or polymerization grade

A example at http://www.china-sd.net/star/qilushihua/jj1.htm:

"乙烯装置 ETHYLENE PLANT
45万吨/年乙烯装置采用美国LUMMUS公司技术，以石脑油、常压柴油、加氢裂化尾油为主要原料，生产乙烯、聚合级丙烯、化学级丙烯、加氢裂解汽油和混合碳四等产品的大型生产装置，是齐鲁乙烯工程的“龙头”。
The 450,000t/a ethylene unit is the upstream plant , with the process of application of Lummus (USA), using naphtha, atmospheric gas oil, hydrocracking tail oil as the feedstock to produce ethylene, propylene (polymer grade , chemical grade) , hydrocracking gasoline and mixed C."

I was personally involved in importation of this plant in 1980's.


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Note added at 2004-02-12 08:56:50 (GMT)
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Polymer-grade means the monomer\'s (单体) purity level is high enough for polymerization to take place successfully. Impurities in the monomer(s) would stop polymerization.

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Note added at 2004-02-12 09:25:44 (GMT)
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正己烷在乙丙橡胶和某些化纤的生产中是溶液聚合过程所使用的溶剂，故其纯度必须达到聚合级。