Engineering Chemistry

Wednesday, June 30, 2010

Unit 3- Class 14- High Polymers (poly methyl methaacrylate)

PMMA (poly methyl methaacrylate or plexi glass):

It is obtained by the polymerization of methylmethacrylate using hydrogen peroxide as initiator.

Methyl metheacrylate is obtained by the following method. Acetone with hydrogen cyanide gives acetone cyanohydrin. The hydrolysis of acetone cyanohydrin with sulphuric acid yields methylacrylic acid, which on estrification with methyl alcohol gives methyl methacrylate.

Plexiglass is a linear thermoplastic. It has excellent optical properties. It is highly resistant to heat, chemicals and water. It readily allows UV rays to pass through it. Hence it is used for making lenses, artificial eyes, light fixtures etc. It also finds uses as paints and adhesives. Air craft windows, instruments, dentures (set of artificial teeth).

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