RESUMO
Agricultural waste corn stover has little economic value. Cellulose was extracted from corn stover by the processes of alkali treatment and delignification, resulting in aâ¯>â¯93% purity. The particle size of the extracted cellulose was reduced by mechanical shearing through high pressure homogenization. When passing through a homogenizer thirty times, the cellulose nanofibril (CNF) can be obtained. The diameters of the CNF ranged between 5 and 50â¯nm, and the lengths were microns. The mechanical properties of the films, made by corn stover cellulose, with and without high pressure homogenization shearing were evaluated using an Instron instrument. The films made by cellulose without shearing exhibited weaker mechanical properties, while the CNF films exhibited stronger mechanical properties. The linear rheological properties of CNF suspensions were also investigated and results show solid-like viscoelastic behavior. Our findings regarding corn stover CNF are similar to those CNF from other sources reported in the literature.
RESUMO
Graft copolymers of waxy maize starch and poly-γ-glutamic acid (PGA) were produced in an aqueous solution using microwave irradiation. The microwave reaction conditions were optimized with regard to temperature and pH. The temperature of 180°C and pH7.0 were the best reaction conditions resulting in a PGA graft of 0.45% based on nitrogen analysis. The average graft content and graft efficiency for the starch-PGA graft copolymer prepared at 180°C and pH7.0 were 4.20% and 2.73%, respectively. The starch-PGA graft copolymer produced at 180°C and pH7.0 could absorb more than 20 times its own weight amount of water and form a gel. The preliminary rheology study revealed that the starch-PGA graft copolymer gel exhibited viscoelastic solid behavior while the control sample of waxy starch showed viscoelastic liquid behavior.