M. Iriarte

Crystallization and melting behaviour of poly(bisphenol A hydroxy ether)/poly(ethylene oxide) blends

Abstract The crystallization and melting behaviour of solution-cast films of poly(bisphenol A hydroxy ether)/poly(ethylene oxide) (PEO) blends were investigated as a function of composition by means of optical microscopy, differential scanning calorimetry and dilatometry. All blends show only one single value of glass transition temperature, intermediate between those of the pure polymers. The growth rate of PEO spherulites (G) as well as the observed equilibrium melting temperature, for a given ΔT, decrease as the phenoxy content increases. These results suggest that this blend is miscible for every composition investigated. Temperature and composition dependences of the radial growth rate G and the overall kinetic constant K have been employed to calculate the surface energy of folding σe. The interaction energy density B has been determined from the dependence of the equilibrium melting-point depression upon composition.

Polymer–solvent interaction parameters in polymer solutions at high polymer concentrations

Molecular mass and temperature dependences of the polymer-solvent interaction parameter have been investigated in the extreme interval of high polymer concentration using inverse gas chromatography (IGC). The observed molecular mass dependence has been compared with the predictions of a theoretical model, which emphasises the role of intramolecular contacts in the polymer chain. The model reproduces reasonably well the molecular mass dependence. However, enthalpic and entropic contributions of the interaction parameter, obtained from IGC measurements at different temperatures, exhibit behaviours difficult to explain in the framework of the current models.

Miscibility and carbon dioxide transport properties of blends of bacterial poly(3-hydroxybutyrate) and a poly(vinylidene chloride-co-acrylonitrile) copolymer

The purpose of this work is to study the CO2 transport properties of isotactic poly(3-hydroxybutyrate) (iPHB) blended with a miscible second component, a copolymer of vinylidene chloride (VDC) and acrylonitrile (AN) units. All the investigated blends are rubbery, allowing a reasonable strategy to tough PHB without impairing its original biodegradability. The miscibility required for this purpose was confirmed by differential scanning calorimetry, measuring both the glass transition and melting temperatures of the blends. The melting point depression induced by the copolymer was used to quantify the interactions between the components of the blend. Carbon dioxide transport properties of blends having less than 50% by weight of the copolymer were measured by gravimetric sorption experiments in a Cahn electro balance. The effect of the VDC-co-AN copolymer was to decrease the diffusivity and permeability of the pure iPHB due to its well-known high barrier character.