Layered silicate particles filled polymer nanocomposite for barrier application

A polymer clay nanocomposite (PCN) system for barrier applications has been studied and various materials have been utilized to achieve a better barrier solution. This study aims at making progress in the packaging industry toward super barrier materials by tailoring processing parameters to the creation of new barrier solutions and also by systemizing theoretical background knowledge. Comparisons of several barrier models were made in order to develop a new model and to assist with material selection and experimental design.;PCN consisting of synthetic layered silicate (Laponite) in polyvinyl alcohol (PVA) was applied to atmospheric plasma treated, semi-rigid polypropylene (PP) samples. PCN coating bonded to polyolefins offers a simpler method to achieve higher barrier properties without modifying commodity materials.;Highly filled PCN coating layers, with parallel arranged dense structures of Laponite were studied. An investigation on effects of pH of poly(acrylic acid) (PAA) on PCN coating system performance suggested that enhanced barrier properties were achievable with the aid of positively charged poly(acrylic acid) and a shear coating processes. This work also suggested another PCN coating system that incorporates a dense stratified structure of silicate platelets using a polymer as a linkage molecule.;Benefits of dispersing smaller nanoparticles between larger ones in a polymer matrix (PC2N) were explored and a barrier model to estimate relative permeability of the PC2N system was proposed. It was demonstrated that total volume fraction of particles determined barrier properties and this was confirmed by experiment. No significant difference in oxygen transmission rate of three composite films was found. A film containing only Cloisite had a lower oxygen transmission rate than that of Laponite and PC2N films because of the relatively larger aspect ratio of Cloisite; however Laponite and PC2N films had better optical transmittance due to the smaller aspect ratio resulting in lower numbers of scattering events.;Achieving good flexibility and high barrier properties was possible with PAA negatively charged organic molecules as linkage molecules and poly(vinyl butyral) (PVB) exterior layers. Unlike the observed 'house of cards' structure formed in Laponite aqueous solution, the large aspect ratio of Cloisite Na+ (CNa) clay platelets resulted in parallel arrangement as observed by scanning electron microscopy (SEM). Result showed that the layered structures had various features depending upon the amount of linkage polymer applied. In addition, enhancement of barrier properties and flexibility was achieved after PVB coating. A barrier model based on Nielsen's detour theory or Beall's filling void theory predicted overall barrier properties experiments.