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Modelling of elastomeric materials and products

The Rubber in Engineering Group (RIEG) was formed as part of the Institute of Rubber Industries more than 60 years ago. Today, it is the most vibrant committee of the Polymer Society at the Institute of Materials, Minerals and Mining. The group has an active committee of 20 members from a wide range of industries and academia. We typically arrange about five meetings each year, as well as conferences and publications, with the principal aim of promoting understanding of the behaviour of rubber from an engineering perspective. In 2019, the committee is helping organise the International Rubber Conference which will be hosted in the UK for the first time in 18 years on the 3–5 September 2019. The group’s meetings are popular often with more than 100 delegates from around the world joining the discussions. The need for these meetings is in part a result of ever-increasing performance requirements for engineered rubber products such as tyres, anti-vibration mountings, hoses and seals. These requirements are likely to continue to become ever more demanding in future. As simple examples, the trend of weight reduction in transportation applications or the trend for increasingly demanding higher and lower operating temperature requirements for seals in the oil and gas sector has made it increasingly difficult to meet service life requirements. All the while elastomeric components are being required to last longer because of an increase in warranty periods offered for vehicles and engineered devices. In the tyre industry, the conflicting demands of weight reduction and reduced rolling resistance coupled with increases in abrasion resistance and wet and dry friction performance also make the tyre designer’s role increasingly difficult. Therefore, all rubber components will have to be designed and manufactured using robust engineering principles to ensure that they comply with expected performance and longevity requirements. In light of these requirements, the RIEG organised a two-day conference on the 7–8th December 2016 on the topic of ‘Innovations in Rubber Design’. This special edition is made up from four selected papers presented from different sessions at this conference. One of the key aspects that needs to be considered when designing with elastomer materials is the ability to recycle the materials. Most elastomer materials are thermosetting and are therefore difficult to recycle. The first paper considers this carefully by examining what Wilma Dierkes et al. [1] refer to as cradle to cradle loops. In their paper devulcanisation of vulcanised elastomers and the subsequent reuse of devulcanisates in virgin rubber compounds are explored. Two elastomer types: EPDM and SBR, are compared to determine their ease of devulcanisation with optimised devulcanisation aids, which were hexadecylamine for EPDM and diphenyl disulfide for SBR. The second paper looks at the failure mechanisms that are often present in large tyre type application. Radek Stocek et al. [2] discuss what they refer to as ‘chipping and chunking’, while trying to develop a methodology to measure this behaviour under laboratory conditions. This type of rubber failure is often seen in off-road tyre applications or other conditions where the road surface is poor. The third paper by Davide de Focatiis et al. [3] examines how the properties of a material in terms of its viscoelastic behaviour can be restored after a suitable heat treatment. It explores how the mechanical properties that are broken down during a cyclic strain history can be recovered. This is an important manifestation of what is widely known as the Mullins effect and the processes that control it and the subsequent recovery are explored. The fourth paper by Colin Li Pi Shan [4] examines how the optimum properties for a foamed EPDM can be achieved in practice. They explore how EPDM metallocene catalyst to produce new EPDMs for production of automotive sponge weatherstrip. These new EPDMs provide more homogeneous mixing during production, faster curing and foaming. The design and microstructure of these EPDMs are tailored to impart superior collapse resistance in the extruded profiles to allow the development of more complex profiles. The themes of these papers reflect the direction that rubber research is moving and also reflect both the topics that were explored by the RIEG at this conference and the scientific literature for elastomer and rubber materials. These same themes are reflected in the various papers that have been published recently in this Journal. The papers presented in this special edition give just a snap shot of a subset of these recent developments in rubber materials. It is hoped that the leading researchers in the rubber materials field will continue to choose Plastics, Rubber and Composites: Macromolecular Engineering as their Journal of choice for publishing their findings. Members of the Institute of Materials, Minerals and Mining have free online access to these articles and to other Institute journals through the IOM3 website at www.iom3.org. The Rubber in Engineering Group continues to host regular meetings themed on all aspects of engineering with rubber. They typically run three or four afternoon technical discussion meetings a year that are free to members of the IOM3 and run a major conference almost every year including the International Rubber Conference in London from the 3-5 September 2019. The meetings