WALDKRAIBURG, Germany—Kraiburg TPE GmbH and Co. KG, a manufacturer of thermoplastic elastomers, has sped up product development for automotive industry applications such as high-quality exterior applications.
The developments include TPE compounds with adhesion to EPDM, such as the materials from the Thermolast K series, which have been specifically developed for two-component parts used for automotive exterior applications. Kraiburg said the series features good adhesion to EPDM and excellent UV resistance.
The compounds are meant for automotive applications such as window trims and sealing profiles made of EPDM with molded corner joints and end elements made of TPE. Particularly with large vehicle series, styrene-butadiene compounds and crosslinked thermoplastic vulcanized rubber have been used for these applications in the past.
Kraiburg said its material solutions, with adhesion to EPDM when processed by injection molding, offers new opportunities: It has launched a new TPE series onto the market for the segment of sealing and window trim systems with EPDM.
The first compounds in the series, TC7EAZ and TC7EFZ, combine EPDM adhesion properties with long-term resistance to UV radiation and thermal effects with a hardness of 70 Shore A, Kraiburg said. Weathering tests showed the surface quality of the compounds were superior to competing materials. The compounds were developed with a focus on adhesion (TC7EAZ) and processability as well as on low fogging values (TC7EFZ).
In adhesion tests with LWB Steinl GmbH, a machine manufacturer based in Altdorf, Germany, the new materials received good results with both foamed and compact EPDM workpieces, Kraiburg said. In addition to the adhesion tests of EPDM/TPE specimens in accordance with the VDI-2019 standard, tests bases on ISO 37 were also performed.
Kraiburg said lasting heat resistance and weathering resistance was simulated by exposing material specimens to hot air in accelerated aging tests and to environmental conditions resembling those in Florida and the Kalahari Desert. The AD/EPDM/UV series had stable mechanical properties and featured significantly dry and non-adhesive surfaces.
Increased process stability means lower scrap rates, and reducing the typical cycle time was an additional goal for those involved in the new compounds.
Kraiburg said the new EPMD adhesion compounds feature economical processing, at relatively low temperatures of 200°C to 220°C. That results in lower cooling times, and in combination with the minimized hold pressure time, can accelerate the cycle and the overall production process as well. The initial adhesion of the specially developed TPE compounds to EPDM materials ensures that the finished parts can be removed from the mold more easily, which also reduces cycle times.
The permanent adhesion and weathering resistance of the materials is not impaired. Kraiburg also offers custom-engineered color balancing, accounting for gloss level, relative to the individual EPDM or the manufacturer's color specification.