Use of Halloysite Nanotubes for the Production of Poly (lactic acid) Nanocomposites
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Use of Halloysite Nanotubes for the Production of Poly (lactic acid) Nanocomposites
Canan E. Yeniova1, Assoc. Prof. Dr. Guralp Ozkoc2 and Prof. Dr. Ulku Yilmazer1 1
METU Department of Chemical Engineering, 06800, Ankara / TURKEY
2
Kocaeli University Department of Chemical Engineering, 41380, Kocaeli / TURKEY
ABSTRACT Environmental concerns emphasize the urgent need for the development of biodegradable polymers. In this study, poly (lactic acid) (PLA), being a biodegradable polymer matrix, was used together with poly (ethylene glycol) (PEG) to enhance its low toughness. In addition, the deterioration in mechanical properties owing to plasticization was tried to be overcome by addition of nanofiller. As nanofiller, two nanotubular halloysite (HNT) types, one local (ESAN HNT) and an imported one (Nanoclay HNT) supplied by Aldrich, were used. As the first step, characterization and purification of local HNT was performed. In the second step, plasticized and unplasticized PLA matrix composites containing 3, 5 and 10 wt % were prepared and their morphological and mechanical analysis were performed. Upon the addition of both ESAN HNT (local HNT) and Nanoclay HNT (imported HNT) no improvement was observed in the basal spacing of the clay layers owing to poor interaction between the matrix and the surface of the nanotubes which should be modified for better dispersion.
INTRODUCTION The future outlook for advancement in the area of biodegradable plastics is promising. These plastics begin their lifecycle as renewable resources, and then are formed into the specific end products to be used by consumers. Poly (lactic acid) (PLA) is a common polymer based on agricultural (crop growing), biological (fermentation), and chemical (polymerization) sciences and technologies. It has one of the highest potentials among bio-based polymers owing to its reasonable price and availability in market. However, its lower fracture toughness compared to many petro-chemical polymers restricts its usage area in the sector. To secure its foothold, it is desirable to enhance its toughness by introducing a plasticizer. In order to optimize the other properties lowered by the introduction of plasticizer, fillers can be added. The nanocomposite family of composite materials exhibits remarkable improvements of mechanical and material properties when compared with virgin polymers or conventional micro- and macro-composites. Owing to their unique tubular morphology, that resembles CNT, and the same chemical structure with that of layered silicates, halloysite is an attractive research topic for nanocomposites [1]. As
a naturally occurring alumina silicate halloysite (HNT), AlSi2O5(OH)4.2H2O, exhibits unique surface chemical property due to the multi-layered structure with hydroxyl groups on its surface. It is chemically similar to kaolinite, but differs mainly in the morphology of crystals and unit layers that are separated by a monolayer of water molecules. In the first step of this work, characterization and purification of a local HNT was perfor
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