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Properties and uses of thermoplastics

Short answer

PVC is strong, chemically resistant, used for pipes, window frames, and flooring. Polyethylene (PE) is tough, waterproof, employed in water tanks, damp-proof membranes, and geomembranes. Expanded polystyrene offers thermal insulation for walls, roofs, and formwork infill.

Explain the properties and uses of three thermoplastic materials which are important from the civil engineering point of view.

Thermoplastics soften on heating and can be remoulded. Three important ones for civil engineering:

1. Polyvinyl chloride (PVC)

Properties: Strong, rigid (unplasticised uPVC) or flexible (plasticised), chemically resistant, does not rust or rot, low cost, good electrical insulator, self-extinguishing, but softens above about 60–70 °C. Uses: Water supply and drainage pipes, conduits and cable insulation, window and door frames, floor tiles, roofing sheets, water stops and rain-water pipes.

2. Polyethylene (PE: LDPE and HDPE)

Properties: Light, tough and flexible, waterproof, excellent chemical resistance, low water absorption, easy to weld; poor UV resistance unless stabilised. Uses: Water storage tanks, water and gas pipes (HDPE), damp-proof membrane and sheeting, geomembranes for ponds and landfills, and cable covers.

3. Polystyrene (PS, expanded polystyrene or thermocol)

Properties: Light, rigid, transparent in solid form, very good thermal insulation in expanded form, low water absorption, but brittle and burns easily. Uses: Thermal insulation panels for walls, roofs and cold stores, formwork infill, ceiling tiles, lighting diffusers.

Others: acrylic (PMMA) for skylights and glazing, and polypropylene for pipes and fibres.

✓ Answer checked by Claude Opus 5.5 (high effort)

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