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Differential Scanning Calorimetry (DSC) for Interdiffusion Studies in PVC/PnBMA Blend: A Quantitative Analysis



Differential scanning calorimetry (DSC) was used to study interdiffusion in an initially demixed blend, prepared as particle-matrix system of the intrinsic miscible polymers poly(vinyl chloride) (PVC, particle, 30 wt.-%) and poly(butyl methacrylate) (PnBMA, matrix, 70 wt.-%) during isothermal annealing at 110 °C. A detailed interpretation of the experimental DSC curves was realised using a core-shell model for the particle matrix system, a calculated concentration-distance profile across the particle-matrix interface, and a parameterised concentration dependent curve for the heat flow of mixed blend states derived from experiments. The calculated curves were fitted to the experimental data by variation of the concentration dependence of the diffusion coefficient and its concentration averaged value. Both parameters determine the concentration-distance profile. From the evolution of the concentration-distance profile with the annealing time the parameters of the interdiffusion kinetics were analysed. The growth of the mean width of the interfacial phase with time follows a power law with an exponent of k = 0.42. A coefficient of mutual diffusion, equation image, increasing linearly by one order of magnitude from pure PVC to PnBMA, and its concentration averaged value of equation image m2/s were concluded from the experiments.

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Half width parameter \sigma _{{\rm av}}^* of the interphase for the initially phase-separated blend PVC/PnBMA = 70/30 wt.-% vs. the annealing time ta at 110 °C.

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