Shanghai Daoqin Plastics Co., Ltd.

 一, injection molding

TPU most processing 手段莫 于 screw type injection molding machine 械. use usually long degree mono 螺纹, screw can production very good uniform melt material. if need high can force （ production amount ）, can use relatively long screw (图1.1).

图 1 processing TPU injection molding screw

short pressure shrink screw due to high force suitable. TPU need high can amount, requirements screw has high 扭矩驱动. 扭矩不足会导致 screw speed and non-uniform.

in degree inner, relatively high temperature degree generate good 结果, tube/pipe 会冒材 material hot 危险. and 螺筒头 通路应 design formed has 死角, make material can 够射入而不致受 to hot bad. and add hot system temperature degree control is key points. attention/notes ensure in long degree uniform hot. anti in upper material local hot and can can cold. melt TPU is 即无腐蚀 property abrasion loss type. this 里理由, screw 不需任何特殊 alloy or add strong/high plating.

图 2 换档手柄 injection molding

二, and mold temperature degree setting

1. injection mono 元

TPU in 190 to 220 °C between melt temperature degree lower processing. for/regarding hard grade melt temperature degree can can improve/increase to 240°C. specific grade 别TPU melt temperature degree scope/range in related product table/sheet in can to. 图 2.1 示 is different Shore hardness lower for and add hot setting value.

图 3 different hardness temperature degree setting

2. mold

mold temperature degree main/primary effect/influence in surface quality and demolding is. effect/influence most structure shrinkage and internal stress （受 cold 时）. positive mold temperature degree application 20 - 40 °C. use 一 改良 TPU grade and use filament filling add strong/high TPU, mold temperature degree improve/increase to 60 °C以 ensure most surface quality. for/regarding thick material product cooling, reduce large 约5 °C can decrease/reduce ring cycle time.

3. 塑化

for/regarding speed degree selection speed rate ultra- 0.3 m/s. amount 行程应 in 1 D and 4 D between. lower 图 示 is different screw lower most large speed degree.

图4 screw speed degree and screw 直径 函数关系

实际 experience is utilizing 螺筒 30 - 75% can force is most 佳. if can force for injection amount non low, melt material in mono 元停留太 long time. 会导致熔 melt material hot loss bad.

图 5TPU熔 melt material in processing in separation understanding

4. injection pressure, maintain pressure, back pressure force, injection speed degree

for/regarding processing, key points is for pressure and injection speed degree 不间断 control. its can control injection and maintain pressure in 100 to 1200 bar scope/range inner.

is 均化必 must has back pressure force, usually setting in injection pressure 1 to 2.5% between. injection speed degree main/primary 基于壁 thick. usually for/regarding thick material product mold need slow filling, thin material product need fast filling. for/regarding injection speed degree remove thick and type type, mold gas important color, its has 助于避免 high pressure hot gas 导致 谓“烧痕”.

injection pressure / maintain pressure add relatively large effect/influence is in stability property and demolding property. molding high injection pressure, meanwhile low maintain pressure generate 凹痕. molding ultra- 载 demolding more difficult. use pressure as is can 取, use ratio injection pressure relatively low maintain pressure. 按规则, injection pressure 50% maintain pressure is 适当. this can use most small internal pressure production material product.

图 6 TPU processing type ring steps

5.循 ring time

决定循 ring time is material product 形状, thick, mold cooling and material 本身. lower 图 示 is thick for injection ring cycle effect/influence, TPU amount is grade 别: hard, in and other, soft.

图7 循 ring time for thick and hardness 关系

6. demolding

TPU made mold need detailed 叙述. soft grade TPU very 奇特, its can generate generally material product. this must in design mold is 通盘考虑. demolding can use demolding agent. silicon demolding agent 如Baysilon M 效果良 good. silicon demolding agent can, must frequency use.

三, waste material ring

waste material, gate, combined product and other made formed powder material if and drying can made formed pellets recycled utilizing. for/regarding injection molding, in pure material in add to 30% powder material effect/influence product property can. if processing powder material, molding material product must requirements testing can meet/satisfy property can requirements. for/regarding extrusion pure material in mixed and powder material is 不适当 (因 is viscosity different). if is pure powder material used for extrusion, is for can, used for injection molding is full can.

四, mold design / outer structure

1. injection molding tool

TPU mold using/adopting types used for hot molding manufacturing. simple small type product toward using/adopting aluminum alloy manufacturing. for/regarding parts mold can positive use 插入铸造 resin or pressure metal. lower mold type type can processing TPU:

• sheet/slice mold

• sheet/slice mold

• di mold

• full pressure mold

• more mold

2. gate

TPU usually use below/following type type gate:

• film gate

• film gate

• gate

• ring gate

• gate

• 隧道式浇

• hot gate

for/regarding gate, and 注道应 ratio hard plastics large 25 - 50% (图4.1). in gate system especially pressure decline.

图8 注道衬 sleeve/set design

浇道越远越应 attention/notes, 流路必 must design formed full use 整 一 浇道直径, and its in or semi mold upper (图 4.2). in more mold upper, sheet/slice or sheet/slice type, 浇道应布置 formed basic is same long degree (图 4.3).

图9 浇道截面

图 10 more mold 浇道

针点 gate must has low in gate 截面以 ensure dry 净 撕掉. large gate must in parts upper belt/tape 任何喷射 or its it pressure 痕发生. for/regarding toward for parts, can can use ring or film gate more good anti formed 流线. mold filling and gas must maintain in control lower. (图 4.4).

图11 gate 形式

图12 "衣架式" film gate

if 浇注点 is to, 隧道式 gate is most solutions. (图 4.6).

3. hot technology and hot 浇道射嘴

hot 浇道喂 material system combined thermoplastic property plastics 越 越流行. TPU也同样, this technology by anti using/adopting. 图4.7 列出 this methods main/primary 规则.

图13 hot system requirements

4.例 1: gate 开放射嘴

（1）不 use plastics 隔离帽 开放射嘴

processing TPU不 commonly used, is hot separation good, 导致 "眼圈", light 晕, viscous and material 滴流.

图14 不 use plastics 隔离帽 开放射嘴

（2） use plastics 隔离帽 开放 射嘴

隔离帽 and cooling system relatively good hot separation 离(图 4.9).

图15 use plastics 隔离帽 开放 射嘴

（3） use 鱼雷头 开放射嘴

狭 narrow ring 形缝隙导致 large force. generally 不适于TPU (图4.10).

图16 belt/tape 鱼雷头 开放射嘴

5. 【例 2】 belt/tape gate 开放射嘴

this system is main/primary used for large type mold （ mono / more 模穴）. specific has is pressure loss low and hot separation good (图4.11).

图17 belt/tape gate 开放射嘴

6.【例 3】 belt/tape 针阀 射嘴

清洁 浇注点 can 直接放置 in parts upper. this system performance has hot and low pressure loss 失(图4.12).

图18 belt/tape 针阀 射嘴

7. mold flow features

TPU flow is basic and its it thermoplastic property material same. runner 动路径 long degree 决定于 melt temperature degree, filling parts thick, injection speed degree and material 流变学 features. according to equipment and technology conditions injection speed degree various 各样. lower 图 示 is TPU flow and melt temperature degree 关系.

图19 flow long degree and melt temperature degree 关系

8. mold gas

especially for/regarding TPU thick parts, important is good 模穴排 gas. in separation upper 0.02 to 0.05mm deep degree and 5mm wide degree 凹槽认 is combined (图4.14). if certain non mold separation 模线区域空 gas by pressure shrink through use and use combined 适 办 method 插入适当排 gas is can 行.

图20 排 gas 开槽示意图

9. shrinkage

for/regarding thermoplastic polyurethane (TPU) its can in mold design stage/phase material product outer in 一定限 degree inner shrinkage data, its thick and processing conditions for shrinkage generate heavy large effect/influence. mold design large 致规则 setting shrinkage large 约1%. need 差别靠良 good elastic property 形变抵消. use soft grade TPU and thin material product ratio use hard grade TPU and relatively large thick material product rear shrinkage is large. 图4.15 to in 整 区域 full shrinkage 状况.

图21 TPU shrinkage scope/range comparison

10. demolding

(1) surface

一 mold surface coarse degree to 0.5 - 0.6 μm decrease/reduce demolding and TPU additives 喷出. demolding force is use its it coarse degree or coating material in most small comparison 而言.

(2) demolding degree

mold degree less is 5°, use soft grade 别TPU manufacturing relatively obvious. 交错 锥 degree improvement from upper 脱开(图4.16).

图22 demolding degree

(3) ejection plant/unit

for/regarding TPU, ejection plant/unit surface amount large, 以避免 formed product material parts deformation (图4.17).

图23 ejection plant/unit

TPU high elastic force 允许底部 demolding and in material product. made molding can use pressure shrink gas made (图4.18).

图24 blow molding

11. color

TPU generally provide natural color. color is simple process and can use machine 处理. use TPU masterbatch pellets is simple also can 靠. polystyrene (PS) and SAN resin masterbatch strong/high can, that polyolefin and PVC for/regarding TPU is combined 适. material and color can used for color. need add amount 决定于 material product thick, material color concentrated degree and color degree. generally add amount is: color masterbatch: 1.0 -4.0 % color 浆: 0.5 -1.0 % 颜 material: 0.2 -0.5 % can utilizing standards 商业装备 in use TPU时添 add and mixed combined color agent. for/regarding color can use mixed combined machine or use mixed combined machine and other similar plant/unit. ensure color agent or its it additives 不含任何 water separation is non important. types mixed combined device toward large improvement color dispersion and decrease/reduce color agent use amount.

12. additives

is improvement processing features and 特殊行 is, recommendation add commonly used functional masterbatch 如:

• resistant viscous agent

• demolding made

• outer light stabilizer

add front must drying.