Question

Write the preparation, properties and uses of PMMA and Buna-S.

Answer 1

1. POL YMETHYL METHACRYLATE (PMMA).
• PREPARATION.

This is an important thermoplastic resin. It is obtained by polymerisation of methyl methacrylate which is an ester of methyl acrylic acid, CH₂ = c( CH₃)COOH, in presence of acetyl peroxide or hydrogen peroxide. It is an acrylic polymer.

PROPERTIES.

1. lt is hard, fairly rigid material with a high softening point of about 130-14rfC.
2. lt becomes rubber-like at a temperature above 6S°C.
3.  It has an outstanding shape-forming properties due to wide span of temperature from its rigid state to viscous.
4.  It has high optical-transparency.
5. lt has high resistance to sunlight and ability of transmission light accurately.

• USES.

1.  For making lenses ,optical parts of instruments, air craft, light fixtures, artificial eyes, wind screen, bone splints, decorative articles etc.
2.  It is found in paint. Acrylic "latex" paints often contain PMMA suspended in water.
3. Used in making window glasses.
4. BUNA-S (or STYRENE RUBBER)

• PREPARATION:

This is the most important type of synthetic rubber which is produced by copolymerization
of butadiene ,CH₂ = CH - CH = CHz(75% by weight) and styrene ,C₆ H₅CH = CH₂(25% by weight).

• PROPERTIES

1. Styrene rubber resembles natural rubber in processing characteristics as well as quality of
   finished products.
2. lt posses high abrasion-resistance, high load-bearing capacity and resilience
3. lt swells in oils and solvents.

• USES

1. Mainly used for the manufacture of motor tyres.
2. Other uses of this elastomer are floor tiles, shoe soles, gaskets, foot-wear components, wire and cable insulations, carpet backing, adhesive, tank-lining, etc.