End-capping 是一个化学专用名词。
End-capping 封端(反应)
End-capping reagent 封端剂
(英汉化学化工词汇)

See http://www.xyqchem.com/product1.htm

"Applications:It is used as end capping agent, cleaning agent, and mould release agent mainly in the organic chemical industry and medicine chemical industry."
Also, see its Chinese webpage http://www.xyqchem.com/product-c1.htm.

"用 途: 本品作为封头剂、清洗剂、脱膜剂，主要用于有机化工及医药化工生产中。"



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Note added at 2004-02-23 07:07:48 (GMT)
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See http://www.bondch.com/lunwen/2001/o22.htm

“硅烷用于交联

硅烷一直用于聚合物的封端如硅树脂和聚氨酯，以此来增强模量及拉伸强度而减小伸长率。除聚合物的封端外，硅烷还可通过自由基聚合或与聚合物链上的活性基团反应进入聚合物链。”


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Note added at 2004-02-23 07:42:05 (GMT)
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Thank you, but I can\'t be always right. I am just very careful about providing an answer. I do appreciate luzou\'s attitude. When he is not sure, he says \"not sure, or just guess\". He did a good search, but the translator who translated that web is misleading.

You are right about 脱模剂 － mould release agent. I didn\'t even notice the typo. 脱模剂 is applied to moulds so that molded parts can be easily taken out of the moulds. (mould = mold)

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Note added at 2004-02-23 08:19:13 (GMT)
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\"End-capping agent\" is also ok.