Novel Starch Nanocomposites

Abstract

Thermoplastic materials using bio-derived renewable resources are studied intensively and are widely used in applications including packaging, agriculture and other consumer goods. Starch-based plastics exhibit a good balance between environmental benefits, mechanical properties, processability, and low cost. Recently, there have been numerous efforts to amplify the positive effects on the environment while maintaining competitive physical properties in order to meet the needs of the market. Canadian companies have developed new starch-based products to amplify the positive environmental impacts. Polymer Specialties International developed a new thermoplastic starch copolymer resin with competitive characteristics. However, there is very little information on the reaction mechanisms and chemical compositions. Another Canadian company, Ecosynthetix, is producing starch nanoparticle materials for applications such as paper coating. Recent studies conducted by our research group showed promising results by applying these materials as filler in polyethylene composites. These research problems generated opportunities to investigate and develop new applications. The goal of this research was to develop a technology to characterize and process environmentally friendly materials using starch as co-polymer and as nanoparticle. The research aimed to extend the range of properties of starch materials while maintaining environmental benefits and competitive physical properties for applications such as packaging and agriculture. The first research objective was to characterize the new thermoplastic starch copolymer resin. In-depth characterization of its molecular structure and measurement of its thermal and mechanical properties were conducted. The material was also investigated in the presence of nanocellulose as reinforcement. Furthermore, the esterification process using maleic anhydride was done through three different systems: a reactive microwave reactor, a vacuum rotary evaporator, and a twin-screw extruder. A series of studies was conducted and the materials were compared via chemical composition analysis. Mechanisms for maleation were confirmed and this is an important step for manufacturing copolymer resin. The second objective was to investigate the application of starch as nanoparticle. The focus was on the dispersion of starch nanoparticles in a green polyethylene matrix. Achieving uniform distribution and desired particle size through tuning of the processing conditions and additives were the keys. Detailed characterization of the composite materials were conducted. By designing and applying a systematic approach, uniform nano-sized dispersions of the fillers were achieved within the matrix, and this was confirmed by morphological analysis.