a. PMMA

• Properties of PMMA : It is transparent and colorless plastic, easy to mould in desired shape, Refractive index is 1.59, at lower temperature it is brittle and rigid

• Applications of PMMA : Widely used in the optical industry, PMMA has been used as an effective replacement of intraocular lenses in eyes. Rigid contact lenses are often composed of the PMMA polymer, and it is a preferred material used in the making of hard lenses owing to the ease of customization that it offers

b. Buna-S

Synthesis of Buna :

Properties :

1. It has good abrasion resistance

2. It has good aging stability

3. It is harder and not rubbery

4. It is protected by additives

Applications:

1. It is used for making tires of car, scooter and bicycle.

2. It is used for making gaskets.

3. It possesses different applications in footwear industries

4. It is used as replacement for natural rubber

c. Silicone Rubber. SILICON RUBBER STRUCTURE

Properties of silicone Rubber : Silicone rubber offers good resistance to extreme temperatures, being able to operate normally from −100 to 300 °C (−148 to 572 °F).

Some properties such as elongation, creep, cyclic flexing, tear strength, compression set, dielectric strength (at high voltage), thermal conductivity, fire resistance and in some cases tensile strength can be at extreme temperatures far superior to organic rubbers in general, although a few of these properties are still lower than for some specialty materials.

Silicone rubber is a material of choice in industry when retention of initial shape and mechanical strength are desired under heavy thermal stress or sub-zero temperatures.

Organic rubber has a carbon-to-carbon backbone which can leave it susceptible to ozone, UV, heat and other ageing factors that silicone rubber can withstand well.

This makes silicone rubber one of the elastomers of choice in many extreme environments.

Applications of silicone Rubber:

Silicone rubber is highly inert and does not react with most chemicals.

Due to its inertness, it is used in many medical applications including medical implants.

It is bio-compatible, hypoallergenic, which makes it suitable for baby care products and food contact in general.

Silicone rubber is a reliable solution (as opposed to rubber and thermoplastic elastomers) for migration or interaction problems between the main active ingredients. Its chemical stability prevents it from affecting any substrate it is in contact with (skin, water, blood, active ingredients, etc.)

d. Poly urethane Rubber

Structure of polyurethane :

Properties of Polyurethane :

Polyurethane is highly resistant to oxidation because of their saturated character

They also show good resistant to organic solvents but are attacked by acids and alkalis especially concentrated and hot.

The polyurethane foams are foams are light, tough and resistant to heat abrasion , chemicals and weathering

Uses: For surface coating and manufacture of foams and spandex

e. Phenol Formaldehyde

Linear structure of phenol formaldehyde Novolak

Network structure of phenol formaldehyde Bakelite

Synthesis of Phenol formaldehyde: Phenol is trifunctional in nature. It contains methylene or ether linkages or either or. Linear structure is called as Novolak and network structure is called Bakelite.

Properties of Phenol formaldehyde

Bakelite has a number of important properties. It can be molded very quickly, decreasing production time. Moldings are smooth, retain their shape and are resistant to heat, scratches, and destructive solvents. It is also resistant to electricity, and prized for its low conductivity.

Applications of phenol Formaldehyde:

They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth, as with fire-resistant FR-4circuit board materials.