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materials | Thermoplastic elastomers


Right: Specimen bars for the new VDI 2019


adhesion test


grips do not get sticky during the ride,” the company notes. Grades can be made to be bondable to PA and PP. PolyOne says it is helping customers add a new twist


to the popular metallic look in cosmetic and personal care packaging with new GLS TPEs that “combine a lush, soft feel with lustrous metallic effects.” At the recent Packaging of Perfume Cosmetics & Design show, the company showed soft-touch TPEs with gold, silver and copper effects. Target applications include over-moulded caps for packages such as perfumes and shampoos, closures for containers such as lotions and serums, and cases for eye shadows and other cosmet- ics. PolyOne does not identify the chemistry in its TPEs.


Testing the bond Just how well TPEs bond to substrates is of obvious concern to potential specifiers. Several weeks ago, compounder API presented the VDI 2019 standard which it helped develop to measure the adhesion of TPEs on injection-moulded substrates. API has its own centre for the study and development of TPE for multi-component applications at its headquarters in Mussolente, Italy. It says equipment at its research centre is in full compliance with the VDI 2019 standard. VDI 2019 defines a peel test for measurement of


bond strength of soft TPE on a rigid thermoplastic. API says it could soon be expanded to cover the adhesion of TPEs on non-plastic rigid substrates. The new standard harmonises various different methods previously used for the determination of the bonding strength between soft component and hard substrate.


Below: PolyOne GLS’s latest TPEs provide a soft feel with a metallic effect for cosmetics applications


Bio-based options TPEs derived from renewable resources are still quite uncommon, but ongoing developments may change the picture in the coming years. For the moment, most activity seems to be in polyurethanes but there are moves elsewhere. Hexpol TPE recently launched the Dryflex Green range of TPE compounds based on raw materials from renewable resources such as plant and


vegetable crops. The range includes several series with amounts of renewable content to over 70% (AS D 6866) with hardnesses from 50 to 80 Shore A. The compounds are said to display mechanical and


physical properties comparable to TPE from fossil based raw materials. They offer flexibility and tensile properties with a soft-touch feel. They can be processed using traditional polymer technologies such as injection moulding and extrusion. Dryflex Green TPE compounds adhere to bio-based polymers such as PLA and conventional polymers such as ABS and SAN—as well as polyolefins, which can be made from fossil fuels and from sugar – for 2K and multi-component applications. Dryflex Green TPE compounds are also fully recyclable and can be easily coloured. Looking ahead, TPE market analyst Patrick Ellis


speculates that the development of natural rubber from sources other than Hevea brasiliensis may boost development of bio-based TPEs, especially TPVs. “NR-based TPV technology has been known for the last thirty years, but as yet its potential has never been fulfilled,” he says. “Certainly, NR has never been as low cost as it is today. The developments of guayule, Russian dandelion and sunflower-sourced NR may well encourage the use of NR in TPEs and to some extent, possibly replace EPDM in TPVs.”


Click on the links for more information: ❙ www.hexpoltpe.comwww.dsmep.comwww.teknorapex.comwww.polyone.comwww.dynasolelastomers.comwww.evonik.comwww.elastron.comwww.basf.comwww.fostercomp.comwww.kraiburg-tpe.comwww.softergroup.comwww.polymaxtpe.comwww.apiplastic.com


42 INJECTION WORLD | May 2016 www.injectionworld.com


PHOTO: API


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