色综合久久无码五十路人妻,婷婷射精av这里只有精品,欧美成人精品高清在线蜜芽,国产精品综合日韩精品已满

"The scientific name of nylon is polyamide, which is also a general term for thermoplastic resins. There are many kinds of nylon, with large production capacity and wide application. And its molecular structure is nylon fiber.

Nylon has good comprehensive properties, and its fiber strength is 1-2 times higher than that of cotton. It has the significant advantage of replacing steel, iron, copper and other metals with plastics in production and manufacturing, and is an important engineering plastic.