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Ionomers are polymers containing a low mole fraction of ionic groups bound to the polymer backbone. These ionic groups produce major changes in their structure and mechanical properties. Recently, we introduced a new family of crosslinked poly(Bd)/poly(Bd-co-MAA) core shell nanoparticles (1,3butadiene and methacrylic acid) that could be ionically crosslinked and cast as nanostructured ionomer films from aqueous dispersions [Pinprayoon et al., Soft Matter, 2011, 7, 247]. The MAA units in the core-shell particles were neutralised by Zn 2+ . Here, we explore the structure-property relationships for these new architecturally controlled nanocomposites by investigating 6 new poly(Bd)/poly (Bd-co-MAA) dispersions and films. In this study we varied the extent of covalent crosslinking in the core and the shell at constant ionic crosslinking for the first time. We used dynamic mechanical thermal analysis to establish a general phase map for the new nanostructured ionomers. Stress-strain data show that our nanostructured films have well controlled, and adjustable, modulus and strain at break values. The data show that the core-shell nanoparticle geometry allows the often observed trade-off between elasticity and ductility to be tuned in a manner that is not possible for conventional ionomers. We show that the chain transfer agent (CTA) concentrations used during the preparation of the nanoparticle cores and shells can be used to independently tune the mechanical properties of the films. This is due to variation of the extents of covalent crosslinking. The results of this study should apply to other covalently crosslinked core-shell nanoparticles containing RCOOH groups in the particle shells.

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The frequency of occurrence of paint chips and glass fragments on the outer clothing and footwear of 213 high school students from different areas of the city of Vancouver was determined. Paint and glass respectively were found on ca. 14% and 2% of the outer clothing items, and on ea, 24% and 5% of footwear. These figures are significantly lower than figures reported in similar studies in the last 25 years. RESUMELa frequence avec laquelle des ecailles de peinture et des fragments de verre se retrouvent sur les vetements exterleurs et les chaussures de 213 etudtants du secondaire de differents quartiers de la ville de Vancouver a ete determlnee, De la peinture et du verre ont respectivement ete trouves sur environ 14% et 2% des articles vestimentaires exterleurs, et sur environ 24% et 5% des chaussures. Ces chiffres sont plus bas, et ce, de manlere significative que les chiffres rapportes dans des etudes semblables lors des 25 dernleres annees,

In this article, we examine the rate of film build-up and the evolution of polymer volume fraction in coagulant dipped films. The results are for nitrile and natural rubber compounds. We describe a model for the build-up of a latex film that coagulates onto a former as a wet gel and consolidates by a wet sintering process. We achieve this by applying diffusion and reaction kinetics for the coagulant transporting from a former into the latex bath. Wet sintering, the underlying mechanism for serum exudation from the wet gel, is modelled for a consolidating aggregate of latex particles. The parameters used in the models are either measured in separate experiments or are available from the literature. We compare the model predictions with the experimental results. The first, rapid, stage of film build-up is modelled successfully by simple diffusion of the coagulant cations. At longer dwell times, it is found that the reaction between coagulant and surfactant is the primary mechanism for the rate reduction. The rate of consolidation of the wet gel could be modelled reasonably well using a previously developed equation for latex film formation. The rate was chiefly dependent on the stress relaxation modulus of the polymer.

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Coagulant dipping, the process used in thin glove manufacture, involves electrolyte ions diffusing from the surface of a hand-shaped former into latex compound, causing a deposit (wet gel) to accumulate...