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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(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，就會(huì)形成無須烘干的情況。如過必須要進(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多，更多的原因是因?yàn)槲锪辖?jīng)過多次再加工處理。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(jì)

模具溫度可以設(shè)置為40℃。而且流道整個(gè)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(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(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(shí)間

在200℃的溫度之下，機(jī)筒滯留時(shí)間大多不能超過5分鐘。當(dāng)溫度是210℃，機(jī)筒滯留時(shí)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(hào)部分物性表

EVA (ethylene vinyl acetate copolymer #) /11203/ America flintcomb ash
Use: Film
Characteristic notes: good toughness, good heat resistant seal under low temperature conditions
Important parameters: melt flow rate: 2 g/10min density: 0.934 g/cm3 tensile strength: 10.7 MPa breaking elongation: 325% hardness: 46 VEKA softening point: 75 C
Manufacturer: American flint Hill resources
EVA (ethylene vinyl acetate copolymer #) /H 900B/ Japan Dong Cao
Use: other
Characteristic notes: good adhesion, weatherability and solvent resistance
Important parameters: density: 1.07 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer #) /PA-440/ Repsol of Spain
Use: hot-melt
Characteristic notes: contains antioxidants
Important parameters: melt flow rate: 7 g/10min density: 0.95 g/cm3 tensile strength: 22 MPa breaking elongation: 760% hardness: 39
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /UE-2866/32/ Brazil Quattor
Use: hot-melt
Feature notes: good elasticity and flexibility
Important parameters: melt flow rate: 6.6 g/10min density: 0.948 g/cm3 tensile strength: 12 MPa breaking elongation: 884% hardness: 30 VEKA softening point: 46 C
Manufacturer: Quattor Petrochemical Industries Co, Brazil
EVA (ethylene vinyl acetate copolymer # /PX1007/ Leander Basil)
Use: other
Important parameters: melt flow rate: 3.1 g/10min density: 0.931 g/cm3 tensile strength: 22.3 MPa breaking elongation: 650% VEKA softening point: 78 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer # /PX1164/ Leander Basil)
Use: other
Important parameters: melt flow rate: 3.8 g/10min density: 0.928 g/cm3 tensile strength: 27.2 MPa breaking elongation: 460% VEKA softening point: 58 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer # /PX5125/ Leander Basil)
Use: other
Important parameters: melt flow rate: 5.7 g/10min density: 0.924 g/cm3 tensile strength: 23.7 MPa breaking elongation: 730% VEKA softening point: 96 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer #) /3135SB/ DuPont dow
Use: Film
Note: the characteristics of smooth agent, heat stabilizer, antioxidant BHT, opening agent
Important parameters: melt flow rate: 0.35 g/10min density: 0.93 g/cm3 VEKA softening point: 81 centigrade filler content: 12%
Manufacturer: Dow DuPont Co
EVA (ethylene vinyl acetate copolymer #) /CL12-3/ Ishida
Use: other
Characteristic notes: high transparency, good heat sealing
Important parameters: melt flow rate: 2 g/10min density: 0.924 g/cm3, tensile strength: 20 MPa, elongation at break: 700% hardness: 43 VEKA softening point: 82 temperature embrittlement temperature: -70 C, filler content: 7%
Manufacturer: Zhao he electrician Co., Ltd.
EVA (ethylene vinyl acetate copolymer #) /11E573/ DuPont dow
Use: other
Characteristic notes: compliance of smooth food contact
Important parameters: melt flow rate: 8 g/10min density: 0.93 g/cm3 VEKA softening point: 68 C
Manufacturer: Dow DuPont Co
EVA (ethylene vinyl acetate copolymer #) /1834/ Korea China
Use: other
Characteristic notes: high elasticity, copolymer, smoothness, antioxidation, and good processability
Important parameters: melt flow rate: 18 g/10min density: 0.96 g/cm3 fracture elongation: 1000% hardness: 65 embrittlement temperature: -76 C
Manufacturer: Korea Hwa comprehensive chemical company
EVA (ethylene vinyl acetate copolymer #) /EF522/ West Lake
Use: other
Characteristic notes: good clarity, low temperature hot sealing and foaming application
Important parameters: melt flow rate: 2.5 g/10min density: 0.933 g/cm3 tensile strength: 22 MPa breaking elongation: 800% VEKA softening point: 70 C
Manufacturer: West Lake Chemical Co., Ltd.
EVA (ethylene vinyl acetate copolymer #) /V28280/ Taiwan poly
Use: other
Characteristic notes: low crystal point, high transparency
Important parameters: melt flow rate: 28 g/10min density: 0.951 g/cm3, tensile strength: 11.76 MPa, elongation at break: 800% hardness: 23 VEKA softening point: 40 C embrittlement temperature: -70 C.
Manufacturer: Asian aggregated Limited by Share Ltd
EVA (ethylene vinyl acetate copolymer #) /HERI 07/ Fainplast in Italy
Use: other
Characteristic notes: foamed properties can be crosslinked
Important parameters: density: 0.18 g/cm3 molding shrinkage: 3% tensile strength: 2.6 MPa fracture elongation: 330% hardness: 57
Manufacturer: Italy Fainplast company
EVA (ethylene vinyl acetate copolymer #) /WPP551E27/ Southern
Use: other
Important parameters: melt flow rate: 6.5 g/10min density: 0.924 g/cm3 fracture elongation: 800% flexural modulus: 18.5 MPa hardness: 19
Manufacturer: Southern Polymer, USA
EVA (ethylene vinyl acetate copolymer #) Exxon chemical /UL00220CC3/
Use: Film
Feature remark: VAC content 20%
Important parameters: melt flow rate: 1.8 g/10min density: 0.942 g/cm3
Manufacturer: Exxon Chemicai Company
EVA (ethylene vinyl acetate copolymer #) /E032A/ Han Hua Total
Use: Film
Characteristic notes: characteristics: transparency, good processing and molding
Important parameters: melt flow rate: 0.5 g/10min filler content: 3.5%
Manufacturer: Han Hua Total Ltd.
EVA (ethylene vinyl acetate copolymer # /V215/ Ube)
Use: foaming
Feature remark: features: VA content 15%
Important parameters: melt flow rate: 2 g/10min density: 0.93 g/cm3, tensile strength: 21 MPa, elongation at break: 740% flexural strength: 60 MPa hardness: 92 VEKA softening point: 68 degrees.
Manufacturer: Japan Ube
EVA (b)