聚氯乙烯，英文簡(jiǎn)稱PVC(Polyvinyl chloride)，是氯乙烯單體(vinyl chloride monomer, 簡(jiǎn)稱VCM)在過氧化物、偶氮化合物等引發(fā)劑;或在光、熱作用下按自由基聚合反應(yīng)機(jī)理聚合而成的聚合物。氯乙烯均聚物和氯乙烯共聚物統(tǒng)稱之為氯乙烯樹脂。
PVC為無定形結(jié)構(gòu)的白色粉末，支化度較小，相對(duì)密度1.4左右，玻璃化溫度77~90℃，170℃左右開始分解，對(duì)光和熱的穩(wěn)定性差，在100℃以上或經(jīng)長(zhǎng)時(shí)間陽光曝曬，就會(huì)分解而產(chǎn)生氯化氫，并進(jìn)一步自動(dòng)催化分解，引起變色，物理機(jī)械性能也迅速下降，在實(shí)際應(yīng)用中必須加入穩(wěn)定劑以提高對(duì)熱和光的穩(wěn)定性。
工業(yè)生產(chǎn)的PVC分子量一般在5萬~11萬范圍內(nèi)，具有較大的多分散性，分子量隨聚合溫度的降低而增加;無固定熔點(diǎn)，80~85℃開始軟化，130℃變?yōu)檎硰棏B(tài)，160~180℃開始轉(zhuǎn)變?yōu)檎沉鲬B(tài);有較好的機(jī)械性能，抗張強(qiáng)度60MPa左右，沖擊強(qiáng)度5~10kJ/m2;有優(yōu)異的介電性能。
PVC曾是世界上產(chǎn)量最大的通用塑料，應(yīng)用非常廣泛。在建筑材料、工業(yè)制品、日用品、地板革、地板磚、人造革、管材、電線電纜、包裝膜、瓶、發(fā)泡材料、密封材料、纖維等方面均有廣泛應(yīng)用。
Polyvinyl chloride, referred to as PVC(Polyvinyl chloride), is vinyl chloride monomer (vinyl chloride monomer, referred to as VCM) in peroxide, azo compounds and other initiators; Or under the action of light and heat according to the mechanism of free radical polymerization polymerization polymer. Vinyl chloride homopolymer and vinyl chloride copolymer are called vinyl chloride resin.
PVC is a white powder of amorphous structure, the branching degree is small, the relative density is about 1.4, the glass transition temperature is 77~90 ° C, about 170 ° C begins to decompose, the stability of light and heat is poor, above 100 ° C or after a long time of sunlight exposure, it will decompose and produce hydrogen chloride, and further automatic catalytic decomposition, causing discoloration, physical and mechanical properties are also rapidly declining, In practical applications, stabilizers must be added to improve the stability of heat and light.
The molecular weight of industrial PVC is generally in the range of 50,000 ~ 110,000, and has a large polydispersity, and the molecular weight increases with the decrease of polymerization temperature; Without fixed melting point, 80-85 ℃ began to soften, 130℃ into viscoelastic state, 160~180℃ began to change into viscoelastic state; It has good mechanical properties, tensile strength of about 60MPa, impact strength 5~10kJ/m2; It has excellent dielectric properties.
PVC was once the world's largest production of general purpose plastic, the application is very wide. In building materials, industrial products, daily necessities, floor leather, floor tiles, artificial leather, pipe, wire and cable, packaging film, bottles, foam materials, sealing materials, fibers and other aspects are widely used.
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