The Society of Plastics Industry SPIs has developed a label code for the type of plastics used in plastics, which is a symbol of numbers in the middle of a triangle consisting of three arrows representing cycles. They attach triangular recycling labels to plastics and use numbers 1 to 7 and abbreviations to refer to the type of resin used in plastics. In this way, the identification of plastic varieties becomes simple and easy, and the cost of recycling is greatly reduced. Today, many countries in the world have adopted the SPI identification scheme. China in 19 In 1996, almost the same identification standards were established.