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The relaxation of the orientation induced by the action of a magnetic field on a thermotropic liquid crystalline polymer is examined. The polymer is a main-chain random copolyester available as a molecular weight series covering the range 4600-14 400. The rate of loss of orientation is modelled using a similar function to that used to describe the orientation process, all induced orientation being...
The miscibility, crystallization and morphology of poly(β-hydroxybutyrate) (PHB)/poly(d,l-lactide) (PLA) blends were investigated by means of differential scanning calorimetry, polarizing optical microscopy and scanning electron microscopy studies. The results indicated that PHB/PLA blends prepared by casting a film from a common solvent at room temperature were immiscible over the range of compositions...
Films of optically active polyaniline salts (PAN/HCSA) have been obtained by casting from solutions of emeraldine base doped with (1S)-(+)- or (1R)-(-)-10-camphorsulfonic acid (HCSA) in various solvents (NMP, DMF, DMSO or CHCl 3 ). The mirror-imaged circular dichroism spectra for the salt films derived using (+)- and (-)-HSA, respectively, indicate enantioselectivity in the doping process...
Physical ageing in polystyrene (PS) has been studied by means of modulated differential scanning calorimetry (m.d.s.c.). The results show that there exists a characteristic annealing temperature at which relaxation enthalpy has a maximum value. When annealing below 65 o C, another relaxation peak has been found. The position of this relaxation peak, which changes with annealing temperature,...
We present phase diagrams of binary blends (or mixtures) of a homopolymer H, with a block copolymer, A-B, in which there is an exothermic interaction between two types of segments, H and A. In trying to construct phase diagrams, we extend the approach of predicting phase separation behaviour in such binary blends where H is chemically identical with one of the blocks of the copolymer, e.g. A. A...
The concentration profile of a symmetrical binary (AB) polymer mixture confined between two 'neutral' repulsive walls is studied by Monte Carlo simulation of the bond fluctuation model, using a chain lengthN = N A = N B = 32 and a distance of D = 20 lattice spacings between the walls. Choosing volume fractions and temperatures such that one stays inside the coexistence curve, one...
Poly(styrene-co-glycidyl methacrylate) (PS-GMA) is used as an in situ compatibilizer for incompatible (or immiscible) blends of poly(butylene terephthalate) (PBT) and polystyrene (PS). The epoxy group in PS-GMA reacts with the carboxylic acid group in PBT, thus PS-graft-PBT copolymer is formed and acts as a compatibilizer between PS and PBT during the melt blending. The degree of the reaction is...
A series of seven fractions of branched polyethyleneimine (BPEI) spanning a molecular weight range 1.7 x 10 4 -5.3 x 10 6 g mol -1 were characterized by means of laser light scattering and viscometry at 35 o C. The weight-average molecular weight, M w , the second virial coefficient, A *2 , the z-average radius of gyration,R G , the...
Studies on the solution properties of three linear crystal-violet-tagged polycationic electrolytes in dipolar aprotic solvents, viz. propylene carbonate (PC) and sulfolane, have been carried out over a small temperature range (298.15 +/- 5 K for PC and 308.15 +/- 5 K for sulfolane). The polycations studied have N-alkylammonium ions, with ethylene moieties in the parent chain of the macro-ion, and...
Interactions of carbon black with nitrile rubber (NBR) and carboxylated nitrile rubber (XNBR) were studied by measurements of bound rubber, physical and dynamic mechanical properties of the vulcanizates and Monsanto rheometric studies on the rubber-filler mixes. Compared with NBR, XNBR shows a higher degree of interaction with the filler and oxidation of the filler surface increases the extent of...
The influence of u.v. irradiation on the surface morphology of some commercial polymers was investigated using scanning electron microscopy (SEM). The photodegraded samples exhibited a high degree of surface damage. The formation of cracks and holes resulting from the degradation and evolution of volatile products was observed. In polymers undergoing photocrosslinking, the agglomeration of particles...
The application of inverse gas chromatography (i.g.c.) for the examination of surface properties of solid materials is discussed. A group of analogous poly(dimethacrylate)s differing only by the presence and type of the heteroatom in the ester group and two reference polymers were characterized by means of this method. In this paper the dispersive properties expressed by γ ds andC ...
Poly(lactic acid) (PLA) was melt blended with poly(vinyl acetate) (PVA) using a single-screw extruder. The extruded films obtained were characterized for miscibility, physical properties, degradation and surface morphology. Differential scanning calorimetry showed that all the as-extruded films were amorphous, and that the blends were compatible as only one glass transition temperature was observed...
Zinc sulfonated ethylene-propylene-diene terpolymer (EPDM) behaves as an ionic thermoplastic elastomer. Both paraffin oil and dimethyl sulfoxide (DMSO) act as plasticizers for this polymer; while paraffin oil plasticizes the hydrocarbon backbone, DMSO plasticizes the ionic domains. Results obtained from dynamic mechanical analysis (d.m.a.) show that DMSO does not affect the glass-rubber transition...
A model is described for predicting the elastic behaviour of two-phase isotropic materials, based on Takayanagi's model, but taking transverse constraints into account. The model is compared with experimental results on SiO 2 -filled epoxy and starch-filled poly-3-hydroxybutyrate (PHB) and PHB/3-hydroxyvalerate composites.
Polyurethane (PU) anionomers were synthesized from phthalic anhydride, neopentyl glycol, isophorone diisocyanate and dimethylolpropionic acid (DMPA) according to a prepolymer-mixing process. Emulsion characteristics and basic structure-property relationships of the emulsion-cast film were studied with regard to the DMPA concentration, degree of neutralization (DN), prepolymer molecular weight (M...
X-ray methods have been used to investigate the solid-state structures of wholly aromatic thermotropic copolyesters prepared from equimolar amounts of p-hydroxybenzoic acid, biphenol and thiophenyl- or oxyphenyl terephthalic acid. We have also compared these structures with that of the unsubstituted copolymer. The scattering data for melt-spun fibres show that the presence of the side chains results...
Polymers have been prepared by solution-free radical polymerization from new monomers made from bile acid derivatives. Two approaches were used to improve the hydrophilicity of the polymers: first, the monomers were copolymerized with methacrylic monomers such as methacrylic acid and 2-hydroxyethyl methacrylate; second, the methyl ester groups on cholic acid of the homopolymers were also removed...
Several semicrystalline poly(aryl ether ketone)s (PEK, PEEK and different isomers of PEKK) were melt-blended at T > 400°C with three high temperature thermoplastic polyimides. The compatibility and crystallization properties of the blends were studied by differential scanning calorimetry (d.s.c.). Blends of a semicrystalline New-Thermoplastic PolyImide (N-TPI) showed some surprising differences...
Hydrogen-bonding formation in amorphous cellulose was characterized by the analysis of Fourier transform infra-red (FTi.r.) spectra. Films of regioselectively substituted methylcelluloses were used to model components of amorphous cellulose. An artificial infra-red (i.r.) spectrum for amorphous cellulose was quantitatively synthesized by a suitable mathematical combination of the i.r. spectra obtained...
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