Preparation And Characterization Of Wood Powder/ PLA Composites

With the gradual deepening of modernization, the environment deteriorates and the energy source is depleted. Therefore, to produce new composite materials by utilizing reproducible natural resources and materials becomes one of the hot foci in the realm of material studies. PLA is a kind of synthesized polymeric material that is non-toxic, nonirritant, and that has favorable biocompatibility and biodegradability. As a completely degradable environmental-friendly resin, PLA is produced by polymerization of lactic acid molecules, which are produced by hydrolyzation and fermentation of some reproducible natural resources such as starch, cellulose and polysacchirade. Discarded to natural environment, PLA will degrade to carbon dioxide and water after hydrolysis or biodegradation. Besides its biocompatibility, PLA also has excellent mechanical property and process-ability.Wood flour/PLA composite has the competitive edge of industrialization, and it is promising to be applied to the realm of polymer /plant fiber composite materials. Based on the producing of wood flour/PLA composite synthesized by Alamo wood flour and PLA, this thesis preliminarily researched on how the treatment and dosage of wood flour affects the property of the composites, laying the foundation of further studies.This content of this thesis includes:the produce of wood flour/PLA composite materials through fusion and extrusion of wood flour and PLA and then the optimal preparation technology, optimizing the formula of preparation, systematically research on the impact to the compatibility of wood flour/PLA made by the kinds of compatibility agent, the dosage of compatibility agent, MAH, and coupling agent, and characterization of the properties of wood flour/PLA.(1)The one objective of this study was to investigate the effect of the mesh and ratio of wood powder on mechanical properties of composites. The experimental results indicated that the mechanical properties of composite materials to achieve the best when wood powder mesh for the 40-60 project. It was also shown that the elongation at break decreased significantly in the 100-120 mesh, and the water absorption rate first increased and then decreased with the increase of mesh while the rate is minimum in 40-60 mesh. In addition, when changing the proportion of wood flour, the result indicated that the mechanical properties of composite materials were the best while the ratio of wood flour and poly (lactic acid) was 3:7, and the elongation at break and the water absorption increased with the increasing ratio.(2)Glycerol, ethylene glycol and polyethylene glycol were chosen as the compatilizer in order to improve the compatibility between wood flour and poly (lactic acid) of composites. The results showed that the composite materials possessed well compatibility and then got the better performance of composites when using the glycerol as compatibilizer. Besides that, when using different amount of glycerol as a compatible agent is added to the wood flour/ poly (lactic acid) composites, it showed that the composites had best compatibility and performance under the 6% glycerol addition. At the same time, the thermal stability and the elongation at break were better than ethylene glycol and polyethylene glycol.(3) Adding maleic anhydride (MAH), the compatibility of composite material was improved by the grafting reaction between wood flour (WF) and polylactic acid (PLA). The results showed adding MAH was beneficial to the properties of composite material. The optimal condition to obtain composite material with best mechanical properties, elongation at break and water adsorption was as follows:MAH%=1%. When the MAH addition exceeded 1%, the properties of composite material remained almost unchanged.(4)The silane coupling agent (KH-550、KH-560 and KH-570) was added to modify the properties of WF/PLA composite material. The result illustrated KH-550 worked best. Under this situation, the effect of KH-550 addition on the properties of composite material was investigated. The results elaborated the composite material had best performance under the 1.5% KH-550 addition.