Classification of Materials

Polymers:
Polymeric materials are grouped into three categories: Thermoplastics, Thermosets and Elastomers

Thermoplastics:

• Polyethylene (PE): The elastic modulus in sheet form ranges between 0.03-1.4 GPa, while in fibre form between 160-175 GPa. The strength again in film/sheet form varies between 8-30 MPa while that of a fibre is extremely high (3.3 GPa). The density is also quite low (970 Kg/m3). However the service temperature is limited up to 100⁰C. Use of PE as fibers is quite
  popular in composites. In film/sheet form Low and High Density PEs (LDPE and HDPEs) are mostly used as containers.
  
  
• Polymethyl Methacrylate (PMMA): PMMA, commonly known as Acrylic is a transparent thermoplastic having a higher elastic modulus than PE in sheet/rod form (2.3-3.8 GPa) and a high strength (53-74 MPa). Due to its higher stiffness and low density (1200 Kg/m3) coupled with good optical properties, it has extensive aerospace applications as cockpit-canopies. It is also used extensively in developing lenses and CDs.
  
  
• Polyamide (Nylon): Nylon, like PE, has good uses both as fibre (E-3GPa, and tensile strength 830 MPa) as well as in molded components like exterior covers or small mechanical components like gears, sprockets and bearings. The reason behind choosing for the later applications is due to its low coefficient of friction, ease of casting and a slightly higher range of service temperature (-80 to 120oC).
  
  
• Polystyrene (PS): PS is available in three different forms – thin film, blended form with Polybutadyne and also as foams. The modulus of elasticity varies from 2-3.5 GPa and the tensile strength from 30-60MPa. PS foams are widely used in disposable cups and utensils.
  
  
• Polyvinyl Chloride (PVC): PVC is one of the cheapest yet functionally attractive polymer. With a modulus and strength similar to PS, the corrosion resistance and UV resistance properties of the polymer has made it ideally suitable for pipes, fittings and floorings.