Study On Preparation And Properties Of Graded Bamboo Power Reinforced PHBV Composites

Environmental protection and innovation have engraved the theme of the new era.Bamboo,with its abundant resource reserves and excellent natural properties,is gradually replacing wood to create tremendous potential and utilization space in green economy and green industry.Nowadays,China is moving towards a beautiful country and a prosperous countryside.In order to promote the efficient and refined utilization of bamboo,and promote the economic development of bamboo producing areas,the research of bamboo and bamboo matrix composites has become an important part.In this paper,bamboo fibers from Xinchang,Zhejiang Province were divided into three modulus levels according to their bending modulus,and the properties of bamboo fibers with different modulus levels and their composites mixed with poly（3-hydroxybutyrate and 3-hydroxy valerate）（PHBV）were studied.In addition,in order to improve the interfacial bonding of bamboo fiber/PHBV composites and the properties of the composites,rice husk-based SiO₂ was prepared by pyrolysis of rice husk acid as reinforcing material.Then,bamboo fiber and rice husk based-SiO₂ were treated by silane coupling agent and rare earth coupling agent.The changes of properties of bamboo fiber,rice husk-based SiO₂ and PHBV ternary composites were investigated.This paper mainly studies from three aspects.Firstly,the properties of modulus graded bamboo fibers are analyzed,and the effects of modulus on the chemical composition,morphology,anatomical characteristics and pyrolysis properties of bamboo fibers are explored.Secondly,bamboo fiber and PHBV were used to prepare composite materials.The effects of bamboo fiber content,modulus grading and types of coupling agents on mechanical properties,water absorption and thermal stability of the composite materials were investigated.Finally,rice husk based-SiO₂ was added to bamboo fiber/PHBV composites to explore the effect of content of rice husk-based SiO₂ and the treatment of coupling agents on different modes composites.The following conclusions can be drawn from the study:（1）The chemical compositions of bamboo raw materials with different modulus grades are different.The contents of holocellulose and a-cellulose increase with modulus increasing,while the lignin content decreases.The air-dry density and moisture content of bamboo raw materials also increase with modulus increasing.The length,diameter,aspect ratio and crystallinity of bamboo fibers increase with the increase of modulus.The length-diameter ratio and crystallinity of bamboo fibers with modulus greater than 13 GPa（LMBF）are 228.89%and 58.89%respectively.With the increase of modulus,the microfibril angle of bamboo fibers decreases.The thermal stability of bamboo fibers less than 11 GPa（SMBF）is the worst,which may be due to the highest content of unstable hemicellulose in SMBF,which can be decomposed first at lower temperature during pyrolysis.（2）The results of mechanical properties test show that the tensile strength and modulus of pure PHBV are 17.74 MPa and 420.16 MPa,while the flexural strength and modulus are 43.61 MPa and 669.76 MPa.The tensile strength of bamboo fiber/PHBV composites increases first and then decreases with the increase of bamboo fiber content.When the bamboo fiber content is 10%,the maximum tensile strength is 20.37 MPa;the flexural strength of the composites decreases with the increase of bamboo fiber content;the tensile modulus and flexural modulus of the composites increase with the increase of bamboo fiber content.The tensile and flexural properties of bamboo fibers/PHBV with different modulus grades increased with the increase of modulus of bamboo fibers.Scanning electron microscopy showed that bamboo fibers treated with silane coupling agent and rare earth coupling agent could effectively improve the interface bonding between fibers and matrix.Compared with pure PHBV and pre-treated composites,the mechanical properties,water absorption and thermal stability of bamboo fiber/PHBV composites treated with coupling agent were improved to a certain extent.（3）Fourier infrared spectroscopy（FTIR）and X-ray diffraction（XRD）analysis showed that rice husk-based SiO₂ prepared by acid pretreatment-pyrolysis at 550℃ was amorphous nano-SiO₂ with amorphous structure,and a small amount of micro-SiO₂ existed.Rice husk based nano-SiO₂ is uniform spherical particles,most of which aggregate into larger spherical clusters,and only a few are single SiO₂ nanoparticles.Adding rice husk based-SiO₂ to bamboo fiber/PHBV composites can effectively improve the mechanical properties of the composites.When the content of SiO₂ in rice husk was 1.5%,the mechanical properties of LMBPC10 composites were the best,the tensile strength and modulus were 22.20 MPa and 624.76MPa,respectively,and the flexural strength and modulus were 43.72 MPa and 1492.39 MPa,respectively.Compared with pure PHBV and without rice husk-based SiO₂,the mechanical properties of bamboo fiber/PHBV composites with different modulus grades were improved by adding rice husk-based SiO₂.（4）Bamboo fibers and rice husk-based SiO₂ were modified by silane coupling agent and rare earth coupling agent.The binding properties of bamboo fibers,rice husk-based SiO₂ and PHBV were improved significantly.The tensile strength and flexural strength of the composites reached the maximum,22.42 MPa and 47.61 MPa,respectively.The initial degradation temperature of the composites was higher than that of the untreated rice husk-based SiO₂ reinforced bamboo fiber/PHBV composites.The maximum degradation temperature was also increased,and the thermal stability of the composites was enhanced.The water absorption of the composites was also improved compared with that of the untreated rice husk-based SiO₂ reinforced bamboo fiber/PHBV composites.