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News Release from: Smithers Rapra | Subject: TPE 2005
Edited by the Processingtalk Editorial
Team on 23 September 2005
A review of Thermoplastic Elastomers
Conference
The eighth International Conference on TPEs, held in Berlin 14-15 September 2005, was very well attended: some of the papers presented are reviewed here by Rapra
The eighth International Conference on TPEs, held in Berlin 14-15 September 2005, was very well attended with delegates from 21 countries covering all global regions Papers were presented on new material developments, automotive applications, processing and a new session on TPEs from recycled materials
This article was originally published on Processingtalk on 12 Feb 2004 at 8.00am (UK)
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New and improved grades continue to be developed.
Multibase (Dow Corning) has entered the highly competitive market offering a PP/EPDM (Multiflex TEV) claiming good compression set and stress relaxation performance.
For improved high temperature performance Du Pont presented process details of a "Vamac/Hytrel" TPV launched at K2004.
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The relatively soft material has been specifically developed for extruded products.
GLS have developed a nylon overmould TPE that can be used for all nylon grades and formulations and does not need the nylon insert to be pre-dried prior to moulding.
No details of the polymer were provided other than it being a polymer alloy.
Liquid polyisobutylene can be used in SEBS formulations as a flow promoter for soft touch applications without loss in frictional performance.
Softer TPU grades are entering the market: Elastogran now have aromatic and aliphatic versions from 65 Shore A: Bayer now have an aromatic TPU grades from 60 Shore A.
To widen material choice within the TPE industry, the development of compatibilisers is being pursued: Kuraray has developed compatibilisers for use between polar polymers (eg TPU) and non-polar polymers (eg SBC).
Two materials were presented "TU-Polymer", a HSBC-TPU block copolymer and TM-Polymer, a HSBC-PC block copolymer.
These materials were shown to have good potential for polymer modification, compatibilisation and adhesion.
BASF have developed a styrene-butadiene block copolymer, Styroflex, which is more polar and bridges the gap between SBS and TPV.
The product was originally developed to substitute PVC cling film but due to its intermediate polarity shows good compatibility and adhesion to many different polymers.
One of the difficulties of using any rubber phase in TPV elastomers is that a different crosslinking system can be required.
Dow Corning presented details of Hydrosilylation based on organosilane technology, well established in the rubber industry.
The product is still in development but offers improves adhesion both to the polymer matrix and to any substrate as part of two-shot moulding.
90% of automotive sealing applications are still EPDM.
Opportunities to introduce TPEs depend on the design and performance requirements of the seal.
In working towards TPV foams achieving the dynamic seal requirements, Trexel and Exxon Mobil Chemicals have developed a TPV grade for use with a supercritical fluid, Mucell technique.
The use of nitrogen creates a closed cell microcellular structure, which dramatically reduces water absorption and offers a better surface aspect.
One approach being used by material suppliers to introduce TPEs into sealing applications is to show test data after initial loading.
Performance is significantly improved but a change in design philosophy is required to accommodate the initial set on first loading.
For automotive airbags covers, two solutions were presented to facilitate painted surfaces to be used whilst still achieving the -40C deployment test criteria.
Sumitomo have developed a TPO that can be coloured in-mould and simultaneously painted.
DSM have developed a new system (paint, primer and TPV) through understanding of the material property requirements and the development and identification of appropriate test methods.
The ELV directive is driving the greater use of recycled materials but applications remain non-structural.
Vita Thermoplastic Compounds has successfully developed a TPE incorporating post-consumer polypropylene waste and tyre crumb (tread).
The final material can contain up to 80% recyclate.
The material has been accepted by the automotive industry and examples of commercial applications were presented (mud-flaps, wheel arch liners).
The grades are currently only available in black, however, Faru have developed TPEs incorporating up to 50% tyre crumb, which permits some colouring.
Limited technology was presented on the former materials, however, Research from the Semenov Institute of Chemical Physics, Russia, showed that the particle size of the ground rubber has a significant influence on properties.
Particles less than 0.1mm offer the best mechanical and rheological properties.
TPE 2006 will be held in Munich 8-9 November 2006 - the closing date for offering a paper is 8th May 2006.
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