Polyelectrolyte gels that are known as super-absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications. Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels. However, no super-absorbent polymers for volatile organic compounds (VOCs), and especially for nonpolar organic solvents (epsilon<10) have been reported, because common polyelectrolyte gels collapse in such solvents owing to the formation of a higher number of aggregates of ions and ion pairs. Here, we report that a novel class of polyelectrolyte gels bearing tetra-alkylammonium tetraphenylborate as a lipophilic and bulky ionic group swell in some nonpolar organic solvents up to 500 times their dry size. Dissociation of the ionic groups even in low-dielectric media (3<epsilon<10) enhances the swelling ability by expansion of the polymer networks. This expands the potential of polyelectrolytes that have been used only in aqueous solutions or highly polar solvents, and provides soft materials that swell in a variety of media. These materials could find applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.

/pdf/lipophilic-polyelectrolyte-gels-as-super-absorbent-polymers-4i8z3o5lfo.pdf

Lipophilic polyelectrolyte gels as super-absorbent polymers for nonpolar organic solvents.

Castor oil based polyurethane adhesives for wood-to-wood bonding

Equilibrium swelling is a feasible and simple experiment to determine the cross-link density of networks. It is the most popular and useful approach; however, in most of the cases, the given values are highly uncertain if not erroneous. The description of the complex thermodynamics of swollen polymer networks is usually based on the Flory−Rehner model. However, experimental evidence has shown that both the mixing term described by the Flory−Huggins expression and the elastic component derived from the affine model are only approximations that fail in the description and prediction of the rubber network behavior. This means that the Flory−Rehner treatment can only give a qualitative evaluation of cross-link density because of its strong dependence on the thermodynamic model. In this work, the uncertainties in the determination of the cross-link density in rubber materials by swelling experiments based on this model are reviewed. The implications and the validity of some of the used approximations as well a...

Uncertainties in the Determination of Cross-Link Density by Equilibrium Swelling Experiments in Natural Rubber

This paper presents an overview of the recent literature on flame retardancy of poly(vinyl chloride) (PVC). A short overview of mechanisms of thermal decomposition of PVC, especially those which lead to char formation, isalso presented because this gives insight into the mechanisms of flame retardant action. New developments in the area are mostly focused on combinations of various flame retardants and smoke suppressants in the search for synergistic effects. Because different additives show different mechanisms of action, synergistic combinations are very probable. New developments in phosphate ester plasticizers are reported in the literature.

Overview of the recent literature on flame retardancy and smoke suppression in PVC

Vacuum pyrolysis of commingled plastics containing PVC I. Kinetic study

Role of the polyurethane component in the adhesive composition on the hydrolytic stability of the adhesive

Characterization of the natural rubber vulcanizates obtained by different accelerators

The thermal degradation process of poly(vinyl chloride)/acrylonitrile-butadiene-styrene blends (PVC) was investigated by dynamic thermogravimetic analysis in the temperature range 50-650 oC in air. The thermooxidative degradation takes place in three steps. The first step, dehydrochlorination, is the most rapid. The maximal rate of dehydrochlorination for the PVC blends containing up to 20% ABS-modifier is achived at average conversion of 23.5-20.0%. The apparent activation energies and preexponential factors were calculated after the Kissinger method.

Thermooxidative degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene blends

GPC and structural analysis of polyurethane degradation

Swelling measurements in six organic solvents were carried out on samples of dicumyl peroxide crosslinked ethylene–propylene–diene (EPDM) having various crosslink densities. The Flory–Huggins interaction parameter χ was determined for EPDM vulcanizates 312 and 812 as well as their mixture 312/812 using the Flory–Rehner equation. The results show that the χ parameter for the crosslinked polymer is greater than for the uncrosslinked one and is a linear function of the crosslink density. The swelling behavior of the networks were also interpreted by the Flory–Erman theory using the structural factor F4′ to characterize the network and its behavior during the swelling. The obtained χ values indicate that broadening of the molecular mass distribution, in the Gaussian region of distribution, mixture 312/812, increases interactions with solvents. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:991–999, 1997

Mladen Bravar

Papers

Role of the polyurethane component in the adhesive composition on the hydrolytic stability of the adhesive

Characterization of the natural rubber vulcanizates obtained by different accelerators

Thermooxidative degradation of poly(vinyl chloride)/acrylonitrile–butadiene–styrene blends

GPC and structural analysis of polyurethane degradation

Influence of the network on the interaction parameter in system EPDM vulcanizate–solvent