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Blends of polyoxymethylene (POM) and phenoxy were obtained by melt‐blending to determine their phase behavior and to determine, among others, their dynamic and static mechanical properties. The dynamic mechanical spectrum of POM showed an unusually wide peak below the melting temperature that was attributed to amorphous POM close to, and hindered by, the predominant crystalline phase. The Tg of phenoxy was constant with composition, as was probably that of POM, proving their complete immiscibility. The overall mechanical properties of the blends, however, were those of a compatible blend. The synergism in ductility observed in POM‐poor blends was partially attributed to their lesser crystalline character. © 1996 John Wiley & Sons, Inc.

Melt‐mixed blends of polycarbonate/phenoxy were obtained before and after Interchange reactions by controlling the processing time. The dynamic mechanical analysis of the physical and reacted blends confirmed the immiscibility of the pair and the displacement of the glass‐transition temperatures of the mixtures; this displacement was seen more clearly in the reacted mixtures, and at phenoxy‐rich contents, even a single phase can appear. The exchange reactions resulted in a mechanical behavior that showed both a higher modulus and greater tensile strength in the reacted blends. The ductility was close to linearity for the physical blends and probably would be improved in the reacted mixture with a lower processing time.

The miscibility of the polycarbonate of bisphenol A with the polyhydroxyether of bisphenol A was analyzed using differential scanning calorimetry and the results are compared with the torque data obtained using a Brabender Plasticorder. The possibility of interchange reactions was analyzed by means of the observation of the melt-viscosity variation versus processing time in the mixer-bowl. These reactions form graft-copolymers that develop into crosslinked copolymers at higher residence times. I t was also shown that the speed of these reactions depends on the processing temperature. The variation produced on the glass-transition temperature because of branching was also analyzed.

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