The mechanical properties and strain-induced crystallization (SIC) of elastomeric composites were investigated as functions of the extension ratio (λ), multiwalled carbon nanotube (CNT) content, and carbon black (CB) content. The tensile strength and modulus gradually increase with increasing CNT content when compared with the matrix and the filled rubbers with same amount of CB. Both properties of rubber with CB and CNT show the magnitude of each CNT and CB component following the Pythagorean Theorem. The ratio of tensile modulus is much higher than that of tensile strength because of the CNT shape/orientation and an imperfect adhesion between CNT and rubber. The tensile strength and modulus of the composite with a CNT content of 9 phr increases up to 31% and 91%, respectively, compared with the matrix. Differential scanning calorimetry (DSC) analysis reveals that the degree of SIC increases with an increase in CNT content. Mechanical properties have a linear relation with the latent heat of crystallization (LHc), depending on the CNT content. As the extension ratio increases, the glass-transition temperature (Tg) of the composite increases for CB- and CNT-reinforced cases. However, the LHc has a maximum of λ = 1.5 for the CNT-reinforced case, which relates to a CNT shape and an imperfect adhesion with rubber. Based on these results, the reinforcing mechanisms of CNT and CB are discussed.

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The mechanical properties of short-fiber reinforced polychloroprene rubber have been investigated as functions of interphase condition, fiber content, and fiber aspect ratio. The tensile strength of reinforced rubber exhibits a dilution effect in each interphase. Both the yield strength and tensile moduli are significantly improved with the fiber content. The bursting pressure of reinforced rubber increases up to 8.73 times compared to virgin material. The bursted shape of virgin rubber shows a radiating shape while that of reinforced rubber shows a fluctuating straight line. The better the interphase condition shows the smaller the changing rate of the spring constant. The temperature of rubber matrix increases about 2.6 times and those of the reinforced rubber show a 1.4-2.2 times increase after the fatigue test. The better the interphase condition shows the smaller the changing rate of temperature with the same fiber content. In this study, the interphase model 'E' with double coatings of the bonding agent 402 and a rubber solution becomes the best interphase model in comparison to the five different models.

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