This thesis describes the investigation of compatibilized and uncompatibilized blends of Poly(vinylidene fluoride) (PVDF) and Poly(ethylene oxide) (PEO). Poly(vinyl acetate) (PVAc) was used a compatibilizer for the system. Modeling of crystallization exotherms, high -temperature phase behavior and partitioning of the components in the above blend systems are considered in detail. Only blends having PVDF as the continuous phase are studied. The crystallization behavior as observed by differential scanning calorimetry (DSC) of PVDF seemed unchanged upon blending with PEO for both compatibilized and uncompatibilized systems. However, PEO showed a significant depression in its crystallization temperature when blended with PVDF. As the concentration of PEO increased above 10%, two distinct crystallization peaks were observed. Optical microscopy revealed that at lower concentrations, PEO, is segregated into domains that are -10 micron in diameter. These domains nucleate at very low temperatures, yet grow nearly instantaneously once nucleated. As the concentration of PEO increases, somewhere between 10 to 20 wt %, larger PEO domains of about 100 micron size are formed that crystallize at a temperature close to that of pure PEO. High temperature optical microscopy images suggested that PEO and PVDF are incompatible in the molten state. The studies on PVDF/PEO/PVAc blends performed by using DSC and HATRFTIR revealed that PVAc acts as a diluent for the PEO phase. There was no appreciable change in the crystallization behavior of PVDF. The compatibilizer increased the degree of supercooling for PEO crystallization and made the domain size distribution for the PEO domains more or less uniform. A model based on modifying the Avrami equation to handle samples of finite thickness was developed. The model was shown to work well for DSC exotherms of pure PEO. The present model does neither takes into account finite domain size of the crystallizing element nor the domain size distribution of the discontinuous phase. Further investigations regarding the domain size distribution and modifications in the existing model to account for domain size must be undertaken to obtain a good fit between actual data and model predictions.

Library of Congress Subject Headings

Polymers--Thermal properties; Polyvinyl chloride; Vinyl chloride polymers; Ethylene oxide; Polymerization

Publication Date


Document Type


Department, Program, or Center

Center for Materials Science and Engineering


Langner, Andreas


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