Plastics can be divided into two categories, thermosetting and thermoplastic. The former cannot be reshaped and used, and the latter can be repeatedly produced.
There are basically two types of plastic polymer structures: the first is a linear structure, the polymer compound having such a structure is called a linear polymer compound, and the second is a body structure, and the polymer structure having such a structure It is called a bulk polymer compound. Some polymers have branches, called branched polymers, which are linear structures. Although some polymers have crosslinks between molecules, they are less crosslinked and are called network structures, which are body structures.
Two different structures exhibit two opposite properties. The linear structure (including the branched chain structure) polymer has elasticity and plasticity due to the presence of independent molecules. It can be dissolved in a solvent and melted by heating. The hardness and brittleness are small. Due to the absence of independent macromolecules, the bulk-structured polymers have no elasticity and plasticity, do not dissolve and melt, and can only swell and have greater hardness and brittleness. Plastics have both structural macromolecules. Thermoplastics are made of linear macromolecules and thermosetting plastics are made of macromolecules.