GRAFTING OF THERMOPLASTICS TO STARCH (METHYL, METHACRYLATE, ACRYLATE)

Investigations were conducted on the grafting of thermoplastics to the natural polymer starch and examining the properties of the copolymers. Emphasis was placed on the feasibility of processing these materials as thermoplastics.;Methyl acrylate, methyl methacrylate, and 2-hydroxyethyl methacrylate were grafted to starch using Ce(IV) as a redox initiator. Some parameters influencing efficiency of the grafting process were investigated.;Extensive analyses of all copolymers were carried out using gel permeation chromatography as the primary technique. The chemical properties of the materials were pertinent to the physical and mechanical properties of the processed copolymers.;Processing of copolymers by extrusion and injection moulding focussed on starch-g-PS and starch-g-PMA. These copolymers grafted to starch with high efficiency and processing conditions were found for them that produced a homogeneous extrudate with strength approaching that of the pure thermoplastic. The effects of the plasticizing effects of water on the tensile and dynamic mechanical properties of the material were summarized. The rheological properties of the copolymers during extrusion were summarized. The extrudate swell of the starch-g-PS was compared to that of PS under similar processing conditions.;Parameters influencing the grafting of styrene to starch by (gamma)-irradiation were examined. Electron spin resonance (ESR) spectroscopy was utilized to examine the effects of solvents and starch morphology on (gamma)-irradiated starch free radical yield. It was found that solvents which can swell the starch and diffuse into it also promote the grafting of styrene to starch. The likely spectral components of the (gamma)-irradiated starch which result in the observed ESR signal were determined with the aid of computer simulation. It was also determined that radiolysis of the solvent is important in this grafting reaction.;The rheology of dispersions of starch-g-2-hydroxyethyl methacrylate in water was studied. It was found that the dispersions were pseudoplastic and the viscosities could be dramatically increased through addition of calcium chloride. The viscosities were also pH dependent. The causes of this behavior were discussed.;A preliminary investigation was undertaken on the effect of starch on the swelling behavior of crosslinked poly(vinyl acetate) in methyl ethyl ketone. A theory to explain the effect of starch on restricting the expansion of the polymer network which was based on simple concepts of mechanics had limited usefullness.