Hips/zeolite hybrid composites as active packaging materials: Structure and functional properties

Desiccant composites were prepared from seven high impact polystyrene copolymers (HIPS) with different butadiene content and dispersed droplet size to study the effect of structure on their functional and application properties. A 4A type zeolite was used as desiccant. The thermodynamic analysis of structure development revealed that the embedding of the zeolite into the polybutadiene droplets is the thermodynamically favored process. Comparison of composite stiffness to theoretically predicted values indicated that considerable embedding occurs during composite preparation. The extent of embedding depends on zeolite content, but also on other factors like butadiene content and the droplet size of the elastomer. Composite stiffness and strength decreases with increasing extent of embedding, while functional properties are dominated by zeolite content. The initial rate of water adsorption increases, while overall rate decreases with increasing desiccant loading. Embedding influences only the initial rate of water adsorption which decreases slightly with increasing extent of encapsulation.