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Thermoset vs Thermoplastic: What’s The Difference?

Thermoset vs thermoplastic? There are key differences to know and understand. Read more below.

Thermoset vs Thermoplastic: What's The Difference? - KB Delta

At first glance, you won’t be blamed if you believe Thermoset plastics and Thermoplastic materials are the same. On the one hand, they are the same since they are both polymers. Heck, they even sound somewhat the same. But on the other hand, they behave quite differently when each is exposed to the same level or amount of heat.

Thermoplastics and thermosetting materials also have different properties as well as applications, how they are manufactured, processed, etc. It is crucial to note these differences so that mix-ups don’t occur. Product designers also need to know these significant differences in order to prevent the wrong use of one material over the other during applications.

Before highlighting the differences between thermoset and thermoplastic, let us define each material.



They are also known as thermosetting polymers or thermosetting resin. Thermoset plastics are generally in liquid form at room temperature. But as soon as thermosets are exposed to heat, they begin to harden, in many cases, with the addition of another chemical.

RTM (resin transfer molding) or RIM (reaction injection molding) is the reaction that produces thermoset plastics. It forms chemical bonds that become permanent when cured.

The permanent chemical bonds – known as crosslinks – between the monomer chains in the material effectively hold the molecules. They are responsible for changing the material’s nature and preventing it from returning to a liquid state or melting.

Thermoset materials are efficiently set into a particular solid form without melting when heated. They will never melt or enter a fluid state, even when overheated.

This makes thermoset materials an incredibly useful substance in areas where heat is a significant factor. They are typically used in chemical processing machines or equipment, electronic appliances, housings, etc., due to their resistance to chemicals and heat as well as extensive structural integrity.

Common thermosets – employed in composites – resist impact and deformation, including phenolic, epoxy resins, and polyimide.


Advantages of Thermoset Plastics


  • They have high structural integrity as a result of variable wall thicknesses.
  • They exhibit excellent resistance to high temperatures.
  • They possess excellent electrical insulation properties.
  • They give room for highly flexible product designs.
  • They can be molded with unique tolerances.
  • They are mostly less expensive alternatives to metallic components.
  • They are resistant to water and corrosion.
  • They have a low thermal conductivity.
  • They possess an incredibly high strength-to-weight ratio.
  • Cheaper tooling and setup costs compared to their counterparts, i.e., thermoplastics.
  • They have robust dimensional stability.
  • Their electrical insulation properties are superb.
  • They are ideal materials for use in preventing mechanical creep or cold flow.
  • They are trusted materials in the defense and aviation industry for many essential operational and structural components.
  • They are flexible and lightweight, making them excellent choices for custom-engineered products or components with strict dimensional specifications.
  • They possess excellent flowability. This is the ability of a particulate solid or liquid to move smoothly by flow. They easily fill all nooks and crannies within a mold. This makes it possible for product designers or manufacturers to create complex geometric shapes and larger parts from the mold.
  • They are available in a wide range of surface finishes and colors.


Disadvantages of Thermoset Materials

Thermoset plastics have some disadvantages that product designers must bear in mind:


  • They cannot be recycled because of their high resistance to heat or high temperature
  • They cannot be remolded or reshaped, no matter what.
  • Exposure to excess heat results in deformation.


Let’s check out its counterpart, i.e., Thermoplastics.



They are often resins but are solids at room temperature. However, they become soft and fluid when exposed to heat for a long period. The melting occurs due to the crossing over of the glass transition temperature or melting of crystal.

Processing thermoplastics involves zero chemical bonding. Thermoplastics can be poured into molds in order to cool and change integrity by turning into a solid, desired shape.

Thermoplastics can be recycled, reheated, and remolded with zero effects on their properties. This is why thermoplastics are used extensively in thermoforming, extrusion, injection molding, etc.

Examples of well-known thermoplastics include:


  • Polyvinylchloride (PVC)
  • Polyethylene (PE)
  • Polystyrene (PS)
  • Polycarbonate (PC)
  • Polypropylene (PP), etc.


Thermoplastics offer strength and excellent elasticity. This is why they are generally used in applications such as plastic bags (for retail), industrial machine components, etc.

If thermoplastics are exposed to prolonged heat sources, they can easily soften and deform. This makes them lose nearly all of their physical properties.


Advantages of Thermoplastics


  • They provide top-notch electrical insulation.
  • They possess high impact resistance properties.
  • They possess excellent adherence properties to metals.
  • They display incredibly high-quality aesthetic finish.
  • They are highly resistant to detergents and chemicals.
  • They can be reshaped and recycled extensively with little to no impact on the material’s properties.
  • They don’t chip.
  • They are resistant to corrosion.
  • They have improved anti-slip properties.
  • It can be used for creating hardened and rubbery crystalline surfaces.


Disadvantages of Thermoplastic


  • They are generally much more expensive than their counterparts, i.e., thermosetting plastics.
  • They are not suitable for use in various applications because they melt easily when exposed to heat or high temperatures.


Thermoset vs Thermoplastic: The Significant Differences

As mentioned earlier, thermoplastics and thermosetting plastics are polymers. But this is where the similarities end.

Both materials behave quite differently in the presence of heat. For instance, thermoplastics have a low melting point and usually melt right after curing. But thermoset plastics are inflexible as they retain their form by remaining as a solid when exposed to heat after curing.

The low melting point of thermoplastics makes them highly suitable for applications that extensively use recycled materials.

In contrast, thermoset plastics are capable of withstanding high temperatures. They never lose their shape, and this makes them highly durable. Thermoset materials are considered better than metals, even though thermoplastics are aesthetically pleasing.



Thermoplastics and thermosets differ in a wide range of ways. But they are, first of all, polymers and sound the same way.

Besides these similarities, thermoplastics and thermosetting plastic portray multiple variations in material properties. This is why they are used for different applications. They cannot be used interchangeably due to these differing variations.

As you can see, each polymer has its respective advantages and disadvantages. This is why product designers must be extra careful when selecting a material for a specific application.



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