Teknor Apex Company’s new styrene block copolymer thermoplastic elastomer (TPE-S), Sarlink ML-2355B, offers improved performance in both processing and de-moulding compared with other elastomers while still providing competitive physical properties and meeting stringent OEM requirements
Approved by VAG for cable ducts, Sarlink ML-2355B is used for automotive interior parts such as cable ducts and grommets.
Used to guide cables in their convoluted route through the spaces in pillars and other structures surrounding the passenger compartment, these ducts are complex parts with long flow paths and many undercuts, making them a challenge to mould and de-mould.
Compared with other elastomers used for cable ducts, new Sarlink ML-2355B exhibits reduced viscosity for improved mouldability, a wider processing window, and greater weld-line strength to facilitate air-assist de-moulding.
Unlike standard TPE-S compounds, it does not exhibit stress marks caused by deformation during mould release, and it avoids the de-moulding difficulties posed by thermoplastic vulcanisates (TPVs) in parts with severe undercuts.
“The enhanced processability of Sarlink ML-2355B compound provides better surface quality than standard TPE-S materials and fewer sink marks, which exhibiting lower processing temperatures, faster cavity filling, and improved mould release,” said Jeffrey E. Dickerhoof, senior sales and marketing manager for the Thermoplastic Elastomer Division of Teknor Apex.
Sarlink ML-2355B TPE-S also provides numerous advantages over thermoset EPDM rubber, starting with a lower density that translates into 20% weight savings, plus the benefit—as a thermoplastic—of scrap recycling.
“Processing improvements versus EPDM include shorter cycle times, easier processing of complex geometries, adhesion to polypropylene through two-component molding, and capability for robot-assisted de-moulding, which is impossible with EDPM,” said Ger L. Vroomen, senior automotive market manager for Teknor Apex. “Sarlink ML-2355B compound also remains elastic over a broader temperature range and provides improved flex fatigue behaviour.”
OEM part requirements for the VAG cable duct include an operational temperature range of -40 to 90 degrees Celsius; burning behavior meeting the TL-1010 flammability standard for passenger compartments; electrical insulation meeting specification PV 1015; a water-tight seal; and passage of natural weathering tests for one year in both hot and humid and desert-dry conditions.
Minimum OEM material requirements for the application include odor and emissions, tensile strength and elongation, property retention after 90 degrees Celsius / 94 hours heat aging, and avoidance of cracks or surface changes after 150degrees Celsius/ 700 hours heat aging.