M.G. Prolongo

Melting behaviour and miscibility of poly(ϵ-caprolactone) + poly(4-hydroxystyrene) blends

Abstract Differential scanning calorimetry has been used to study the melting behaviour, crystallinity and miscibility of poly(ϵ-caprolactone) (PCL) + poly(4-hydroxystyrene) (P4HS) blends. Three different heat treatments were selected. The development of PCL crystallinity was dependent on the blend composition. The increasing glass transition temperature ( T g ) of blends, as they become richer in P4HS, was the cause of this dependence. The miscibility of the polymers was confirmed by detecting only a T g in the blends, which could be closely described by the Fox rule. The thermograms exhibit double melting endotherms. The dependence of the melting temperature on the crystallization temperature shows that the lower endotherm corresponds to less stable crystals and the higher one to stable crystals. The lower endotherm was attributed to a secondary crystallization process. For the higher endotherm the thermodynamic melting temperatures of PCL in the pure state and in the blends were obtained using Hoffman-Weeks plots. The polymer-polymer interaction parameter was calculated from these data using the Nishi-Wang equation. The results are in good accordance with those obtained by inverse gas chromatography.

Thermal properties and interactions in blends of poly(ε-caprolactone) with unsaturated polyester resins

Blends of two linear unsaturated polyester (LUP, commercially named AL-100 and 6603) with poly(e-caprolactone) (PCL) were prepared by the casting method. Differential scanning calorimetry (DSC) has been used to study the miscibility, melting behaviour and crystallinity of 6603+PCL and AL-100+PCL blends. Two different heat treatments (Method 1 and Method 2), were carried out, in both systems. Only by following Method 2 a crystallization temperature (Tc) was selected before monitoring the glass transition and melting behaviour of the blends. When samples were scanned under Method 1, a unique Tg intermediate between the Tg’s of the pure polymers in all the blends studied was found. It indicates that the PCL is miscible with both unsaturated resins in the whole composition range. Nevertheless, when samples were scanned following Method 2 the Tg–composition dependence exhibited an asymmetric behaviour that could indicate a certain lack of homogeneity in the blends at intermediate compositions.

Miscibility and interactions in poly (vinyl methyl ether)/poly(4-hydroxystyrene) blends

Abstract Differential scanning calorimetry, (DSC) and inverse gas chromatography, (IGC) were used to analyze the miscibility and interactions in the poly(4-hydroxystyrene)/poly(vinyl methyl ether) (P4HS/PVME) system. The miscibility was assessed by the measurement of a single glass transition temperature, T g , for each blend composition. The T g —composition curve was analyzed in terms of Fox, Gordon—Taylor and Kovacs theories. The influence of molecular weight of P4HS in the presence of a cusp in the T g —composition curve was discussed by comparison with previous T g data. The IGC retention behaviour of the homopolymers and three blends (0.25,0.5 and 0.75 P4HS volume fractions) was realized at 190°C using selected probes. The polymer—polymer interaction parameters χ 23 calculated from the Scott—Flory—Huggins formalism showed an apparent dependence on the probes. This dependence was analyzed using Hortas method based on the equation-of-state theory and a more simplified method proposed by Desphande. Negative values of χ 23 confirmed the miscibility of the system. A blend composition dependence of χ 23 was found, mainly determined by differences in the molecular surface-to-volume ratio of the polymers.

Influence of Different Organoclays on the Curing, Morphology, and Dynamic Mechanical Properties of an Epoxy Adhesive

The thermal, mechanical, and adhesive properties of nanoclay-modified adhesives were investigated. Two organically modified montmorillonites: Cloisite 93A (C93A) and Nanomer I.30E (I.30E) were used as reinforcement of an epoxy adhesive. C93A and I.30E are modified with tertiary and primary alkyl ammonium cations, respectively. The aim was to study the influence of the organoclays on the curing, and on the mechanical and adhesive properties of the nanocomposites. A specific goal was to compare their behavior with that of Cloisite30B/epoxy and Cloisite15A/epoxy nanocomposites that we have previously studied. Both C30B and C15A are modified with quaternary alkyl ammonium cations. Differential scanning calorimetry results showed that the clays accelerate the curing reaction, an effect that is related to the chemical structure of the ammonium cations. The three Cloisite/nanocomposites showed intercalated clay structures, the interlayer distance was independent of the clay content. The I.30E/epoxy nanocomposites presented exfoliated structure due to the catalytic effect of the organic modifier. Clay-epoxy nanocomposites showed lower glass transition temperature (T g ) and higher values of storage modulus than neat epoxy thermoset, with no significant differences between exfoliated or intercalated nanocomposites. The shear strength of aluminum joints using clay/epoxy adhesives was lower than with the neat epoxy adhesive. The water aging was less damaging for joints with I.30E/epoxy adhesive.

Thermal behaviour of unsaturated polyester resins + poly(3-octylthiophene) blends

Abstract Blends of poly(3-octylthiophene) (POT) with unsaturated polyester (UP) resin have been investigated. Two glass transition temperatures, T g , were detected by differential scanning calorimetry (DSC) in blends of POT+uncured polyester resins, which indicate the partial immiscibility of these systems. It has been demonstrated that the miscibility behaviour of these blends depends up to a point on the solvent used in sample preparation. Also POT was found to be immiscible with crosslinked polyester resins which was concluded from the results of thermal analysis. The influence of the presence of POT on the crosslinking reaction, the miscibility of the crosslinked system and finally the melting behaviour of POT were analysed. The results obtained have been compared in the crosslinked and uncrosslinked blends.