Aging Resistance And Antimicrobial Activity Of Wood Fiber/HDPE Composites

With the wide use of wood plastic composites (WPC) outdoor, aging problem has been paid more and more attention, because WPC are highly susceptible to ultraviolet light, wind, rain, microorganism, and so on. These factors could make WPC impaired and bacteria-grown. In this thesis, some additives have been used to improve the performance of WPC. The properties of wood fiber/HDPE (WF/HDPE) composites with different additives were evaluated after exposed to accelerated ultraviolet aging. Also the type and content of biomass fiber and antibacterial agents were considered variations imposing effects on the mechanical and antibacterial properties of WF/HDPE composites. The main results of the research are concluded as follows:With ongoing of aging time ΔL*and ΔE*increased, surface cracks came into being and gradually became more serious, surface roughness of WPC increased, and ΔE*were mainly resulted from ΔL*basically. In the meanwhile, bending performance also decreased, however bending modulus lost more than bending strength. In the first500h of UV exposing, ΔE*and bending performance changed most; In the500-1500h of aging time, both bending performance and color changed smaller than the first stage. After1500h ultraviolet aging the color of wood plastic composites faded to a certain degree, and became stable.With the processing of UV aging time, the carbonyl index of the controller continuously increased before1500h, however, it decreased in the stage of aging1500-2500h. Adding UV326to the composite reduced the carbonyl index increase comparing to the controller, this suggested that UVA could effectively absorb ultraviolet light effectively to reduce the surface oxidation during ultraviolet aging. On the other hand, cellulose index of the composites containing2%UV326was lower than other samples. After aging500h, all cellulose index of the sample decreases, and then the fiber’s information reduced when exposing to ultraviolet light and moisture500-2500h. FTIR indicated oxidation occurred on the surface during aging, however, a new surface layer naked affected the detection to surface oxidation.Composites added by a certain amount of UV326was found to be superior to the controller in aging resistance, such as changes of color, bending properties and surface chemical oxidation. However, composites with Tin783or Chi944performed worse than the controller. During UV aging, the combination of different kinds of additives may have cooperative effect, which effectively reduced lightness and total color changing, and protected the bending quality from losing and reduced the oxidation magnitude of the composites. Among which the collaborative effect between ZB and UV326was better than the action between ZB and HALS, but the protection of compounded HALS with ZB was worse than ZB alone. So, it is thought that these results may be due to the fact that the activity of HALS did not play out in a short time or the reactive group of HALS was damaged.Preliminary study showed obviously that SHT-115and SHT-860had antimicrobial activities to the pathogenic E. coli and S. aureus, and they were superior to SHT-120.There were obvious bacteriostatic rings when composite materials with SHT-115or SHT-860were researched in antimicrobial test. The type of biomass fiber had a significant impact on the bending strength, bending modulus, impact strength and tensile strength of composites. Wood fiber provided the best quality among bamboo fiber and straw fiber. Three proportion of biomass fiber/HDPE and the type of antimicrobial agents also showed significant influence-on the tensile strength of composites.