The pressure-volume-temperature(P-V-T) properties of natural rubber(NR) composites with different antioxidants were studied.The parameters of Tait equation was calculated and compared with experiments.The results showed that the P-V-T relationship calculated by Tait equation agreed well with the observation results

the residual means between theoretical calculation and experimental values were all less than 0.01 which indicated that the Tait equation can be used to describe the P-V-T relationship of the natural rubber composites.Thermal expansion coefficients () and isothermal compressibility () of nature rubber were evaluated by Tait equations.It's showed that decreases with the increase of pressure

but nearly doesn't change with temperature increasing. will decrease when pressure becomes high and increases with the increase of temperature.This is well explained by molecular simulation that high temperature or low pressure will lead to an expansion on free volume of the system

so that the activity of the molecular chain is enhanced.When there is only one kind of antioxidant in the composites

the values of both and are large

but when these antioxidants are used together

the values of both and are small

and the composite has the best size stability.Furthermore

the cohesive energy density (CED) obtained from molecular simulation shows that the intermolecular interaction force of nature rubber with two kinds of antioxidants is high

so it is hard for or to change.Through accurate description of the changes of and with different pressures and temperatures for the composites

a method with the function of guiding processing and application research was attempted.