materials | Thermoplastic elastomers
Right: BASF says Joubert’s overmoulded Elastollan
snow chains are easier to handle and quick to remove
injection moulding process, so the chains do not have to be assembled. The harder black Elastollan B90A15 material displays very good mechanical properties along with great flexibility at low temperatures, while the red Elastollan B60A10WH is more flexible and easy flowing. The black chain links are over-moulded with the red Elastollan in one mould.
Scratch resistance Synthetic rubber producer Grupo Dynasol (a Grupo KUO/Repsol joint venture) has worked with Evonik on development of TPS (SEBS) compounds containing Evonik’s organomodified siloxanes to improve scratch resistance and coefficient of friction, typically for automotive interior applications. Inés Alonso, responsi- ble for technical service, says tests showed that addition of Evonik’s Tegomer product had a marked effect on surface properties and also improved flow, at addition rates as low as 2%. At this level, important mechanical properties are unaffected. Turkish TPE specialist Elastron recently launched the V206 series of TPVs with low coefficients of friction and high UV resistance, in a hardness range between 60 Shore A and 65 Shore D. They are available in black and natural coloured grades. Elastron is aiming them at applications calling for smooth surface properties and good scratch and abrasion resistance, such as automo- tive weather seal corner mouldings. In the automotive aftermarket, French company Joubert Productions recently introduced snow chains with chain links moulded in two different grades of BASF’s Elastollan TPU. BASF says they are abrasion resistant, flexible at low temperatures, and resistant to loose chippings and road salt. The two Elastollan grades chemically adhere to one another in the
Right: TPEs are finding
applications in a growing range of
medical and healthcare applications
Medical moves Hexpol TPE points to opportunities in medical devices. Medical Technical Manager Niklas Ottosson says there has been a rise in demand for single-use syringes in recent years, and a clear move from rubber to TPE for plunger seals. The company has responded with an expansion of its range of Mediprene TPEs specifically designed for syringe plunger seal applications. Grades are available in a range of hardnesses from 43 to 73 Shore A. They have low compression set to provide a leak-proof seal with the syringe barrel. They are sterilisable with gamma, ethylene oxide and steam. Representative grades have passed cytotoxicity tests according to ISO 10993-5 and biocompatibility tests according to USP Class VI.
The move to single use syringes is driving demand for TPEs, which are used in plunger seals
PolyOne launched two new medical-grade GLS TPE
products earlier this year. Versaflex HC over-moulding grades for medical device housings are claimed to offer enhanced resistance to commonly used antiseptic cleaners. With a Shore A hardness of 48, Versaflex HC 1348 is slightly softer than Versaflex HC 1365 (Shore A 65). Designed for two-shot moulding, they also feature very good bonding to plastics with improved chemical resistance, including polyesters, polycarbonate, rigid TPUs and polyetherimide, many of which PolyOne says are now replacing traditional substrate materials. After repeated exposure to antiseptics, the new TPE
grades resist over-moulding delamination, cracking and loss of resilience. PolyOne says customers have reported that devices made with Versaflex HC TPEs successfully withstood 10,000 antiseptic wipes. The new grades are compatible with PolyOne’s OnColor HC Plus USP Class VI-compliant colourants, which resist fading
38 INJECTION WORLD | May 2016
www.injectionworld.com
PHOTO: POLYONE
PHOTO: HEXPOL TPE
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