Modification of Halloysite nanotubes reinforced polylactic acid bionanocomposites

Packaging materials based on polylactic acid (PLA) represents one of the most promising biopolymers had significantly increased the current interest of biodegradable polymers in the industry. In this study, the PLA bionanocomposites reinforced by five different types of natural halloysite nanotubes (HNTs) obtained from different geographical and geological locations, including the USA, Australia and New Zealand were prepared by solution casting method. In the first part of the study, the impacts of the HNT source and concentration of HNTs on the physical, chemical, morphological, and tensile properties of polylactic acid (PLA)-based nanocomposites as potential materials for food packaging applications were studied. PLA/HNTs nanocomposites were solution-cast with HNT concentrations ranging from 0 to 10 wt%. The PLA/HNTs nanocomposites films showed low moisture content, low water uptake, small contact angles with high density and tensile strength (TS), and good thermal properties as compared to neat PLA film. The increment in clay content (0-5 wt %), pointedly contributed to positive change on TS and elongation at break (EAB). In addition, the changes on HNT type showed insignificant effect on the thermal properties of PLA/HNTs films. The glass transition (Tg) temperature of all films slightly decreased as the HNTs concentration increased at 0–5 wt%. The results indicated that Ultra HalloPure (UHP) halloysites at 5% loading improved the properties of PLA films and enhanced their suitability for food packaging and other plastic applications (it was selected as the optimum filler to reinforce PLA in the next stages). Then, the effects of polyethylene glycol (PEG) and sesame oil (SO) content (0- 30 wt%) as plasticizers on the structure and properties of the PLA/HNTs nanocomposite films were investigated. Films with 30 % of SO exhibited the lowest water vapor permeability (WVP) and Tg and the highest contact angle. Meanwhile, the film with 20 % of PEG showed the higher thermal stability and EAB among other films. The effect of electron beam radiation with different doses (0 – 60 kGy) on the structure and properties of PLA/HNTs nanocomposite films were carried out on third part of the study. Results showed the increment on the TS and thermal stability and dropped in the WVP in the ranges of electron beam radiation (0-20 kGy). The last part of the study investigated the effects of HNTs surface modification by deep eutectic solvent (DES) on the structure and properties of the PLA/mHNTs nanocomposite films. The results designated a good dispersion of mHNTs into PLA, which led to an improvement in mechanical and thermal properties. In summary, the PLA/HNTs properties have improved with the modification of HNTs by DESs solvent, and the optimum properties were gained at the 5 wt. % HNTs loading, to be used in different industrial applications.