Wider niche for TPUs

Oct. 11, 2007
Through innovative design, thermoplastic urethanes help deliver high-performing products on a budget.

Louis Esposito
Business Development Manager
Merquinsa North America
Seabrook, N.H.

It’s almost a given that as products become more complex, they demand better performing materials. This pressures designers to find materials able to meet tougher specs at a competitive cost. In this regard, PVCs (polyvinyl chlorides) are often out of the picture because of consumer complaints and some thermoplastic elastomers (TPEs) have limited performance. This has opened the door for a range of aliphatic and aromatic thermoplastic urethanes (TPUs) made from polyester or polyether formulations.

The advanced TPUs let designers spec alternatives to PVCs and TPEs that are plasticizer and halogen-free, resist yellowing, and are softer, tougher, and more transparent. Additionally, this new class of TPUs sport excellent hydrolysis and microbial resistance, remain flexible at temperatures as low as 70°C (94°F), and depending on grade, can be injection and blow molded, overmolded, or extruded.

TPUs consist of linear-segmented block copolymers composed of hard and soft segments. They are formed by the reaction of diisocyanates with short-chain diols (so-called chain extenders) and diisocyanates with long-chain difunctional diols (known as polyols). The possible combinations of the three reaction compounds give practically unlimited variation in structure and molecular weight. This lets urethane chemists fine-tune polymer structure to the desired final properties.

Military and automotive
TPUs serve in the most rigorous applications thanks to their ability to work at low temperatures combined with good flexibility, abrasion resistance, and general overall durability. Good compression set makes them candidates for seals and gaskets in offshore-oil applications from the North Sea to the North Slope. And the improved properties that TPUs bring to the table also benefit fuel tanks, fuel lines, hoses and cables, and high-wear parts needing a high degree of puncture and chemical resistance.

Automotive designers are also speccing TPUs in place of PVCs. Newer TPUs with a hardness range of 58 Shore A to 75 Shore D are increasingly widely used in luxury cars for gear knobs thanks to their excellent scratch and abrasion resistance, mold-texture reproducibility, adhesion to acetals and nylons, and exceptional colorability. Gear knobs, door panels, and grips in high-end automobiles were once limited to darker colors or grey. But new TPU grades offer a more lightstable (UV resistant) color palette, strong abrasion, and better scratch resistance, along with the desired feel or haptics.

New applications such as dashboard vents and central console parts use TPU skins overmolded onto ABS. The combination gives a quality finish with better economics. TPU films also protect vehicle lower bodies, front and mirror components, and paint layers from sand, stones, and salt.

Sports and Leisure
TPUs have made major inroads into sports and leisure applications as breathable fabrics, goggles, grips, bumper pieces (snowmobiles), ski boots, footwear and decorative parts for sports apparel, to name a few. Here abrasion resistance, durability, low temperature flexibility, sealing (as in seam tapes and adhesive films) along with puncture resistance and breathability are all key differentiators for the new ester and ether-based TPUs.

Make contact:
Merquinsa North America Inc., (603) 474-0971, www.merquinsa.com

Good compression set makes TPUs candidates for seals and gaskets in offshore-oil applications.

Breathable fabrics made with TPUs are making inroads into sports and leisure. Likewise, other applications that rely on the material’s good flexibility at low temperatures include goggles, grips, bumper pieces (snowmobiles), and ski boots.

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