Summary: Three rubber‐based nanocomposites, natural rubber (NR), styrene‐butadiene rubber (SBR), and ethylene‐propylene‐diene rubber (EPDM) matrixes, were prepared with octadecylamine modified fluorohectorite (OC) by melt blending. X‐ray diffraction (XRD) revealed that the SBR/OC and EPDM/OC nanocomposites exhibited a well‐ordered intercalated structure and a disordered intercalated structure, respectively. In the case of the NR/OC nanocomposite, it exhibited an intermediate intercalated and even exfoliated structure. These results were in good agreement with transmission electron microscopy (TEM) observations. Furthermore, in the NR/OC and SBR/OC systems, the mixing process played a predominant role in the formation of nanometer‐scale dispersion structure, whereas the intercalated structure of EPDM/OC formed mainly during the vulcanization process. The tensile strength of SBR/OC and EPDM/OC nanocomposites loading 10 phr OC was 4–5 times higher than the value obtained for the corresponding pure rubber vulcanizate, which could be ascribed to the slippage of the rubber molecules and the orientation of the intercalated OC. For the strain‐induced crystallization NR, the exfoliated OC efficiently improved the modulus of the NR/OC nanocomposite relative to the pure NR. However, its hindrance on NR crystallization during the tensile process may be the main reason for the decrease in tensile strength of NR/OC.XRD diffraction patterns of three nanocomposites containing 10 phr organoclay.magnified imageXRD diffraction patterns of three nanocomposites containing 10 phr organoclay.

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Summary: The changes in both local intercalated structures and spatial distribution states of organoclays (OC) in rubber/clay nanocomposites (RCNs) caused by vulcanization were monitored by using WAXD and TEM, and the corresponding mechanism was studied. It was first discovered that the pressure was the critical factor determining the final microstructures of cured RCNs. The cured RCNs with fine dispersion could be obtained through vulcanization under atmospheric pressure.TEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).magnified imageTEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).

Four organoclay (OC)/ethylene-propylenediene rubber (EPDM) nanocomposites with different ethylene contents were prepared by melt blending. X-ray diffraction spectrum (XRD) and transmission electronic microscope (TEM) photos showed that OC/EPDM nanocomposites were intercalated, and the ethylene content had little influence on the dispersion of OC. The addition of OC prolonged the optimum cure time and reduced the crosslink density of OC/EPDM. The improvement in tensile strength of OC/EPDM nanocomposites with high ethylene contents (67-70%) was larger than that of OC/EPDM nanocomposites with low ethylene contents (52-52.5%). XRD results of the stretched samples testified that the extension promoted orientation of silicate layers, and induced crystallization of polyethylene (PE) segments in OC/EPDM nanocomposites with high ethylene contents. The highly oriented microfibrillar structure and more oriented amorphous chains, which resulted from strain-induced crystallization of PE segments and the orientation of clay layers in OC/EPDM nanocomposites with high ethylene contents (67-70%), should be responsible for larger improvement in tensile strength than that of those nanocomposites with low ethylene contents (52-52.5%)