Question

Which of the following are not thermosetting polymers ?

• A. Bakelite
• B. polystyrene
• C. PVC
• D. Melmac

Answer 1

Answer: (B), (C)

polystyrene
PVC

Thermosetting polymers have different properties to thermosoftening polymers. Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily.

Examples are given below:

• Polyester fibreglass systems: sheet molding compounds and bulk molding compounds
• Polyurithane insulating foams, mattresses, coatings, adhesives, car parts, print rollers, shoe soles, flooring, synthetic fibers, etc. Polyurethane polymers are formed by combining two bi- or higher functional monomers/oligomers.
• Vulcanized rubber
• Bakelite, a phenol formaldehyde resin used in electrical insulators and plasticware
• Duroplast, light but strong material, similar to bakelite used for making car parts

Polyvinyl chloride(PVC) and polystyrene are thermoplastic polymer.
Hence, options B and C are correct.