Synthesis and Processing of Graft Copolymers Prepared from Cereal Flour and Methyl Acrylate

Ceric-initiated graft polymerizations of methyl acrylate onto corn and wheat flour were carried out in a 2-gallon reactor to provide pound quantities of these polymers for characterization and processing. Conversions of monomer to poly(methyl acrylate) (PMA) were nearly quantitative, although considerable homopolymer was formed along with grafted PMA. The resulting polymers were extrusion processed into plastic ribbons, and films were also prepared from these polymers by extrusion blowing. Tensile properties of the products were determined. Comparison of the preparation and properties of PMA-grafted flour with our earlier research on starch-g-PMA revealed some important differences between the two polymerization systems. Graft polymerizations onto flour required a higher concentration of ceric initiator to give a near quantitative conversion of monomer to polymer and yielded a higher percentage of ungrafted homopolymer. Also, extruded ribbons obtained from PMA-grafted flour generally exhibited lower UTS, higher % elongation and higher tear strength than extrudates prepared from PMA-grafted starch. In contrast to our findings with PMA-grafted starch, flour-g-PMA could be processed into continuous extrusion films, even though flour was graft polymerized in the granular state and was not dissolved/dispersed in water prior to graft polymerization. The percent shrinkage of extrusion blown flour-g-PMA at room temperature and 100% relative humidity was less than that observed for analogous starch-based films.