Shanghai Daoqin Plastics Co., Ltd.

long fiber reinforcement thermoplastic property plastics （LFRT） positive in by used for high mechanical properties injection molding application. although LFRT technology can provide good strong/high degree, rigid degree and impact property can, this type of material processing methods for/regarding most rear parts can to how to property can important function.

is formed molding LFRT, for it 们一 独 has features understanding separation necessary. understanding LFRT and reinforcement thermoplastic property plastics between 差异推动 equipment, design and processing technology development, 以发挥LFRT most large value and force.

LFRT and short 切, short glass fiber reinforcement composite/compounding material difference in fiber long degree. in LFRT in, fiber long degree and material long degree same. this is due to large more 数LFRT is through molding process is type mixed production.

in LFRT manufacturing in, glass fiber coarse 纱 连续 filament by 拉入一 模头 in coating and resin, from 模头出 rear, this type of reinforcement plastics strip/profile by short or pelletizing, usually 切至10~12mm long degree. versus ratio lower, short glass fiber (GF) composite/compounding material long 3~4mm short fiber, in type extrusion machine in its long degree 会进一步 decrease/reduce usually 2mm不 to.

LFRT粒 material in fiber long degree has 助于改进LFRT mechanical properties —— impact resistant property or tough property increase, meanwhile maintain rigid degree. need fiber in molding process in maintain long degree, it 们就会形 formed 一 “ internal skeleton/framework ”, provide ultra-high mechanical properties. however, 一 糟糕 molding process long fiber product formed short fiber material. if fiber long degree in molding process in to loss 害, can can obtain need property can water 平.  

is in LFRT molding process in maintain fiber long degree, has important need 考虑: injection molding machine, parts and mold design and processing conditions.

一, equipment precautions

经常 by to has 关LFRT processing issues is: is has can can utilizing has injection molding equipment molding this material. in large more 数 情况 lower, used for molding short fiber composite/compounding material equipment can used for molding LFRT. although type short fiber molding equipment for/regarding large more LFRT部 parts and product is meet/satisfy requirements, for equipment renovation can more good maintain fiber long degree.

一根 tool has type “进 material — pressure shrink —计 amount ”段 general purpose screw non suitable for process, but also through reduce amount pressure shrink ratio can decrease/reduce fiber bad property 剪切. large is 2:1 计 amount pressure shrink ratio for/regarding LFRT product is most 佳. use metal alloy manufacturing screw, machine and other parts has necessary, is LFRT abrasion loss has short glass fiber reinforcement thermoplastic property plastics large.

另一 parts can can from design in equipment is nozzle 尖梢. thermoplastic property material use types toward nozzle processing more easy, it can in material to mold type in formed types high degree 剪切. however this type of nozzle 尖梢会 significantly reduce long fiber composite/compounding material fiber long degree. therefore recommendation use types 100%“自由 flow ” design nozzle 尖梢/阀组 parts, it make long fiber easy through nozzle 进入部 parts in.

in addition, nozzle and gate 孔 直径应该 has 5.5mm（0.250in） or above wide dimensions, and has 锋利 边缘. important is need understanding material material how to injection molding equipment, 并确定剪切会 make fiber 破碎 方.

图: using/adopting “100%自由 flow ” design parts screw and ring 形阀, can most large degree decrease/reduce long fiber fracture

二, parts and mold design

good parts and mold design for maintain LFRT fiber long degree large has 裨益. remove separation 边缘（包括肋线, and other 特征）周围 尖角, can molding parts in necessary force, decrease/reduce fiber abrasion loss.

部 parts using/adopting thick uniform 一致 标称壁 design. thick upper relatively large 变化会导致部 parts in 不一致 filling and need fiber orientation. in must relatively thick or relatively thin 方, need 避免壁 thick 突然变化, 以避免形 formed can can loss bad fiber high 剪切区域, formed is force in 源头. usually gate in relatively thick in, toward thin separation, make filling maintain in thin separation.

general purpose good plastics design 原则建议, maintain thick low 于4mm（0.160in） will promote good uniform flow decrease/reduce and can can property. for/regarding LFRT composite/compounding material, most 佳 壁 thick usually is 3mm（0.120in） left right, most small thick degree is 2mm（0.080in）. thick small 于2mm时, material in mold rear its fiber fracture rate increase.

部 parts is design in 一 方面, 考虑材 material how to mold very important. runner and gate material material type 腔时, if has positive design, a large amount of fiber bad 会发生 in this in.  

当 design molding LFRT composite/compounding material mold 时, full runner is most 佳, it most small is 5.5mm（0.250in）. remove full runner, other runner has 尖角, it in molding process in increase force bad glass fiber reinforcement 效果. tool has 开放浇道 hot runner system is can 接受.  

gate most small thick degree has 2mm（0.080in）. if can can 话, 沿 一 strip/profile retardant material material type 腔 边缘定位 gate. parts surface gate will need 进行90° 转动, anti 止引发 fiber fracture reduce mechanical properties.  

most rear, need attention/notes combined 线 位置, 并知道 it how to effect/influence parts use 时承受载荷（ or force ） 区域. through gate combined 理布局 will combined 线移至应 force water expected relatively low 区域.  

计算 machine analysis can 帮助确定 this combined will 定位 方. structure has analysis （FEA） can use comparison high force and in analysis in 确定 汇 combined 线位置.  

应该指出 is, this parts and mold design is 建议. has very more parts 例子, it tool has thin 壁, thick and or fine 特征, utilizing LFRT composite/compounding material achieve good property can. however, this 建议越远, need more more time and force ensure achieve long fiber technology full benefits.

三, processing conditions

processing conditions is LFRT formed key/critical. need using/adopting positive processing conditions, has can can use general purpose injection molding machine and positive design mold made good LFRT部 parts. 换句话说, make has equipment and mold design, if using/adopting relatively processing conditions, fiber long degree can can loss. this need understanding fiber in molding process will to 情况, and 确定会引起 fiber degree 剪切 区域.

首先, need back pressure. high back pressure for material material generate large force, will reduce fiber long degree. from back pressure and make it increase make screw in material process in uniform 退回, using/adopting 1.5~2.5bar（20~50psi） back pressure usually obtain 一致 喂 material.  

high screw speed has effect/influence. screw 旋转越 fast, solid and 未熔材 material can can screw pressure shrink formed fiber loss 伤. similar for back pressure 建议, amount maintain speed in stability filling screw requirements most low water 平. in molding LFRT composite/compounding material 时, 30~70r/min screw speed degree is Common.  

in injection molding process in, melt through 两 共同 function factors 发生: and hot. is is in LFRT in through decrease/reduce 剪切 保护 fiber long degree, therefore will need more more hot amount. according to resin system, processing LFRT composite/compounding material temperature degree usually ratio molding composite/compounding material high 10~30℃.

however, in simple comprehensive improve/increase machine temperature degree front, need attention/notes machine temperature degree distribution 反置. usually lower, material material from material 斗移动 to nozzle 时, machine temperature degree upper rise; for/regarding LFRT, recommendation in material temperature degree more high. temperature degree distribution make LFRT粒 material in high screw pressure shrink front soft and 熔化, from has fiber long degree maintain.  

has processing most rear attention/notes and use material utilizing. abrasion molding parts or water usually 会导致 more low fiber long degree, therefore, use material add effect/influence overall fiber long degree. is obvious reduce force property can, 建议回 use material most large use amount is 5%. more high use material use amount for impact strong/high degree and other force property can generate negative effect/influence.