The perfect blend of properties

Many thermoplastic elastomers (TPEs) today are offering processors the perfect combination of properties of plastics and elastomers, which significantly improves product design and development. Generally, TPEs are made of two phases, hard which is the thermoplastic component and soft which are the cured rubber particles. Also alternatively put, it has a thermoplastic end block with an elastic mid-block. Technically, thermoplastic elastomers are in mid-range class between plastics and rubber and with their exceptional qualities and benefits, have managed to develop a class propertiesof their own. TPEs offer technical abilities of elastomers and a range of product advantages in addition to their free-flowing ability. They do cost more than thermoset rubber, but offer better effectiveness and environmental benefits.

TPEs offer easy thermoplastic processing, short cycle times, low energy utilisation, thermal stability, recyclable ability and versatile dying options. Simply put, TPEs are flexible materials which are stretchable to double their length and hold the innate ability to return to their approximate original size on release of pressure or stress.

Jiri George Drobny in his book – 'Handbook of Thermoplastic Elastomers' – wrote about the history of thermoplastic materials starting in 1930s with the invention of PVC plasticisation. He writes: "This invention led to further interest in flexible plastics and eventually to the development of blends. These blends, when properly formulated, have a rubber-like look and feel and bridge the gap between liquid plasticised PVC and conventional cured elastomers. Thus, they can be considered as the precursors of thermoplastics elastomers, as we know them today."

Single-use membrane valve made of special TPE from KRAIBURG TPE

According to PlasticsEurope, a leading European trade association of plastic manufacturers, the principal difference between thermoset elastomers and thermoplastic elastomers is the structural crosslinking bond, which is a major factor, offering high elastic properties. The crosslink in thermoset polymers is a covalent bond made during the vulcanisation process while in thermoplastic elastomers; the crosslink is a weaker dipole or hydrogen bond or takes place in one of the phases of the material.

Special characteristics
Each TPE has specific traits characterised by applications and their demands. TPEs not only differ in cost and efficiency but also offer reduced energy consumption. TPEs are used widely in automotive parts, paving and roofing, consumer and personal hygiene products, medical applications, aircraft coating, rail track, sports & leisure equipment, footwear, baby care, electronic appliances, industrial & mining related cables and oil and gas pipelines. The diversity found in TPEs will not keep their utilisation restricted to few industrial applications; in fact, it is expected to find new industries and applications fostering innovation and opportunities.

According to Smithers Rapra, a global leader in rubber, plastics, polymer and composites testing and consulting services, the most significant applications for TPEs are: Automotive - perhaps the most important application in terms of consumption volumes given the size of the industry and continuous replacement of rubber and PVC; Building and Construction - thermoplastic elastomers are used in this sector predominantly for roofs, geotextiles, domestic and industrial window gaskets; Medical - this sector for TPEs is expected to grow at over 7% over the next couple of years; Footwear and Appliances and housewares.

The new TPE types that have emerged are reactor TPO's (R-TPO's), Polyolefin Plastomers (POP's) and Polyolefin Elastomers (POE's). The new POPs and POEs hold low molecular weight and linear low density polyethylenes.

Innovative applications identified
Considering the growth prospects that TPEs hold for innovation, product design and performance, many companies are engineering thermoplastic elastomers. TPEs can also be accounted for multiple domestic, office and academic purposes. THERMOLAST® K, the material that makes pencils and pens easy to grip is a TPE made by Kraiburg TPE. Stabilo is a manufacturer of pens and pencils offering a range of products for writing, drawing and highlighting purposes. All writing utensils created by Stabilo offer a non-slip gripping surface made from thermoplastic elastomers offered by Kraiburg TPE.

Kraiburg TPE is one of the world’s leading manufacturers of thermoplastic elastomers on the basis of hydrogenated styrene block copolymers. THERMOLAST® K is certified for contact with food and offers temperature stability and weather resistance. It is also latex-free and recyclable, keeping a strong check on eco-friendliness and sustainability. Kraiburg TPE also supplies TPE to companies to be used as a membrane for a new single-use membrane valve. The valve prevents cross-contamination with a heat-sealed membrane which stops the medium to come in contact with the staff and the environment.

From the THERMOLAST® family, Kraiburg TPE offers THERMOLAST® V, TPEs for high-temperature applications in the automotive and industrial sectors. Apart from good thermal stability, the material offers good hysteresis behaviour and remarkable compressive stress relaxation. THERMOPLAST® A compounds offer improved UV and scratch resistance and excellent adhesion to PC, ABS and PC/ABS as well as enhanced haptics. It makes the product adaptable for automotive application or production of tool handles.

Kraiburg TPE’s THERMOLAST® W compounds offer a firm grip and feel on materials even if they are wet since TPEs are generally slippery in nature when doused.

In particular, THERMOLAST® M is a unique compound for the medical and pharmaceutical sector. Cross-contamination must be eliminated in valves used for sensitive pharmaceutical process technology. The safest method is to use one-way valves, which until now has meant replacing the entire valve. With its controlled single-use membrane valve GEMÜ SUMONDO®, with a special TPE membrane from Kraiburg TPE, GEMÜ is introducing a safe and cost-effective system. With it, only the valve unit has to be replaced, because thanks to the interior membrane, it is the only part that comes into contact with the pharmaceutical media. The actuator itself remains in the system for re-use. The valve unit, which is manufactured in a cleanroom out of sterilised polypropylene, is equipped with a TPE membrane. The ultrasonically heat-sealed membrane hermetically separates the media from the environment and from the valve’s actuator. Moreover, it also regulates the volume flow in the valve during operation.

THERMOLAST® M has also generated interest thanks to its simple, time-saving, and cost-effective manufacturing process with polypropylene. This processing method enables short cycle times and makes post-processing the component unnecessary. In addition, the procedure makes it possible to create a microbe-proof barrier. THERMOLAST® M allows direct contact with a pharmaceutical medium or blood.

TPE prospects
According to a 2013 published study, global thermoplastic elastomer demand will grow 5.5% annually to 5.8 million metric tonnes in 2017. Asia Pacific will be the largest market and also the fastest growing. The leading TPE product will be Styrene block polymers (SBCs) while (POEs) polyolefin elastomers will grow the fastest.

A report published by Markets and Markets also suggests that the global market for TPEs, estimated at $15.1 billion in 2012 will grow to $23.9 billion by 2018, marking a CAGR of 8.1% in terms of revenues.

The future is bright to say the least. TPEs will be driven by product innovation and will continue to replace conventional plastics and elastomers in multiple applications across industries. The last decade has witnessed a remarkable shift from PVC to TPEs and has also been a cost effective substitute to silicone. As more materials and usages of TPEs are discovered and identified, the market will continue to progress substantially.