---
title: "Define plastic material"
subject: "Civil Engineering Materials"
chapter: 10
key: "semester_3/civil_engineering_materials:define-plastic-material"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/define-plastic-material
site: BCT Engineering
---

# Define plastic material

Civil Engineering Materials · Chapter 10: Asphalt, Bitumen, Tar and Miscellaneous Materials

- Asked in: 2070 Chaitra (old course), 2 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/define-plastic-material
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-10

## Question

Define plastic material.

## Short answer

Plastic is a synthetic organic material of long-chain polymers, moldable under heat and pressure, retaining shape on cooling. It is lightweight, corrosion-resistant, and exists as thermoplastics or thermosettings, used for pipes, sheets, and insulation.

## Answer

**Plastic** is a synthetic or semi-synthetic organic material made of long-chain polymers, which can be moulded into a desired shape by heat and pressure and keeps that shape on cooling or setting. Plastics are made from petroleum, natural gas or coal products with additives (fillers, plasticisers, stabilisers and pigments). They are light, corrosion resistant and cheap, and are used for pipes, sheets, tanks, flooring, insulation and fittings. They are of two types: thermoplastic and thermosetting.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which best defines a plastic?
   A. A natural inorganic mineral that melts at high temperature
   B. A synthetic or semi-synthetic organic material of long-chain polymers that can be moulded by heat and pressure and keeps its shape
   C. A metal alloy that is cast into shape
   D. A glass with high silica content
   Answer: B. Plastics are organic long-chain polymer materials moulded under heat and pressure that retain the shape on cooling or setting. (Key point: Definition)

2. Which are additives added to plastics?
   A. Cement, lime and sand
   B. Fillers, plasticisers, stabilisers and pigments
   C. Boron trioxide and soda
   D. Bitumen and aggregates
   Answer: B. Plastics made from petroleum, gas or coal products contain fillers, plasticisers, stabilisers and pigments. (Key point: Additives)

3. Plastics are of which two types?
   A. Addition and condensation
   B. Natural and synthetic
   C. Thermoplastic and thermosetting
   D. Rigid and flexible
   Answer: C. The two types are thermoplastic and thermosetting. (Key point: Types of plastic)

## Related in other subjects

- [Plastic torque of solid shaft is 4/3](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aplastic-torque-solid-shaft-4-3) — Strength of Materials, chapter 6
- [Limiting plastic moment is 1.5 times elastic moment](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aplastic-moment-rectangular-1-5) — Strength of Materials, chapter 7
- [Plastic moment and shape factor of a beam](https://www.bctengineer.com/question.md?key=semester_5%2Fmechanics_of_solids%3Ashape-factor-plastic-moment-rectangle) — Mechanics of Solids, chapter 12
- [Elastic-plastic torsion of a circular shaft](https://www.bctengineer.com/question.md?key=semester_5%2Fmechanics_of_solids%3Aplastic-torsion-circular-shaft) — Mechanics of Solids, chapter 12