Modification Of Bagasse By Mixed Esterification And The Preparation And Performance Of Superhydrophobic-flame Retardant Composites

Petroleum-based composites have been developed rapidly owing to their excellent properties,but the consumption of resources and damage to the environment are irreversible.A large number of researches in recent years indicate that lignocellulosic biomass can be used to prepare high-performance bio-based composites via esterification,etherification,graft modification,etc.,which are expected to be widely used instead of petroleum-based composites.Bio-based composites have the advantages of wide sources,low price,renewability,natural degradation,and simple modification process.However,the current bio-based composites still exhibit the shortcomings,including poor processing performance,fragility,flammability,and easy moisture absorption and decomposition,which are difficult to practical application.To improve the application performance of bio-based composites,this study proposed the use of mechanically activated solid-phase co-reactant method to prepare highly thermoplastic cellulose acetate oleate(CAO)and esterified bagasse(EB),and magnesium hydroxide(MH)was synthesized by hydrothermal method and was hydrophobically modified with oleic acid(OA)to prepare OA-modified MH(O-MH).(O-)MH/CAO and(O-)MH/EB composites were prepared respectively.The effects of hydrophobic modification and additive dosage on the mechanical properties,flame retardancy,and thermal stability of different composites were investigated.Nano-silica/octadecyl trichlorosilane(NS/OTS)superhydrophobic coating was constructed on the surface of O-MH/EB and the properties were studied.The main research contents and results are as follows:(1)CAO was prepared by mechanically activated solid-phase co-reactant method with bagasse cellulose as raw material,OA as esterifying agent,and acetic anhydride as co-reactant.MH was synthesized by hydrothermal method and was modified with OA to prepare O-MH.MH/CAO and O-MH/CAO composites were prepared by hot pressing method,and ~1H-NMR,XRD,FTIR,SEM,TGA,mechanical properties test,and flame retardancy performance test were used to analyze the structure and properties of the samples.The results show that the increase in the amount of OA led to the increase in the degree of substitution of oleoyl groups and the thermal stability of CAO,and the mechanical properties increased first and then decreased.The optimal molar ratio of cellulose:acetic anhydride:OA was 1:6:0.3.With the increase of MH content,the flame retardancy of MH/CAO composite increased,while the thermal stability and mechanical properties of MH/CAO composite gradually decreased.The effect of O-MH on improving the flame retardancy and thermal stability of O-MH/CAO composite was significant.The mechanical properties of O-MH/CAO composites increased and then decreased with the increase of O-MH content.15O-MH/CAO composite(O-MH addition amount of 15 wt.%)exhibited the best mechanical properties.(2)EB was prepared by mechanical activation solid-phase co-reactant method(molar ratio of acetic anhydride:OA was 6:0.3),and MH/EB and O-MH/EB composites were prepared by hot pressing method.XRD,FTIR,SEM,TGA,and mechanical properties test,and flame retardancy performance test were used to analyze the structure and properties of the samples.The results show that the lower the addition amount of bagasse,the more complete the reaction,but the mechanical properties and thermal stability of EB decreased,and the overall performance of EB with the bagasse amount of 70 g was the best.With the increase of MH addition amount,the flame retardancy performance and thermal stability of MH/EB composites improved,while the mechanical properties increased first and then decreased.10MH/EB composite(MH addition amount of 10 wt.%)exhibited the best mechanical properties.With the increase of O-MH content,the flame retardancy performance and thermal stability of O-MH/EB composites enhanced,and the mechanical properties enhanced first and then decreased.The mechanical properties of 15O-MH/EB(O-MH addition amount of 15 wt.%)exhibited the best mechanical properties.The dispersion of O-MH in EB was much better than that of MH,contributing to better flame retardancy,thermal stability,and mechanical properties of O-MH/EB composite than those of MH/EB with the same addition amount.(3)Using ethyl acetate as solvent and polydimethylsiloxane as silane coupling agent,the NS/OTS super-hydrophobic coating was constructed on the surface of 15O-MH/EB composite,and the microscopic morphology of the coating was analyzed by SEM.The super-hydrophobic performance of the coating was characterized by water contact angle test.The results show that the NS/OTS super-hydrophobic solution formed a stepped multi-level rough structure on the surface of 15O-MH/EB composite.The optimal preparation conditions for super-hydrophobic coatings were as follows:the addition amount of nano-silica was 2 mg/?L,the number of spraying layers was 4,and the dehydration temperature and dehydration time were 120°C and 2 h,respectively.The super-hydrophobic coating was resistant to strong acids and alkalis,and had no negative effect on the flame retardancy and mechanical properties of the composite.