Thermosets and thermoplastics are one of the most important comparisons in the manufacturing industry. Thermoplastic polymers have been the most commonly used type of polymer for injection molding and other plastic machining processes. However, the development of thermosets has given rise to worthy competition. Although these plastic polymers share some similarities, there are also some notable differences.
Thermoplastics are the best option in certain situations, while thermosets are required in others. Because of the similarities of these polymers, manufacturers often use them for similar products. However, this can affect the quality and durability of the final product. Therefore, you need to know the differences between thermosets and thermoplastics to make the best decision.
This guide explains the many differences between these polymers and details their properties and suitable applications. Read on as we find the best type of plastic for your project.
An overview of thermosets
With thermosets, the polymers are cross-linked during the curing process. This creates an irreversible chemical bond. These polymers are generally liquid at room temperature, but harden after heating or adding chemicals.
The cross-linking of these polymers prevents them from melting again at high temperatures. Therefore, a thermoset maintains its shape after shaping. For this reason, they are suitable for high temperature applications.
Common Examples of Thermosets
Thermosets used in the production of plastic parts include, but are not limited to, the following:
- Epoxy
- melamine
- Phenols
- polyester
- Polyimides
- Polytetrafluoroethylene (PTFE)
- Polyurethanes
- Polyvinylidene fluoride (PVDF)
- silicone
- vinyl ester
Due to their impact resistance and high structural integrity, thermosets are suitable for the automotive, electronics, lighting, appliance and energy industries.
Advantages and disadvantages of thermosets
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- High strength/weight ratio
- Greater corrosion resistance
- Excellent electrical insulation and dielectric strength
- Good dimensional stability
- High heat and temperature resistance
- Ensures flexible changes to product design
- Low thermal conductivity
- Excellent aesthetic finishes
- Reduced tooling costs and production costs
Disadvantages
- It is not recyclable.
- It cannot be remodeled or remodeled.
- The rigidity of the material is not suitable for applications with strong vibrations.
Thermoplastics Overview
Thermoplastics are resins that are solid at room temperature. Pellets soften when heated and become more liquid. This fluidity is due to the pellets exceeding the glass transition temperature. Unlike thermosets, there is no chemical bonding in the processing of thermoplastics.
Thermoplastic polymers can be remelted multiple times and molded into different shapes. You can also reheat, reshape and recycle these plastics without affecting their properties. They generally provide excellent elasticity and strength and are resistant to shrinkage. Therefore, these materials are best suited for processes such as plastic extrusion, injection molding, and thermoforming.
Common Examples of Thermoplastics
There are several thermoplastics available today, each with different properties and uses. Some of the most common are:
- Polyoxymethylene acetal copolymer
- Polyoxymethylene homopolymer acetal
- Acrylic
- nylon
- Polycarbonate (PC)
- Polyethylene (PE)
- Polyethylene terephthalate (PET)
- Polypropylene (PP)
- Polystyrene (PS)
- Polyvinyl chloride (PVC)
- Teflon
Advantages and Disadvantages of Thermoplastics
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- Can be remodeled and remodeled
- Easily recyclable
- Excellent quality aesthetic finish
- High impact resistance and chemical resistance
- Excellent corrosion resistance
- Better electrical insulation
- Improved anti-slip properties
- High flexibility
Disadvantages
- Not suitable for some applications as it may soften when heated.
- Relatively more expensive than thermosets.
Main differences between thermoset and thermoplastic
Despite some similar properties of these resins, there are some differences you need to be aware of. We will explore the main differences between thermoplastics and thermosets in the following titles:
1. Microstructure
Thermosets consist of rows of highly interconnected molecules. As already mentioned, this cross-linking results in a rigid molecular structure. You can heat them the first time and make them any texture you like. However, over time they become firm and rigid. This rigidity is permanent and prevents them from being remodeled.
Thermoplastics, on the other hand, do not have cross-linked molecular chains. The chains are not linked together by chemical bonds, but only by intermolecular forces. Its macromolecules are therefore predominantly located close to each other. At high temperatures, the currents move slightly against each other. Therefore, plastic can be easily reshaped and redesigned.
2. Physical and chemical properties
When selecting materials, it is important to consider physical and chemical properties to ensure optimal performance. Here is a detailed comparison of the properties of thermosets and thermoplastics:
2.1 Melting point
The main difference between thermosets and thermoplastics is their behavior when heated. Thermosets have a melting point higher than the decomposition temperature, while thermoplastics have a lower melting point.
After hardening, thermosets maintain their solid shape when heated. Thermoplastics, on the other hand, melt or decompose when heated further. Therefore, thermosets have higher melting points than thermoplastics. For this reason, manufacturers use thermoplastics for recyclable components.
2.2 Corrosion resistance
Both types of plastic polymers are sufficiently resistant to rust and corrosion. Therefore, they are suitable for external applications and may come into contact with corrosive media. However, thermoplastics are more resistant to chemical attacks than thermosets. Therefore, they are more resistant to corrosion.
2.3 Durability
If you want to manufacture automotive or electrical appliances, you need to ensure heat resistance and durability. Thermosets are significantly more durable than their counterparts. These plastic polymers are generally lighter and have excellent strength, toughness and impact resistance.
You can strengthen them further with reinforcing materials like fiberglass and carbon. Their excellent structural advantages and dimensional stability make them better than thermoplastics in terms of durability.
The following table “Duroplasts and thermoplastics” compares the physical and chemical properties of these plastics:
| Property | Thermosets | Thermoplastics |
| Molecular structure | They are network polymers with high cross-linking and strong molecular bonds. | They are linear polymers in a straight chain with weak molecular bonds. |
| Mechanically | Inelastic, rigid and stable due to the network. | Flexible, elastic and extremely resistant to shocks thanks to the crystalline structure. |
| fusion point | The melting point is higher than the decomposition temperature. | The melting point is lower than the decomposition temperature. |
| solubility | They do not dissolve in organic solvents. | They dissolve in organic solvents. |
| Chemical resistance | Good thermal and chemical resistance. | Greater chemical resistance. |
| operating temperature | Higher continuous use temperature (CUT) than thermoplastics. | Lower CUT than thermosets. |
| Recyclability | Not recyclable. | Recyclable and reusable by heating. |
3. Editing process
Thermoplastics processing can be done using several methods, including injection molding, extrusion molding, vacuum forming, and thermoforming. The machinist introduces the granular material into the mold, usually using spherical resins about 3 mm in diameter. The resins are then heated to high temperatures until their melting point.
Thermoplastics are excellent thermal insulators. Therefore, they take longer to cool than other plastics. Most manufacturers use rapid cooling to achieve high production rates by immersing them in water baths or spraying them with cold water. As it cools, the plastic material shrinks, affecting the crystallization and internal structure of the material. Therefore, it is important to specify the shrinkage rate of thermoplastics.
Thermosets, on the other hand, are processed in liquid form. The main processes used are Resin Transfer Molding (RTM) and Reaction Injection Molding (RIM). The curing process often includes inhibitors, curing agents, plasticizers, hardeners or fillers. The choice of reinforcements depends on the desired result.
4. Aesthetics
Thermoplastics are popular options for achieving high-quality finishes. However, the RTM and RIM processes described above make the surface treatment of thermosets unique. With these techniques you have unique opportunities to achieve first-class aesthetics. They allow direct spraying into the mold before injecting the thermosetting plastic resin.
These processes also allow molds to be painted and coated. This creates stronger bonds between the plastic surface and the paint. This will help you ensure proper adhesion and prevent the plastic from cracking, chipping, peeling, and other manufacturing defects.
Furthermore, thermosets such as epoxy resins, phenols, silicones, etc. They are suitable for high gloss and matte surfaces. Painted parts made from thermosets often feature finely detailed textures. Thanks to their excellent fluidity, they can also achieve fine aesthetic details.
5. Costs
Thermoplastics are generally cheaper than thermosets in terms of overall production costs. However, it is important to consider the factors that impact the development of plastic prototypes. In addition to the material itself, it is necessary to consider the cost of tools, labor, production time and choice of finish.
6. Common Applications
Thermosets are used in many industries because they are comparatively more economical. They also ensure that products meet desired specifications. Thermosets offer an excellent combination of thermal stability, structural robustness and chemical resistance.
The resins are also flexible enough to ensure perfect formation of complex geometries. Therefore, they are an excellent replacement for some metallic materials. RTM and RIM techniques also guarantee considerable consistency in manufacturing. Its typical applications include:
- Chemical production and processing tools, including tubing, cell caps and accessories
- Medical and electrical components and housings
- Boxes, panels and doors for transport and heavy construction
- Auto parts for cars and tractors
- Components for military vehicles
On the other hand, the application areas of thermoplastics vary in different industries. Due to their high chemical and corrosion resistance, they are good metal substitutes. However, it is important to note that they cannot withstand as much heat as thermosets.
Thermoplastics are raw materials suitable for diverse industries, including automotive, chemical, biomedical, electronics, and food and beverage. Some of its areas of application are:
- Construction of industrial machining components
- Chemical Piping Systems
- Laboratory equipment
- Electrical or electronic insulating and encapsulating materials
- Non-stick cookware
- Protective covers for hard tools
- Liquid Storage Tanks
Thermoset vs. Thermoplastic: Which Polymer is the Best Option?
Both thermoplastic and thermosetting plastics are available in a wide variety of materials with different applications. These polymers are the best choice for your products. However, the option chosen depends mainly on the application of the desired product. Remember that the wrong choice of materials can affect the functionality of a product, even if it is well constructed.
When choosing a material, you must carefully consider its impact resistance, strength, heat resistance and other factors. For example, thermosets are best suited for applications where heat is a concern, including electrical devices and housings. Their heat and chemical resistance, as well as excellent structural integrity, also make them ideal for chemical processing plants.
Thermoplastics are best suited for products exposed to corrosive materials. They also help you produce parts in large quantities easily and at competitive prices. Thermoplastics also allow you to obtain detailed geometric shapes, making them good substitutes for metal. They are also recyclable and reusable, which can reduce costs in the long run.
University Degree
Thermoplastics and thermosets have several differences in their properties, recyclability, cost and other characteristics. Therefore, they are ideal for different applications depending on the required physical and chemical properties. While thermosets are suitable for high temperature applications, thermoplastics are better known for their corrosion resistance and recyclability.
Common questions
Why are thermosets harder than thermoplastics?
Thermosets are harder than thermoplastics because three-dimensional networks are created when they harden. Polymer chains maintain their strong covalent bonds and their shape. Their greater crosslinking density gives them greater mechanical resistance and hardness. Therefore, they are preferred due to their structural integrity and heat resistance.
Is thermoplastic toxic?
Any raw material can be potentially toxic depending on several factors. Thermoplastic polymers are not inherently toxic and are safe for many applications, including biomedical devices.
Which thermoplastics or thermosets are most temperature resistant?
Thermosets can generally withstand higher temperatures than thermoplastics. Furthermore, they have strong covalent cross-links between their polymer chains. Therefore, they cannot soften when heated further. Therefore, thermosets are more stable than their counterparts.
