Study On The Properties And Structure Of Wood Fiber/PVC Flexible Composites Reinforced By Nano-SiO₂

The wood-plastic composites were reinforced with nano-SiO₂ particles surface-modified with coupling agent KH-550.The SiO₂ particles before and after modification were observed,characterized and analyzed by FTIR,SEM and laser particle size analyzer.The FTIR,SEM,XRD and synchronization were used.The thermal analyzer analyzes the structure and analysis of nano-SiO₂ reinforced wood-plastic composites.By adding plasticizer DOP flexible wood plastic composite can be prepared.?1?The particle size of the SiO₂ particles before the modification is in the range of 100 to 140 nm,and the agglomeration is obvious and does not reach the nanometer level.After the dispersion modification,most of the particles were less than 100 nm in diameter,concentrated in the vicinity of 60 nm,and reached the nanometer level.SEM shows that the particle size distribution of the modified SiO₂ particles is uniform,the interface is clear,and the dispersion condition is good.There are no large-sized block-like agglomerates.?2?FTIR indicated that after the modification of SiO₂ particles,the absorption peaks of the characteristic functional group-C=O of KH-550,the bending vibration absorption peak of-NH bond,and the stretching of-CH₃ appeared at 1739,1531,and 3000 cm^-1,respectively.Vibration absorption peak,and the intensity of the-OH stretching vibration absorption peak at 3431 cm^-1 becomes small,indicating that after modification of the nano-SiO₂ particles,partial reactive hydroxyl groups on the surface react with KH-550 and decrease,indicating that KH-550 has been successful.Grafted onto the surface of SiO₂ particles.?3?The tensile strength,flexural strength and flexural modulus of wood-plastic composites are positively related to the wood-plastic ratio,while the impact strength is just the opposite,with the wood-plastic ratio increasing gradually decreased.When the wood-plastic ratio is 7:3,the tensile strength,bending strength and bending modulus are optimal,which are 29.7 MPa,45.6 MPa and 4.0 GPa,respectively,increased by 53.09%,68.27%and 90.48%,and the impact performance is reduced.52.11%.?4?After treated with KH-550,the tensile strength of wood fiber increased by 1.63%to 24.9MPa,the impact strength increased by 10.64%to 5.2kJ/m²,the modulus of elasticity hardly changed to 3.5GPa,and the elongation at break increased by 23.08%.It reached 1.6%.After treatment with NaOH solution,the tensile strength decreased by 0.82%to 24.3MPa,the impact strength increased by 14.89%to 5.4kJ/m²,the elastic modulus increased by 20.00%to 4.2GPa,and the elongation at break decreased by 15.38%.?5?The content of nano-SiO₂ is 8%,the tensile strength reaches the maximum 31.12MPa,which is 28.91%higher than that without nano-SiO₂ particles.When the content of nano-SiO₂ particles is 10%,the maximum elastic modulus is 4.64GPa,which is 49.68%higher.When the content of SiO₂ particles is 8%,the flexural strength of the composite material reaches a maximum value of 44.06 MPa,an increase of 37.17%,the content of nano-SiO₂ is 10%,and the composite material has a maximum impact strength of 4.11 kJ/m²,an increase of 16.76%.?6?SEM shows that when the content of nano-SiO₂ particles is small,the material structure has more porous holes and gaps.With the increase of nano-SiO₂ content,voids and gaps are reduced,and the interface compatibility of the composites is optimized.When the content of nano-SiO₂ exceeds 10%,it begins to agglomerate and the particle size becomes larger.After the particles begin to agglomerate,it is not conducive to the development of nano-characteristics.?7?XRD showed that when the nano-SiO₂ particles were below 8wt%,they nucleated the cellulose crystallization process and promoted cellulose crystallization.When the nano-SiO₂ is excessive,the progress of the cellulose crystallization process is hindered.