A fungal strain Physisporinus sp. R20 was isolated in Chiba, Japan, and was selected for its ability of growing significantly in the medium containing natural rubber latex as a carbon source. When this strain was cultured in the medium containing styrene-butadiene rubber (SBR) pieces as a carbon source at 25 °C for 1 month, significant hyphal growth was observed. FT-IR and ¹H NMR measurements of the R20 treated SBR revealed formation of the hydroxy group and the terminal CH₃ due to the bio-degradation of polyolefin chains. These changes supposed to be given by the effective activity of this strain on SBR.

Vulcanization, tensile strength and water-resistance of protein-free natural rubber (PFNR) were investigated in a viewpoint of application to a seal-product. The PFNR was prepared by incubation of high ammonia natural rubber (HANR) latex with urea, sodium dodecyl sulfate and acetone followed by washing with a centrifuge, twice. It was vulcanized with sulfur, zinc oxide, accelerator, stearic acid and anti-aging agent at 150 °C. Optimum vulcanization time and crosslink density were prolonged and lowered by removing proteins, respectively. The resulting vulcanized PFNR was characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) and nuclear magnetic resonance spectroscopy (NMR). After soaking in water, stress at break of vulcanized HANR decreased, whereas that of vulcanized PFNR did not. The PFNR in water was proved to be superior in the stress at break due to improvement of water-resistance that was a drawback of natural rubber.

Adhesion mechanism of a polyacrylic block copolymer/tackifier blend as a model pressure-sensitive adhesive was investigated. Special rosin ester resins with different weight average molecular weights of 650, 710, 890 and 2,160 were used as the tackifier and blended with a polyacrylic block copolymer consisting of poly (methyl methacrylate) and poly (n-butyl acrylate) blocks at tackifier content levels of 10, 30 and 50 wt%. From a transmission electron microscopic observation, the number of formed agglomerates of the tackifier with sizes on the order of several tens of nanometers increased with increasing tackifier content and molecular weight of the tackifier in the range from 650 to 890. For the tackifier with a molecular weight of 2,160, micrometer-sized agglomerates were observed. The glass transition temperature of adhesive measured by a dynamic mechanical analysis increased dependent on the number of formed nanometer sized agglomerates. Tack was measured using a rolling cylinder tack tester over wide temperature and rolling rate ranges, and master curves were prepared in accordance with the time-temperature superposition law. Tack increased dependent on the number of formed nanometer sized agglomerates. It was found that the adhesion properties are strongly affected by the nanometer sized agglomerates of tackifier. That is, the structure of a pressure-sensitive adhesive with tackifier is like nanocomposite.

The required performances of tires have been changed with the progress of vehicle technology and surrounding environment. The vehicle industry faces the big change of the so-called “CASE”; Connected, Autonomous, Shares/Service, and Electric. The future tire may not be changed drastically compared with a vehicle, but the performances related to the environment such as rolling resistance and tire noise will be more important than before. Considering the environments surrounding tires, future passenger tires may be classified into five categories: i) Inexpensive pneumatic tire; ii) Expensive pneumatic tire with low aspect ratio which is specialized for performances such as run flat, maneuverability, riding comfort, or etc.; iii) Downsized pneumatic tire with high air pressure which drastically improves both RR and tire noise; iv) Air less tire for small and low speed mobility vehicle; v) Intelligent tire.

In a lecture of this series, the author discusses rubber friction and wear widely experimentally and theoretically to unify them as a new physical concept. Several distinctive features of the rubber friction such as a friction coefficient that is much higher than metal and plastic and the intense stick-slip motion during sliding are all resulted from the sticky rubber surface. Thus, the first paper (Part 1) focuses on the surface characteristics of the rubber to understand the real features existing on the surface of cross-linked rubber, where is shown that the dominant factor encountered during the rubber friction is the adhesion force caused by the meniscus formation in the interface between the uncross-linked phase in the cross-linked rubber and the solid surface.