Yoshiyasu Sato

A Method of Analyzing Large Deformation Behavior of Rubber-Like Materials

A stress-strain relation, f={G-B(1-1/α)+C(αα2-1)}(α-1/αα2), was used to analyse the large deformation behavior of styrene-butadiene rubber (SBR) with various concentrations of oil ranging from 0 to 40 PHR. In the above relation, f denotes nominal stress at extension ratio α, G corresponds to rigidity, B and C are coefficients. The theoretical character of this relation will be discussed in another paper5) by one of the authors. The present results can be summarized as follows; The value of G is proportional to the crosslink density νe, but larger than those calculated from νekT. The value of B is almost unaffected by νe and shows almost same tendencies as G against oil concentration υ1 and strain rate e. The value of C is about 1/100 of those of G and B, and had the maximum against νe and e.

Large Elastic Behavior and Fracture of Oil-Extended SBR Vulcanizates

Hereunder is presented a brief report of the test concerning the applicability of the following stress-strain relation f=(A+B/α+Cα2)(α-1/α2) to the stress-strain behavior of styrene-butadiene rubber (SBR) with various concentrations of oil ranging from 0 to 40 PHR, and the dependences of the values of A, B and C on oil concentration, sulfur content (crosslink density) and strain rate were examined. In the above relation, f denoted the tension at extension ratio α, A, B and C were coefficients. This relation had been obtained from the phenomenological theory of finite deformation with second order approximation to the stored energy function. The time-concentration equivalence of the ultimate properties of the data was also examind. The samples of SBR were sulfur cured with various contents of sulfur in the presence of oil at 155°C for 60 minutes. The stress-strain data were determined by means of an Instron type tester at various crosshead speeds between 8mm/min and 800mm/min at the temperature 20°C. The results will be summarized as follows:(1) The values of A decreased with increase of oil concentration and increased with sulfur content and they were unaffected by the strain rate.(2) The values of B decreased with increase of oil concentration and were almost unaffected by the sulfur content, and they showed slight increase against the strain rate at high strain region.(3) The values of C were very small and almost 0 for the data at crosshead speeds below 200mm/min. They decreased with increase of oil conentration and had the maximum aginst the sulfur content and also against the strain rate.(4) Stress at break σb data of samples with different oil concentrations could be represented by a master curve by applying the method of time-concentration superposition, and the shift distances log ac obtained superposing data followed the theory of solution type equation.

Time and Temperature Dependence of Ultimate Property in Fluid Fracture

Time and temperature dependence of ultimate properties in fluid fracture is reported for PVC-DOP solution (volume fraction of PVC, v2=0.04) and liquid polybutadiene (PBD). The method used was such that small quantity of the sample was injected into air from a narrow nozzle and let it fall in drops, namely the sample overloaded by the drop weight. A cylindrical part of the pendant from the nozzle was elongated and took time to break. The time was defined as breaking time tb. The drop weight W corresponding to load at break and associated tb were measured with various drop sizes at different temperatures. Six temperatures were selected in the range from 30°C to 80°C for PVC-DOP solution and from 11°C to 35°C for liquid PBD. In elongation processes, a change of drop sizes was very small and almost negligible. Weight vs. time curves at different temperatures can be superposed into an almost unified master curve by the horizontal shift. It seems that the shift factor for the ultimate properties follows the prediction of the Arrhenius equation.Furthermore, a relation between the shift factors aT for both fluid fracture of PVC solution and creep deformation of PVC-DOP sheets was examined. The creep data were obtained in the temperature range from 2.5°C to 29.5°C for PVC-DOP sheets having different volume fractions of PVC ranging from 0.191 to 0.699.It is found that the shift factor aT for the fluid fracture is almost equal to that predicted from the values of aT for creep deformation. Thus the values of log aT are given by the Arrhenius equation above 30°C, and close to the WLF equation below 30°C.