Thermoplastic elastomers (TPE) explained
Thermoplastic elastomers (TPE) are found in toothbrush handles, car seals and medical tubing. But what actually distinguishes them from rubber and conventional plastics? An overview of their structure, grades, processing – and what ‘recyclable’ really means when it comes to TPE.
Thermoplastic elastomers do not fit neatly into any category. This became apparent when international standardisation bodies sought to assign them standardised names: neither the nomenclature system for rubber (ISO 1629) nor that for plastics (ISO 1043-1) was suitable. Consequently, a separate standard – ISO 18064 – was developed jointly by rubber and plastics experts.
The current version, ISO 18064:2022 (in Germany: DIN EN ISO 18064), describes TPEs as follows: at operating temperature, they behave similarly to vulcanised rubber, i.e. like rubber. At higher temperatures, however, they can be processed like a thermoplastic – and this can be done repeatedly. It is precisely this dual nature that is crucial for material selection.
At a glance: three groups of materials and a hybrid
- Thermoplastics (e.g. polypropylene): not cross-linked. They melt when heated and solidify again as they cool, and this process can be repeated.
- Thermosets (e.g. epoxy resins): tightly cross-linked. Hard and rigid; do not melt.
- Elastomers (e.g. natural rubber, EPDM): loosely cross-linked. Rubber-like in elasticity, but do not melt either.
- TPE: a hybrid of the two. Elastic like rubber in use, but meltable like a thermoplastic during processing.
What distinguishes TPE from rubber and plastic
The difference lies in the cross-linking. Conventional rubber is vulcanised: during this process, the molecular chains chemically bond to form a solid network. This makes it elastic, but the process is irreversible – once vulcanised, rubber cannot be remelted.
TPEs work differently. They consist of hard and soft regions. The soft regions provide elasticity, whilst the hard regions hold the material together – though only physically, not via fixed chemical bonds. When heated, these bonds break and the material becomes fluid. When cooled, it solidifies again.
TPVs are a special case: they also contain chemically cross-linked rubber particles, which are, however, finely dispersed within a thermoplastic. The material can therefore still be melted. The properties can be specifically adjusted by varying the ratio of hard to soft components.
In practical terms, this means:
- Easy processing: TPEs are moulded by injection moulding or extrusion – vulcanisation is not required.
- Less waste: Production offcuts and rejects can be remelted and reprocessed.
- Limitations at high temperatures: As the bond is purely physical, TPEs soften at high temperatures. For applications involving sustained heat or aggressive media, cross-linked rubber is often the better choice.
Recycling of TPE
When it comes to recycling, it is worth taking a closer look. Unlike vulcanised rubber, TPEs can be remelted. Clean, single-grade production waste can therefore be returned to the production process, depending on the material and quality requirements. However, this does not automatically mean that a TPE component will end up in the recycling loop after use. This requires suitable collection, sorting and processing methods. Recycling can be particularly complex for components in which TPE is firmly bonded to other materials. Another crucial factor is whether the recovered material meets the requirements of the next application.
A comparison of four material groups
| Thermoplastic | Thermoset | Elastomers | TPE | |
| Cross-linking | None | chemical, tight | chemical, loose (vulcanised) | physical (in TPV, additionally cross-linked rubber particles) |
| Processing | Injection moulding, extrusion | Moulding and curing | Moulding with vulcanisation | Injection moulding, extrusion |
| Recyclability | Remeltable | Cannot be remelted | Cannot be remelted | Can be remelted during production; post-use recycling depends on collection and sorting |
The TPE classes: seven categories according to the standard
TPE is a collective term. ISO 18064 classifies it into seven classes based on chemical composition. All abbreviations begin with TP:
- TPA – polyamide-
- TPC – copolyester-
- TPO – polyolefin-
- TPS – styrene-based thermoplastic elastomer
- TPU – polyurethane-
- TPV – thermoplastic vulcanisates: a thermoplastic containing finely dispersed, cross-linked rubber
- TPZ – thermoplastic elastomers ( ) comprising all other TPEs
In practical applications, these three classes are particularly important:
TPS – the versatile ones
They range from very soft to relatively hard. They withstand water and acids well and adhere to many other plastics. When it comes to oils and abrasion, however, standard TPS performs less well than TPU.
TPU – the robust ones
They are very strong, abrasion-resistant and resistant to oils and fuels. However, some of them are less tolerant of water – particularly hot water – and must be thoroughly dried before processing.
TPV – the sealing specialists
They are usually made of polypropylene and EPDM rubber, are UV-resistant, tolerate water and acids, and are particularly suitable for extruded seals.
Processing and Application
TPEs are usually supplied as granules and can be processed on the same injection moulding machines as other plastics. According to TWI, cycle times as short as 20 seconds are possible in some cases. Some TPEs, particularly TPU, must be carefully dried beforehand.
A particular strength is the hard-soft composite: in two-component injection moulding, the soft TPE is bonded directly to a hard plastic part, for example to create non-slip surfaces or integrated seals. TPS are considered particularly suitable for this purpose because they adhere well to many plastics.
Typical areas of application include:
- Automotive: seals, window overmoulding, airbag covers, bumpers
- Medical technology: tubing, masks, resuscitation bags, syringe stoppers – increasingly also as a replacement for PVC or rubber
- Consumer goods: toothbrush handles, mobile phone cases, toys, shoe soles
- Industry and construction: hoses, cable sheathing, profiles, window and door seals
When selecting the appropriate TPE, the manufacturer KRAIBURG TPE recommends clarifying the following questions in advance:
- What substances will the component come into contact with?
- What temperatures will it be exposed to?
- Does it need to adhere to other plastics?
- What mechanical loads, colour, UV resistance and standards are required?
TPE suppliers at K
The following TPE suppliers, amongst others, were represented at K 2025 in Düsseldorf:
- KRAIBURG TPE: TPS compounds, including THERMOLAST
- BASF: TPU Elastollan
- Covestro: TPU Desmopan and Texin
- Kuraray: Styrene-based TPE under the SEPTON brand
The unassuming all-rounder
Whether it’s a toothbrush handle, a car seal or a resuscitation bag: TPEs rarely stand out because they simply do the job. Nevertheless, it is worth taking a closer look when selecting materials. Which grade is suitable depends on the media, temperature and adhesion, and indeed on whether the component is to be processed like rubber or like plastic. Those who clarify these questions at an early stage will get the most out of the dual nature of TPEs.
Did you know?
Data sheets often use different abbreviations for the same materials, such as TPE-S, TPE-U or COPE. ISO 18064 aims to standardise this: one material, one abbreviation. The standard abbreviations used today are TPA, TPC, TPO, TPS, TPU, TPV and TPZ.
FAQ
TPEs can be remelted, so production offcuts can be fed back into the process. However, whether a component is recycled after use depends on collection, sorting and separation from other materials.
Rubber is chemically cross-linked and cannot be remelted. In contrast, TPE is held together primarily by physical forces: it is elastic in use and can be moulded when heated. However, it softens at high temperatures.
These are abbreviations in accordance with ISO 18064: TPU stands for polyurethane-based TPE, TPV for thermoplastic vulcanisates, and TPS for styrene-based TPE. There are also TPA, TPC, TPO and TPZ.
Key Takeaway:
Thermoplastic elastomers (TPE) are plastics that are elastic like rubber in use, but can be melted and moulded like thermoplastics when heated. This means they can be injection-moulded and extruded, and production offcuts can be remelted. This distinguishes them from vulcanised rubber, which is chemically cross-linked and can no longer be remelted.
Author: Jennifer Meyer | K-Mag
Jennifer Meyer is part of the K editorial team and is interested in the stories behind trends and technologies in the plastics industry. What drives her? The question of how plastics are changing – and what that means for people. With her eye for detail and a penchant for sustainable concepts, she creates content that is not only informative but also designed to spark curiosity.
