Browsing by Author "Guthrie, James T."
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- Analysis of interactions in multicomponent polymeric systems: the key role of inverse gas chromatographyPublication . Santos, José M.R.C.A.; Guthrie, James T.The properties of a polymeric system are a consequence of the interactions that occur between the various components of these complex systems. These components may vary significantly in terms of chemical nature (e.g. organic/inorganic), physical properties (e.g. particle size, surface area, molecular weight), structural characteristics and proportion in the formulations composition. This review paper addresses the major approaches in use regarding the analysis of the interactions that occur between the polymeric system components and the use of such approaches in the interpretation of the chemical, physical and thermodynamic properties of these systems. Special attention is given to the technique of inverse gas chromatography. A case study is presented, where use was made of inverse gas chromatography to characterize thermodynamically the surface of the major components of pigmented PC/PBT blends. The concept of Lewis acidity/basicity was used in the interpretation of the intermolecular interactions nature and potential in these blends, as encountered in phase separation and phase preferences phenomena and as expressed in the morphology, the physical and the mechanical properties of these commercially important composites.
- Characterisation of the surface lewis acid/base properties of poly(butylene terephthalate) by inverse gas chromatographyPublication . Santos, José M.R.C.A.; Guthrie, James T.; Fagelman, K.The surface of poly(butylene terephthalate) (PBT) was analysed by means of inverse gas chromatography (IGC). The specific component of the adsorption of polar probes on the surface of poly(butylene terephthalate) was found to be endothermic, and the change in the entropy of the system, positive, which is not a common case in IGC. An interpretation is given, based on the contribution of cleavage of hydrogen bonds in the PBT and formation of hydrogen bonds between the probe-molecules and the polymer. The surface Lewis acidity and basicity constants, K and K , respectively, were a b determined and found to correlate well with an analysis of the repeating unit and end-groups in this polymer.
- Characterisation of the surface lewis acid/base properties of the components of pigmented, impact-modified, pc/pbt blends by inverse gas chromatography – phase separation and phase preferencesPublication . Santos, José M.R.C.A.; Guthrie, James T.; Fagelman, K.Inverse gas chromatography was used to study the surface Lewis acid–base properties of the major components of pigmented, impact-modified, polycarbonate–poly(butylene terephthalate) blends. An investigation of the Lewis acid–base interactions in these polymeric systems has been carried out, based on the values determined for the surface Lewis acidity constant (K ), surface Lewis basicity constant (K ) and on the chemical and physical structure of the materials involved. This a b analysis provided the rationale for an interpretation of the phase separation and the phase preference that exist in these polymer blends, and of the consequences to their physical and mechanical properties.
- Lewis acid/base character and crystallisation properties ofpoly(butylene terephthalate)Publication . Santos, José M.R.C.A.; Guthrie, James T.Two grades of poly(butylene terephthalate) were analysed by means of inverse gas chromatography(IGC) and the results correlated with the respective crystallisation properties. The following parameterswere determined by IGC: the dispersive component of the surface tension, the enthalpy and the entropyof adsorption of selected polar and apolar probes, and the Lewis acidity and basicity constants, KaandKbrespectively. The interpretation of the values determined for Kaand Kbis in agreement with the FTIRspectra relating to the carboxyl end-group and the hydroxyl end-group concentrations in these polymers.The differences in the molecular weight values and in the end-group type and concentration, betweenthe two grades of PBT, do not cause differences in the crystallisation activation energy. This observationsuggests that there is a leading contribution of the Lewis basic sites to the crystallisation activation energyof the grades of PBT that were analysed. However, the lower value of Kaand the greater molar mass ofone of the PBT grades lead to a corresponding lower crystallisation degree.
- Polymer blends: the PC-PBT casePublication . Santos, José M.R.C.A.; Guthrie, James T.An example of commercially important binary polymer blends is that of PC–PBT composites. The current knowledge of the physical, mechanical and chemical properties of these blends is reviewed and updated in the light of interpretations based on Lewis acid–base intermolecular interactions, as quantified by inverse gas chromatography, carried out under infinite dilution conditions.
- Study of a core-shell type impact modifier by inverse gas chromatographyPublication . Santos, José M.R.C.A.; Guthrie, James T.Inverse gas chromatography (IGC) has been used to study the Lewis acid–base properties of a technologically and commercially important core-shell type elastomer (MBS rubber). The parameters determined were the dispersive component of the surface tension, the surface free energy, the enthalpy and the entropy of adsorption of polar and apolar probes, the surface Lewis acidity constant (Ka), and the surface Lewis basicity constant (Kb). The results show that the MBS rubber is amphoteric but strongly Lewis basic. It is weakly Lewis acidic. The results are in accord with the analysis of the molecular structure of PMMA, the shell component of this impact modifier (IM). The interactivity of this elastomer with the remaining materials in multicomponent polymeric systems is expected to be strongly influenced by the particular surface energetic properties of the MBS rubber. The results presented would contribute to the interpretation, forecast and optimization of the adhesion properties and phase preferences shown by this impact modifier when incorporated in such complex polymeric systems as polymer blends and composites.