This image was created with artificial intelligence – marked under Art. 50 of the AI Act, Regulation (EU) 2024/1689. It is a placeholder until the company's photos arrive.Thermosets
What are thermosets? Everything about the properties, advantages and typical areas of application of these plastics – explained clearly and with practical relevance.
Thermosets are a class of polymers characterised by their high strength and resistance to deformation after curing. Unlike thermoplastics and elastomers, they cannot be melted or reshaped again after they have been formed.
These properties make them ideal for applications that demand stability, heat resistance and mechanical load-bearing capacity.
The manufacturing process for thermosets involves the polymerisation and cross-linking of the polymer chains, which gives them their final properties.
The advantages of thermosets include their high thermal resistance and chemical resistance, while disadvantages include their brittleness and lack of elasticity.
Fundamentals and properties
Thermosets are polymers whose molecular chains are three-dimensionally cross-linked by strong chemical bonds. This cross-linking gives thermosets their high strength and dimensional stability. After curing, the chains are so firmly bonded to one another that they can no longer move or be deformed.
Thermosets exhibit a range of remarkable properties, including:
- High strength: After curing, thermosets are extremely stable and resistant to mechanical load.
- Heat resistance: Thermosets do not melt when heated, but decompose at very high temperatures.
- Chemical resistance: Many thermosets are resistant to chemicals, solvents and oils.
- Electrical insulating capability: Because of their structure, thermosets are excellently suited as electrical insulators.
- Brittleness: Despite their strength, thermosets are often brittle and can tear or break under extreme mechanical loads.
Application in industry
Thermosets are widely used in industrial and technical fields where high strength and temperature resistance are required. Examples of applications include:
- Electrical engineering: sockets, switches, insulators and housings for electronic components.
- Vehicle construction: body parts, gearbox housings and heat-resistant components.
- Construction industry: coatings, structural components and heat-resistant components.
- Composite materials: thermosets are often used as matrix material in fibre-reinforced plastics (e.g. glass or carbon fibre composites).
Manufacturing process
The manufacturing process for thermosets involves two main steps: polymerisation and cross-linking.
- Polymerisation: In this step, the monomers are linked into polymer chains. This takes place under the influence of heat or through chemical catalysts that trigger the reaction.
- Cross-linking: In the next step, the polymer chains are irreversibly bonded to one another. This takes place through chemical reactions that create a three-dimensional network structure. Once cross-linked, the molecular chains can no longer be shifted or deformed.
Thermosets in electrical engineering
Thermosets are of great importance, particularly in electrical engineering. Because of their electrical insulating properties, they are frequently used for the manufacture of components such as sockets, switches and housings for electrical devices. Their thermal stability ensures that they do not deform even under continuous heat load.
The various thermosets
There is a wide variety of thermosets, which are used for different applications because of their differing chemical compositions and properties. Some of the most important thermosets are:
- Epoxy resins (EP): Known for their high strength and good adhesion properties, epoxy resins are frequently used as adhesives, in coatings and in composite materials.
- Phenolic resins (PF): These resins are heat-resistant and are often used in electrical insulators and heat-resistant materials.
- Melamine resins (MF): These resins are scratch-resistant and heat-resistant and are frequently used in kitchen surfaces and laminates.
- Polyester resins (UP): Frequently used in glass fibre-reinforced plastics, they are ideal for the manufacture of boat hulls and body parts.
- Urea-formaldehyde resins (UF): These resins are characterised by their high strength and hardness and are often used as binders for wood-based materials as well as in electrical components.
- Polyurethane (PU): Polyurethanes can exhibit both elastic and hard properties and are used in foams, coatings and paints, as well as in adhesives.
- Diallyl phthalate (DAP): This resin offers excellent electrical insulation properties and chemical resistance, which makes it ideal for applications in the electronics and automotive industry.
- Silicone resins: These resins are particularly resistant to high temperatures and chemicals, which makes them suitable for electrical insulation and heat-resistant coatings.
Properties and applications at a glance
| Thermoset | Properties | Applications |
|---|---|---|
| Epoxy resin (EP) | High strength, good adhesion | Adhesives, coatings, composite materials |
| Phenolic resin (PF) | Heat-resistant, insulating | Electrical insulators, heat-resistant parts |
| Melamine resin (MF) | Scratch-resistant, heat-resistant | Kitchen surfaces, laminate |
| Polyester resin (UP) | High strength, robust | Boat hulls, body parts |
| Urea-formaldehyde (UF) | High hardness, abrasion-resistant, insulating | Wood-based panels, electrical components |
| Polyurethane (PU) | High abrasion resistance, versatile | Foams, paints, coatings, adhesives |
| Diallyl phthalate (DAP) | High electrical insulation, chemical resistance | Electronic components, automotive parts |
| Silicone resins | Heat-resistant, chemical-resistant | Electrical insulation, heat-resistant coatings |
This overview shows the diversity of thermosets that are used for different industrial and technical applications. They offer a broad range of properties that can be used in various fields as required.
Frequently asked questions (FAQ)
What are the main applications of thermosets? Thermosets are frequently used in electrical engineering, vehicle construction and the construction industry, in particular for heat-resistant and high-strength components.
How are thermosets manufactured? Thermosets are manufactured by polymerisation and subsequent chemical cross-linking of the polymer chains, which gives them their solid structure and resistance.
What advantages do thermosets offer? Thermosets offer high strength, excellent chemical and thermal resistance as well as good electrical insulation properties.
Are there disadvantages to using thermosets? Yes, thermosets are often brittle and can no longer be shaped or recycled after curing.
Why are thermosets so important in electrical engineering? Thermosets are ideal insulating materials because they are electrically non-conductive and heat-resistant.
