伊人yinren6综合网色狠狠_国产午夜精品一区二区三区小说_久久精品视频日本_18美女的隐私网站

Generally speaking, natural rubber refers to an elastic solid made from natural rubber latex collected from the Brazilian rubber tree through processing steps such as coagulation and drying. Natural rubber is a natural polymer compound with cis-1,4-polyisoprene as the main component. Its rubber hydrocarbon (cis-1,4-polyisoprene) content is above 90%. It also contains A small amount of protein, fatty acids, sugar and ash.