THERMOPLASTIC ELASTOMERS | MATERIALS
humid and desert-dry conditions. Minimum OEM material requirements for the application include odour and emissions, tensile strength and elonga- tion, property retention after 90°C / 94 hrs heat aging, and avoidance of cracks or surface changes after 150°C / 700 hrs heat aging. Teknor Apex continues to develop TPVs too. In
February, it announced a new series that it says has key advantages over standard TPVs in their natural or uncoloured form, providing the appearance and tactile properties valued for automotive interiors while also exhibiting excellent colourability for exterior components. Sarlink 6700 Series com- pounds have a very light hue that makes them easy to custom-colour; they are UV-stabilised to meet auto industry specifications for interior compo- nents; they are low-fogging and exhibit high flow for moulding complex parts with thin walls. Recommended interior applications include
floor mats, bin mats, cup-holder liners, and soft- touch grips, knobs, and buttons. When coloured with UV-stabilised masterbatch, Sarlink 6700 Series compounds also can be used for exterior parts such as cowl vent seals, mirror and antenna gaskets, headlight bezels, and window trim. Compounds are available, in natural form only,
in Shore A hardnesses from 55 to 75. Dickerhoof says they represent the next generation of the Sarlink 6100 Series of high-flow TPVs, which are widely used in the automotive industry worldwide.
Silicones for softness Dow Corning continues to expand its TPE offering, once again with automotive in mind. Its long-stand- ing Multiflex compounds from subsidiary Multi- base, for example, combine an SEBS rubber for softness and resilience with a polyolefin for easy processing. Materials are available in Shore hardnesses from 20A to 60D.
The Multiflex range now includes SiE types that
are further modified with silicone. They include Multiflex TPE SiE A 4013 CU1 (introduced last year) which is resistant to scratching and UV light, suitable for a variety of interior and exterior applications, including vehicle components where maintaining aesthetics is critical. (Multiflex TPE SiE is different from the company’s TPE hybrids of thermoplastic urethane (TPU) and crosslinked silicone rubber, which it markets as TPSiV). Christophe Paulo, global segment leader for the Plastics Solutions business, says Dow Corning is currently in advanced development of Multiflex TPE SiE grades with improved adhesion for automotive glass encapsulation. TPVs have the largest share of the market for corner mouldings on automotive glazing. However, they are not the perfect solution, especially as a primer needs to be applied to the glass prior to over-moulding in order to obtain sufficient adhe- sion. No primer will be needed with the Dow Corning product, providing an important cost saving by eliminating one stage from the total process, and also facilitating quality control. Paulo also points out that Dow Corning sells additives for use by other TPE producers. He says the company is working with major suppliers of TPVs on next generation materials containing Dow Corning additives. The company is increasing its focus on specialist additives to modify and improve TPEs, he notes. In addition, he references the increasing desire among end users to avoid low molecular weight plasticisers that may migrate out of the finished product, especially when the product is used in contact with food. “More plasticisers are being scrutinised,” Paulo says, noting that all TPEs with a Shore A hardness below 70 will contain some type of plasticiser. Silicone additives are capable of reducing Shore values by as much as 20.
www.injectionworld.com
Above:
Automotive instrument panel and air bag covers are important target applica- tions for TPE suppliers
Left: Cup holder liners are a target application for new TPVs from Teknor Apex
� September 2017 | INJECTION WORLD 43
PHOTO: DOW CHEMICAL
PHOTO: TEKNOR APEX
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