At Burnetts, we always choose the most suitable materials to match your requirements. That is why we are not only industry experts for thermoset elastomers, but we also lead the way in the use of thermoplastic elastomers (TPE).
TPE is a unique class of engineering materials combining the look, feel and elasticity of conventional thermoset rubber, while at the same time offering the processing efficiency of plastics. Essentially, they have elastic properties that are similar to rubbers, and also allow for repeated deformation and recovery.
A key indicator for this material is the hardness value, as measured on the Shore Durometer scale. Similar to cross-linked rubber, TPEs are available as very soft materials from 5 Shore A up to 90 Shore A and 85 Shore D.
The main characteristics of TPE are:
- Good electrical properties
- Resistance to extreme temperatures from -30C to 140C
- Excellent resistance to chemicals & weathering
- High impact strength
- Excellent flexural fatigue resistance
- Easy thermoplastic processing
- Short cycle times
- Thermal stability, providing large processing windows
- Multi-component processing and reduced assembly costs
- Combination of two materials (hard-soft composite)
- Excellent colourability
- Low specific gravity
Styrenic Block Copolymers
SBS is the highest volume TPE material produced and is commonly used in footwear, lower-specification seals and grips, and soft touch applications. SEBS is characterised by improved heat resistance, mechanical properties and chemical resistance.
(TPE-O or TPO)
These are blends of polypropylene (PP) and uncross-linked EPDM rubber. They are used where there is a need for increased toughness over conventional PP copolymers – for instance in vehicle bumpers and dashboards. They are restricted to the top end of the hardness scale, typically >80 Shore A.
(TPE-V or TPV)
These are compounds of PP and EPDM rubber, however they have been dynamically vulcanised. They are used for automotive seals, pipe seals, and other applications where a heat resistance of up to 120C is required. Shore hardness values are available from 15 Shore A to 50 Shore D.
(TPE-U or TPU)
Thermoplastic polyurethanes can be based on polyester or polyether urethane types and are used in applications where a product must have excellent tear strength, abrasion resistance, and flex fatigue resistance. Examples include shoe soles, industrial belting, ski boots, and wire and cable. Hardness is restricted to the high end of the Shore A scale, typically >80 Shore A.
(TPE-E or COPE or TEEE)
These are used when a chemical and heat resistance of up to 140C is needed. They exhibit good fatigue resistance and tear strength and so are used in automotive applications such as blow moulded boots and bellows, wire and cable, and industrial hose applications. Hardness is restricted to the high end and is typically between 85A to 75D.
Melt processable rubber
MPR is designed for more demanding applications requiring chemical resistance, particularly resistance to oil and grease, where it replaces cross-linked nitrile rubber. MPR has properties similar to vulcanised rubber in noise-dampening and stress-relaxation properties. Uses include automotive components.
Thermoplastic polyether block amides
TPE-A offers good heat and chemical resistance, and bonding to polyamide engineering plastics. Applications include cable jacketing and aerospace components.