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Hybrid clay polymer nanocomposites (CPNs) based on blends of natural rubber (NR) and chloroprene rubber (CR) with different compositions (100/0, 95/5, 90/10, 85/15, 80/20), reinforced with various contents of organomodified montmorillonite (OMMT), were prepared by a two-roll mill via a vulcanization process. Curing data of the prepared compounds indicated a reduction in scorch time (t 5 ) and optimum cure time (t 90 ) with increasing the nanoclay content. Mechanical properties of samples were markedly enhanced upon nanoclay inclusion, due to the proper level of interactions established between nanoclay particles and the rubber matrix as it was evidenced by SEM photomicrographs. Results of X-ray diffraction proved the expansion of the interlayer distance, and transmission electron microscopy micrographs further confirmed that the prepared CPN samples exhibit intercalated/partially exfoliated structures. Moreover, the reinforcement effect of OMMT was reflected in the stress-induced crystallization and network structure of the CPNs based on the rubber-elasticity and tube model theories as well as rheological properties. POLYM. COMPOS., 39:1562-1574

Nanoreinforcing fillers have shown outstanding mechanical properties and widely used as reinforcing materials associated to polymeric matrices for high performance applications. In this study, a series of multiwalled carbon nanotubes (MWCNTs)-, nano-Al 2 O 3 -, nano-SiO 2 -, and talc-reinforced epoxy resin adhesives composites were developed. The influence of different types and contents of nanofillers on adhesion, elongation at break, and thermal stability (under air and nitrogen atmospheres) of diglycidyl ether of bisphenol A (DGEBA)/epoxy novolac adhesives was investigated. A simple and effective approach to prepare adhesives with uniform and suitable dispersion of nanofillers into epoxy matrix was found to be mechanical stirring combined with ultrasonication. Transmission electron microscopic and scanning electron microscopic investigations revealed that nanofillers were homogeneously dispersed in epoxy matrix at optimized nanofiller loadings. Adhesion strength was measured by lap shear strength test as a function of nano-Al 2 O 3 and MWCNTs loadings. The results indicated that the lap shear strength was significantly increased by about 50% and 70% with addition of MWCNTs and nano-Al 2 O 3 up to a certain level, respectively. The highest lap shear strength was reached at 1.5 wt % of nano-Al 2 O 3 loading. MWCNTs at all loadings (except 3 wt %) and nano-Al 2 O 3 have enhanced onset of degradation temperature and char yield of the adhesives. By combined incorporation of 0.75 wt % nano-Al 2 O 3 and 0.75 wt % MWCNTs into the epoxy novolac/DGEBA blend adhesives a synergistic effect was observed in the thermal stability of the adhesives at high temperatures (800 C).

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A multiscale finite element analysis was performed for short carbon fiber (SCF) reinforced rubber composites under uniaxial tensile loading with periodic geometries and random distributions of the short fibers. Three different zones were considered, including the rubber matrix, SCF as the inclusion phase, and a thin matrix layer as the interphase. A nonlinear hyper‐viscoelastic model was selected for the matrix, while linear viscoelastic and elastic models were considered for the interphase and reinforcing phases, respectively. The analyses were carried out on an incremental basis from a lower loading‐unloading rate of 10 mm/min to a higher rate of 100 mm/min. Two interface conditions were considered between the polymer matrix and the SCF phases: perfect bonding and partial debonding. The partial debonding was modeled via extended FEM (XFEM) with a crack initiation criterion. An integral averaging technique was employed to predict stress and strain at the macro‐scale. Based on the observations in this work, hysteresis and energy dissipation decrease with the addition of the short fibers to the neat rubber and surface modification of the fibers under three‐cycle loading. For example, in the first cycle and for a constant stress of 0.45 MPa, the strain value decreases from 0.25 to 0.17 MPa at the loading‐unloading rate of 10 mm/min. The high‐fidelity model developed in this work for short fiber/rubber composites is able to predict the stress and strain responses of the SCF/SBR composites, confirming the accuracy of the utilized multiscale approach.