As motorization continues to grow, the requirements of automobile noise reduction has been gradually raised. Such requirements are bringing accomplished by improving the damping property for rubber vibration insulators for vehicle parts. However, in the current status of rubber technology, lowering the damping properties, usually results in decreasing the life time for performance of rubber mounting.
Therefore it is necessary to increase the fatigue life time of performance with the improvement of noise reduction for engine mounting. Generally, the evaluation of performance of engine mounting is performed by the road test of automobiles and bench fatigue test. As the above test method, it is necessary to practice the experiment for long time to obtain the good results.
Therefore, in order to get the excellent result of fatigue life time and have the short-time test cycle, we expected the development of new method of fatigue test. As the result, we have studied to obtain the new fatigue test, which is able to expect the fatigue life for rubber parts, by using of the correlations with actual vehicle parts by conventional fatigue test, at the stage of material development test. This report show the fatigue test by newly designed test piece, which is supposed to simulate actual parts strain by FEM (Finite Element analysis Method), and also show the relationship between test piece fatigue life and actual parts, using FEM analyzed strain as a parameter.
In this study, by using the parameter of maximum strains appearing at the locations, we can prove the relations between fatigue life and strain, and the correlations between test piece test and bench tet of acutual parts.

View full abstract

Polyurea elastomers were prepared by one-shot method from 2, 4-TDI, 3, 3′-dichloro-4, 4′-diaminodiphenylmethane, and PTMG-based polyether diamine.
Static mechanical, dynamic mechanical, and thermal properties of the elastomers were studied. The structure of the polyurea networks was also characterized by the measurement of elasticity, IR spectra, and DSC. For comparison, polyurethane elastomers of similar formulation were prepared and studied.
Thermal stability of polyurea elastomers at high temperature was improved by physical crosslinks through strong intermolecular hydrogen bonding of urea linkages.

View full abstract

The tire structure is forced usually to deform complexly and seriously on the roadway, to realize the fundamental performances of automobiles of running, turning and braking. The tread rubber block, as a constituent element of tire, plays an important role of holding the frictional forces between the tire and the road, for enabling car steering and breaking.
While the tread rubber block is subjected to compressive and shearing forces in contacting with the roadway, a phenomenon of the block edge detaching takes place, which leads to the contact area reduction and further the tread rubber wear.
An experimental study and a numerical analysis by using the finite element method based on a nonlinear elasticity law given by Mooney-Rivlin, have been conducted previously on this phenomenon, with predicting good agreement between them on the contact pressure distribution.
In this paper, an approximate analysis is presented on the contact deformation of a rubber block under compressive and shearing forces, by using the energy method based on the linear Hooke′s law with considering the incompressibility of rubber, to reveal the critical condition of the detaching phenomenon. Good agreement is obtained among these analytical, numerical and experimental results for contact pressure distribution and detaching condition.

View full abstract

We examined effects of microbes on 4 types of polymers, PS, UF, PVC and LDPE, which were concealed for 32-37 years in a relatively highly microbial active soil. The results were that with regard to both PS and UF, no alterations were recognized. In PVC, while no change in appearance was evident, similarly as, in PS, a decrease in the amount of plasticizer and oxidative deterioration of polymer near its surface were recognized. LDPE underwent the whitening phenomenon, with both front and back surfaces of its film which had been in contact with soil crumbled, witnessing to its severe collapsing and decomposition. In parts where films were piled one upon another and so were not in contact with soil, their transparency and gloss were kept, but in samples taken near the ground surface where aerobic bacterial were active, a phenomenon of especially violent degradative decomposition was observed. In LDPE films, no existence of antioxidant was recognized at all.
In FT-IR differential spectra of whitened parts and transparent parts of LDPE, existence of C=O group was recognized. Further, as similar FT-IR analyses wre made of ethyl ether extracts (low molecular weight compounds) of these two parts, the peaks of OH, OOH, and COOR appeared, with increasing amounts of C=O group. Where deterioration was very severe, the amount of C=O was small, being equal in level to that in the parts not being in contact with soil. The amount of ethyl ether extracts was twice as large in the whitened parts as in the transparent parts, suggesting that in the former, a deplymerization was in progress under the influence of microbes. This vindicated that normal LDPE was strongly affected by microbes in such a long period as more than 32 years.

View full abstract