The Preparation And Properties Of Bamboo Plastic Composites With Weathering Resistance

Wood plastic composite?WPC?has higher weathering resistance than natural solid materials,like wood and bamboo.However,the weathering of WPC is critically severe when it is used in the applications with high temperature and moist.Normally,the high weathering resistance of WPC has an positive effect on their widely applications.Bamboo plastic composite?BPC?is one of the most important compositions of WPC,which is reinforced or filled with bamboo particles.Therefore,in this paper BPC was taken as the objective.The effects of various combinations of primary antioxidant and secondary antioxidant,ratios and contents were studied for evaluating the thermo-oxidation resistance of BPC.The effects of antioxidants on other select properties of BPC that are fundamental to its application were also assessed.The stable TiO₂ sol was spraying on the bamboo flour or polypropylene?PP?flour and then nano-TiO₂ was in situ synthesis on their surfaces after mixturing and drying.The effect of spraying method and contents of nano-TiO₂ on the xenon-arc accelerated weathering and natural weathering resistance of BPC were discussed in this paper.As a comparison,the BPCs with commercial antiaging agents were also prepared and studied.The modified nano-TiO₂ or nano-ZnO was directly added into BPC or through spraying on the bamboo flour surface based on the modified nano particle suspension.The effect of adding method and contents of nano particle on the xenon-arc accelerated weathering resistance of BPC were studied.A simple method to physically separate bamboo fiber?BF?and bamboo parenchyma cell?BP?from bamboo particle was proposed in this paper.The effect of different fillers on the xenon-arc accelerated weathering and natural weathering resistance of BPC was also discussed.The main conclusions of the above research are summarized as follows:?1?Oxidation induction time?OIT?can be used as a simple indicator for a rapid screening of antioxidants for WPC production.The OIT values of composites were significantly increased after adding a few of antioxidants and this is one of the most effective method to enhance the thermal weathering resistance for BPC.The anti-photodiscoloration,anti-surface erosion and the retention of flexural properties of composites after 900 h of thermal oven weathering were improved with the application of antioxidants,as well as decreased the weight loss.These were mainly attributed to the limitation of surface thermal oxidation with antioxidants.The addition of minor antioxidants in BPC has little effect on their water absorption,dynamic mechanical properties and thermal properties.The optimal parameters were the antioxidant combination of 1076 and DLTP mixed at the ratio of 2:1 with the total concentration prepared at 0.2 wt% based on PP matrix.?2?Although the dispersion of nano-TiO₂ could be improved through in situ synthesis nanoTiO₂ on bamboo flour or PP surface,the anti-photodiscoloration of BPC was not increased and the surface erosion was more obvious during xenon-arc accelerated weathering and natural weathering.Normally,the negative effect was more significant with an increase in the content of nano-TiO₂,due to the acceleration of BPC degradation with the mineral acid acted as a catalyst.The mechanical reduction of BPC during weathering was intensified with bamboo flour modification or PP modification after drying with low temperature,while declined with PP modification after high drying temperature.?3?In situ synthesis nano-TiO₂ on bamboo flour surface had negative effect on the origin physical-mechanical properties,while the properties were nearly kept consistent or significantly improved through in situ synthesis nano-TiO₂ on PP surface.When the modified PP was drying with low temperature and the content of nano-TiO₂ was 0.2% or 0.5%,the flexural strength and modulus were approximately increased by 21% and 18%,respectively.And the water absorption and thickness swelling for 24 h were approximately decreased by 40% and 45%,respectively.Therefore,the interfacial property of BPC was significantly enhanced through in situ synthesis nano-TiO₂ on PP surface with low drying temperature,as well as by controlling the suitable content of nano-TiO₂.?4?The origin flexural strength and modulus were slightly improved after adding minor commercial anti-aging agents.Among them,the reinforcement was better for BPC with the combination of antioxidant 1076 and DLTP and the photostabilizer?GW-327?than that of with untreated commercial nano-TiO₂ and nano-ZnO particles.And the anti-aging agents have little effect on the water absorption for BPC.During the xenon-arc accelerated weathering and natural weathering,the enhancement of anti-photodiscoloration for BPC was observed and the increment in BPC with the combination of antioxidants and photostabilize was optimal.And the surface erosion and loss of mechanical properties of BPC during weathering were restricted with the application of anti-aging agents.The commercial nano-Zn O has a optimum effect on it,while the commercial nano-Ti O₂ had little effect.?5?The particle size distribution of nano-TiO₂ and nano-ZnO were significantly decreased after their surfaces treated with the corporation between KH-570 silane and ultrasonic dispersion.And the dispersion of nano particles was also improved.The flexural strength and modulus were were greatly increased with the application of modified nano-TiO₂ and nano-Zn O,and the water absorption was significantly declined at the same time.When the nano particles were added through spraying and their contents at o.1%,the flexural strength and modulus were improved by 23.3% and 36.8% for nano-TiO₂,and 28.6% and 26.5% for nano-ZnO,respectively.And the corresponding water absorption and thickness swelling for 24 h were declined by 59.7% and 66.7%,and 85.2% and 52.8%,respectively.Results found that the anti-photodiscoloration for BPC with surface modified nano-TiO₂ and ZnO was enhanced and the reinforcement was more obvious during the initial stage of weathering.However,the surface modification for nano particles had little effect on improving the anti-surface erosion for BPC.Although,most of the drop rates for flexural strenth and modulus of BPC with modified nano particles during weathering were larger than that of without nano particle,the absolute average values were still higher than the latter.?6?The reinforcement effect of different fillers for BPC was significantly different,ranked as follows: BF,wood fiber,?BF+BP?and BP.Compared with BP/PP composite,the flexutral strength and modulus were significantly increased by 26.5% and 50.3%,respectively.And the corresponding water absorption and thickness swelling were declined by 32.8% and 24.1%,respectively.It was found that the composites reinforced with different lignocellulosic fillers were fading obviously and their surface had several crackings during weathering.The flexural properties and storage modulus were also declined.Gernally,the loss of mechanical properties of BF/PP was lower than that of BP/PP,while the anti-photodiscoloration of the latter was better than the former.Thus the weathering resistance of BPC could be improved by controlling the considerable ratio between BF and BP in composites.In summary,adding the optimal combination of antioxidants could not only improve the thermal weathering resistance for BPC,but also enhance the anti-photodiscoloration and antisurface erosion during photo-oxidation.The mechanical properties of BPC were significantly increased with the application of surface modifided nano-TiO₂ and nano-ZnO,and the water absorption was significantly declined at the same time.The photo-oxidation resistance of BPC could be reinforced to a certain extent after adding minor organic photostabilizer or by controlling the considerable ratio between BF and BP in BPC.