Modified Porous Clay Heterostructures by Organic-Inorganic Hybrids for Nanocomposite Ethylene Scavenging/Sensor Packaging Film

Porous clay heterostructures (PCHs) were prepared by the surfactant-directed assembly of mesostructured silica within the two-dimensional galleries of clays. PCH is an interesting material for use as an entrapping system (for example, as an ethylene scavenger) because of its high surface area with uniform and specific pore sizes. In the present work, the PCH was synthesized within the galleries of bentonite by the polymerization of tetraethoxysilane (TEOS) in the presence of surfactant micelles. In addition, mesoporous clay was modified by an organicinorganic hybrid material through the co-condensation reaction of TEOS with the functional groups (methyl and thiol) designated as hybrid organicinorganic PCH (HPCH) and mercaptopropyl functionalized PCH (MPPCH), respectively. The synthesized PCH, HPCH and MPPCH were blended with polypropylene (PP) to produce PCH/PP, HPCH/PP and MPPCH/PP for ethylene scavenging blown films. All nanocomposite films were evaluated as ethylene sensors by measuring the conductivity changes by the attachment time with the ethylene gas. According to the surface characterization, the specific surface areas of modified PCHs increased from 31 to about 500m2/g. From the ethylene adsorption results, the PCH, HPCH and MPPCH show higher efficiency in adsorbing ethylene gas than those of bentonite because of the non-polar property of the modified functional groups. Subsequently, the electrical conductivity of the nanocomposite films decreased when they react with the longer attachment time to the ethylene gas, and the largest conductivity drop resulted from the MPPCH/PP nanocomposite films. Copyright (c) 2011 John Wiley & Sons, Ltd.