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Rubber and Elastomers in Engineering |
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Topics: · Elastomers in Civil Engineering · Engineering Product Development Online DocumentsRelated links:· TARRC |
Elastomer or
Rubber?
The distinction between "elastomer" and "rubber" is often blurred among engineers; according to BS 3558-1:1997 ISO 1382:P1996 rubbers are a subset of elastomers, being the materials with irreversible crosslinking, and hence those much more suited for demanding quantitative engineering specifications: "Elastomers = macromolecular material which returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress. "Rubber = elastomer which can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, methyl ethyl ketone and ethanol toluene azeotrope, and which in its modified state cannot be easily remoulded to a permanent shape by the application of heat and moderate pressure. NOTE: a rubber in its modified state, free of diluents, retracts within 1 minute to less than 1.5 times its original length after being stretched at normal room temperature (18°C to 29°C) to twice its length and held for 1min before release" With official definitions like these, and the tendency of some engineers to think of "rubber" as natural rubber and, not, for example applying to Neoprene (ie the Dupont tradename for polychloroprene, used by engineers in vulcanized form so that it certainly is a rubber), it is little wonder that engineers are tempted to use the general term elastomer. Elastomers for Engineering: Future Trends
The Rubber in Engineering Committee of the IOM3 organised a one day conference on Elastomers for Engineering: Future Trends in November 2006 (a review is available at that website). David Lowe of TARRC presented a paper on "Reinforcement of Natural Rubber by Organoclays"; related work is presented at www.tarrc.co.uk. Ian Stephens of TARRC presented "Polymer-based Pressure Membranes for Fatigue Tests on Turbofan Compressor Casings", discussing the limitations of elastomers at high temperature. Fatigue of Elastomers
The Rubber in Engineering Committee organises regular afternoon discussion meetings on engineering applications of elastomers, and fifty delegates attended one on Fracture and Fatigue of Rubber on 23rd March 2007. Four papers were presented, covering fracture mechanics of rubber (Vince Coveney), high speed fracture of rubber (Prof Alan Thomas), "damage" to rubber through stress-cycling (Dr John Kingston) and use of Dr Will Mars's post-processing software for predicting durability of elastomeric products from FEA stress-strain outputs (Dr Roly Whear). The meeting lived up to its designation, with a lively discussion continuing into the evening. The Engineering Integrity Society organised a very successful and enjoyable international conference on Durability and Fatigue (Fatigue 2007) at Queens' College, Cambridge at the end of March. Although the primary interest of most of the delegates was metals, biomaterials, thermoplastics and ceramics were also addressed, and John Kingston and Alan Muhr of TARRC presented papers on "Effects of strain crystallisation on cyclic fatigue of rubber" and "Computation of energy release rates for small cracks in rubber components". The EIS has kindly provided permission for the papers to be downloadable from this site. This conference was a descendent of Fatigue '81, held at Warwick University in March 1981 and organised by the Fatigue Group of the Society of Environmental Engineers, at which TARRC reprint 928 "Fatigue resistance of NR in compression" by P B Lindley & A Stevenson was presented. The EIS was formed by a break-away group from the SEE in 1986 and held its first international conference that year; it has run fatigue-related international conferences every 3-4 years since, and the first conference under the "Fatigue XXXX" banner was Fatigue 2000. |
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Last Updated: 02/05/08Comments to: webmaster@rubber.demon.co.uk |