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PVC塑料注塑成型工藝過(guò)程分析

pvc也叫做硬PVC，它主要是氯乙烯單體經(jīng)過(guò)聚合反應(yīng)之后而做成的一種無(wú)定形熱塑性樹(shù)脂，在通過(guò)添加一定的添加劑，例如穩(wěn)定劑、潤(rùn)滑劑、填充劑等組合而成的一種產(chǎn)品。

除了用添加劑之外，還采用了與其它樹(shù)脂進(jìn)行共混改性的相關(guān)辦法，使它更加具有明顯的實(shí)用價(jià)值。這些樹(shù)脂有CPVC、PE、abs、EVA、MBS等。

UPVC的熔體粘度較高，流動(dòng)性較差，即使提高注射壓力以及熔體溫度，流動(dòng)性的變化也較小大。此外，樹(shù)脂的成型溫度與熱分解溫度非常接近，可以進(jìn)行成型的溫度范圍較窄，它是一種比較難于成型的材料。

1、塑料的處理

處于室溫24小時(shí)之后，吸水量如果是少于0.02%的話(huà)，就會(huì)形成無(wú)須烘干的情況。如過(guò)必須要進(jìn)行干燥處理，可以放到60-70℃的熱氣爐3小時(shí)，或著80℃的干燥機(jī)大概1-1.5小時(shí)。

回收料最多可以用20%與新料進(jìn)行混合，回收料的用量要看制品的最終用途而確定。濫用回收料可能會(huì)導(dǎo)致注塑工作失敗，不單是回收了的成分過(guò)多，更多的原因是因?yàn)槲锪辖?jīng)過(guò)多次再加工處理。回收料每多回收一次質(zhì)量會(huì)出現(xiàn)逐漸下降的狀況。

2、注塑機(jī)選用

UPVC因?yàn)槿垠w粘度較較大、所以分解較為容易，分解產(chǎn)物對(duì)于鐵有著較大的腐蝕作用，其注塑成型必須要用專(zhuān)用的塑化部件和溫控系統(tǒng)。

華美達(dá)在產(chǎn)品覆蓋的每一種鎖模力型號(hào)，都有專(zhuān)門(mén)的UPVC塑化注射系統(tǒng)，并配合UPVC管件產(chǎn)品抽芯的要求備有專(zhuān)用的安全門(mén)裝置。一般情況下只要注射量可以滿(mǎn)足重量要求，選用這一系列UPVC專(zhuān)用注塑裝置可以成型出高質(zhì)量的產(chǎn)品。

3、模具及澆口設(shè)計(jì)

模具溫度可以設(shè)置為40℃。而且流道整個(gè)長(zhǎng)度一定要短，直徑則要比較大，用來(lái)逐漸減小壓力損失以及保壓能傳遞到模腔。澆口越短越好，模切面一定要圓形，射嘴口的直徑最小是6mm，成圓錐形，內(nèi)角成5。

主流道的模切面也要圓形，與冷料井組合而成，通過(guò)切面半徑連接主流道和澆口，直徑可為7mm。

澆口應(yīng)用切圓面形的半徑連接塑件，越短越好，模切面要順滑。

冷料井可防止半凝固的物料進(jìn)入模腔，它的重要性常被忽略。

澆口的位置要正確，使物料在流道上順利流動(dòng)，不會(huì)停留在尖角、碎片和金屬的痕跡里，以免出現(xiàn)壓縮或減壓的情況，應(yīng)保持流道順滑流暢。

模具應(yīng)用不銹鋼鑄造，鉻的含量至少13%，最好16%，洛氏硬度至少有55，硬鋼模具可經(jīng)鍍鉻處理，形成保護(hù)作用。

生產(chǎn)完后，應(yīng)用溫和的堿液小心將模面清洗干凈后再?lài)娚嫌唾|(zhì)噴霧或硅質(zhì)噴霧。

4、熔膠溫度

可用空射法度量，由185-205℃不等。從射出的物料光滑程度可得知UPVC的準(zhǔn)確熔膠溫度。如物料在射出后粗糙不平，就證明物料并非均一(塑化不足)，表示所定的溫度太低;如射出后起泡沫并冒出大量煙霧，就表示溫度過(guò)高。

5、注射速度

射速要慢，否則過(guò)分剪切會(huì)使物料降質(zhì)，利用UPVC生產(chǎn)極度光滑的厚壁制品時(shí)，應(yīng)采用多級(jí)注塑模具填充速度。

6、螺桿轉(zhuǎn)速

應(yīng)該進(jìn)一步配合模塑周期而確定螺桿轉(zhuǎn)速。螺桿面速度不要超過(guò)0.15-0.2m/s

7、背壓

背壓可以達(dá)到150bar，當(dāng)然數(shù)據(jù)是越低越好，常見(jiàn)的數(shù)值是5bar。

8、滯留時(shí)間

在200℃的溫度之下，機(jī)筒滯留時(shí)間大多不能超過(guò)5分鐘。當(dāng)溫度是210℃，機(jī)筒滯留時(shí)間就不可以超過(guò)3分鐘。

以上就是UPVC塑料原料的注射成型工藝分析匯總，提醒大家的是在注射速度以及背壓方面需要的別注意。

部分型號(hào)部分物性表

EVA (ethylene vinyl acetate copolymer #) /2020/ Brazil Braskem
Use: Film
Feature notes: luster, high, excellent printability, oxidation resistance, weldability, good surface finish, clarity, high, thermal stability, good quality.
Important parameters: melt flow rate: 2 g/10min density: 0.931 g/cm3 tensile strength: 19 MPa breaking elongation: 700% hardness: 93 VEKA softening point: 79 C
Manufacturer: Brazil chemical company
EVA (ethylene vinyl acetate copolymer #) /PA-420-L/ Repsol of Spain
Use: other
Characteristic notes: low speed freezing point, antioxidation, and compliance of food contact
Important parameters: melt flow rate: 20 g/10min density: 0.94 g/cm3 hardness: 30 VEKA softening point: 53 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer # polyolefin /H2181/ Singapore)
Use: foaming
Characteristic notes: characteristics: excellent processability, toughness, elasticity, crack strength and low temperature endurance
Important parameters: melt flow rate: 2 g/10min density: 0.94 g/cm3, tensile strength: 29 MPa, elongation at break: 800% flexural strength: 49 MPa, embrittlement temperature: -75 C, filler content: 18%.
Manufacturer: Singapore polyolefin Private Companies
EVA (ethylene vinyl acetate copolymer #) /E168L/ Han Hua Total
Application: coating
Characteristic notes: spinnability (glass fiber) bonding, transparency Neck In
Important parameters: melt flow rate: 20 g/10min density: 0.936 g/cm3, tensile strength: 12 MPa, elongation at break: 750% hardness: 38 VEKA softening point: 65 C embrittlement temperature: -70 C.
Manufacturer: Han Hua Total Ltd.
EVA (ethylene vinyl acetate copolymer # polyolefin /H2020/ Singapore)
Use: other
Feature notes: good processing performance, good environmental stress and low temperature resistance.
Important parameters: melt flow rate: 1.5 g/10min density: 0.93 g/cm3 tensile strength: 21.6 MPa fracture elongation: 800% hardness: 58.8 embrittlement temperature: -75 C
Manufacturer: Singapore polyolefin Private Companies
EVA (ethylene vinyl acetate copolymer #) /CA-3720A/ Repsol of Spain
Use: Film
Feature notes: stabilizers (colorless), ultraviolet absorbents and antioxidants
Important parameters: melt flow rate: 0.4 g/10min density: 0.949 g/cm3 tensile strength: 23 MPa breaking elongation: 650%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /CA-1400G/ Repsol of Spain
Use: Film
Feature notes: stable antioxidants. High transparency and antifogging effect of composite films
Important parameters: melt flow rate: 0.8 g/10min density: 0.937 g/cm3 tensile strength: 23 MPa breaking elongation: 500%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /PA-524/ Repsol of Spain
Use: Film
Feature remark: excellent environmental pressure and crack resistance. Antioxidant additives contained
Important parameters: melt flow rate: 0.4 g/10min density: 0.925 g/cm3 tensile strength: 17 MPa breaking elongation: 630% hardness: 45 VEKA softening point: 80 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer # /UE672006/ Leander Basil)
Use: other
Characteristic notes: good elasticity, good heat seal, good impact resistance, excellent toughness
Important parameters: melt flow rate: 0.45 g/10min tensile strength: 29.8 MPa fracture elongation: 600% VEKA softening point: 80 C embrittlement temperature: -76 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer # /UE672317/ Leander Basil)
Use: other
Characteristic notes: good elasticity, good heat seal, good impact resistance, excellent toughness
Important parameters: melt flow rate: 0.45 g/10min tensile strength: 29.8 MPa fracture elongation: 600% VEKA softening point: 80 C embrittlement temperature: -76 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer #) /7310M/ Taiwan chemical fiber
Use: other
Characteristic notes: copolymer, processability, good, cross linkable, good flexibility, good chemical resistance
Important parameters: melt flow rate: 2.5 g/10min density: 0.928 g/cm3, tensile strength: 14.7 MPa elongation at break: 700% bending modulus: 35.3 MPa hardness: 47 VEKA softening point: 90 C embrittlement temperature: -70 C
Manufacturer: Taiwan chemical fiber Limited by Share Ltd
EVA (ethylene vinyl acetate copolymer #) /CN8092/ Brazil Braskem
Use: Film
Characteristic notes: moistureproof, antioxidation, good processability, good sensory characteristics, good adhesion, good thermal stability, halogen-free, low hardness
Important parameters: melt flow rate: 8.5 g/10min density: 0.934 g/cm3 fracture elongation: 720% hardness: 44 VEKA softening point: 62 C
Manufacturer: Brazil chemical company
EVA (ethylene vinyl acetate copolymer #) /HMP-366/ Ravago
Use: other
Characteristic notes: the copolymer has good flexibility, good flexibility, low temperature resistance and good climate impact resistance.
Important parameters: melt flow rate: 9 g/10min density: 0.93 g/cm3 tensile strength: 11.7 MPa flexural modulus: 95.1 MPa thermal deformation temperature: 37 C
Manufacturer: Ravago American company
EVA (ethylene vinyl acetate copolymer #) /H H6410M/ Japan Dong Cao
Use: wire and cable material
Feature notes: good stickiness, solubility, and good weather resistance.
Important parameters: density: 0.95 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer #) /PA-569/ Repsol of Spain
Use: Profile
Characteristic notes: high molecular weight, antioxidation, good processability, compliance of food contact
Important parameters