Thermosetting plastics

Thermosets are permanently cross-linked plastics that remain dimensionally stable even under high mechanical, thermal and electrical loads. Unlike thermoplastics, thermosetting plastics cannot be melted or reshaped again after curing.

Martan Plastics supplies thermosetting materials and component solutions for industrial applications where high strength, electrical insulation, temperature resistance or dimensional accuracy are required. Depending on your application, we support you in selecting a suitable material grade and in the technical implementation.

Thermosetting plastics for industrial applications

Thermosets are used in particular where conventional plastics reach their limits due to high temperatures, mechanical loads or electrical requirements. The three-dimensional cross-linking of the polymer structure means the materials retain their shape even under demanding operating conditions.

Depending on the resin system, reinforcement and material structure, thermosetting plastics can be specifically adapted to the respective application. For example, glass-fibre-reinforced or fabric-reinforced grades are possible for components with high mechanical strength and dimensional stability.

Martan Plastics supports industrial companies in the procurement and selection of suitable thermosets for individual parts, spare parts, prototypes and series applications.

Properties of thermosetting plastics

Thermosets are characterised by a wide range of technical advantages:

• High heat resistance: Resistant to extreme temperatures without deformation
• Mechanical strength: Particularly robust and durable
• Chemical resistance: Insensitive to aggressive substances
• Electrical insulating capability: Ideal for applications in electrical engineering
• Low water absorption: High dimensional stability even under the influence of moisture
• Good dimensional stability: Minimal material expansion under temperature fluctuations
• Low weight: Reduced material load combined with high strength
• Flame retardancy: Resistant to fire and high temperatures depending on composition

Which thermoset is suitable for your application?

The selection of a thermosetting plastic is not based solely on maximum temperature resistance. What matters is the interaction of mechanical load, ambient conditions, electrical requirements and desired service life.

Requirement	Important selection criteria
High mechanical load	Compressive strength, flexural strength, type of reinforcement and wear behaviour
High temperatures	Continuous service temperature, short-term peak temperature and heat deflection temperature
Electrical insulation	Dielectric strength, tracking resistance and moisture absorption
Chemical contact	Resistance to oils, fuels, acids, alkalis or cleaning agents
Dimensionally accurate components	Thermal expansion, water absorption and behaviour under continuous load

For a reliable material recommendation, the specific operating conditions should therefore always be considered. These include temperature, type of load, contact media, dimensions, tolerances and the planned quantity.

Manufacturing processes

Thermosetting plastics are created by an irreversible chemical curing reaction (polymerisation, polyaddition or polycondensation). They usually consist of a resin system (e.g. epoxy resins, phenolic resins or melamine resins) and reinforcing materials such as glass fibres or carbon fibres. Processing typically takes place by:

• Pressing (hot pressing)
• Injection moulding
• Laminating
• Casting
• Pultrusion for continuously reinforced profiles
• Autoclave curing for maximum mechanical stability

Once cured, thermosetting plastics can no longer be reshaped or melted.

Thermosets or thermoplastics?

The essential difference lies in the internal structure of the plastics. Thermoplastics become soft when heated and can be reshaped again. Thermosets, by contrast, cure permanently through a chemical cross-linking reaction.

This cross-linking provides high dimensional stability and heat resistance, but restricts subsequent formability. Thermosetting components are therefore brought into their final shape during manufacturing or subsequently machined.

Which plastic group is better suited depends on the application. Thermoplastics often offer advantages with complex shapes, weldability and recycling. Thermosets are particularly interesting when dimensional stability, electrical insulation or load capacity at elevated temperatures are the priority.

Further information on the distinction can be found in our article on engineering plastics and alternative materials.

Areas of application

Due to their special properties, thermosetting plastics are used in numerous high-tech industries, our thermosets for industry. Typical uses in heavy-duty operation: crane and lifting technology as well as mechanical and plant engineering.

Mechanical engineering

Thermosets are used for high-load components such as plain bearings, gears and housings. Their outstanding wear resistance and temperature resistance make them a long-lasting alternative to metals. Mechanical engineering companies also benefit from the corrosion resistance of thermosets, which, unlike metals, do not rust.

Medical technology

Thermosets are valued in medical technology for their hygienic properties and chemical resistance. They are used in surgical instruments, prostheses, diagnostic systems and sterile packaging. The material's resistance to disinfectants and high temperatures is a further plus point.

Vehicle construction

In the automotive and aerospace industries, they play an important role as heat-resistant and lightweight components. Typical applications are engine covers, brake system components, structural parts and housings for electronic control units. The advantage over metal lies in the low weight, which reduces fuel consumption and improves energy efficiency.

Electrical engineering

Thanks to their high electrical insulating capability, thermosetting plastics are indispensable in high-voltage engineering. They are used in switches, connectors, insulators and circuit boards. The high dielectric strength makes them ideal for complex electrical systems.

Aerospace technology

Here, thermosetting composite materials (e.g. CFRP with epoxy resin) are used to create extremely lightweight yet stable structures for aircraft and spacecraft. The high mechanical requirements in aviation make thermosets a preferred choice for load-bearing elements in aircraft fuselages, interior fittings and satellite structures.

Construction

Thermosetting plastics are increasingly used in the construction sector, in particular for insulating materials, load-bearing structures, weather-resistant cladding and floor coatings. Their durability, moisture resistance and high mechanical strength make them ideal for extreme environmental conditions. In addition, some thermosets offer outstanding thermal insulation properties, which contribute to the energy efficiency of buildings.

Machining of thermosetting plastics

Cured thermosets cannot be melted again. Further shaping therefore takes place, among other things, through machining processes. Depending on the material, reinforcement and component geometry, milling, turning, drilling or waterjet cutting are possible, for example.

For fibre- or fabric-reinforced grades, tool selection, cutting parameters and machining direction must be matched to the respective material. This allows clean edges, precise dimensions and the lowest possible damage to the reinforcement structure to be achieved.

Further information can be found on our page on plastic machining.

What thermosets are there?

Thermosets differ primarily in the resin system used and the reinforcing materials employed. Commonly used thermosetting materials include:

• Phenolic resins (PF): high dimensional stability, good electrical properties and good temperature resistance
• Epoxy resins (EP): high strength, good adhesion and very good electrical insulating properties
• Melamine resins (MF): hard, scratch-resistant surfaces as well as good heat and chemical resistance
• Unsaturated polyester resins (UP): often used as a matrix for glass-fibre-reinforced plastics
• Fibre-reinforced thermosets: combination of a thermosetting matrix and glass, carbon or fabric reinforcement

Technical laminates and laminated materials are produced, among other things, from thermosetting resins and reinforcements. Glass-fibre-reinforced polyester and epoxy laminates are used, for example, for applications subject to mechanical, thermal and electrical stress.

Examples of thermosetting plastics and products

Thermosetting plastics are used in particular where components must remain dimensionally stable even under heat, electrical load or high mechanical forces. Typical products and components include, for example:

• electrical insulating parts and insulating sheets
• switch and housing components
• technical laminates and laminated materials
• high-strength structural parts
• glass-fibre-reinforced profiles and sheets
• CFRP components based on epoxy resin
• components for transformers and high-voltage applications

Thermosetting composite materials can be used as sheets, profiles or individually machined finished parts.

What disadvantages do thermosets have?

The permanent cross-linking is at the same time an important limitation of thermosetting plastics. After curing, they cannot be melted or thermally reshaped again. Changes to a finished component are therefore mainly made by mechanical machining.

Further limitations depend on the respective material structure. Fibre- and fabric-reinforced thermosets may, for example, require adapted tool selection and machining strategy. The recycling options also differ fundamentally from those of classic thermoplastics, since the material cannot be processed again by melting.

Request thermosets and select material

Do you need a thermosetting plastic for a technically demanding component? Martan Plastics supports you in selecting a suitable material solution and takes into account, among other things, temperature, mechanical load, electrical requirements, contact media and component geometry.

Send us your drawing, dimensions, desired quantity and the most important operating conditions. On this basis, we will assess the technically and economically suitable implementation.

Request thermosets and components now