Thermoplastic polyurethanes play an important role in giving vehicles a feel of quality and luxury. They have surfaces with a pleasant feel or good haptics, in the language of automotive interiors. They are durable, and can be hypoallergenic. Additionally, it is possible to replace materials such as leather.
Covestro is taking a second look at its Desmopan 6 family of TPUs in the automotive sector. It believes that the products could have interior component uses.
‘Desmopan 6 has been in the market for a while,’ said Mark Scheller, business development manager at Covestro. ‘It has some advantages, which appeared with time. It is a relaunch, as we launched it eight years ago. At the time, it suffered from a negative perception because of the earlier C3-based TPUs, but the properties are good in comparison.
One area where the materials are claimed to be good is in fogging and VOC, something that became clear after discussions with an automotive interior customer. ‘We thought that the values could not be true, so we tried with a black masterbatch-coloured material, and still the fogging values were very good,’ Scheller said.
Covestro decided to develop the Desmopan 6 C3 materials because they are back-integrated into the C3 stream from its crackers. This gives it a cost advantage, and the chance to make useful materials, said Scheller.
The range does have some limitations, however. ‘88 Shore A is, and will be, the hardest grade in this series because once the materials get harder than that, then mechanical properties go down,’ he said. ‘There is an overlap between the Desmopan 6 range, which can span the gap between 70 Shore A and 80 Shore D, and the Desmopan 9 range that covers hardness from 64 Shore A to 88 Shore A.’ There is a hardness gap between that and the softest of the Desmopan 9 grades. These are sold in Europe without plasticisers or fillers.
At the other end of the spectrum, the company is looking to extend the range, for the 9 series making them even harder to 85 Shore D. ‘For the 6 Series we are aiming for very soft materials, and we are trying to achieve 45ShoreA,’ he added.
TPUs bond well with polar polymers such as ABS, ad polycarbonates, glass-filled polyamides and glass filled PBT, and can be co-injected for parts such as gear lever knobs. The products are available as ether and ester grades. The latter are preferred for hydrolysis resistance.