Stored energy accompanying cyclic deformation of filled rubber

Abstract

International audienceThe hysteresis observed in the mechanical response of filled rubbers is classically assumed to be due to viscosity. In this study, a complete energy balance is carried out during cyclic deformation of a filled acrylonitrile-butadiene rubber. Results show that for the studied material, viscosity is not the preponderant contribution to the hysteresis loop: the mechanical energy brought to the material is not entirely dissipated into heat but a contrario is mainly used by the material to change its microstructure. Moreover, no significant hysteresis loop is observed in the unfilled material. Hence, the filler network stores elastic energy during its deformation, leading to a change in the internal energy. The higher the stretch applied, the higher the relative stored energy, but the higher the stretch rate applied, the lower the relative stored energy in the filler network. This has been evidenced by defining a ratio γse in terms of energy. As hysteresis loop in rubbers does not systematically mean that intrinsic dissipation is produced, predicting changes in temperature, and consequently the self-heating, is not possible from the mechanical response only. To conclude, this study presents the first estimation of stored energy in a filled rubber. © 2017 Elsevier Lt

Agricultural proteins as multifunctional additives in ZnO‐free synthetic isoprene rubber vulcanizates

“…This suggested that at low protein filler loading, more strain energy applied during extension was recovered upon retraction compared to unfilled and highly filled rubber compounds. 55,56 Hysteresis decreased with repeat cycling and, after a few extension/retraction cycles, known as the conditioning period, the hysteresis reached a relatively constant value. There are many applications that require low hysteresis at elongations of several hundred to thousand percent, such as rubber bands, gloves, balloons, and threads/fibers for golf balls, among others.…”

“…52,53 In tire treads, low hysteresis is important to lowering rolling resistance. 55,56 Low protein filler loadings of 1-2 phr resulted in more energy storage, especially compared to ZnO filler, at increased extension/retraction cycles [- Figure 5(a)]. ZnO has high thermal conductivity and so can reduce heat build-up.…”

Energy stored during deformation of crystallizing TPU foams

“…Else, it is necessary to distinguish the part of the mechanical energy converted into heat from the one stored by the material to change its microstructure. For that purpose, the ratio γ s e recently proposed by Le Cam and co‐workers() is used: where .…”

“…The material stores part of the mechanical energy brought and releases it (or a part of it) with a different kinetics. ()…”

“…In the case of filled uncrystallizable nitrile butadiene rubber (NBR), only a part of the mechanical energy is dissipated into heat, due to viscous effect induced by carbon black fillers. () Indeed, adding fillers also induces energy storage. To further discuss on the relative contribution of the energy stored in the hysteresis loop of rubbers, authors proposed a ratio γ s e , written in terms of energies over one mechanical cycle as follows(): …”