Use of inorganic natural nanotubes and synthetic carbon nanotubes in poly(lactic acid)

Erpek Yeniova, Canan Esma
Poly(lactic acid) (PLA) is one of the most important biodegradable aliphatic polyesters, which has attracted great attention in the recent years owing to its excellent material properties. The main objective of this study was to process and characterize Halloysite nanotube (HNT)/PLA nanocomposites. The constituents were observed to be incompatible when processed by classical melt mixing methods, without HNT pre-treatments or addition of plasticizers which act as compatibilizer. In order to achieve the desired physical properties different mixing methods were tried: Direct melt mixing for 3 minute (DM3), direct melt mixing for 10 minute (DM10), masterbatch melt mixing (MMA), solvent casting followed by melt mixing (SC), suspension addition to melt mixing (SA). In addition, HNT minerals were subjected to different pre-treatments: Purification of HNT (p-HNT), functionalization of HNT by grafting with organo-silane (o-HNT), modification of HNT with quaternary salt (m-HNT), and evacuation pre-treatment (e-HNT) to improve the compatibility between PLA and HNT. Among the pre-treated HNT minerals, only the samples prepared by e-HNT showed nanocomposite formation due to the removal of water layer that had remained between the layers of silicate which might hinder the desired compatibilization. For plasticization of PLA, and to provide compatibilization between PLA and HNT two types of blends were processed: PLA plasticized with poly(ethylene glycol) (PEG), P-PLA, and PLA toughened with elastomeric thermoplastic polyurethane (TPU), T-PLA. Addition of HNT was observed to greatly contribute to the improvement of the elongation at break of T-PLA polymers due to the relatively better compatibilization effect of TPU. The results obtained in this study with the local ESAN HNT were cross checked with a reference imported Nanoclay HNT. Also, the comparison of the properties of HNT based composites with the properties of composites prepared with synthetic carbon nanotube (CNT) was performed. According to results, HNT minerals have no chance to compete with CNT as a filler in PLA matrix unless: The residual water between silica layers are removed or a perfect compatibilizer is used.


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Citation Formats
C. E. Erpek Yeniova, “Use of inorganic natural nanotubes and synthetic carbon nanotubes in poly(lactic acid),” Ph.D. - Doctoral Program, Middle East Technical University, 2015.