MATERIALS | BIOPLASTICS
Above: Avients’s ReSound OM TPEs contain bio-content and are suitable for overmoulding applications
Shore A hardness of 84 or 93. They offer a soft- touch surface and good resistance to kinking and deformation, allowing them to substitute TPE-O and PVC in many injection moulding applications.
Renewable TPEs A number of new TPE grades are also available from Hexpol TPE, which recently extended its Dryflex Green range of bio-based TPE Compounds. The series now includes grades based on styrenic block copolymer (TPS) and thermoplastic polyolefin (TPO) technologies, with renewable content said to be more than 90% (ASTM D 6866-12). Hardness values range from 15 Shore A to 60 Shore D. Dryflex Green TPE compounds contain raw
Right: Bio- based Dryflex Green TPEs from Hexpol meet automo- tive interior emission requirements
materials from renewable resources, predominantly plant-based polymers, fillers, plasticisers and additives. According to Hexpol TPE, they can usually be used as a drop-in solution for conven- tional TPEs without the need for tool modification. Mechanical and physical properties are compara- ble to petrochemical-based TPEs. The grades offer good bonding behaviour to PE and PP in over- moulding applications, with special grades available that will bond to ABS, PC/ABS and PET. They are said to be recyclable and easy to colour, with some grades also compliant with food contact regulations. The materials can also be used for automotive interior applications and have been tested for compliance with Vehicle Interior Air Quality (VIAQ) and other relevant standards regarding odour, fogging and VOC. Hexpol TPE says odour and fogging tests on representative Dryflex Green grades demonstrate low emissions performance. For example, a 75 Shore A Dryflex Green com- pound with a renewable content of 20% showed VOC (42,8 μg/g) and Fog (474 μg/g) in the ther- modesorption test according to VDA 278 and odour 3.0 in the VDA 270 C3 test. Such results
26 COMPOUNDING WORLD | September 2020
mean the materials are a good choice for applica- tions such as floor mats, cup holder liners, fascia, trim and inlay mats. Kraiburg TPE has also been developing thermo- plastic elastomers containing variable proportions of renewable raw materials. The company says that while it is technically possible to produce bio-based materials with very high proportions of renewable raw materials, the costs for such materials are usually high and mechanical properties can be limited. However, it says its modular approach to formulation allows it to develop customer-specific materials with different proportions of renewable raw materials that meet requirements in terms of specific mechanical properties such as tensile strength and elongation. Other typical require- ments include good processing, heat resistance and adhesion to ABS/PC or PP and PE. Kraiburg says it sees tremendous potential for custom-engineered thermoplastic elastomers with adjustable proportions of renewable raw materials of up to 90%. Potential applications exist in the con- sumer, industrial and automotive markets, such as toothbrushes and hypoallergenic elastic watch straps to fender gaskets. Avient (formerly PolyOne) has developed its
ReSound OM — overmoulding — TPEs as the latest addition to its sustainable solutions portfolio. The new formulations use between 40 and 50% bio-renewable content, derived from sugarcane and offer hardness levels and performance comparable to standard TPEs. Commercially available in all regions, the product portfolio consists of four overmoulding grades suitable for use with rigid polypropylene and one for over- moulding onto ABS. All ReSound OM grades are formulated for dura- bility, delivering property retention and UV resist-
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IMAGE: AVIENT IMAGE: HEXPOL TPE
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