The effect of mixing on filler dispersion has been shown to have remarkable affects on material properties. Many methods of measuring filler dispersion have been developed. However, none of them provides a filler dispersion index that gives the best way to control a mixing process.
We developed a new method of measuring filler dispersion named FDI in order to evaluate objectively a kneading state of the compound that consists of EPDM, carbon black, and oil. A filler dispersion index (FDI) is defined as a percent ratio of complex modulus G^* at 1% strain versus that at 0.01% strain.
A FDI value increases along with an increase of mixing time. A FDI value of cured EPDM is proportional to that of uncured EPDM. Treating the rubber composition with an open role does not affect on a FDI value. Consequently, the FDI is found to be a better method to measure carbon dispersion comparing the optical microscope method of ASTM 2663-69.
A free induction decay curve of pulsed NMR indicates a presence of hard segments with a short spin-spin relaxation time (T2). The short-T2 value measured by pulsed NMR increases along with an increase of mixing time, which is similar to the FDI.

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It was found recently that ethylene-propylene diene rubber (EPDM) compounded with peroxide could be adhered directly to steel during vulcanization after a polymer plating of steel in 6-diallylamino-1, 3, 5-triazine-2, 4-dithiol monosodium (DAN)/sodium carbonate aqueous solution. The rubber adhesion of the polymer plated steel is studied here with emphasis on the effect of the polymer film thickness and the contents of the compounding ingredients, such as HAF carbon black, process oil and peroxide. In order to evaluate the effect of the compounding ingredients, a three variable central composite designed experiment based on a Box-Wilson response surface methodology is employed. The results show that the thickness of the polymer plating film should be controlled in an optimum range from about 20nm to 200nm in order to obtain enough peel strength of adherend. On the other hand, the peel strength is affected by carbon black, process oil and peroxide contents, and high interactions among these factors are observed. These factors show their respective optimum contents, which is explained as a result of the balance of reactions between peroxide/rubber and peroxide/polymer plating film occurred at the adhesion interface during vulcanization. The adherends under the optimum compounding show excellent heat aging resistance, moisture aging resistance, and water aging resistance.

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The curing processes of EPDM, NBR, SBR, BR with various peroxides are estimated using an oscillating rheometer. It is difficult to treat the whole reaction process due to existence of induction period of reaction on the curing process of rubbers. In this paper, the active state of rubber was taken into the reaction model in order to cope with this problem.
Consequently, relative cure states at arbitrary time has been presumed with sufficient accuracy. Moreover, it is elucidated that the temperature dependence of the apparent rate constants can be validly expressed with the Arrhenius equation, and obtained relations give not only the rate constants at arbitrary temperatures but also activation energies of radical production reactions. Therefore, the rate constants of curing processes with peroxide can be evaluated at arbitrary temperatures, and the curing processes can be analyzed even at unsteady temperature distributions in actual rubber products.

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Hindered phenol compound 3, 9-bis{1, 1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl} -2, 4, 8, 10-tetraoxaspiro[5, 5]-undecane (AO-80) is polymorphous material with different physical structures. The initial AO-80 is highly crystalline, whereas AO-80 obtained by cooling from melt is an amorphous material. Annealing treatment below the melting point of AO-80 results in structural development. The mixture of chlorinated polyethylene (CPE) and vitrified AO-80 particles exhibits a dramatic change in the dynamic mechanical properties during heat treating at 130°C. The change can be attributed to the decomposition of the vitrified AO-80 particles and the hybridization of two constituents. The vitrified AO-80 particles can crystallize again in a CPE matrix by annealing at 100°C, but the crystal is different from the initial AO-80 in the microstructure. In addition, the incorporation of CPE chains with AO-80 caused a dramatic increase in the modulus. As a result, the AO-80 crystal particles containing some CPE chains act as multifunctional cross-links and the CPE/AO-80 hybrid was found to be a new type of elastomer.

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Previously, polytetrafluoroethylene (PTFE) was believed to be a typical polymer decomposed by ionizing radiation. However, it was found that, when PTFE is heated to a high temperature near its melting point and subjected to ionizing radiation under an inert gas atmosphere, across-linking reaction occurs between its atoms. Technology based on this discovery was developed in Japan. The cross-linking technology and its characteristics were examined. We found that cross-linked PTFE drastically improves abrasion resistance and creep resistance. We established the elemental technology based on cross-linking.At present, we have developed a wide selection of basic materials according for various uses and furthured the development of applied products.

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Pulsed NMR, which is used for measuring spin-spin relaxation time, T₂, and spin-lattice relaxation time, T₁, has a unique advantage over other techniques because it can provide direct information on molecular motion and volume fraction of each component in the composites1), 3), 4), 20), 25), 60). Rubber-Carbon black interactions are very important to study the reinforcement of rubbers. The T₂ signal of the bound rubber was resolved into two components, short T₂ component and long T₂ component. In a two-phase model for interpreting the reinforcement, one phase was the immobilized rubber layer around carbon blacks, and the other was the rubber away from the filler surface1), 29), 34), 36), 60) On the other hand, Folland and co-workers3), 4) suggested that unfilled isoprene rubber crosslinked by irradiation consisted of two components such as network structures and non-network structures. Recently, Noguchi and co-workers48) reported the results from a pulsed NMR spectroscopy with Hahn echo method for EPDM specimens and their relations with the dynamic fatigue behaviors. The retention of stress under fatigue for peroxide-crosslinked EPDM filled with carbon black, calcium-carbonate, or silica, tended to decrease as the network T₂3), 4) became longer and the non-network fraction became larger. This result suggests the relationships between the fatigue behavior and the non-network fraction as well as the molecular mobility of the network component.

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