THE COMMON TYPES OF PLASTIC

Different types of plastics that are used in construction industry are described below.

1. Polyethylene Plastic (PE)

Polyethylene plastic is made from the polymerized vinyl monomers.

Monomer is a kind of simple compound, which can be polymerized to become macromolecular compound. Three ways are used to polymerize the monomer: high-pressure process, middle-pressure process, and low-pressure process.

Different ways make different degrees of crystallinity and density. High pressure polyethylene has low crystallinity and density while low-pressure polyethylene has high crystallinity and density. As the crystallinity and density increases, on one hand, the hardness, softening point, and strength increase accordingly; On the other hand, the impact toughness and elongation decrease.

Polyethylene plastic has better chemical stability and water resistance. Even though its strength is not high, it is quite flexible in low temperature. A certain amount of carbon black can strengthen the aging resistance of polyethylene.

2. Polyvinyl Chloride Plastic (PVC)

Polyvinyl chloride plastic is a kind of common building plastic made from the polymerized vinyl chloride monomer. Polyvinyl chloride plastic has better chemical stability and aging resistance, but poor heat resistance. It may decompose and metamorphose if the temperature exceeds 100°C. Usually, it should be used at temperature of below 60-80°C. By adding different amounts of plasticizer, hard and soft polyvinyl chloride plastic can be made.

3. Polystyrene Plastic (PS)

Polystyrene plastic is made from the polymerized styrene monomer. It has the merits of good light transmittance, easy pigmentation, better chemical stability, water resistance, light resistance, easy processing, and low price.

However, polystyrene plastic has the disadvantages of weak stiffness, poor impact toughness, weak heat resistance and easy flammability. These weak points set restrictions to its uses.

4. Polypropylene Plastic (PP)

Polypropylene plastic is made from the polymerized acrylic monomer. It has the properties of light weight (density 0.90g/cm²), strong heat resistance (100-120⁰C), regular ductility and water resistance. The weak points are that it has poor stiffness in low temperature; and poor air resistance. Therefore, polypropylene plastic is fit to be used indoors. Recent years have seen the rapid development of polypropylene. Polypropylene, together with polyethylene and polyvinyl chloride, has become the main varieties of building plastic.

5. Polyrmethyl Methacrylate (PMMA)

Thermoplastic resin, also called organic glass, can be made from the

Polymerized polymethyl methacrylate. It has the advantages of good light transmittance, high strength at low temperature, low water absorption, better heat resistance, better aging resistance, and easy to be processed. However, it has the disadvantages of poor abrasive resistance and high price.

6. Polyester Resin (PR)

Polyester resin is made by condensing diatomic or polybasic alcohol and diatomic or polybasic acid. Polyester resin has the properties of good bonding capacity, elasticity, better colourability, flexibility, heat resistance and water resistance.

7. Phenolic Resin (PF)

Phenolic resin is made by polymerizing phenol and aldehyde under the influence of acid catalyst or alkaline catalyst. Phenolic resin has better cohesion strength, light resistance, water resistance, heat resistance, corrosion resistance, and electrical insulation. However, it has poor stiffness. Phenolic resin, added by filling material and curing agent, can be made into phenolic plastic. Phenolic plastic is smooth, strong, durable, and cheap. It has become a type of commonly used plastic.

8. Organic Silicon Resin (SI)

Organic silicon resin is made by hydrolysing of one or more types of organic silicon monomer. Organic silicon resin has the properties of heat resistance, cold resistance, water resistance, and corrosion resistance. However, it is poor in mechanical performance and cohesive force. These two weak points can be improved by adding synthetic resin (phenolic aldehyde, epoxy, and polyester), glass fiber, and asbestos, etc.