Rotational molding has several advantages, such as suitable for small-lot manufacturing and will be needed for the 21st century. In this paper, after describing briefly the feature and the molding materials used for rotational molding, PP wax is taken up as one example of developing elastomeric materials. Research and development of the elastomeric materials were seldom done until now for the reason that the elastomeric material does not fit normal temperature pulverization. However, application is broad, such as products which combine rigidity and surface softness by multi-layer molding, and the breakthrough in material’s R&D is expected.

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Latex state NMR spectroscopy and field gradient fast magic angle spinning solid state NMR spectroscopy were used for structural characterization of vulcanized butadiene rubber and vulcanized natural rubber. High resolution NMR spectra for elastomers were achieved either through Brownian motion of a latex dispersion or fast magic angle spinning for a solid. Sequence distribution of cis-1,4-, trans-1,4- and 1,2-butadiene units was investigated for polybutadiene through latex state NMR spectroscopy. Crosslinking junctions of vulcanized natural rubber were analyzed by field gradient fast magic angle spinning solid state NMR spectroscopy.

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Relationship between an optical transparency and a filler loading in cross-linked rubber is reviewed using our results of hydrophilic and hydrophobic silica-filled peroxide cross-linked natural rubbers (NRs). The loading of hydrophilic silica shows an optical anomaly, in which the optical transparency initially decreases and then increases with increasing an amount of the loading. The optical transparencies of the hydrophobic silica filled samples, on the other hand, are almost same without depending on the amounts. The difference is ascribed to characteristics of silica networks in these samples, which are revealed by three-dimensional transmission electron microscopy. With an increase of isolated filler chains in the rubber matrix, the optical anomaly of hydrophilic silica-filled cross-linked NR is found to be significantly accelerated. Light scattering equation is also formulated using a product of the number density and squared length of the isolated chains to explain the differences.

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Tensile properties of cross-linked rubber such as tensile strength, tensile elongation and tearing energy change 2~3 orders of magnitude according to the variation of temperature and velocity within rubbery state. These phenomena result from the dominant contribution of the viscosity to the rubber elasticity. This seems to indicate that a phase separation between elastic and viscous parts takes place, and thus macroscopically bi-continuous structures are formed in real cross-linked rubber.

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