In 1959, the first thermoplastic elastomer was released. Since then, a wide range of variations has been developed. TPE can be easily processed and coloured, TPE materials offer a number of desirable properties and can be used in a diverse range of applications, across a variety of industries, from medical and aerospace to automotive and manufacturing.
But what are thermoplastic elastomers, how are they made, and what are their benefits? Read our guide to find out more.
TPE is a polymer material that offers the favourable characteristics of both thermoset vulcanised rubber and thermoplastic. At room temperature, it offers the high elasticity of thermoset vulcanised rubber, while at high temperature it delivers the good processability of thermoplastic.
All TPEs have three essential characteristics:
They can be processed as a melt at elevated temperatures
The have the ability to be stretched to moderate elongations and upon the removal of stress, return to their original shape
The absence of significant creep
How are TPE's made?
TPEs are usually produced in pellet form. They are made by copolymerising two or more monomers. This can be done using one of two methods:
Block polymerisation - creating long-chain molecules with various sequences or blocks of hard and soft segments
Graft polymerisation - one polymer chain is grafted to another as brances
Whichever technique is used, one of the monomers develops a hard or crystalline segment. This then acts as a thermally stable component, softening and flowing under shear. The other monomer develops a soft or amorphous segment, contributing to the rubber-like characteristics of the TPE.
The properties of the finished TPE can be controlled by adjusting the ratio of the monomers used, as well as the lengths of the hard and soft segments.
What is TPE used for?
TPEs are suitable for use in a wide range of applications. They are widely used in the automotive industry, as well as domestic applications, medical applications, construction applications, and more.
What are the benefits of TPEs?
TPEs offer a number of advantages, including:
Exceptional electrical insulation properties
Heat and oil resistant (within a specific temperature range)
Good thermal properties, resistant to low and high temperatures (-30°C to +150°C)
Good material properties, including low permeability, excellent flexural fatigue resistance, strong tear and abrasion resistance, high impact strength and elongation, low specific gravity, and excellent resistance to weathering and chemicals.
Easily coloured by most dyes
Shorter fabrication times mean simpler processing, lower energy consumption, and lower finished part costs
Can be easily insert-moulded without the need for adhesives, using olefin materials such as PP
Can be produced in a range of hardness grades
Like plastics, TPEs can be recycled and reused. They can also be ground down and turned into 3D printing filament.
What are the disadvantages of TPEs?
As with any material, there are a number of potential disadvantages to consider when working with TPEs, including:
Although TPEs offer good temperature resistance, they melt at high temperatures meaning they are unsuitable for certain applications.
Low resistance to aromatics
Relatively high production costs compared to thermoset rubbers
If processed at high temperatures, TPEs will lose their rubber-like properties
When exposed to sustained temperature or pressure stress, creep can occur.
Types of TPEs
TPEs are grouped into six different classes, depending on their characteristics:
Thermoplastic Styrenic Block Copolymers (TPE-S)
This is the largest group of TPE materials. They are also the most versatile, as they can be produced with a variety of hardness grades. They are commonly used in applications such as footwear, adhesives, and seals & grips.
Thermoplastic Elastomer Polyolefins (TPO or TPE-O)
This is a relatively new TPE class. These TPEs are blends of polypropylene or polyethylene and ethylene-propylene-diene rubber and nitrile rubber. TPE-Os are generally used in applications that require an enhanced level of toughness, including automotive bumpers and dashboards.
Thermoplastic Vulcanisates (TPV or TPE-V)
Like TPE-Os, TPE-Vs are compounds of PP and EPDM rubber. However, TPE-Vs vary because they are dynamically vulcanised during the compounding step. TPE-Vs are commonly used in applications where heat resistance up to 120 °C is required.
Thermoplastic Polyurethanes Elastomer (TPU or TPE-U)
TPUs are block copolymers with urethane backbone linkages. They offer good abrasion resistance and tear strength, as well as good oxygen, ozone, and weather resistance. TPUs are typically used in applications such as shoe soles, industrial belting, wires, and cabling.
Thermoplastic Copolyester Elastomer (TPC or TPE-E)
TPCs offer outstanding strength, as well as excellent high-temperature resistance, creep resistance, solvent resistance, and impact resistance. They are commonly used for automotive applications, wires and cables, and industrial hose applications.
Thermoplastic Polyamide Elastomer (TPA or TPE-A)
This is a newly developed class of alternating block copolymer elastomers. TPAs offer impressive heat resistance and chemical resistance, as well as bonding to polyamide engineering plastics. They are widely used in applications such as cable jacketing.
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