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2007 is the 50th Anniversary of DuPont Performance Elastomers Viton®, the world's first fluoroelastomer - and the birth of the fluoroelastomers industry. Beginning with Viton® A in 1957 to the latest generation of specialty fluoroelastomers - Viton® Made with Advanced Polymer Architecture - it is also a celebration of 50 years of innovation.
The 50th Anniversary of Viton® will be the subject of features in the industry press, and a special website www.viton50.com . Visit the site for a timeline of major events in the first 50 remarkable years of the world's leading fluoroelastomer, and read more about the fascinating history of Viton® from its invention to today.
When American scientists J.S. Rugg and A.C. Stevenson stood up to give a paper to the rubber industry at the Washington Rubber Group conference on May 10, 1957, they were about to announce a breakthrough in synthetic rubber technology that was to change the world of rubber for ever.
Their paper, entitled "Viton® A as a New Fluorine-Containing Rubber" described vinylidene fluoride-hexafluoropropylene fluoroelastomer (VF2/HFP), and heralded the beginning of the global fluoroelastomers industry. Fifty years later, in 2007, total annual global sales volume of fluoroelastomers is expected to reach an estimated 20 million tonnes.
According to the former Rubber Age, publishing the paper in October that year, the exciting new polymer promised to overcome the inherent weaknesses of natural rubber - poor resistance to oil, heat, oxygen, ozone and UV light - and offer a versatility and development potential that would far outstrip the natural product.
This year, 2007, is the 50th anniversary of that event, and of the commercialization of Viton®, the world's first fluoroelastomer (FKM). But the story really began in April 1954, when Dr. Dean R. Rexford of the DuPont Organics Chemicals Department in Wilmington, Delaware, USA, was experimenting with a new elastomer with high temperature and chemical resistance. Unfortunately, there was one major barrier. Polymerization of the materials used to make this product was not permitted for safety reasons. It was up to Dr. Rexford, chemist and inventor, to overcome these barriers. Here's an excerpt from his patent and paper:
"It is known that Teflon® polytetrafluoroethylene shows good stability and exceptional resistance to attack by chemical agents. This product, however, is not considered an elastomer since it does not have characteristic elastomeric properties. It is the object of this invention to produce a new and improved elastomer which has excellent thermal stability exceeding 400°F (204.4°C), also exhibits excellent resistance to chemical attack, can be worked on conventional rubber equipment, and which can be readily and economically manufactured."
Following a controlled reaction involving hexafluoropropene, vinylidene fluoride and polymerization initiators, an elastic 60/40 HFP/VF2 copolymer was obtained. Its elastomeric properties were sufficiently exciting for the company to file U.S. Patent application # 504,351 on April 27, 1955, to protect the discovery.
Records show that 100 grams of the new product, known at that time as RCD-2077, were sent for sampling by an organization in Ohio, USA, on April 10, 1956. Other customers and institutes were also selected to do pioneering fluoroelastomer trial work in aerospace, and automotive applications. By December 1956 the name Viton® had been chosen from five other proposals, and the first use of the now familiar trademark was claimed. Commercial scale production of Viton® A fluoroelastomer began in August 1957 with an original Mooney viscosity specification of 30 to 60!
Compared to other elastomers available at that time, Viton® A provided step change improvements in high temperature stability and compression set resistance, and in resistance to many aggressive fluids. Its ability to withstand aviation fuels and oils, in particular, made it a natural fit for the aerospace industry.
The next step change in fluoroelastomers was the introduction of Viton® E-60C in 1970. This was the first commercially available bisphenol AF curative containing precompound. It provided outstanding processing improvements combining excellent scorch safety with fast cure, and reached new heights in compression set resistance. The next major advance in fluoroelastomer technology occurred in the mid-seventies with the invention by DuPont of the peroxide curesite monomer, and the use of perfluoromethylvinyl ether. Called Viton® GLT, this pushed the low temperature level of fluoroelastomer sealing down below -30°C for the first time, without sacrificing resistance to high temperature and fluids. Better low temperature performance was important for the automotive and oil industries, and critical for aerospace applications.
Through the 80s and 90s fluoroelastomer producers continued to improve the versatility of the polymer's highly polar chemistry and saturated carbon backbone structure, a structure completely different from nonpolar natural rubber and without the limitations of an unsaturated backbone. This period saw significant improvements in fluids resistance for the chemical process industry - made possible by the first 70 percent fluorine content terpolymer fluoroelastomer - and the introduction of a plastics processing aid called Viton® FreeFlowT 10 for improved film clarity and processability.
When, in 1996, the US Food and Drug Administration determined that six Viton® standard bisphenol-cure precompounds could be used in compliance with FDA regulation 26 CFR 177.2600, it was a signal to the food processing industry that the fluoroelastomer was appropriate for repeat food contact use. This testimony to the purity and cleanliness of Viton® opened up a valuable new industry sector for fluoroelastomer sealing.
Specialty fluoroelastomers are designed for the top end of FKM performance in the most demanding operating environments, but they had always been more difficult to process than the standard products. Fluoroelastomer producers strived to combine the best of both - the processability of the standard types with the outstanding performance of the specialties.
A technical breakthrough in 2001, resulting from a USD 60 million investment program by the former DuPont Dow Elastomers, now DuPont Performance Elastomers (DPE), made this possible. Called Advanced Polymer Architecture (APA), this was to signal another significant step forward in fluoroelastomer capability. APA is a result of a proprietary advance in polymer structure and the development of new cure site technology. It offers flow, cure and mold release processibility approaching that of a standard fluoroelastomer, with the final part performance of the best specialty products. This was realized by the commercialization of the first APA polymers in 2002 - Viton® GF-S, GBL-S, GLT-S, GBLT-S and GFLT-S. Since then, DPE has added steadily to the growing portfolio of APA 'S' types including new low temperature, peroxide and base resistant products.
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