ABSTRACT:We investigated the sound absorption characteristics of an organic hybrid material comprised of chlorinated polyethylene (CPE) as the matrix polymer and N,NЈ-dicyclohexyl-2-benzothiazolyl sulfenamide (DBS) as the second component of an organic low-molecular-weight compound. We found specific crystallites, obtained by annealing, that generated new absorption for a low-frequency sound in a CPE/DBS blend. We observed two sound absorption peaks, around 300 and 1000 Hz, in the annealed CPE/DBS (50 : 50 w/w) blends, whereas those peaks were not observed in the untreated sample. There were two kinds of crystals with different melting points in the annealed samples. It was confirmed that the crystals with the lower melting point brought about sound absorption at a low frequency. The crystals that had the lower melting point were smaller and/or more disordered than the crystals that had the higher melting point. We calculated the fraction of these two types of crystals from differential scanning calorimetry and wide-angle X-ray diffraction measurements. The annealing or reannealing temperature specified the fraction of the crystal with the lower melting point, and the obtained crystal fraction characterized sound absorption frequency. Therefore, it is possible to control the sound absorption frequency of an organic hybrid by heat treatment such as annealing.
In this study, the effects of plastic deformation and failure of the folded part on the folding behavior of non-crosslinked ethylene propylene diene terpolymer/ paraffin oil/silica gel composites were investigated. The folding behavior was evaluated by the residual fold angle of a folded specimen; a lower fold angle indicates an enhanced folding performance. The fold angle decreased with increasing oil and silica content and was correlated with the tensile yield strain, which is generally related to plastic deformation. Furthermore, the test speed dependence of the fold angle for each set of oil contents and test temperatures was investigated. The fold angle decreased with a decrease in the test speed and an increase in the test temperature. Scanning electron microscopy revealed that the low-fold angle, which indicates an improvement in the folding behavior, was caused by the destruction (voids, crazes, and cracks) of the folded part.
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