Plastics in Engineering – Types, Properties, and Industrial Applications

Plastics are synthetic polymer materials widely used in modern engineering, manufacturing, construction, automotive systems, and consumer products. Due to their lightweight structure, corrosion resistance, electrical insulation capability, and ease of processing, plastics have become essential alternatives to metals in many industrial applications.

Unlike metals, plastics can be molded into complex geometries with high production efficiency and reduced manufacturing cost. Their mechanical and thermal properties vary depending on molecular structure, additives, and processing method.

From an engineering perspective, plastics are classified into two main categories:

• Thermoplastics

• Thermosetting Plastics (Thermosets)

Understanding the difference between these two groups is critical for correct material selection in design and manufacturing.

Accurate material selection requires proper measurement and verification using precision instruments such as micrometers and gauges. You can explore more in our Measuring Tools Guide. 

Plastic piping systems must comply with correct thread standards to ensure proper sealing and compatibility. Learn more in our detailed Thread Standards Comparison Guide. 

Engineering Comparison Table between thermo-set and thermo-plastic

1️ ) Thermoplastics

Thermoplastics are polymers that soften when heated and solidify when cooled. This process can be repeated multiple times without significant chemical change. Because of this property, thermoplastics are recyclable and widely used in injection molding, extrusion, thermoforming, and 3D printing.

Thermoplastics generally consist of linear or branched molecular chains with weak intermolecular forces, allowing them to melt under heat.

Key Characteristics of Thermoplastics

• Can be reheated and reshaped

• Recyclable

• Good impact resistance

• Moderate heat resistance

• Suitable for mass production

• Lower structural rigidity compared to thermosets

ABS (Acrylonitrile Butadiene Styrene)

ABS is a tough, impact-resistant thermoplastic commonly used in automotive components and electronic housings.

Properties:

• Density: ~1.04 g/cm³

• High impact strength

• Good machinability

• Moderate heat resistance

• Shrinkage: 0.4% – 0.7%

• Working Temperature: -20°C to 80°C

Applications:
Automotive dashboards, protective helmets, tool housings, appliance covers, 3D printing filament.

PP (Polypropylene)

Polypropylene is a lightweight and chemically resistant material widely used in packaging and piping systems.

Properties:

• Density: ~0.90 g/cm³

• Excellent chemical resistance

• High fatigue resistance

• Moisture resistant

• Shrinkage: 1.0% – 2.5%

• Working Temperature: 0°C to 100°C

Applications:
Pipes and fittings, automotive interior components, containers, living hinges.

PP (Polypropylene)

Polypropylene is a lightweight and chemically resistant material widely used in packaging and piping systems.

Properties:

• Density: ~0.90 g/cm³

• Excellent chemical resistance

• High fatigue resistance

• Moisture resistant

• Shrinkage: 1.0% – 2.5%

• Working Temperature: 0°C to 100°C

Applications:
Pipes and fittings, automotive interior components, containers, living hinges.

HDPE (High-Density Polyethylene)

HDPE is a durable thermoplastic known for its high strength-to-density ratio.

Properties:

• Density: ~0.95 g/cm³

• Excellent chemical resistance

• High impact strength

• Moisture resistant

• Shrinkage: 1.5% – 3.0%

• Working Temperature: -50°C to 120°C

Applications:
Water pipes, fuel tanks, industrial containers, plastic lumber, chemical storage tanks.

PS (Polystyrene)

Polystyrene is a rigid and low-cost plastic widely used in disposable products and packaging.

Properties:

• Density: ~1.05 g/cm³

• Lightweight

• Brittle

• Low cost

• Shrinkage: 0.4% – 0.7%

• Working Temperature: -10°C to 70°C

Applications:
Disposable cups, packaging materials, insulation boards.

EPS (Expanded Polystyrene)

EPS is a foam version of polystyrene primarily used for insulation and protective packaging.

Properties:

• Very low density

• Excellent thermal insulation

• Shock absorbing

• Shrinkage: 0.2% – 0.8%

• Working Temperature: -50°C to 75°C

Applications:
Protective packaging, building insulation, cold storage panels.

EPS (Expanded Polystyrene)

EPS is a foam version of polystyrene primarily used for insulation and protective packaging.

Properties:

• Very low density

• Excellent thermal insulation

• Shock absorbing

• Shrinkage: 0.2% – 0.8%

• Working Temperature: -50°C to 75°C

Applications:
Protective packaging, building insulation, cold storage panels.

GPPS (General Purpose Polystyrene)

GPPS is a clear, rigid grade of polystyrene.

Properties:

• Transparent

• Easy to process

• Brittle

• Good dimensional stability

• Shrinkage: 0.4% – 0.7%

• Working Temperature: -10°C to 80°C

Applications:
Display items, packaging, disposable consumer goods.

PA (Polyamide – Nylon)

Polyamide, commonly known as Nylon, is a high-performance engineering thermoplastic widely used in mechanical components due to its strength and wear resistance.

Properties:

• Density: ~1.14 g/cm³

• High mechanical strength

• Excellent wear resistance

• Good fatigue resistance

• Moderate moisture absorption

• Shrinkage: 0.7% – 2.0%

• Working Temperature: -40°C to 120°C

Applications:
Gears, bearings, bushings, mechanical housings, cable ties, industrial machine components.

POM (Polyoxymethylene – Acetal / Delrin)

POM is a highly crystalline engineering plastic known for its dimensional stability and low friction properties.

Properties:

• Density: ~1.41 g/cm³

• High stiffness and rigidity

• Excellent dimensional stability

• Low friction coefficient

• Good wear resistance

• Shrinkage: 1.5% – 2.5%

• Working Temperature: -40°C to 140°C

Applications:
Precision gears, sliding components, conveyor parts, pump components, automotive mechanical parts.

PPS (Polyphenylene Sulfide)

PPS is a high-performance thermoplastic with excellent thermal and chemical resistance.

Properties:

• Density: ~1.35 g/cm³

• Very high heat resistance

• Excellent chemical resistance

• Low moisture absorption

• High dimensional stability

• Shrinkage: 0.2% – 0.7%

• Working Temperature: Up to 200°C

Applications:
Electrical connectors, automotive under-hood components, pump housings, industrial equipment.

PET (Polyethylene Terephthalate)

PET is a strong, lightweight thermoplastic commonly used in packaging and engineering applications.

Properties:

• Density: ~1.38 g/cm³

• Good mechanical strength

• Excellent chemical resistance

• Low moisture absorption

• Good dimensional stability

• Shrinkage: 1.2% – 2.0%

• Working Temperature: -40°C to 120°C

Applications:
Bottles, electrical components, mechanical parts, food packaging, textile fibers.

PVC (Polyvinyl Chloride)

PVC is a versatile thermoplastic available in rigid and flexible forms.

Properties:

• Density: ~1.38 g/cm³

• Good chemical resistance

• Flame retardant properties

• Good electrical insulation

• Shrinkage: 0.1% – 0.5%

• Working Temperature: -15°C to 60°C

Applications:
Pipes, cable insulation, window frames, industrial tubing.

PC (Polycarbonate)

Polycarbonate is a transparent engineering plastic known for its high impact strength.

Properties:

• Density: ~1.20 g/cm³

• Very high impact resistance

• Good heat resistance

• Transparent

• Good dimensional stability

• Shrinkage: 0.5% – 0.7%

• Working Temperature: -40°C to 130°C

Applications:
Safety shields, lenses, machine guards, automotive lighting components.

2️ ) Thermosetting Plastics (Thermosets)

Thermosetting plastics undergo a permanent chemical change during curing. Once hardened, they cannot be remelted or reshaped. Their molecular structure forms strong cross-linked bonds, providing high thermal stability and dimensional strength.

Thermosets are commonly used in electrical insulation, high-temperature environments, and structural applications.

Key Characteristics of Thermosets

• Cannot be remelted

• High heat resistance

• Strong dimensional stability

• Excellent electrical insulation

• More brittle compared to thermoplastics

Bakelite (Phenol Formaldehyde)

Bakelite was one of the first synthetic plastics and remains widely used in electrical insulation.

Properties:

• Excellent electrical insulation

• High heat resistance

• Rigid and stable

• Shrinkage: 0.1% – 0.5%

• Working Temperature: Up to 150°C

Applications:
Electrical switches, insulating components, circuit breakers, handles.

Melamine Resin

Melamine is a hard and durable thermoset commonly used in surface laminates.

Properties:

• High surface hardness

• Scratch resistant

• Chemical resistant

• Shrinkage: 0.2% – 0.6%

• Working Temperature: Up to 120°C

Applications:
Kitchenware, laminated boards, decorative panels.

Vulcanized Rubber

Rubber becomes a thermoset after vulcanization, forming cross-linked molecular chains.

Properties:

• Elastic

• Shock absorbing

• Wear resistant

• Flexible

• Shrinkage: 1.0% – 2.0%

• Working Temperature: -40°C to 120°C

Applications:
Seals, gaskets, tires, vibration dampers, shock absorbers.

Excellent 👌
Adding Epoxy Resin is very important — it is one of the most widely used thermosetting polymers in engineering, composites, and structural applications.

Here is the professionally structured section you can add under your Thermosetting Plastics category.

Epoxy Resin (Thermoset)

Epoxy resin is a high-performance thermosetting polymer widely used in structural bonding, composite materials, electrical insulation, and protective coatings. Once cured through a chemical reaction (usually with a hardener), epoxy forms a rigid, cross-linked molecular structure that provides excellent mechanical strength and thermal stability.

Epoxy materials are commonly used in industries requiring high adhesion strength, dimensional stability, and resistance to chemicals and environmental conditions.

Properties:

• Density: ~1.15 – 1.30 g/cm³

• Excellent adhesion to metals, plastics, and composites

• High mechanical strength

• Very good chemical resistance

• Excellent electrical insulation

• Low shrinkage during curing: 0.1% – 0.5%

• Working Temperature: Typically up to 120°C – 180°C (depending on formulation)

Note :

The final mechanical and thermal properties of epoxy systems depend on the curing agent, reinforcement material, and curing conditions. Reinforced epoxy composites significantly increase tensile strength and stiffness, making them suitable for load-bearing structural applications. 

Applications:

• Structural adhesives

• Composite materials (carbon fiber, fiberglass)

• Printed circuit boards (PCB laminates)

• Protective industrial coatings

• Marine applications

• Aerospace components

Important Engineering Note

Shrinkage values depend on processing method (injection molding, extrusion, compression molding) and material grade. Working temperature refers to recommended continuous service temperature under normal loading conditions.

Material selection must consider mechanical load, temperature exposure, chemical environment, and manufacturing method.

Engineering calculations related to shrinkage and dimensional tolerances can be supported using practical tools available in our Engineering Apps & Calculators section. 

Conclusion

Plastic materials play a fundamental role in modern engineering design and industrial manufacturing. Thermoplastics provide flexibility and recyclability, while thermosetting plastics offer superior heat resistance and structural stability.

Selecting the appropriate plastic material ensures durability, safety, cost-efficiency, and performance in mechanical, electrical, and structural applications.

Understanding material properties such as density, shrinkage, and working temperature is essential for accurate engineering design and production planning.

For CAD modeling and material design references, explore our 2D and 3D Engineering Downloads.