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Rubber compounds are reinforced with fillers such as carbon black and silica. In general, filled rubber compounds show smooth rheological behaviour in measurement of Mooney viscosity or Mooney scorch time. Variation in rheological behaviour was studied in terms of the filler composition using natural rubber compounds filled with both carbon black and silica (carbon black/silica = 60/20,40/40, and 20/60 phr). The compound filled with carbon black/silica of 60/20 phr showed normal rheological behaviour. However, the compounds filled with carbon black/silica of 40/40 and 20/60 phr showed abnormal rheological behaviour, in which the viscosity increased suddenly and then decreased at a certain point during the measurement. The abnormal behaviour was explained by the strong filler–filler interaction of silica. Moreover, the abnormal rheological behaviour was displayed more clearly as the storage time of compounds is increased. © 2003 Society of Chemical Industry

This article reviews the noise absorption capacity of thermally bonded nonwovens in the range of audible frequencies (125-2500 Hz). First, we focus on the effects of the properties of the fibers, which constitute nonwovens, on the sound absorption properties, and then we consider the web orientation angle of nonwovens. We also investigate a composite model of the sound absorption properties of nonwovens, including the surface roughness and panel vibration. We have used an impedance tube interferometer, which provides the normal incidence sound absorption coefficient of materials, for the determination of the noise absorption properties of nonwovens produced under different conditions. The noise absorption capacity of nonwovens depends primarily on the thickness and surface characteristics of specimens, but the effects of the fiber contents are only marginal. Interestingly, when there is a panel in front of nonwovens, the noise absorption capacity increases significantly at low and medium frequencies (250 -1000 Hz).

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Styrene-butadiene rubber (SBR) is a copolymer of styrene and butadiene, and the butadiene unit is composed of cis-1,4-, trans-1,4-, and 1,2-components. Fillerpolymer interactions of each component of SBR in silica-filled SBR compounds were examined by microstructure analysis of the bound and unbound rubbers. The composition ratio of butadiene and styrene units (butadiene/styrene) of the bound rubber was higher than that of the compounded rubber. Of the butadiene units, the 1,2-component of the bound rubber was more abundant than the cis-1,4-and trans-1,4-components. The filler-polymer interaction of the butadiene unit with silica was stronger than that of the styrene unit, and the interaction of the 1,2-component was stronger as compared with the others. The butadiene-styrene ratio of the bound rubber of the compounds containing the silane coupling agent was lower than for the compounds without the silane.