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日本钢铁公司等研究了以平模挤压法在为辅设远距离输送天然气和石油管线的大直径钢管上涂覆聚乙烯的工艺。本工艺特点是,当管子在旋转前进中,熔融聚乙烯薄膜就缠绕在其外表.为获得均匀和外观好的涂层,所采用的聚乙烯应具有熔融张力高、熔融指数低和收缩应力少的特性,涂覆后要快速冷却.以确保它在低温时具有良好的耐冲击性。
Nippon Steel and others studied the process of coating polyethylene with a flat-die extrusion method on large-diameter steel pipes that support the long-distance transportation of natural gas and oil pipelines. The process is characterized by the fact that when the tube is spinning, the molten polyethylene film is wound around its outer surface.To obtain a uniform and good appearance coating, the polyethylene used should have high melt tension, low melt index and low shrinkage stress The characteristics of the rapid cooling after coating to ensure that it has good low temperature impact resistance.