Shanghai Daoqin Plastics Co., Ltd.

         in engineering plastics development process in, usually through add glass fiber (GF) increase material strong/high degree. add glass fiber not only can improve/increase plastics products modulus, meanwhile can improves plastics products heat resistant temperature degree.

        但 in glass fiber reinforced nylon injection molding process in, “ fiber exposure ” phenomenon 经常出现. 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 plastics parts surface formed 放射状 white 痕迹, plastics 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, glass fiber and material specific gravity 差异

         in plastics melt flow process in, due to glass fiber (GF) and resin flow property has 差异, but also 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, glass fiber and resin versus property 差

         plastics melt in flow process in to screw, nozzle, runner and gate scratch 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, “喷泉”效应

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

        由此 can 见, 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.

         glass fiber reinforced plastics as is use electrical appliances, automotive parts and other important outer trim parts 之一, not only requirements has relatively high flame retardant, strong/high degree, hardness, impact resistant property and wear resistance, but also appearance requirements very high, surface 不允许 has gas marks, water 花, 凹陷, fiber exposure, and other defect. that 么, how to solution “ fiber exposure ” phenomenon 呢?

        传统 methods is in molding material in add increase agent, dispersant, lubricant and anti glass fiber (GF) outer agent and other additives glass fiber (GF) and resin between interface versus property, improve/increase dispersion versus and versus uniform property, increase interface adhesion strong/high degree, decrease/reduce glass fiber (GF) and resin separation 离, from improvement fiber exposure phenomenon. this additives large more price 不菲, not only increase production cost, but also for material force property can has effect/influence. year has add short or glass beads methods, utilizing small dimensions short or glass beads tool has relatively good flow property and dispersion property features, achieve improvement fiber exposure 目, 但不足之处 is make material impact property can decline.

        事实 upper, solution “ fiber exposure ” issues also can through molding process improvement fiber exposure phenomenon. combined molding process conditions, for/regarding improvement fiber exposure phenomenon important. injection molding process elements for glass fiber reinforced plastics products effect/influence same, lower 面进行 simple introduction.

         temperature degree

        首先 is material temperature degree. due to glass fiber reinforced plastics melt flow rate 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. attention/notes: material temperature degree is high good, temperature degree high add large 基体材 material 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.

         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 淤积而形 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 coarse degree, decrease small orientation and deformation is has 利. 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 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.

         pressure

         injection molding pressure for glass fiber reinforced plastics molding effect/influence very large, relatively high injection molding 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 molding pressure upper add large. injection molding pressure selection remove and products thick, gate dimensions and other factors has outer, also and glass fiber (GF) content and has 关, generally glass fiber (GF) content high, glass fiber (GF) long degree long, injection molding pressure large. screw back pressure for/regarding glass fiber (GF) in melt in uniform dispersion, melt flow property, melt degree, products appearance quality and material force property can has important effect/influence, usually high back pressure has improvement fiber exposure phenomenon. high back pressure for long glass fiber (GF) generate relatively large function, make melt easy hot degradation, 导致变 color and force property can 变差.

         injection speed rate

         using/adopting relatively fast injection speed rate can improvement fiber exposure phenomenon. this is is improve/increase injection speed rate, can 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 small orientation property, improve/increase 熔接痕 strong/high degree and reduce products surface coarse degree. need attention/notes 避免因 injection speed rate fast in nozzle or gate 处发生“喷射” phenomenon, formed 蛇形纹 defect, effect/influence plastics parts appearance.

         screw speed

         glass fiber reinforced plastics 塑化时, screw speed high, 以避免摩 scratch force large for glass fiber (GF) formed 伤害, bad glass fiber (GF) surface 状态, reduce glass fiber (GF) and resin between adhesion strong/high degree, add 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 plastics parts strong/high degree and other, force property can unstable.

         through above analysis can 知, using/adopting high material temperature, high mold temperature, high pressure, high injection speed rate, low screw speed injection, for improvement fiber exposure phenomenon comparison has 利. in addition also need attention/notes raw materials drying and products wet 处理. 举 例子 说, PA66 吸 wet property large, but also has water property, add hot melt in has micro amount water separation make its degradation, will heavy effect/influence products appearance and property can, therefore in molding front must dry water separation.