Discrete Relaxation Spectrum and K-BKZ Constitutive Equation for PVC, NBR and Their Blends

Frequency sweep experiments were performed on poly(vinyl chloride) (PVC) and acrylonitrile butadiene rubber (NBR) as well as their miscible blends; i.e. PVC/NBR by mechanical EOHQGLQJ DW C o . In order to investigate the validity of time temperature superposition (TTS) principle, curves of loss angle ) (d versus the logarithm of absolute value of complex modulus, *) log( G , have been plotted. It has been shown that the TTS principle is not valid for the above-mentioned polymer materials and therefore, they are not t hermorheologically simple. Meanwhile, master curves of PVC, NBR and PVC/NBR OHQG ZHUH REWDLQHG approximately. Using a nonlinear regression method, discrete relaxation spectra have been determined for 39& 1 %5 DQG 39& 1 %5 7R VWXG non-linear viscoelasticity behavior, the experiments of steady shear, start up steady shear and step strain have been carried out. The damping function was determined by the step strain experiments. Using K-BKZ equation, the shear viscosity and the shear stress growth function were calculated from the discrete relaxation spectra and the damping function, and then compared to experimental data. The K-BKZ constitutive equation provides very good prediction over the entire range of experimental results, particularly; it predicts the main features of the experimental data.

کلیدواژه ها:

rheology ، poly (vinyl chloride) ، acrylonitrile butadiene rubber ، time temperature superposition ، miscible blend ، shear viscosity ، KBKZ constitutive equation