(i) Polymethyl methacrylate (PMMA)

Acrylic PMMA (Polymethyl Methacrylate) is both a thermoplastic and transparent plastic. Two of the most common brand names are Plexiglass and Lucite and it is also commonly known as acrylic glass, acrylic, perspex or plexiglas. It is often used as an alternative to glass and is preferred for many applications because of its moderate properties, easy handling, easy processing and low cost. However, acrylic is not recommended for use in structural applications because of its poor impact resistance.

Common Uses:

• Industrial Uses: water tank liner, hand-held computer case, liquid chemical pump, conveyor rollers, soap dispensers hatch covers, bumper guards.
• Automotive Industry: lenses of exterior lights, trunk release handles, master cylinder, dashboard lighting.
• Consumer products: aquariums, motorcycle helmet lenses, paint, furniture, picture framing, umbrella clamps, cell phone antennas, bicycle air pumps, AV wall outlets, visors.

• Medical applications: lens implants, hard contact lenses, dentures, fillings,

   

Physical Properties:

• Specific Gravity - 1.18 g/cm
• Tensile Strength - 9400 psi
• Flexural Strength - 1300 psi

• Impact Strength - 0.4 ft-lb/in

   

General Properties:

• Good Weatherabiity
• Clear/colorable – excellent clarity
• Good Insulation Properties
• UV resistant
• Good abrasion resistance
• Good stiffness
• Low smoke emission

• Low water absorption

   

Processing:

• Injection Molding

• Extrusion

   

(ii) Urea formaldehyde

Urea formaldehyde is chemically known as the urea-methanal. It is a non-transparent thermo setting resin or plastic and is made from urea and formaldehyde heated in the presence of a mild base such as ammonia or pyridine. The resins are very useful in adhesives, and also in the MDF, and the  molded objects.

Synthesis of Urea Formaldehye

The chemical structure of UF resins can be described as that of polymethylene. This description leaves the details of the structure undetermined, which can vary linearly and branched. These are grouped by their average molar mass and the content of different functional groups. Changing synthesis conditions of the resins give good designing possibilities for the structure and resin properties.

Properties of urea formaldehyde

• It has a very high tensile strength.
• Urea formaldehyde has the property of flexural modulus.
• Has the property of heat distortion temperature.
• Has the capacity of low water absorption.
• It has the property of mould shrinkage.
• Has a property of high surface hardness.
• It can be elongated at break.

• It is volume resistance in nature.

   

About 1 million metric tons of urea-formaldehyde are produced every year and is used world wide as the data provided and over 70% of this production is then put into use by the forest industry products and also used as a great resin for bonding particleboard (61%), medium density fiberboard (27%), hardwood plywood (5%), and laminating adhesive (7%).

Uses of urea formaldehyde

Urea formaldehyde is the very common chemical and is mostly used because of its chemical properties. Examples are textiles, paper, foundry sand molds, wrinkle resistant fabrics, cotton blends, rayon, corduroy, etc. also used to glue wood together. Urea formaldehyde is mostly used when producing electrical appliances casing also desk lamps.

It is widely chosen as an adhesive because of its property of high reactivity, wonderfull performance and low price. It is a chemical combination of urea and formaldehyde and is not poisonous in nature. The examples of amino resins include tires from automobile industry in order to improve the bonding of rubber to tire cord, paper for improving tear strength, molding electrical devices, molding jar caps, etc.

Urea formaldehyde is also used in agricultural field as a source of nitrogen fertilizer and its rate of decomposition is into CO2 and NH3 and is determined by the action of microbes found naturally in soils. The activity of these microbes, and the rate of nitrogen release is temperature dependent. The optimum temperature for microbe activity is approximately about (70-90)°F.

(iii) Buna-S

Synthesis of Buna S

It is a random co-polymer formed by the emulsion polymerization of a mixture of 1:3 butadiene and styrene in the presence of peroxide catalyst at 5 degree Celsius and therefore the product is called as cold rubber. The rubber obtained is also called Styrene butadiene rubber (SBR).

In Buna-S, Bu stands for butadiene and, Na for sodium and S for styrene. It is vulcanized with sulphur. The rubber is slightly inferior to natural rubber in its physical properties.

Properties of Buna–S:

• It is very tough and a good substitute for natural rubber.
• It possesses high abrasion resistance.

• It has high load bearing capacity.

   

Uses of Buna–S:

• It is used for manufacturing automobile tyres.

• It is used for making floor tiles, footwear components, cable insulation etc.

   

Applications:

• It finds application due to its high resistance to abrasion.
• It is used for the manufacture of passenger car tyres and treads,motor cycle and scooter tyres, cycle tyres and tubes.
• They are also used for the manufacture of conveyor belts, foot-wares, shoe soles, hoses and electrical insulation.