The residue produced by the bacterial decomposition of synthetic rubber has potential for reuse in industrial applications. We attempted to cultivate Bifidobacterium bifidum, which produces conjugated bile-salt hydrolase (CBHase), in Bifidus medium supplemented with rubber residue filtrate with Sep-Pak^TM (RRF-Sep).

RRF-Sep promoted CBHase activity but did not promote the growth of Bifidobacterium.

In addition, RRF-Sep was extracted with different organic solvents and the components were separated by thin layer chromatography. Multiple fractions were detected in this extract, which varied depending on the type of solvent used for extraction.

CBHase activity of bifidobacteria and the nisin productivity of lactic acid bacteria were measured in growth media supplemented with these extracts. A range of activities were observed, depending on the type of extraction solvent used.

The results indicate that the metabolism in Bifidobacteria and lactic acid bacteria might be influenced by different components of the extract.

The changes in tensile properties of black-filled ethylene propylene diene terpolymer (EPDM) in sodium chlorite (NaClO₂) solution and chlorine dioxide solution (ClO₂) were studied. The diffusion behaviors of Cl and O atoms were investigated by electron probe micro analysis. The deteriorated layer in which Cl and O atoms were diffused was formed on the surface of EPDM immersed in the NaClO₂ solution and the ClO₂ solution. Dissociated chlorite ion (ClO₂^-) did not diffuse into EPDM, but ClO₂ did and undissociated chlorite acid (HClO₂) possibly did. It was suggested that chlorine dioxide diffuses into EPDM faster than hypochlorous acid (NaClO). The tensile properties strongly depended on the depth of diffusion of O (D_O) into EPDM, regardless of the type of solution. The hardening of the deteriorated layer enhanced the stress at 100% strain (S₁₀₀), and the cracks generated in the deteriorated layer resulted in the decrease in the tensile strength (T_B) and the elongation at break (E_B). The relationship between T_B and D_O was similar to that between T_B and the length of the physical notch given by the razor. The thickness of the degraded layer was found to be equivalent to the physical notch.

The NMR methods with the ILT analysis method is enable to describe precisely the structural changes occurring in the rubber network and with respect to chain mobility. With the help of this method, it was possible to quantify structural changes with crosslinking or aging. It is possible to be divide into 3 category of the shares such as physical/chemical cross-links, free chain ends and free chain fragments. In practice, sealing materials are subject to various aging processes as a function of ambient factors, for example, temperature and oxygen, frequently manifested in stress relaxation impacted critically with respect to the long-term functioning of the seal. In order to understanding it, further development of innovative characterization methods called low-field time-domain NMR spectroscopy with inverse Laplace transformation (ILT) was done. All the aforementioned material parameters were found to have a significant impact on the aging-related rubber structural change. The new characterization methods allow for a much more precise description, and thus a markedly better understanding, of aging process the stress relaxation mechanism among elastomers.

There are three types of rubber molds: compression vulcanization molds, trans-ferrous vulcanization molds and injection molding molds. These molds differ in configuration, performance and features. In designing a rubber mold, it is necessary to make it easy to feed the unvulcanized rubber compound, easy to take out the molded product, and easy to finish the burrs. Also, in designing the rubber mold, it is necessary to take into consideration the mold framework (mold size, mold vulcanization method, vulcanization machine, number of cavity, and design framework), basic structure, and elemental technologies specific to the mold. In the era of electric discharge machining, NC milling machines, and two-dimensional NC, the shapes are manufactured with high precision, but in recent years, the surface precision of rubber products has been required, and only finishing is done by hand. In the future, it is expected that the flow mechanism of unvulcanized rubber compound in cavities and channels will be clarified, and the rubber mold will be designed taking them into account to create a high function rubber mold.

A synchrotron radiation experiment and a large-scale simulation are indispensable for development new functional rubber materials in recent years. In this series of lectures, I will try to explain about an analysis of structure of filled rubber vulcanizates by cooperation of a synchrotron radiation experiment and a large-scale simulation. In this second article, I will discuss a large scale coarse-grained molecular dynamics simulation of end-modified styrene butadiene rubber compounds conducted on the K-computer. Filler aggregates are modeled by reverse Monte Carlo method from a part of ultra-small angle X-ray scattering data of rubber compounds obtained in the large-scale synchrotron radiation facility SPring-8. The difference of experimental stress-strain curves between end-modified SBR and non-modified SBR has been reproduced qualitatively by simulation. Behaviors of large strain region of experimental SS curves can be explained by the difference of maximum elongation of network chains due to the difference of number of bonds between filler in end-modified SBR and non-modified SBR. Difference of small strain region of experimental SS curves reveals to be due to the difference of structure of filler aggregates in end-modified SBR and non-modified SBR.