Thermosets vs. Thermoplastics
What is the difference between thermoset and thermoplastic materials? It comes down to how each reacts to heat. There are similarities in thermoset properties and those of thermoplastics, so it’s the differences you need to pay attention to. This guide will help you understand these materials, covering:
Introduction to Thermoplastics: Versatility and Adaptability
What are thermoset plastics or thermosetting plastics? ? Thermoplastics belong to a class of polymers known for their capacity to soften and become pliable when subjected to heat. This distinctive behavior arises from their molecular structure, consisting of repeating monomer units that form long chains or networks. Types of thermoplastics include:
- Nylon
- Polyethylene (PE)
- Polyvinyl Chloride (PVC)
- Polycarbonate (PC)
- Polypropylene (PP)
Thermoplastic polymers do not experience any chemical bonding during the curing process, which makes them re-moldable and recyclable. They maintain their chemical integrity even after melting, allowing them to be reshaped multiple times without degradation. That, in turn, makes them a versatile material that can adapt to almost any manufacturing process, including injection molding, extrusion, and blow molding.
Our experts explain injection molding and the different thermoplastics used in this process in our Knowledge Center, where you learn more.
Exploring Thermosets: Durability and Heat Resistance
What are thermoset plastics? Thermosetting polymers owe their outstanding durability and resistance to heat to their distinctive chemical structure and curing process.
Thermoset plastics form permanent chemical bonds during curing, typically induced by heat or a catalyst. This reaction leads to the cross-linking of individual polymer chains, forming a three-dimensional network structure. The tightly interconnected network of chemical bonds affects thermoset properties, giving the material its high density and durability.
This cross-linking process is irreversible, rendering thermosetting polymers infusible and incapable of being re-melted or re-molded without significant degradation.
Common examples of thermoset plastics include:
- Silicone
- Epoxy resins – used in adhesives and coatings
- Phenolic
- Polyimide
- Polyvinylidene fluoride (PVDF)
Strengths and Weaknesses of Thermoplastics and Thermosets
Specific properties depend on the type of thermoset or thermoplastic polymers we’re talking about. For example, nylon’s properties are different to that of polycarbonate, even though they’re both thermoplastic resins.
Also, what you consider a weakness can be a strength to another engineer – it depends on the application. That said, there are still some general observations we can make that will help you see the difference between thermoset and thermoplastic materials.
Thermoplastics: Characteristics
Moldability: When heated to their specific softening point, thermoplastics can be easily shaped using various molding techniques like thermoset injection molding, extrusion, blow molding, and thermoforming. This flexibility facilitates the production of intricate and complex shapes, rendering them suitable for a wide array of applications.
Recyclability: Their reversible phase change enables thermoplastics to be recycled through re-melting and reprocessing. This capability supports sustainability efforts by reducing waste and promoting the creation of new products.
Diverse Material Range: Thermoplastics encompass a wide range of materials, each possessing unique properties and characteristics. This diversity empowers engineers and designers to select materials tailored to specific requirements, be it for strength, flexibility, or other factors.
Application Across Industries: Thermoplastics find extensive use in industries like automotive, healthcare, consumer goods, aerospace, packaging, and more. Their adaptability makes them suitable for a variety of components and products.
Lightweight and Durable: Many thermoplastics strike a balance between low density and high strength, making them an optimal choice for applications where weight reduction and durability are crucial, such as in the automotive and aerospace sectors.
Chemical Resistance: Certain thermoplastics exhibit remarkable resistance to various chemicals, rendering them suitable for applications where exposure to corrosive substances is a concern.
Ease of Fabrication: Thermoplastics can be processed through various techniques, including injection molding, extrusion, and blow molding. These methods offer efficiency and precision in shaping the material.
Thermosets: Characteristics
The key factors contributing to the characteristics of thermoset materials are:
High Cross-Linking Density: The cross-linking of polymer chains creates a tightly interconnected network of chemical bonds. This high density gives thermoset plastics exceptional mechanical strength, rigidity, and resistance to deformation, which results in its high durability.
Thermal Stability: The densely cross-linked structure of thermosetting polymers grants them exceptional resistance to thermal degradation, even at elevated temperatures. They can maintain their structural integrity and mechanical properties in environments where most thermoplastic would soften, melt, or deteriorate.
Chemical Resistance: The structure also confers upon thermoset plastics a high degree of resistance to chemical interactions or degradation when exposed to a wide range of chemicals. This makes them suitable for applications where protection against corrosive substances is vital.
Low Coefficient of Thermal Expansion (CTE): Thermoset plastics typically exhibit a low coefficient of thermal expansion, indicating that they undergo minimal expansion or contraction with changes in temperature. This property is crucial in applications where maintaining dimensional stability under varying temperatures is a critical requirement.
Electrical Insulation Properties: Owing to their high density and the absence of free-moving charge carriers, thermoset plastics serve as excellent electrical insulators. This property proves invaluable in applications where electrical insulation is imperative to prevent electrical current leakage or short circuits.
Thermoset plastics vs. Thermoplastics
Not all thermoset materials and thermoplastics are the same. Stabilizers can be added to both to bring out the characteristics you want. For example, nylon is a thermoplastic, which means it can age and discolor when exposed to UV rays. But the material can be formulated to withstand UV.
Below are general characteristics of thermosetting polymers and thermoplastics, but keep in mind the properties of any resin can be altered.
At a glance
| Characteristic | Thermosets | Thermoplastics |
|---|---|---|
| Resistance to high temperature | x | |
| Can be re-molded and reshaped | x | |
| Hard and rigid | x | |
| Good aesthetics finishes | x | x (Better) |
| High mechanical strength | x | |
| Excellent dimensional stability | x | |
| Recyclable | x | x |
| Excellent electrical insulation | x | x |
| Easier to surface finish | x | |
| Good thermal conductivity | x | |
| Adhesive to metal | x | |
| Excellent impact resistance | x | |
| Can degrade when exposed to UV | x | |
| Excellent corrosion resistance | x | x |
| Chip resistant | x | |
| More lightweight, due to lower density | x |
Thermosets and Thermoplastics: Applications
Thermosets vs. thermoplastics. To help you better understand why and when these materials are used, we’ve pulled together examples from our range of small components. You can also download free CADs and try before you buy with free samples.
Thermosets
Silicone masking caps and plugs
The high-temperatures inherent in masking processes make silicone an ideal material for protecting parts in your application. Our masking caps and plugs here can withstand temperatures of up to 600°F. We tell you more about silicone in our guide, What is Silicone Rubber?
Another thermoset, polyimide, is used extensively in high-temperature masking tapes. Discover the components in our extensive ranges made of these thermoset plastics.
Browse silicone components |
Browse polyimide components |
Secure multilobed grip to position, tighten, and hold fixtures, equipment, and machinery. Ergonomic grip for controlling, positioning and tightening your application. Our clamping knob is also available in thermoplastics, such as polypropylene.
Phenolic’s mechanical strength makes it the ideal choice if the knob will endure heavy loads, constant use, or high-temperature environments. If weight is a critical factor, then choose a thermoplastic. For example, polypropylene is more lightweight – and the better choice if exposure to chemicals is a possibility.
Browse phenolic components
Thermoplastics
Light weight, resisting vibration, chemicals, electricity and corrosion. Nylon’s properties make it a common material for plastic fasteners. We explain this thermoplastic in more detail in our guide, Nylon 6 vs. Nylon 6/6, where you can learn more.
Explore our vast range of nylon components to find out other ways this important thermoplastic is used.
Browse nylon components
As a thermoplastic, polypropylene (PP) has moderate flexibility. This makes it an ideal material for cable ducts, as it can adapt to various cable layouts. You can learn more about this thermoplastic in our guide, Everything You Need to Know About PP Plastic.
Get to know our range of polypropylene components now.
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Polyethylene can be either high density (HDPE) or low density (LDPE). This is an example of LDPE, which offers flexibility, ease of molding, and impact resistance – exactly what you need when you’re protecting pipes and hoses from ingress and damage. We help you understand the difference between polypropylene and polyethylene in PP vs. PE: Which is Best for Your Component?
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PVC is a widely used thermoplastic known for its high dielectric strength and resistance to moisture, making it ideal for insulating electrical terminals and connections. We explain more about this incredibly versatile material in our guide, What is PVC (Poly Chloride)?
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Polycarbonate (PC) is a naturally translucent thermoplastic. While it’s often formulated to be opaque, it's PC’s transparency that makes it ideal for LED light pipes. It provides exceptional light transmission properties and is highly resistant to both heat and impact. Our PC light pipes have an operating temperature range between -40°F to 266°F.
Browse polycarbonate components
Choosing the Right Material: Thermosets vs. Thermoplastics
Choosing between thermosetting polymers and thermoplastics involves considering several key factors to determine which material is the most suitable for your specific application. Use these steps as a guideline.
If you’re uncertain about the appropriate choice, consult with our material experts or engineers who can provide guidance based on their experience and knowledge. Call 1-800-847-0486.
- Application Requirements: Start by clearly defining what your application needs. Consider factors such as temperature, mechanical strength, chemical exposure, electrical properties, and desired lifespan.
- Thermal Properties: If your application involves exposure to high temperatures, thermosets are typically more suitable due to their ability to withstand heat without softening.
- Mechanical Properties: Evaluate the mechanical properties required, such as tensile strength, impact resistance, and rigidity. Thermosets tend to offer better mechanical strength.
- Resistance to Chemicals: Consider the chemicals or solvents the material may come into contact with. Some thermosets and thermoplastics have varying levels of resistance to different chemicals, so choose accordingly, so you’ll need to look at the specific material.
- Electrical Properties: If electrical insulation is important, select a material with the necessary dielectric properties. Both thermosets and thermoplastics are good insulators, but again, look at the specific material.
- Processing and Design Flexibility: Think about the manufacturing processes and design flexibility required. Thermoplastics are easier to mold and reshape, making them suitable for intricate designs and rapid production. Thermosets typically require more complex curing processes.
- Cost Considerations: Determine your budget constraints. Thermosets can be more expensive due to their production processes, while thermoplastics are generally more cost-effective.
- Environmental Impact: Consider sustainability and recycling requirements. Thermoplastics can be recycled more easily than thermosets, making them a more eco-friendly choice in some cases.
- Testing and Prototyping: Perform material testing and prototyping to validate your choice. This helps ensure that the selected material meets the specific performance criteria of your application.
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If you’re not quite sure which solution will work best for your application, our experts are always happy to advise you.
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