Question

What is the primary defining difference between a thermoset and a thermoplastic material? (please explain with details)

Answer 1

Plastics are one of the most common materials used to manufacture goods today, from the keyboard you’re typing on to the International Space Statio.

There are two types of plastic

A. Thermoplastics

B. Thermosets

The primary defining defference between thermosets and thermoplastics

Thermosts are unique and quite different from traditional plastic materials such as thermoplastics, Unlike traditional thermoplastic parts that melt and disfigure when exposed to excess heat, thermoset components as implied by their name become set in their physical and chemical properties after an initial heat treatment and therefore are no longer affected by additional heat exposure. The process is very similar to hard boiling an egg. Once the egg is boiled, additional reheating does not cause disfiguration – similar to the curing or polymerization process associated with a thermoset part. After initial heat forming, thermoset material’s ability to exhibit resistance to heat, corrosion, and mechanical creep make them perfectly suitable for use in components that require tight tolerances and excellent strength-to-weight characteristics, while being exposed to elevated temperatures.   

Explanation of why Thermosets disfigure while thermoplastics does not

The curing or polymerization process, or vulcanization, creates an irreversible chemical reaction that makes permanent connections called cross-links. These crosslinks are formed by sulfur atoms between two linear chain of polymer. You can visualize these cross-links as chemical bridges, which gives the vulcanized polymer a three-dimensional structure that makes the material more rigid prior to curing. After the initial heat forming, and once the thermoset cures, it cannot be reheated or otherwise remolded.

The fabrication process for thermosets differs from thermoplastics. Thermoset cures in two stages involving the material supplier and the molder. For example, the thermoset plastic known as phenolic undergoes partial polymerization at the supplier. The supplier reacts under intense heat and pressure, and stops the chemical reaction at the stage of most of the linear chain formations. The final stage of vulcanization occurs in the molding press, where the unreacted portion of the phenol liquefies under heat and pressure, which creates a crosslinking reaction between molecular chains.