| Due to the sharp deterioration of the environment, it has become a hot topic of society that using a kind of renewable, non-polluting and biodegradable new material replaces oil-based traditional plastics. Polylactic acid(PLA), a high strength, transparency and easy processing material, can eventually be biodegraded into carbon dioxide and water in the environment, thus becoming one of the most hotspot biodegradable materials. Among numerous kinds of degradable polymers, polylactic acid, an aliphatic polyester and biocompatible thermoplastic, is currently a most promising and popular material with the brightest development prospect. In this thesis, using the conventional mechanical blending method for preparing a common starch / polylactic acid composite material, and its performance improvement; By chemical modification, it was prepared a new cheap modified sweet potato slag / PLA composites using the modified low-cost industrial byproducts sweet potato residue(SPS) blended with polylactic acid.By mechanical blending manner, starch and Polylactic Acid, adding coupling agents and plasticizers in different proportions, extruded into strands in the high temperature by twin-screw extruder, and granulated into many samples by injection molding machine. Composites were prepared by Polylactic Acid and starch with the different mass ratio. The characterization of composites was studied through tensile mechanical testing, melt index, DSC and water absorption test. The test results showed that the mechanical property, melt flow and improve absorption of the PLA material greatly enhance, when it blended with an appropriate amount of starch in the role of coupling agents and plasticizers.The modified sweet potato residue was made by SPS grafted with acrylic acid(AA) by single factor experiment and orthogonal test method. The optimal grafting percentage was 257.4% under the condition that acrylic acid and sweet potato residue ratio of 3:1, the reaction time 1.5 h, the reaction temperature 80℃, initiator added 10 mmol / L. The characterization of the composite was studied through IR and XRD.The modified sweet potato residue was blended with Polylactic Acid in dimethyl sulfoxide to prepare a novel biodegradable material. The characterization of the composite was studied through melt index and SEM. The result showed that compatibility of the modified acrylic-Starch/PLA blends was greatly improved by the acrylic modified sweet potato residue.When acrylic acid content of 50%, processing flow properties of composites was the best and the degree of the mixture was relatively uniform. Compared with the starch / PLA composite melt index is not very different, but added inexpensive sweet potato slag greatly reduces the cost of the composite. |
