my country’s polyacrylonitrile fiber output continues to decline

Polyacrylonitrile fiber, also known as acrylic fiber, refers to synthetic fibers made of polyacrylonitrile or acrylonitrile copolymer with an acrylonitrile content greater than 85.0% (mass percentage). Polyacrylonitrile fiber was first put into research and development in the 1930s, and it was not until 1950 that large-scale production was achieved. Polyacrylonitrile fiber has the advantages of…