--- title: "Properties and uses of thermoplastics" subject: "Civil Engineering Materials" chapter: 10 key: "semester_3/civil_engineering_materials:three-thermoplastics-uses" source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/three-thermoplastics-uses site: BCT Engineering --- # Properties and uses of thermoplastics Civil Engineering Materials · Chapter 10: Asphalt, Bitumen, Tar and Miscellaneous Materials - Asked in: 2057 Chaitra (old course), 6 marks - Video: [7 Different Types of Plastic and Their Uses | Orange Plastics Academy](https://www.youtube.com/watch?v=PbuiIhr0LVA) — Orange Plastics Academy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/three-thermoplastics-uses - Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-10 ## Question Explain the properties and uses of three thermoplastic materials which are important from the civil engineering point of view. ## 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. ## Answer 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which set describes PVC? A. Rigid (uPVC) or flexible (plasticised), does not rust or rot, but softens above about 60-70 °C B. Very good thermal insulation, brittle and burns easily C. Waterproof but with excellent UV resistance without any stabiliser D. Rusts slowly but is a good conductor Answer: A. PVC resists chemicals and does not rust or rot, but it softens at about 60-70 °C. (Key point: PVC properties) 2. Which uses suit polyethylene (HDPE/LDPE)? A. Thermal insulation panels for cold stores B. Window frames and floor tiles only C. Skylights and glazing D. Water storage tanks, water and gas pipes, damp-proof membrane and geomembranes Answer: D. PE is waterproof, tough and chemically resistant, so it is used for tanks, pipes, DPC sheets and geomembranes. (Key point: Polyethylene uses) 3. Why is expanded polystyrene (thermocol) used in walls, roofs and cold stores? A. It is very strong in tension B. It is a very good thermal insulator and light C. It is highly UV resistant and flexible D. It does not burn Answer: B. Expanded polystyrene is light with very good thermal insulation; it is brittle and burns easily. (Key point: Polystyrene role) 4. What is a stated weakness of polyethylene? A. Poor chemical resistance B. High water absorption C. Cannot be welded D. Poor UV resistance unless stabilised Answer: D. PE needs stabilisers because it has poor UV resistance; otherwise it is waterproof, chemical resistant and easy to weld. (Key point: Polyethylene limitation) ## Related in Civil Engineering Materials - [Important properties of civil engineering materials](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aimportant-properties-civil-materials) — Civil Engineering Materials, chapter 1, asked 8× - [Importance and scope of civil engineering materials](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aimportance-scope-subject) — Civil Engineering Materials, chapter 1, asked 8× - [Classification of civil engineering materials](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aclassification-civil-materials) — Civil Engineering Materials, chapter 1, asked 2× - [Asphalt properties and uses](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aasphalt-properties-uses) — Civil Engineering Materials, chapter 10, asked 4× - [Types of lime, properties and uses](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Atypes-of-lime-uses) — Civil Engineering Materials, chapter 4, asked 3× - [Properties and uses of glass](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aproperties-uses-of-glass) — Civil Engineering Materials, chapter 10, asked 3× ## Related in other subjects - [Storing and stacking of civil engineering materials](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Astoring-stacking-materials) — Construction Management, chapter 3 - [Properties and uses of soft magnetic materials](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Asoft-magnetic-properties-uses) — Electrical Engineering Material, chapter 4