The use of thermoplastic elastomers (TPEs) is advancing at an impressive rate, as last autumn’s K 2007 exhibition in Düsseldorf / Germany – a large “display case” for TPEs – certainly indicated. Some 80 exhibitors of this class of material were present. "Overall, diversification is increasing, as more and more medium-sized compounders find their niches," Ulrich Kückelmann, account manager polymers & additives at C.H. Erbslöh (Krefeld / Germany; www.cherbsloeh.de), told PIE.

Two well-known research institutes are predicting substantial expansion in global demand for TPEs over the next several years. Rapra Technology (Shawbury, Shrewsbury / UK; www.rapra.net) forecasts a growth rate of 6.2% up to 2009 from 2.8m t in 2007. Its figures are backed by a recent study published by US market research group Freedonia (Cleveland, Ohio / USA; www.freedoniagroup.com), which assumes 6.3% growth up to 2011, for a total of 3.7m t by 2011.

Freedonia predicts that China will expand its share of the TPE market from less than 30% in 2006 to more than 33% by 2011, and that consumption there will broaden to a number of industries from the current focus on footwear. It says China is “significantly diversifying” into compounded thermoplastic polyolefins (TPOs) and thermoplastic polyurethanes (TPUs).

While the biggest growth prospects are clearly in the developing world, the US group nevertheless sees the bulk of global TPE sales as remaining concentrated in the developed markets of the US, western Europe and Japan. This applies in particular to higher performance materials such as copolyester elastomers and thermoplastic vulcanisates. The automotive market is expected to remain the largest altogether, buoyed by applications that require high heat- and oil resistance as well as scratch resistance. Freedonia says TPEs will begin to increasingly substitute EPDM and PVC in automotive interiors.

PIE’s own research indicates a shift in market shares of the individual TPE grades over the past three years. In particular, olefin- (up 2%) and urethane-based grades (up 4%) have expanded at the expense of the styrene-based grades (down 6%).

Overview of thermoplastic elastomers
TPE grade	Name	Morphology	Alternative name	Percentage of total TPE (%)	Price range 2007 (EUR/kg)	Price range 2004 (EUR/kg)
TPA	Polyamide TPE	Block polymer	TPE-A (COPA)	2	9 - 13	9 - 15
TPC	Copolyester TPE	Block polymer	TPE-E (COPE)	4	5 - 8	5 - 8
TPO	Olefin-TPE	Blend	TPE-O	6 (+2)	2 - 2.80	2 - 3
TPS	Styrene-TPE	Block polymer	TPE-S	44 (-6)	2 - 4	2 - 5
TPU	Urethane-TPE	Block polymer	TPE-U	20 (+4)	4 - 10	3 - 12
TPV	Partly vulcanised TPE	Blend	TPE-V	8	3 - 4.50	3 - 6
TPZ	Other TPEs			16

Nico Vossers, head of thermoplastics at Nordmann Rassmann (Hamburg / Germany; www.nrc.de) asserts that “the TPE market is more keenly contested than ever." This apparently has shored up prices. Compared with 2004, TPE notations were virtually unchanged at the end of 2007, while all the other polymers have been rising by an average of around 8% a year. The peak TPE price levels have eroded, with copolyesters the only exception, Franz Hinterecker, managing director of Kraiburg TPE (Waldkraiburg / Germany; www.kraiburg-tpe.com), told PIE. He added that the lower end of the scale, with the exception of TPUs, has held steady.

The price stability for this group of plastics is all the more surprising when considering that it also is highly dependent on oil. Compounds of base polymer normally supplied as flakes or powder, TPEs are made up to more than 50% of white oil (by weight), a crude oil derivative. In the production process, the two components are mixed together in batches in a so-called turbo-mixer, and then coloured and finished according to the customer's wishes in a twin-screw extruder.

The white oil is responsible for TPE's "soft" properties, for example elongation at break factors of up to 1,200% and extremely soft hardness levels of 3 Shore A without tackiness. As the main customer for white oil is the cosmetics industry, the plastics sector is unable to exert a major influence on the price – currently EUR 1.10-1.30/kg. For thermoplastic polyolefins, the basic polymer is a blend of PP and EPDM.

The market for TPEs and TPOs is dynamic and many new developments have been introduced recently:

Vita Thermoplastic Compounding (VTC, Manchester / UK; www.vtctpe.com), which unites Italy’s Francheschetti Elastomeri, Sweden’s Elastoteknik, and the UK’s Vita Thermoplastic Polymers (VTP) under the roof of British Vita, is now offering so-called "repro” grades. These are TPOs with a defined content of post-consumer waste. Granulated tyre rubber is also used. Under the trade name "Dynalloy", GLS Corporation (McHenry, Illinois / USA; www.glscorp.com) is marketing a type of TPO from "Infuse", a polyethylene block copolymer from Dow.

In styrene grades (TPS), the picture is now dominated by SEBS (hydrogenated styrene-butadiene-styrene). The compounds are often blended by small and medium-sized companies from starting materials produced by the market leaders Kraton, Kuraray and Repsol. Under the name "Badaflex", Bada (Bühl / Germany; www.bada.de) markets compounds. In its “Dryflex” range, VTC also offers TPS grades in which the material expands through the absorption of water to eight times its original volume. The main area of application for this is for sealants in the construction industry.

At K 2007, the market leader for SEBS, Kraiburg TPE, showcased a new range of transparent adhesion compounds that provide a soft-touch finish and can also be enhanced with colour. The soft compound from the non-polar styrene component is made compatible through modification with the rigid component of engineering plastics such as polycarbonate and ABS. They are processed by two-component injection moulding.

At a late 2007 meeting of plastics specialists in southern Germany organised by the local economic development agency of Ansbach / Germany at the site of PTS Plastic Technologie Service (Adelshofen / Germany; www.pts-marketing.com), participants were able to gain a first-hand look at production of adhesion compounds. Used to make handles of electric toothbrushes, shavers, beer crates and electric drills, they cost 4-6/kg on average.

Even those well versed in elastomer technology were surprised to see that these TPE blends were still pourable, despite their high white oil content and also felt dry.