Principle of formation of thermoplastic elastomer TPE
The principle of formation of thermoplastic elastomer TPE: The properties of thermoplastic elastomer TPE are determined by its composition, and its composition and use are also different.
Phase structure and phase properties of TPE
1.1 Phase structure
Almost all TPEs share a common feature, namely a phase separation system in which one phase is a hard polymer and the other phase is a rubber phase. For most TPEs, the two phases are linked by chemical bonds through block or graft copolymerization, and some TPEs require only one polymer to form a small dispersed phase in the other polymer. The hard phase gives the TPE strength. When heated or under the action of a solvent, the hard phase can flow freely and is easy to process. When the cooling or solvent evaporates, the hard phase solidifies and the elastomer returns to elasticity.
1.2 Phase properties
Since most TPEs are phase separation systems, they exhibit many of the characteristics of their constituent polymers, such as each phase having a white glass transition temperature (Tg). The physical properties of TPE are strongly related to the melting point (Tm) of the hard segment in the molecular structure and the Tg of the soft segment. The rubber elasticity of the TPE is exhibited at a temperature of Tm to Tg, and TPE is melt-flow molded at a temperature of Tm or higher, and is brittle at a temperature of Tg or less.
2 TPE formation principle
Regardless of the TPE, its molecular structure consists of a soft segment and a hard segment. The soft segment is a soft linear long molecular chain which gives the TPE a certain elastic deformation; the hard segment refers to a shorter rigid chain which gives the TPE a certain rigidity and heat resistance. Therefore, TPE is a polymer material between vulcanized rubber and thermoplastic. The formation mechanism of TPE is briefly described by taking polyurethane TPE, polyolefin TPE and polyether ester TPE as examples.