Abstract
Selection of a suitable thermal aging process could render desirable mechanical properties of the rubbers or blended rubbers. In this work, the effect of the aging processes on the mechanical properties and activation energies of natural rubbers (NR) and NR/chloroprene rubbers (CR) blends with low CR contents (5–10%) was investigated. Three aging processes including heat aging (at 110°C for 22 hours), mechanical aging (under dynamic loading to 140% strain for 16000 cycles), and complex aging (heat and mechanical aging) were studied. The results revealed that the compatibility of CR in natural rubber matrix had a significant effect on the dynamic properties of the blended rubber and negligible effect on the static properties. The changes in activation energies of the blended rubber during aging processes were calculated using Arrhenius relation. The calculated changes (ΔUc, ΔUd, and ΔUT) in activation energies were consistent with the results of mechanical properties of the blended rubber. Interestingly, the change in activation energies using complex aging conditions (ΔUc) was mostly equal to the total changes in activation energies calculated separately from heat aging (ΔUT) and mechanical aging (ΔUd) conditions. This indicates that, in complex aging conditions, the heat and dynamic loading factors act independently on the properties of the blended rubber.
Highlights
Natural rubber (NR), a very important elastomer, has been widely used in wide range of technical and civil applications
It is of note that when the chloroprene rubber (CR) contents increase, the swelling value of NR/CR blends decreases. is is ascribed to the swelling of each rubber in solvent and the interaction of rubber on interphase surface. e NR/CR blends with low compatibility of rubbers and poor interaction on the interphase surface lead to solvent penetration into the interphase area easier than into rubbers, and as a result, the swelling property increases
Low swelling behavior of CR might reduce the swelling of NR/CR blends. erefore, at a low percentage of CR in the blend, the swelling decreases because the decreased swelling of CR is not enough to compensate the increased swelling from rubbers incompatibility
Summary
Natural rubber (NR), a very important elastomer, has been widely used in wide range of technical and civil applications. Utilization of heat aging process and various accelerator systems resulted in the change of dynamic properties of rubber [12, 13]. E simultaneous effect of two factors (aging processes and mechanical loading) on the rubber service life has been studied in many works [18,19,20,21,22]. Change in activation energy of the blended rubbers during the aging processes, which lead to change in mechanical properties, has not yet fully studied. Based on the determination of aging coefficients and Arrhenius-type equation for tensile strength, change in activation energy will be quantitatively evaluated, while rubbers are affected by the aforementioned factors simultaneously and separately
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