 add large.

         injection pressure selection remove and products thick, gate dimensions and other factors has outer, and glass fiber (GF) content and has 关, generally glass fiber (GF) content high, glass fiber (GF) long degree long, injection pressure large.

        ② back pressure

         screw back pressure large small for/regarding glass fiber (GF) in melt in uniform dispersion, melt flow property, melt degree, products appearance quality and machine physical properties has important effect/influence, usually using/adopting high back pressure comparison has 利, has improvement “ fiber exposure ” phenomenon. high back pressure for long generate relatively large function, make melt easy hot degradation, 导致变 color and force property can 变差. therefore will back pressure ratio non reinforcement plastics high can.

         injection speed degree

         using/adopting relatively fast injection speed degree, can improvement “ fiber exposure ” phenomenon. improve/increase injection speed degree, make glass fiber reinforced plastics fast speed mold cavity, glass fiber (GF) flow direction as fast speed toward 运动, has increase glass fiber (GF) dispersion property, decrease/reduce orientation property, improve/increase 熔接痕 strong/high degree and products table/sheet light degree, need attention/notes 避免因 injection speed degree fast, in nozzle or gate 处发生"喷射" phenomenon, formed 蛇形纹 defect, effect/influence parts appearance.

         screw speed

         glass fiber reinforced plastics 塑化时, screw speed high, 避免摩 scratch force large for glass fiber (GF) formed 伤害, bad glass fiber (GF) surface interface 状态, reduce glass fiber and resin between bonding strong/high degree, add 剧“ fiber exposure ” phenomenon, especially is glass fiber (GF) relatively long 时, 会因部 separation glass fiber (GF) fracture 而出现 long short phenomenon, formed parts strong/high degree and other, products force property can unstable.

         process summary:

         through above analysis, can using/adopting high material temperature, high mold temperature, high pressure, high speed, low screw speed injection, for improvement “ fiber exposure ” phenomenon comparison has 利.