Synthesis of polymer hybrid latex polystyrene methylmethacrylate-co-butylacrylate with organo-montmorillonite as filler through miniemulsion polymerization for barrier paper application

Nanocomposite have a huge potential in the future technologies and scientific communities. It is possible to design new materials with a simple modification and new materials have different properties and improvement in its mechanical properties and application fields. Hybrid latex based on monomer styrene (St), butyl acrylate (BA) and methylmethacrylate (MMA) have been studied and used for barrier paper applications in food industries in order to replace polypropylene (PP), polyethylene (PE) or polyethylene terephthalate (PET) materials. To achieve better hybrid materials, various techniques and materials have been utilized, montmorillonite (MMT) from smectite family have been selected as filler in order to synthesize polymer clay nanocomposites (PCNs). The selection of MMT as filler due to its high aspect ratio, high modulus and high cation exchange capacity (CEC). MMT was not susceptible to common polymer due to its organophobicity, low basal spacing, and incompatible to common monomers phase. Surface modification of MMT with traditional ion exchange method can be done through ion exchange with quaternary alkyl ammonium surfactants. The objective of surface modification of MMT are to change its nature hydrophilicity to organophilicity, in the same time to increase its basal spacing. Various quaternary alkylammonium cationic surfactants have been used; in this study, three type of alkylammonium were selected to be used due to its different in alkyl carbon chain lengths. Intercalation of surfactants cation in MMT depend on the layer-charge alkyl carbon chains, selection of myristyltrimethylammonium bromide (MTAB) with C17 carbon chains, cetyltrimethylammonium bromide (CTAB) with C19 carbon chains and octadecyltrimethylammonium bromide (OTAB) with C21 carbon chains could give an answer of the selection of organoclay that compatible with St, BA and MMA. This study focuses on the microstructure of organo montmorillonite (OMMT) after surface modification and the potential to be used as filler in synthesis of hybrid latex through miniemulsion polymerization technique. The intercalation or exfoliation of MMT through ion exchange with alkylammonium surfactant were studied, interlayer spacing of OMMT were analysed with X-ray diffraction, small angle X-ray scanning (SAXS) technique, presence of cationic surfactant in the interlayer space and bond character and arrangement of surfactant ions were analysed by Fourier Transform Infrared (FTIR), Thermogravimetric analysis (TGA) and Transmission Electron Microscope (TEM). Synthesis of hybrid latex was done by miniemulsion polymerization technique with selected OMMT filler. Series of experiments were performed to study the polymerization variables such as filler loading, role of surfactant/cosurfactant and filler solubility in monomer emulsions. The results shown that water soluble surfactant SDS in miniemulsion polymerization resulted lower coagulum and smaller particle size compare to non-ionic surfactant (TX405) and cationic surfactant (OTAB). Combination of non-ionic surfactant (TX405) with ionic surfactant (SDS) with ration 1:2 showed the better results than SDS alone, with lowest coagulum, narrow particle size distribution, and lowest Broekfield Viscosity. Scale up loading level of OMMT filler in miniemulsion to 5.0 wt%, resulting instability before and after polymerization with regard to high coagulum content and low monomer conversion rate (<90%). The hybrid latex resulted from miniemulsion polymerization will be applied on paperboard with hand rod coater with coating weight 15-20 gsm. The coated paperboard tested on its water vapour transmission rate (WVTR) together with paperboard coated with PE from melt blending process. Paperboard coated with hybrid latex comparable to paperboard coated with PE, indicated improvement in its WVTR value compare to paperboard coated with latex without filler addition. The main target of this research was to synthesis polymer hybrid latex for super barrier material for food packaging in order to replace unrecyclable PP, PE or PET. The utilization of polymer hybrid latex could benefit paper and paperboard packaging industries.