Why thermosetting plastics can not be remoulded?

Answer 1

There are two types of plastic: thermosetting and thermoplastic.

Thermosetting plastics, such as Bakelite, use resins that are baked into their final form, usually in a mould. The chemical reaction of baking changes the resin so that it can no longer become fluid if reheated. These plastics cannot be "remolded", only powdered and put to other uses.

Thermoplatics (the bulk of plastic materials) use resins that are not baked in their moulds. Thermoplastics are heated until they flow, then cast into shape. Because they are only heated to flow temperature, no chemical reaction of heating occurs, and they can be re-moulded in a recycling process.

p.s. Bakelite is named for its inventor, Baekland, not because of its processing. True Bakelite is dark brown to black, so light-coloured "hard plastic" radio cabinets are *not* Bakelite - they are commonly Catalin, urea formaldehyde, or some other resin.

Answer 2

Thermosetting plastics are condensation polymers of two different types of monomers as Bakelite plastic is the polymer of Phenol and formaldehyde, on melting such polymer become decomposed into smaller molecules and are unable for remoulding.

Answer 3

Thermosetting plastics cannot be remoulded because they undergo a chemical change when heated, forming cross-links that give them a rigid and stable structure. These cross-links are irreversible, meaning the plastics cannot be melted and reshaped without degrading their properties.

Answer 4

Thermo plastics will soften when heated and can be reshaped.

Thermo-setting plastics undergo a chemical change when heated and will then retain their shape even when re-heated.

Answer 5

Bond b/w the chains are too strong so they do not break and hence they can not be remoulded.