Resin can be divided into natural resin and synthetic resin. Natural resin refers to amorphous organic substances obtained from the secretions of natural animals and plants, such as rosin, amber, shellac and so on. Synthetic resin refers to resin products obtained by chemical synthesis of simple organic matter or chemical reaction of some natural products, such as phenolic resin and polyvinyl chloride resin, among which synthetic resin is the main component of plastic.