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Plastics

Types of Plastics

Draw and describe the structure and bonding of a thermoplastic

Thermoplastics are linear chain molecules, sometimes with side bonding of the molecules, but with weak, secondary bonding between the chains.

Explain the effect of load on a thermoplastic, with reference to orientation of chains

Deformation occurs in two ways: elastic in which initially coiled chains are stretched and plastic at higher loads, where secondary bonds weaken and allow the molecular chains to slide over each other. Creep and flow are important. No quantitative details required

Explain the reversible effect of temperature on a thermoplastic, with reference to orientation of chains

Increase in temperature causes plastic deformation.

Discuss the properties and uses of two thermoplastics including:

Polypropene

Polyester

Draw and describe the structure and bonding of a thermoset.

Thermosets are formed by making primary (covalent) bonds which form strong, primary cross-links between adjacent polymer chains. This gives the thermosets a rigid three-dimensional structure.

Explain the non-reversible effect of temperature on a thermoset.

Heating increases the number of permanent cross links and so hardens the plastic

Discuss the properties and uses of two thermosets including:

Polyurethane.

Vulcanized Rubber

Discuss the importance of the properties of plastics on the recycling of plastics.

Evaluate the importance of the properties of thermoplastics and thermosets on product design

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Page last modified on March 16, 2008, at 02:41 AM