日韩中文字幕美少妇视频,一级A一片在线播放高,亚洲成aⅴ人影院在线观看,黑人中文字幕一区二区精品在线

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.