Abstract
Some basic stress-strain behaviors of plasticized PVC have been investigated in terms of the Mooney-Rivlin equation as a function of temperature, strain-rate and the sort and concentration of plasticizer.From these results, it was found that the pattern of the Mooney-Rivlin isotherm is parabolic below Tg, and turns out convex above TgA linear isotherm can be observed both around Tg and well above Tg.
In order to elucidate this behavior theoretically, the three-elements modle comprising an ideal rubber element (ER) combined in parallel with a Maxwell unit (EH, η;η/EH=τH) was presented as the simplest system manifesting the simultaneous reaction of the entropy tension and the energgy tension thermodynamically not in eguilibruim.
On the bas is of the present model, the two constants in the Mooney-Rivlin equation are related with the mechanical parameters as follows: 2C1=ER, 2C2=EH/3 and 2C2=ηγ. The theoretical Mooney Rivlin isotherm in accordance with the experiments reveals the change of the pattern from parabolic to convex with an increasing value of reduced relaxation time, τHγ
Some experimental verifications of the theory were made in comparison with the data obtained from the capillary-flow and the stress relaxation measurements.
