Silicone elastomer conference draws wide audience

Rapra Technology's First International Conference on Silicone Elastomers attracted over 120 delegates from as far away as Australia, Brazil, Russia and the USA.

Rapra Technology's First International Conference on Silicone Elastomers took place in Frankfurt on 19th and 20th September 2006, attracting over 120 delegates from as far away as Australia, Brazil, Russia and the USA.

Presentations covered silicone elastomer materials, liquid silicone rubber, the processing of silicone elastomers, additives and finishing for silicone elastomers.

Delegates praised the breadth of the programme content and the practical nature of many of the papers.

Speaking at the conference, Thomas Tangney, European Area Industry Director, Dow Corning Corporation talked of the cross-industry transition towards silicones brought about by higher performance, application temperature and chemical performance requirements as well as rising oil costs.

Tangney said the market for silicone elastomers is anticipated to grow by 9% per annum, nearly double the total elastomer market.

This is mainly due to RTVs (sealants) for the construction market, LSR and fluorosilicones rather than HCR, which remains relatively static.

Growth is mainly from better application of existing grades and taking advantage of demand from emerging economies.

New grades continue to be developed to overcome limitations in performance or processing.

The automotive, electrical and consumer industries, he said, present the greatest opportunities for growth for easy to process, high performance materials such as FSRs, LSRs and FLSRs.

For example within the automotive sector new emissions regulations, increased warranty standards for fuel and safety systems are driving the need for materials with low permeability and good chemical and temperature resistance.

Mr Tangney commented that India and China are expected to have the greatest impact on future consumption because of their extensive infrastructural development and growing economies.

Oliver Franssen, Industry Manager - Automotive at GE Bayer Silicones spoke of the use of fluorinated silicone elastomers in automotive applications.

The two categories, heat cured elastomers (FSE) and liquid silicone rubber (FSL), offer superior resistance to automotive fuels, chemicals and solvents gas under wide-ranging temperatures.

More importantly fluorosilicones, he said, can withstand blow-by gas, a harsh mixture of exhaust gases, un-burnt fuel and combustion byproducts such as water, acids and engine sump oil.

Dr Maike Benter from Nanon in Denmark discussed new opportunities for using silicone rubber.

The hydrophobic surface properties of silicone rubber make painting and gluing almost impossible.

Dr Benter described two surface treatment processes that have been developed to overcome these problems.

The first involves a low pressure plasma treatment and polymerisation of a nano-scale layer with hydrophilic functional groups on the silicone rubber surface allowing the permanent layer to bond strongly to glue or paint.

The second: "cold tempering" process, includes the removal of undesired residues from the silicone rubber using supercritical or liquid CO2 to post-cure silicone rubber rather than using a traditional and often problematic heat cure process.

This has found to be not only cheaper and quicker, but research being undertaken also suggests that supercritical CO2 has a sterilising effect.

Describing the practice of bonding silicone elastomers to metal substrates, Dr Aissa Benarous of Chemical Innovations, gave a detailed account into the use of one-coat bonding systems where adhesives act as both primers and cover coats.

Dr Benarous spoke about the need for good wetting of the dried bonding agent coating by the elastomer which enables Van der Waals dispersion forces, polar attraction, hydrogen bonding and chemical bonding.

Although bonding of silicone elastomers is a reliable process, Dr Benarous highlighted some of the pitfalls that can occur through contamination, applying an inappropriately thick layer of bonding agent or insufficient drying of the coatings.

Of particular interest to the delegates was the paper presented by Prof David Jones, of Queens University of Belfast, who have a fascinating insight into the pharmaceutical and medical device applications of novel silicones.

Prof Jones described the important work undertaken in the development of biomaterials to counter problems commonly associated with medical devices - microbial attachment, encrustation, poor coefficient of friction and fracture.

These problems have been addressed using a novel approach for the synthesis of silicones using alternative cross-linker agents, namely a series of higher molecular weight alcohols.

These cross-linkers have been shown to vastly reduce microbial adherence and encrustation bringing about new potential for drug delivery systems, urological devices and cosmetic implants for example.

A number of papers were given by LSR machine and tool suppliers (Elmet, Battenfeld, Arburg, Engel).

Processing of LSR is not easy as the material cures extremely quickly (seconds) and the viscosity is very low.

These drawbacks, however, open the opportunities for manufacture of very small intricate parts, 2K or inserts moulding and gas injection.

Special shutoff valves and nozzles, good tool design, vacuum or venting aids, control of injection pressure and clamping force are required to achieve high quality parts.

Any variation in batch viscosity can significantly influence processability.

All electrical drive machines can improve processing due to reduced cycle times, very fast and precise clamping, lower energy consumption and high shot weight consistency.

Their main drawback is higher cost but the price is decreasing.

In all cases, machine selection is very much dependent on the application.

In support of two-component injection moulding, Clemens Trumm from GE Bayer Silicones presented a paper on new LSR systems that have been developed to provide improved chemical adhesion to a variety of substrates.

The conference was followed by a drinks reception hosted by Rapra Technology.

The next Silicone Elastomers conference is scheduled to take place in March 2008.

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