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PVC塑料注塑成型工藝過程分析

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

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

UPVC的熔體粘度較高，流動性較差，即使提高注射壓力以及熔體溫度，流動性的變化也較小大。此外，樹脂的成型溫度與熱分解溫度非常接近，可以進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小時之后，吸水量如果是少于0.02%的話，就會形成無須烘干的情況。如過必須要進行干燥處理，可以放到60-70℃的熱氣爐3小時，或著80℃的干燥機大概1-1.5小時。

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

2、注塑機選用

UPVC因為熔體粘度較較大、所以分解較為容易，分解產(chǎn)物對于鐵有著較大的腐蝕作用，其注塑成型必須要用專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，都有專門的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用的安全門裝置。一般情況下只要注射量可以滿足重量要求，選用這一系列UPVC專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

模具溫度可以設(shè)置為40℃。而且流道整個長度一定要短，直徑則要比較大，用來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，不會停留在尖角、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噴上油質(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，就表示溫度過高。

5、注射速度

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

6、螺桿轉(zhuǎn)速

應(yīng)該進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，常見的數(shù)值是5bar。

8、滯留時間

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

部分型號部分物性表

EVA (ethylene vinyl acetate copolymer #) /E180F/ Han Hua Total
Use: foaming
Feature remark: characteristics: good mechanical strength.
Important parameters: melt flow rate: 2 g/10min tensile strength: 28 MPa elongation at break: 800% flexural strength: 49 MPa hardness: 38 VEKA softening point: 64 temperature embrittlement temperature: -70 C, filling content: 18%
Manufacturer: Han Hua Total Ltd.
EVA (ethylene vinyl acetate copolymer #) /1316/ Korea China
Use: foaming
Characteristic notes: excellent foaming forming characteristics, excellent mechanical properties, and excellent elastic properties of sponges
Important parameters: melt flow rate: 1.8 g/10min density: 0.94 g/cm3, tensile strength: 13 MPa, elongation at break: 850% hardness: 90 VEKA softening point: 59 temperature embrittlement temperature: -76 C, filler content: 18%
Manufacturer: Korea Hwa comprehensive chemical company
EVA (ethylene vinyl acetate copolymer #) /7140F/ Taiwan plastic
Use: other
Characteristic notes: characteristics: high toughness, high optics, no BHT.
Important parameters: melt flow rate: 0.7 g/10min density: 0.934 g/cm3, tensile strength: 19 MPa, elongation at break: 600% bending modulus: 22 MPa hardness: 92 VEKA softening point: 75 C, embrittlement temperature: -70 C, filler content: 14%.
Manufacturer: Limited by Share Ltd of Taiwan plastic industry
EVA (ethylene vinyl acetate copolymer #) /7350F/ Taiwan plastic
Use: other
Characteristic notes: characteristics: high toughness, high optics, no BHT.
Important parameters: melt flow rate: 1.8 g/10min density: 0.938 g/cm3, tensile strength: 14 MPa, elongation at break: 600% bending modulus: 39 MPa hardness: 88 VEKA softening point: 60 C, embrittlement temperature: -70 C, filler content: 18%.
Manufacturer: Limited by Share Ltd of Taiwan plastic industry
EVA (ethylene vinyl acetate copolymer #) /1501/ America flintcomb ash
Use: Film
Feature notes: excellent impact strength, good heat seal and good clarity.
Important parameters: melt flow rate: 0.5 g/10min density: 0.927 g/cm3 tensile strength: 17 MPa breaking elongation: 750% hardness: 47 VEKA softening point: 87 C
Manufacturer: American flint Hill resources
EVA (ethylene vinyl acetate copolymer #) /1651/ America flintcomb ash
Use: Film
Characteristic notes: excellent low temperature strength, good clarity and good thermal seal
Important parameters: melt flow rate: 0.5 g/10min density: 0.93 g/cm3 tensile strength: 19 MPa breaking elongation: 910% hardness: 45 VEKA softening point: 84 C
Manufacturer: American flint Hill resources
EVA (ethylene vinyl acetate copolymer #) /1504/ America flintcomb ash
Use: Film
Feature notes: excellent balance optics and strength, toughness and elasticity, good thermal seal performance
Important parameters: melt flow rate: 1 g/10min density: 0.925 g/cm3 tensile strength: 17 MPa breaking elongation: 800% hardness: 46 VEKA softening point: 87 C
Manufacturer: American flint Hill resources
EVA (ethylene vinyl acetate copolymer #) /1158/ America flintcomb ash
Use: other
Characteristic notes: excellent optical, strength and toughness, good heat resistant sealing performance under low temperature conditions
Important parameters: melt flow rate: 7 g/10min density: 0.922 g/cm3 tensile strength: 12 MPa breaking elongation: 900% hardness: 41 VEKA softening point: 89 C
Manufacturer: American flint Hill resources
EVA (ethylene vinyl acetate copolymer #) /FD50/ Italy
Use: Film
Characteristic notes: good optical and sealing performance, high elasticity and toughness
Important parameters: melt flow rate: 0.4 g/10min tensile strength: 30 MPa fracture elongation: 700% hardness: 39 VEKA softening point: 67 C embrittlement temperature: -80 C
Manufacturer: Italy Eni
EVA (ethylene vinyl acetate copolymer #) /FF55/ Italy
Use: Film
Characteristic notes: high elastic, high fracture mechanical properties (impact resistance)
Important parameters: melt flow rate: 0.7 g/10min tensile strength: 34 MPa fracture elongation: 700% hardness: 38 VEKA softening point: 60 C embrittlement temperature: -80 C
Manufacturer: Italy Eni
EVA (ethylene vinyl acetate copolymer #) /FC 25/ of Italy
Use: hot-melt
Characteristic notes: good creep resistance, high impact resistance, high tensile strength
Important parameters: melt flow rate: 0.3 g/10min tensile strength: 28 MPa breaking elongation: 630% VEKA softening point: 85 C
Manufacturer: Italy Eni
EVA (ethylene vinyl acetate copolymer #) /4320/ DuPont dow
Use: other
Characteristic notes: 1 wt% methacrylic acid thermal stabilizer: molecular weight, high viscosity in BHT antioxidants
Important parameters: melt flow rate: 150 g/10min density: 0.947 g/cm3 filler content: 25%
Manufacturer: Dow DuPont Co
EVA (ethylene vinyl acetate copolymer #) /E141/ Han Hua Total
Use: other
Characteristic notes: good processing performance, low temperature resistance, high impact resistance, ESCR
Important parameters: melt flow rate: 1.5 g/10min density: 0.937 g/cm3
Manufacturer: Han Hua Total Ltd.
EVA (ethylene vinyl acetate copolymer #) /E201/ Han Hua Total
Use: other
Characteristic notes: good processing performance, low temperature resistance, high impact resistance, ESCR
Important parameters: melt flow rate: 1.5 g/10min density: 0.942 g/cm3
Manufacturer: Han Hua Total Ltd.
EVA (ethylene vinyl acetate copolymer #) /20-20/ France akema
Use: other
Characteristic notes: antioxidation, good stability, good flexibility and softness
Important parameters: melt flow rate: 17 g/10min density: 0.94 g/cm3 tensile strength: 14 MPa breaking elongation: 600% hardness: 82 VEKA softening point: 47 C
Manufacturer: Arkema
EVA (ethylene - acetic acid B)