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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過聚合反應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,例如穩定劑、潤滑劑、填充劑等組合而成的一種產品。
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過多次再加工處理。回收料每多回收一次質量會出現逐漸下降的狀況。
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。
華美達在產品覆蓋的每一種鎖模力型號,都有專門的UPVC塑化注射系統,并配合UPVC管件產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量的產品。
3、模具及澆口設計
模具溫度可以設置為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,以免出現壓縮或減壓的情況,應保持流道順滑流暢。
模具應用不銹鋼鑄造,鉻的含量至少13%,最好16%,洛氏硬度至少有55,硬鋼模具可經鍍鉻處理,形成保護作用。
生產完后,應用溫和的堿液小心將模面清洗干凈后再噴上油質噴霧或硅質噴霧。
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,利用UPVC生產極度光滑的厚壁制品時,應采用多級注塑模具填充速度。
6、螺桿轉速
應該進一步配合模塑周期而確定螺桿轉速。螺桿面速度不要超過0.15-0.2m/s
7、背壓
背壓可以達到150bar,當然數據是越低越好,常見的數值是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 # /750/ TOSOH)
Use: other
Characteristic notes: good flexibility, weatherability, high definition, high elasticity, high crack (anti stress crack), high gloss, high impact resistance
Important parameters: density: 0.953 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer #) /CA-3730A/ Repsol of Spain
Use: Film
Characteristic notes: high solar radiation resistance and transmittance
Important parameters: melt flow rate: 0.4 g/10min density: 0.941 g/cm3 tensile strength: 23 MPa breaking elongation: 650%
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /PA-410/ Repsol of Spain
Use: hot-melt
Characteristic notes: moderate low viscosity. Highly compatible adhesives and wax
Important parameters: melt flow rate: 150 g/10min density: 0.937 g/cm3 tensile strength: 7.8 MPa breaking elongation: 648% hardness: 30 thermal deformation temperature: 53 C
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer #) /PA-460/ Repsol of Spain
Use: hot-melt
Characteristic notes: a higher bond resin can be provided with more than 28%VA
Important parameters: melt flow rate: 25 g/10min density: 0.956 g/cm3 tensile strength: 6 MPa breaking elongation: 825% hardness: 74
Manufacturer: YPF of Spain
EVA (ethylene vinyl acetate copolymer # /UE662009/ Leander Basil)
Use: other
Characteristic notes: good processing performance and good adhesion
Important parameters: melt flow rate: 32 g/10min tensile strength: 8.96 MPa fracture elongation: 700% hardness: 30 VEKA softening point: 54 C embrittlement temperature: -76 C
Manufacturer: Liane Basel Industrial Corporation
EVA (ethylene vinyl acetate copolymer #) /H H6051/ Japan Dong Cao
Use: wire and cable material
Feature notes: good stickiness, solubility, and good weather resistance.
Important parameters: density: 0.97 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer #) /7440M/ Taiwan chemical fiber
Use: other
Characteristic notes: high elasticity, copolymer, cross linkable, good flexibility, high fluidity
Important parameters: melt flow rate: 4 g/10min density: 0.934 g/cm3, tensile strength: 14.7 MPa elongation at break: 700% bending modulus: 22.6 MPa hardness: 43 VEKA softening point: 70 C embrittlement temperature: -70 C
Manufacturer: Taiwan chemical fiber Limited by Share Ltd
EVA (ethylene vinyl acetate copolymer #) /RS-2817SB/ Japan Kuraray
Use: other
Characteristic notes: Low to No Water Absorption copolymer biodegradable medium water soluble medium viscosity
Important parameters:
Manufacturer: krei Co., Japan
EVA (ethylene vinyl acetate copolymer #) /V2510J/ Germany BASF
Use: other
Characteristic notes: impact resistance, good fluidity, ESCR and transparency
Important parameters: melt flow rate: 2.7 g/10min density: 0.9245 g/cm3
Manufacturer: German Basf Inc
EVA (ethylene vinyl acetate copolymer #) /V2520G/ Germany BASF
Use: Film
Characteristic notes: impact resistance, fluidity, ESCR, transparency
Important parameters: melt flow rate: 1.05 g/10min density: 0.9255 g/cm3
Manufacturer: German Basf Inc
EVA (ethylene vinyl acetate copolymer #) /V3510K/ Germany BASF
Use: other
Characteristic notes: good fluidity, good ESCR, good impact resistance, suitable for profile, sheet, etc.
Important parameters: melt flow rate: 4 g/10min density: 0.932 g/cm3
Manufacturer: German Basf Inc
EVA (ethylene vinyl acetate copolymer #) /V3910DX/ Germany BASF
Use: other
Characteristic notes: good transparency, good impact resistance and good cracking resistance to environmental stress
Important parameters: melt flow rate: 0.3 g/10min density: 0.932 g/cm3
Manufacturer: German Basf Inc
EVA (ethylene vinyl acetate copolymer #) /1153/ Korea China
Use: Film
Feature notes: excellent high speed processing, low thermal bonding temperature, excellent transparency, excellent adhesion to various plastic materials
Important parameters: melt flow rate: 12 g/10min density: 0.939 g/cm3, tensile strength: 13 MPa, elongation at break: 880% VEKA softening point: 65 C embrittlement temperature: -76 C, filler content: 15%.
Manufacturer: Korea Hwa comprehensive chemical company
EVA (ethylene vinyl acetate copolymer # polyolefin /D5010/ Singapore)
Use: other
Feature notes: good processing performance, good environmental stress and low temperature resistance.
Important parameters: melt flow rate: 70 g/10min density: 0.924 g/cm3 hardness: 58.8 embrittlement temperature: -75 C
Manufacturer: Singapore polyolefin Private Companies
EVA (ethylene vinyl acetate copolymer #) /H K502C/ Japan Dong Cao
Use: other
Characteristic notes: good adhesion, good weatherability and solvent resistance
Important parameters: density: 0.96 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer #) /H S102C/ Japan Dong Cao
Use: other
Characteristic notes: good adhesion, good weatherability and solvent resistance
Important parameters: density: 0.96 g/cm3
Manufacturer: Tung Cao Co., Ltd., Japan
EVA (ethylene vinyl acetate copolymer # polyolefin /MA-10/ Singapore)
Use: other
Feature notes: good color stability, transparency
Important parameters: melt flow rate: 40 g/10min density: 0.952 g/cm3, tensile strength: 5.9 MPa, elongation at break: 880% hardness: 18 VEKA softening point: 36 C embrittlement temperature: -50 C.
Manufacturer: Singapore polyolefin Private Companies
EVA (ethylene vinyl acetate copolymer # polyolefin /KA-40/ Singapore)
Use: other
Feature notes: good color stability, transparency