Παρασκευή Και Μελέτη Νέων Πολυεστερικών Νανοσύνθετων Υλικών Συσκευασίας

Abstract

The scope of the present study was the development and study of new polymer nanocomposites, which could substitute common polyolefin packaging materials. Three biodegradable aliphatic polyesters were used, specifically poly(e-caprolactone), poly(ethylene succinate) and poly(butylenes succinate), as well as poly(ethylene terepthalate), being a fully recyclable material. For the improvement of mainly their poor mechanical properties and gas permeability new nanocomposites were developed with different fillers, such as fumed silica nanoparticles, montmorillonite and multi-walled nanotubes. Appropriate treatment of the nanofillers was carried out to obtain a better dispersion in the polymer matrix. Nanocomposites with different nanoparticles' concentration were prepared, using two different preparation techniques, in situ and melt mixing, and the subsequent materials were extensively studied. The surface silanol groups of fumed silica and carboxylic groups of the modified carbon nanotubes led to significant interactions between the nanoparticles and the polymers and in many cases covalent bonds were formed. The presence of the nanofillers in the reaction mixture affected the final molecular weight of the polymers in an unpredictable way. The nanoparticles acted as nucleating agents, accelerating the crystallization rate. In contrast, the formation of crosslinks with the filler led to decreased crystallization rates. The crystallization temperature from melt and the Τ g of the polymers were shifted to higher temperatures with the addition of the nanoparticles. The presence of the nanoparticles also led to significant improvements of mechanical properties, dynamic mechanical properties and gas permeability rates. The enzymatic hydrolysis rates were reduced with the presence of the nanoparticles; however the materials did not lose their biodegradable character. The reaction rates during SSP were accelerated at low nanoparticles' concentration, while at higher a substantial rate reduction was observed. The basic hydrolysis reaction was accelerated by the presence of the nanoparticles.