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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

背壓可以達到150bar，當然數(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 #) /PA-420/ Repsol of Spain
Use: other
Feature notes: good flexibility. Good compatibility of wax, bitumen and filler
Important parameters: melt flow rate: 20 g/10min density: 0.94 g/cm3 tensile strength: 11 MPa breaking elongation: 780% hardness: 30 VEKA softening point: 53 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /UE-1203/ Brazil Quattor
Use: Film
Characteristic notes: good processability and compatibility, good mechanical strength and high resistance to stress cracking at low temperature
Important parameters: melt flow rate: 0.32 g/10min density: 0.933 g/cm3 tensile strength: 17 MPa breaking elongation: 770% hardness: 47 VEKA softening point: 76 C
Manufacturer: Quattor Petrochemical Industries Co, Brazil
EVA (ethylene vinyl acetate copolymer #) /FD23/ Italy
Use: Film
Characteristic notes: good optical properties, high impact resistance, tensile strength, elongation at break, low creep
Important parameters: melt flow rate: 0.5 g/10min tensile strength: 26 MPa fracture elongation: 600% hardness: 44 VEKA softening point: 85 C embrittlement temperature: -80 C
Manufacturer: Italy Eni
EVA (ethylene vinyl acetate copolymer #) /CA-2220G/ Repsol of Spain
Use: Film
Characteristic notes: ultraviolet absorbents and antioxidants
Important parameters: melt flow rate: 0.28 g/10min density: 0.935 g/cm3 tensile strength: 21 MPa breaking elongation: 700%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /CA-2720G/ Repsol of Spain
Use: Film
Characteristic notes: ultraviolet absorbents and antioxidants
Important parameters: melt flow rate: 0.25 g/10min density: 0.949 g/cm3 tensile strength: 23 MPa breaking elongation: 750%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /CA-2721G/ Repsol of Spain
Use: Film
Characteristic notes: ultraviolet absorbents and antioxidants
Important parameters: melt flow rate: 0.45 g/10min density: 0.953 g/cm3 tensile strength: 26 MPa breaking elongation: 750%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /CM22-1/ Ishida
Use: other
Feature remark: good resistance to stress cracking, good machinability, transparency and good surface gloss
Important parameters: melt flow rate: 25 g/10min density: 0.924 g/cm3, tensile strength: 12 MPa, elongation at break: 650% hardness: 41 VEKA softening point: 73 temperature embrittlement temperature: -70 C, filler content: 7%
Manufacturer: Zhao he electrician Co., Ltd.
EVA (ethylene vinyl acetate copolymer #) /7350M/ Taiwan chemical fiber
Use: other
Characteristic notes: high elasticity, copolymers, crosslinkable, good flexibility and good chemical resistance
Important parameters: melt flow rate: 2.5 g/10min density: 0.938 g/cm3, tensile strength: 14.7 MPa elongation at break: 800% bending modulus: 14.7 MPa hardness: 38 VEKA softening point: 60 C embrittlement temperature: -70 C
Manufacturer: Taiwan chemical fiber Limited by Share Ltd
EVA (ethylene vinyl acetate copolymer #) /7660M/ Taiwan chemical fiber
Use: other
Characteristic notes: copolymers, optical properties, machinability, good, cross linkable, good thermal sealing and good toughness
Important parameters: melt flow rate: 20 g/10min density: 0.94 g/cm3, tensile strength: 10.8 MPa, elongation at break: 800% bending modulus: 12.7 MPa hardness: 32 hot deformation temperature: 60 C, embrittlement temperature: -70 C.
Manufacturer: Taiwan chemical fiber Limited by Share Ltd
EVA (ethylene vinyl acetate copolymer #) /PA-536/ Repsol of Spain
Use: Profile
Characteristic notes: antioxidation, good processability, compliance of food contact
Important parameters: melt flow rate: 0.7 g/10min density: 0.941 g/cm3 fracture elongation: 800% VEKA softening point: 62 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /YV 1055/ TPI in Thailand
Use: hot-melt
Characteristic notes: high elasticity, good mechanical properties, thermal stability, low temperature resistance, no slip, no adhesion
Important parameters: melt flow rate: 400 g/10min density: 0.95 g/cm3 fracture elongation: 800% hardness: 15
Manufacturer: Thailand TPI Polene Co., Ltd.
EVA (ethylene vinyl acetate copolymer #) /PA-539/ Repsol of Spain
Use: Film
Characteristic notes: mechanical and optical properties of excellent processing performance. Antioxidant additives contained
Important parameters: melt flow rate: 2 g/10min density: 0.937 g/cm3 tensile strength: 22 MPa breaking elongation: 640% VEKA softening point: 64 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /PA-444/ Repsol of Spain
Use: hot-melt
Characteristic notes: low melting and melting viscosity. Good compatibility and adhesive resin and wax
Important parameters: melt flow rate: 50 g/10min density: 0.95 g/cm3 tensile strength: 8 MPa breaking elongation: 750% hardness: 76
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /UE-1220/31F/ Brazil Quattor
Use: Film
Characteristic notes: appropriate strain capacity, good compatibility and high mechanical strength
Important parameters: melt flow rate: 2 g/10min density: 0.932 g/cm3 tensile strength: 13 MPa breaking elongation: 885% hardness: 40 VEKA softening point: 69 C
Manufacturer: Quattor Petrochemical Industries Co, Brazil
EVA (ethylene vinyl acetate copolymer # /UE662157/ Leander Basil)
Use: other
Characteristic notes: good adhesion, good processing performance, high opening, high sliding
Important parameters: melt flow rate: 32 g/10min tensile strength: 8.96 MPa fracture elongation: 700% hardness: 30 dimension