Validity of Flory's model for describing equilibrium strain-induced crystallization (SIC) and thermal behavior in natural rubber

The Flory's model for high polymers is based on the assumption that the final stretched state is achieved by two separate steps: stretching and strain-induced crystallization (SIC). This assumption is valid in fast stretching process, where SIC cannot occur instantaneously. We check if Flory's assumption can influence the equilibrium crystallinity of SIC (C-e) for different elongation rates in natural rubber (NR). It is found that the C-e is independent on the elongation rate. Thus, the calculation of C-e in Flory's model is valid for all the equilibrium states of different elongation rates, not to be limited by the Flory's assumption. Furthermore, the calculated C-e in Flory's model is used to calculate the elastocaloric temperature change (Delta T), which agrees with the directly measured one. It can meet the theoretical requirement for the new potential cooling application of NR. (C) 2016 Elsevier Ltd. All rights reserved.