1993 рік

This paper deals with the compatibility of a chlorine-containing polycarbonate with poly(methyl methacrylate) (PMMA). The polymer-polymer interaction parameter, ~, has been determined from the experimental phase diagram by means of the Flory-Huggins theory. The interfacial tension, interfacial thickness and interfacial density profile have also been calculated from the experimental value of Z by means of Helfand's mean-field treatment. The calculated interracial thickness has been compared to experimental data from optical, transmission and scanning electron microscopy.

Детальніше...  

Polyelectrolyte complex formation involving carboxymethylcellulose and quaternized poly(vinylpyridine) as the polyions has been studied using viscosity and u.v. spectroscopic methods. The influence of charge density and molecular weight of two polycations on the composition of the complex has been investigated at two different concentrations. The charge density of the polycation is found to have different influences on the composition at different concentrations. The molecular weight of the polycation and the location of the ionic site on the polycation do not show any effect on the composition. A drastic increase in the viscosity of the polyion mixture containing quaternized poly(2-vinylpyridine) in the non-stoichiometric ratio shows evidence for the existence of the soluble polyelectrolyte complex. The results are analysed on the basis of the relative extension of the polyelectrolyte chains

Детальніше...  

The frequency dependence of the dynamic shear modulus and mechanical losses have been measured for interpenetrating polymer networks (IPNs) based on crosslinked polyurethane and weakly crosslinked poly(butyl methacrylate) with component ratios (by weight) of 65/35 and 50/50. The frequency range used was 0.l-100 Rad s -1 over the temperature range from 133 to 413 K. According to the experimental data the IPNs have a two-phase structure with a segregation degree of 0.35~).40. For each phase the apparent activation energy has been determined and relaxation spectra have been constructed using the method of reduced variables. The conclusion is that the relaxation behaviour of IPNs is dependent on the phase composition and morphological features

Детальніше...  

Poly(diaza-18-crown-6) (1) was mixed with alkali metal perchlorates (MC104; M = Li, Na, K, Rb and Cs). Curved Arrhenius plots for ion conductivity were found for all dry samples, suggesting that ion migration occurs with segmental motion in 1. The potassium cation showed the lowest ion conductivity, reflecting a stronger interaction with the crown ether structure.

Детальніше...  

Poly(oligo oxypropylene) methacrylate (P(MPO)) was prepared, and a series of alkali metal perchlorates (MC104; M = Li, Na, K, Rb and Cs) was dissolved in it to measure ionic conductivity. The lithium ionic conductivity was ~ 10-65 cm-1 at 303K, and the conductivity decreased monotonously with increasing radius of the alkali metal cation. This tendency was totally the inverse to that observed for the poly(ethylene oxide) derivatives. As the solubility of LiC104 was higher than for other perchlorate salts, various lithium salts were dissolved to investigate the effect of the anion on ionic conductivity. The ionic conductivity decreased with increasing lattice energy of the salts. Arrhenius plots of ionic conductivity and glass transition temperature measurements indicated that ionic conductivity was mainly governed by the solubility of the salt in P(MPO). The dissociation energy of the salt is important for ionic conductivity when salts with higher solubility in PPO were used. In a poly(propylene oxide) derivative, the solubility of the salts was concluded to be the most important factor for ionic conductivity.

Детальніше...  

A thermotropic liquid-crystalline polymer (LCP) was found to be miscible with poly(ethylene terephthalate) (PET) for LCP contents up to 35 wt% and immiscible at higher LCP contents. The melts of the miscible blends are isotropic under the polarizing microscope. They crystallize with a single transition during rheological cooling measurements. In the solid state, the miscible blends showed a single glass transition, as represented by a single peak of loss modulus G" versus temperature, which decreased linearly with LCP content. Addition of a small quantity of LCP has a dramatic effect on rheology. For example, addition of 2 wt% LCP reduces the viscosity by about 60%. This effect is most pronounced for PET of higher molar masses. The melt viscosity decreases exponentially with the LCP content in the range of composition where the blends are miscible, but there is no significant further reduction of viscosity when the LCP content exceeds 50 wt% as the phase separation appeared. Addition of LCP also changes the distribution of the relaxation times of PET and broadens the zero-shear viscosity regime.

Детальніше...  

Using contact angle data for poly(vinylidene fluoride-co-hexafluoro acetone) with various organic liquids, such as dispersion, polar and hydrogen-bonding liquids, the Good~3irifalco interaction parameter, Oc, work of adhesion, IV=, and interfacial tension, YSL, were calculated. The values of O6, W~ and YSL were dependent on the surface tension )'L and the species of liquid.

Детальніше...  

A range of commercially available alkyl ethoxylates with different hydrophobes and degrees of ethoxylation have been acrylated to produce structurally analogous polymerizable surfactants. The latter have been polymerized in water using a photochemical free radical initiating system to yield a mixture of linear soluble oligomer and crosslinked polymer. The starting amphiphiles, their acrylate derivatives and their soluble oligomers have been extensively characterized in terms of their molecular structure and their amphiphilic properties. The latter have been discussed in terms of the molecular structure of the series of molecules. Selected examples of the alkyl ethoxylates and their acrylate derivatives have been compared as sole emulsion stabilizers in the polymerization (separately) of styrene, methyl methacrylate and vinyl acetate. In general the conventional surfactants provide better stability, though both an acrylated derivative and its precursor surfactant perform well in styrene polymerizations. The effect of added electrolyte in flocculation studies confirms the superiority of the conventional surfactant. The results are discussed in terms of current colloid and emulsion polymerization theories and practice, and suggestions are made for the improved design of polymerizable amphiphiles.

Детальніше...  

Blends of isotactic polypropylene (PP) and linear low density polyethylene (LLDPE) have been analysed by thermal analysis and wide-angle X-ray scattering to determine the effect of thermal history on morphology and mechanical behaviour. The blends were quenched directly from the melt, slow cooled and annealed at 130°C. In all cases it was observed that the two components were insoluble and the crystallization behaviour was determined by the blend morphology, particularly in dispersed PP domains in which heterogeneous nucleation was the rate determining step. Slow cooled specimens with the higher degree of crystallinity had the highest yield stresses, and the lowest elongation to break was achieved in the vicinity of 50% blends, characteristic of the effect of blend morphology on properties

Детальніше...  

A blend membrane consisting of 5.3 wt% copoly(N-isopropylacrylamide/1H,1H,2H,2H-perfluorododecyl acrylate) and poly(dimethylsiloxane) showed a high ethanol permselectivity (~tEt°"= 19.7 at 24°C) in pervaporation of 2.5 wt% aqueous ethanol solution. The value of ~t Et°" had a maximum at about 36°C. This behaviour was due to the water repellency and thermal transition Of the copolymer accumulated at the membrane surface.

Детальніше...