Chemical/Hydrothermal Modification Of Moso Bamboo Particles And Characterization Of Its Rinforced PVC Composites

Bamboo plastic composites were fabricated with polyvinyl chloride and moso bamboo sawdust from bamboo processing industry in this paper. And in order to obtain composites with outstanding mechanical properties, the influences of materials properties and moulding technical on the mechanical properties of moso bamboo particles reinforced PVC composites were studied. With this base, the roles of chemical/hydrothermal modification on characteristic of bamboo particles and properties of the composites were investigated. Results showed that:1) A better mechanical properties of moso bamboo particles reinforced PVC composites will be obtained when the particle size of moso bamboo particles is 0.9mm with a moisture content of 3%, and the weight ratio of bamboo and polyvinyl chloride is 50:50. Optimized parameters of molding technical is 8min compressing at 180℃.2) The highest tensile strength of the composites is 15.72MPa with 5wt% Na2SiO3 aqueous solution treatment. The best modulus of elasticity and modulus of rupture of the composites are obtained with 5wt% and 2wt% NaOH aqueous solution treated respectively, and the values are 4362.48 MPa and 44.73MPa. The lowest values of 2h and 24h thickness swelling and water absorption are obtained with 0.5wt% NaOH aqueous solution treatment. The compatibility of different content of the composites is improved with NaOH, Na2SiO3 and NaHSO3 solutions and the most uniform distribution of moso bamboo particles in PVC composites is observed with NaHSO3 solutions treatment.3) Tensile strength of moso bamboo particles reinforced PVC composites get its maximum value of 13.79MPa with 0.5% potassium permanganate treatment while modulus of rupture and modulus of elasticity reach their highest values of 30.36MPa and 3261.89MPa respectively at 0.2% concentration. Potassium permanganate treatment enhanced elongation at break and flexural deformation. A uniform dispersion of moso bamboo particles in PVC matrix was obtained after potassium permanganate treatment. Low concentration would oxidize hydroxyl groups of moso bamboo cellulose and too high concentration would make moso bamboo cellulose degrade.4) Hydrothermal modification improve the surface structure of moso bamboo particles and wipe out hemicelluloses, lignin, pectin and etc.. A uniform dispersion of moso bamboo particles in PVC matrix is observed with hydrothermal treatment. Tensile strength, modulus of elasticity and modulus of rupture of moso bamboo particles get their maximum values of 15.79Mpa, 6702.26MPa and 39.57MPa respectively with 180℃hydrothermal modification. The highest values of elongation at break and flexural deformation are 3.75%±0.20%(with 200℃hydrothermal modification) and 36.22%±2.70%(with 140℃hydrothermal modification). The lowest values of 2h and 24h of water absorption and thickness swelling are 1.18%±0.08%,3.34%±0.20%,0.49%±0.13% and 1.3%±0.41% respectively.5) The type and concentration of the catalyst have remarkable influence on characteristic of moso bamboo particles and the properties of the composites in the process of hydrothermal modification. A lowest content of protein, saccharine, amylum and pectin is obtained with 0.5wt% Na2SiO3 catalyzed. The lowest content of hemicelluloses is 7.58wt% which is catalyzed with 0.5% H2SO4 at 120℃hydrothermal modification. The lowest content of lignin is 11.31wt% which is catalyzed with 1%NaOH at 160℃hydrothermal modification. The largest tensile strength of the composites is 26.98±4.69MPa which is treated with 2wt% Na2SiO3 at 200℃. The highest modulus of elasticity and modulus of rupture are 6089.49±347.49MPa and 52.16±2.54MPa respectively which is treated with 2wt% K2CO3 at 160℃. The largest elongation at break of the composites is 4.41±0.03% which is catalyzed with 2wt% Na2CO3 at 140℃and the largest flexural deformation of the composites is 91.92±2.79% which is treated with 2wt% NaOH at 160℃. The lowest 2h water absorption of moso bamboo particles reinforced composites is 1.61±0.07% which is treated with 0.5wt% H2SO4 at 120℃hydrothermal condition. The lowest 24h water absorption of moso bamboo particles reinforced composites is 3.43±0.50% which is treated with 2wt% Na2SiO3 at 180℃hydrothermal condition. The lowest 2h thickness swelling of composites is 0.52±0.15% which is treated with 0.5wt% Na2SiO3 at 140℃hydrothermal condition and the lowest 24h thickness swelling of composites is 2.43±0.13% which is treated with lwt% Na2SiO3 at 160℃hydrothermal condition.The most important contribution of this research is surface modification of the composites with hydrothermal technology and the investigation of water absorption mechanism of the composites. The results of this manuscript will give an innovation thinking and method to surface modification of natural fibers and interface improvement of wood plastic composites. The results of our research also give some references to the applications of wood plastic composites.