J. J. Iruin

Thermal and infra-red spectroscopic investigations of a miscible blend composed of poly(vinyl phenol) and poly(hydroxybutyrate)

Thermal properties of poly(vinyl phenol) (PVPh) and poly(hydroxybutyrate) (PHB) blends were investigated by differential scanning calorimetry over the entire range of composition. Mixtures with both bacterial (tactic) PHB and synthetic (amorphous) PHB were considered. In all cases, blends showed a unique glass transition temperature. The presence of 40% PVPh prevents bacterial PHB crystallization. Infra-red spectra showed the presence of hydrogen-bonded carbonyl signals which increased with PVPh fraction, showing the extent of specific interactions.

Survey on transport properties of liquids, vapors, and gases in biodegradable poly(3-hydroxybutyrate) (PHB)

The transport properties of carbon dioxide, water, and different organic solvents in bacterial poly(3-hydroxybutyrate) (PHB) at 30°C were investigated. CO2 sorption was measured by the gravimetric method using a recording microbalance at subatmospheric pressures. Results were adequately interpreted in terms of Henrys law. Organic solvent and water permeabilities for both vapors and liquid were measured using a gravimetric cell. The data were interpreted in different terms depending on the units in which permeability was measured. Most of the solvent-polymer systems showed the typical time-lag plot, but in liquid permeation experiments, some anomalous behaviors were observed, with a transient period of rapid permeation at the beginning of the experiment before reaching the steady state. The transport properties of PHB were compared with those of other polymers, either from synthetic or biodegradable origin.

Inverse gas chromatography in the characterization of polymeric materials

Different experimental results are presented for the use of inverse gas chromatography in the determination of the physico-chemical properties of pure polymers, polymer solutions and polymer blends. Using poly(hydroxy ether of bisphenol-A) (Phenoxy), its solutions and its blends with other polymers, thermal transitions, polymer solubility parameters, polymer-solvent and polymer-polymer interaction parameters and diffusion coefficients of small molecules in pure Phenoxy have been measured by inverse gas chromatography.

Water transport properties in poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biopolymers

Water sorption and diffusion have been investigated in poly(3-hydroxybutyrate) (PHB) and three poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymers [P(HB-HV)] by means of a Cahn electromicrobalance. Permeability of these samples have been determined using a gravimetric permeation cell. Two experimental setups were used for the gravimetric sorption measurements, under dynamic and static conditions, respectively. The differences observed in the results obtained using these techniques are discussed. The sorption measurements have evidenced the tendency of water molecules to form aggregates or clusters in the polymer. In addition, the static sorption method revealed the potential of PHB and P(HB-HV) to undergo molecular relaxations, eventually leading to a partial desorption of the previously sorbed water after an induction period. The clustering effect was adequately described by the polycondensation model. On the other hand, the interpretation of the diffusivity in terms of mobility coefficients has revealed a competition between a plasticization effect and clustering. As a whole, water transport properties in PHB and its copolymers can be considered to be very close in magnitude to those of common thermoplastics such as PVC and PET.

Concerning the self‐association of N‐vinyl pyrrolidone and its effect on the determination of equilibrium constants and the thermodynamics of mixing

Hydroxylated (co)polymers form miscible blends with a wide variety of (co)polymers that contain proton acceptor groups, such as esters, ethers, pyridines, etc. The former strongly self-associate through the formation of OH/OH hydrogen bonded interactions, while the latter do not self-associate to any measurable exent. With appropiate self- and interassociation equilibrium constants and anthalpies of hydrogen bond formation, we have been able in the past to successfully predict the phase behavior of such hydrogen bonded polymer blends. At first glance, the vinyul pyrrolidone group appears to be just another proton acceptor and if the appropiate interassociation equilibrium constant value is determined we should be able to predict the phase behavior of hydroxylated (co)polymer blends with (co)polymers containing the vinyl pyrrolidone group. However, it is not that simple. Using infrared spectroscopy we demnstrate in this work that the pyrrlidone group strongly self-associates through transition dipole coupling. Ramifications to the determination of equilibrium constants, the free energy of mixing and the phase behavior of blends involving the vinyl pyrrolidone group are discussed.

Ester exchange reactions in polyarylate/poly(ethylene terephthalate) blends

Abstract Blends coagulated by a solution/precipitation procedure of a polyarylate (PAr) based on bisphenol A and tere/isophthalates with poly(ethylene terephthalate) (PET) have been studied by a variety of experimental methods. Differential scanning calorimetry experiments have shown that in blends containing more than 30% PET, conditioning of the blends at high temperatures required for calorimetric measurements resulted in progressive ester exchange reactions. The 10% and 20% PET mixtures, in which this extreme conditioning was not required, showed a single glass transition, contrary to the behaviour of the other PET compositions. These differences may be attributed to the shape of the spinodal curve, which has been simulated according to the McMaster model for polymer mixtures. The progression of the interchange reactions has been followed by solvent extraction of the resulting products and subsequent Fourier transform infra-red spectroscopy analysis. A parallel decrease in the PET heat and temperature of fusion in the insoluble fractions was observed. In our opinion this was due to the incorporation of PAr units in the PET chains, which caused a decrease in their crystallizable segment length.

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.

Phenoxy blends: an approach to the miscibility by FTi.r. and chemical modification of the interacting sites

Abstract In this work, FTi.r. spectroscopy has been used in order to verify the proposed influence of the hydroxyl group, present in each monomeric unit of the phenoxy (PH) resin, in the observed miscibility of this polymer with a variety of other polymer families such as polyoxides or polyesters. Two different approaches have been used for this purpose. First, FTi.r. studies at different temperatures have been carried out on mixtures of PH with polyoxides, in order to demonstrate the higher strength of the hydrogen bonds in the mixture with respect to those existing between pure PH molecules. Second, chemical modification of the PH resin, with a controlled elimination of the repetitive hydroxyl, has been carried out intending to relate the percentage of hydroxyl substitution to the observed miscibility of PH. In the second approach, mixtures of PH and modified PH with poly(N-vinyl-2-pyrrolidone) have been studied.

Blends of bacterial poly(3-hydroxybutyrate) with synthetic poly(3-hydroxybutyrate) and poly(epichlorohydrin): transport properties of carbon dioxide and water vapour

Abstract The water vapour and carbon dioxide transport properties have been measured of bacterial (isotactic) poly(3-hydroxybutyrate) (iPHB) and its blends with synthetic (atactic) PHB (aPHB) and poly(epichlorohydrin) (PECH) have been measured. The purpose of this work is to study the transport properties of iPHB blends with a miscible second polymer, intended as a polymeric toughener that does not impair the original iPHB biodegradability. Thus, only iPHB rich blends containing up to 40% of aPHB or PECH were considered. The effect of aPHB on the blends is to increase the sorption and permeability with respect to pure iPHB due to the reduction in the level of crystallinity, while PECH tends to decrease the water and carbon dioxide solubilities of the blend. The blends have essentially the same permeability to CO 2 , although the water transmission rates are lower for the iPHB/PECH system.

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.