Shanghai Daoqin Plastics Co., Ltd.

 做 molding 手写笔 同事都知道, if use POM material injection molding, product surface 会出现 very more similar 流纹, gas marks, water and other this 样 东西, make is adjustment injection molding process parameters, appearance upper is very difficult 满意. if formed PC/ABS, ABS, PC 做, adjustment injection molding process parameters, can 以 to appearance very product.

is what causes 呢?

appearance 不漂亮 causes, main/primary is melt in 充填 时候不 is stability expand toward front expand 展, is has 扰动形 formed 乱流造 formed. melt can in 充填 时候形 formed stability expand 展流, remove and mold design, molding process has outer, also and melt hot material property has 关.

lower introduction lower plastics hot material property several related concept.

一, specific heat capacity

for/regarding injection molding 讲, can is is in pressure lower 进行, therefore can is is pressure specific heat capacity.

定 pressure specific heat capacity is mono quality material in pressure conditions lower, temperature degree rise high or decline 1℃ absorption or can amount.

specific to injection molding 讲, specific heat capacity large 就意味 plastics solid formed melt absorption hot amount more, melt cooling formed solid 体时放出 hot amount more.

二, hot rate

hot rate has 时也称“ thermal conductivity ”, is material thermally conductive can force amount degree, is types different between hot can force.

specific to injection molding 讲, is melt and mold surface hot 传递. hot rate high, melt toward mold hot fast, melt cooling speed degree fast.

三, hot expand dispersion 系数

hot expand dispersion is hot amount in material inner speed degree, is material internal temperature degree can force.

specific to injection molding 讲, is melt internal between different liquid between hot can force. hot expand dispersion large, melt table/sheet drop temperature rear, in 心层会即时 will hot amount to table/sheet 层, in temperature degree very fast reduce.

四, melt flow index

melt flow index is types table/sheet plastics material processing flow property value. it is USA amount standards 协会(ASTM) according to USA DuPont company use plastics features methods made formed, its testing methods is let plastics in time （10 separation 钟） inner, temperature degree and pressure （ various material standards different ） lower, melt formed plastics 流体, rear through 一直径 is 2.1mm圆 tube/pipe 流出 克（g）数. its value large, table/sheet plastics material processing flow property 越佳, 反之则越差. （回复“ testing ”）

through upper introduction, lower comparison POM, ABS, PC, PA66四 types material thermal properties parameters. PC/ABS因没 has to related parameters, has as comparison, 但应该 is 处于ABS and PC between.

through comparison, 就会发现:

1, POM specific heat capacity large, cooling 时释放 hot amount more, this is injection molding POM material mold and product temperature degree high, causes.

2, POM thermally conductive rate and hot expand dispersion 系数都 low. hot rate low table/sheet 明POM melt and mold surface hot speed degree slow, 冻结层 relatively thin. hot expand dispersion low table/sheet melt internal hot amount can force 差, make is surface melt temperature degree reduce, can very fast in melt temperature degree reduce, in melt still relatively high temperature degree and relatively good flow property. melt in 充填 时候, very easy breakthrough thin table/sheet 皮层, formed 乱流.

3, POM melt flow index. although table/sheet in to is scope/range, melt flow index high low and molecular weight large small has 关. generally production 手写笔 this type of requirements high product, selection price low, molecular weight low material, therefore melt flow index versus for relatively high, POM tool has relatively high flow property.

this types comprehensive performance, is use POM material injection molding 手写笔时, difficult 以稳态 filling, easy 出现扰动, 乱流, therefore difficult injection molding 出漂亮 appearance

mold design 时候, gate need amount design large, 避免形 formed 喷射流. injection molding process adjustment 时候, 应该尽 amount reduce speed degree, formed filling. injection molding machine in low speed lower stability property good, injection speed degree low screw front 进时会出现颤抖, therefore melt 会出现振动 generate 震纹, has 时反而不如充填 speed degree fast appearance good.

through upper analysis can 看出, POM material material injection molding 手写笔时 difficult obtain combined appearance, use PC/ABS, PC, ABS material very easy through process adjustment to, is is this types material thermal properties good versus 反, specific heat capacity large, hot rate and hot expand dispersion high, melt flow index low, melt filling can obtain flow 缘故.

PA66 and POM tool has more property 质, difficult obtain comparison good appearance, 也一并列出 its parameters, can analysis comparison.