Choosing the Right Polymer: Thermoplastics, Elastomers, and Thermosets Explained
When selecting a material for a manufacturing or engineering project, one of the first and most important decisions involves choosing the right type of polymer. The three main categories of polymers—thermoplastics, elastomers, and thermosets—each offer unique properties, performance capabilities, and manufacturing considerations.
At Pexco, we are experts at material selection, and we help clients navigate these choices every day. In this blog, we’ll walk you through the key characteristics, advantages, and typical applications of each polymer type to help determine which material might be best for your specific product or design.
Understanding the Basics
What Are Thermoplastics?
Thermoplastics are a class of polymers that become pliable or moldable when heated and harden upon cooling. This heating and cooling process is, meaning thermoplastics can be reshaped multiple times without undergoing any significant chemical change. This reusability makes them a popular choice in many high-volume manufacturing applications.
Common Properties of Thermoplastics:
- Reversible Processing: Can be melted and reshaped repeatedly.
- Mechanical Strength: Offers good durability and toughness.
- Impact Resistance: Many types withstand shocks and physical stress.
- Recyclability: Most are recyclable, contributing to sustainability efforts.
Examples of Thermoplastics:
- Polyethylene (PE): Used in packaging, plastic bags, and containers.
- Polypropylene (PP): Found in automotive parts, textiles, and medical devices.
- Polystyrene (PS): Often used in disposable food containers and insulation.
- Polyvinyl Chloride (PVC): Common in plumbing pipes, cables, and flooring.
Thermoplastics are compatible with a variety of production processes, including injection molding, extrusion, vacuum forming, and even 3D printing. This versatility makes them suitable for a wide range of applications—from consumer electronics and automotive components to packaging and everyday goods.
What Are Elastomers?
Elastomers are polymers known for their elasticity—their ability to stretch under stress and return to their original shape once the stress is removed. This behavior is made possible by the unique structure of elastomers: long-chain molecules with occasional cross-links that allow movement while maintaining structural integrity.
Key Properties of Elastomers: Examples of Elastomers:
- Natural Rubber: Widely used in tires and industrial belts.
- Silicone Rubber: Known for heat resistance; used in kitchenware and medical devices.
- Polyurethane Elastomers: Offer a balance of strength and flexibility.
Examples of Elastomers:
Polyurethane Elastomers: Offer a balance of strength and flexibility.Because of their resilience and flexibility, elastomers are widely used in:
- Natural Rubber: Widely used in tires and industrial belts
- Silicone Rubber: Known for heat resistance; used in kitchenware and medical devices.
- Polyurethane Elastomers: Offer a balance of strength and flexibility.
Because of their resilience and flexibility, elastomers are widely used in:
- Seals and gaskets
- Medical tubing
- Vibration dampeners and bushings
Elastomers can be either thermoplastic elastomers (TPEs) or thermoset elastomers, depending on how they are processed. TPEs combine the elasticity of rubber with the processability of plastics, while thermoset elastomers are cured into permanent shapes.
What Are Thermosets?
Thermosets (or thermosetting polymers) differ significantly from thermoplastics. Once they undergo curing—a chemical reaction typically triggered by heat, pressure, or a catalyst—they become irreversibly hardened . Unlike thermoplastics, thermosets cannot be remelted or reshaped after the initial forming process.
Core Characteristics of Thermosets:
- Permanence: The material hardens permanently once cured.
- High Thermal Stability: Maintains shape and integrity under high temperatures.
- Chemical Resistance: Resists corrosion and chemical degradation.
- Dimensional Stability: Maintains exact form over time, even in harsh conditions.
Examples of Thermosets:
- Polyurethane Thermosets: Found in rigid foams, coatings, and structural parts.
- Epoxy Resins: Common in adhesives, coatings, and circuit boards.
- Phenolic Resins: Used in brake pads, electrical insulation, and appliance parts.
Thermosets are the material of choice for applications where mechanical performance, heat resistance, and longevity are non-negotiable—such as in the aerospace, electronics, and automotive industries.
Comparing the Three: Key Differences
To determine which material class is best suited for your application, it’s helpful to understand the fundamental differences between thermoplastics, elastomers, and thermosets.
| Property | Thermoplastics | Elastomers | Thermosets |
| Heat Behavior | Softens with heat, hardens on cooling | Stretchable, returns to shape | Hardens permanently after curing |
| Recyclability | Highly recyclable | Variable – some recyclable | Difficult to recycle |
| Elasticity | Rigid to semi-flexible | Highly elastic | Usually rigid |
| Durability | Good | Excellent fatigue resistance | Excellent heat and chemical resistance |
| Typical Applications | Packaging, automotive, consumer goods | Tires, seals, gaskets, footwear | Electronics, aerospace, durable parts |
How to Choose the Right Material for Your Project
When selecting a polymer for your application, consider the following criteria:
- Thermal Requirements: Will the material be exposed to high or fluctuating temperatures?
- Mechanical Performance: Does the application require flexibility, hardness, or impact resistance?
- Chemical Resistance: Will the material be exposed to chemicals, oils, or solvents?
- Reusability and Recycling: Is recyclability a priority for sustainability?
- Manufacturing Method: Will you use injection molding, extrusion, 3D printing, or casting?
- Cost Constraints: Are you working within strict budgetary limits?
Understanding your product’s environment and performance expectations is crucial. For example:
- A food packaging application may call for a recyclable thermoplastic like polyethylene.
- A shock-absorbing pad might require a flexible elastomer like silicone.
- A printed circuit board would benefit from a heat-resistant thermoset like epoxy resin.
Real World Support from Pexco
At Pexco , we work closely with clients across industries to evaluate material options and determine the optimal solution for each unique project. Whether you need precision-engineered thermoplastics for a complex component, high-performance elastomers for dynamic loads, or durable thermosets for harsh environments, our team can help guide you through the selection and design process.
We bring decades of experience in custom polymer solutions, leveraging deep technical knowledge to support:
- Innovation
- Quality
- Efficiency
- For more information on Pexco’s Injection Molding & Extrusion capabilities, please request information at pexco.com/contact-us.