一级特黄色片在线免费播放,久久精品一级一级片。,www高清无码精品极品,成人看黄A在线观看

What is the new material PA

The country’s support for rural areas is increasing. In rural areas, the sewage treatment facilities for septic tanks and toilets in rural areas are not perfect. Sewage septic tanks and public toilets in farms lead to odor, fecal agglomeration, and partial discharge of sewage. Some ... Read More

How to measure the viscosity of engineering plastics

PA66 engineering plastic is a kind of high polymer with appropriately high molecular weight. The molecular weight directly affects its physical and chemical properties such as mechanical strength and heat resistance. The method of estimating molecular weight is to determine the relative viscosity of high ... Read More

Engineering plastic polycondensation method

PA66 engineering plastic is a condensation polymer that uses hexamethylenediamine and adipic acid as monomers and is connected by amide bonds. It has high strength, good resistance, and excellent performance such as wear resistance. It is used in automobiles, electronics and textiles. Has a wide ... Read More