Study On Preparation And Multifunctional Of Larch Special Wettability Surface

Wood has been widely used for a long time with the advantages of simple processing,high mechanical strength and sustainable utilization.However,wood absorb water easily because of the large number of free hydroxyl groups exist on wood surface.The absorption and evaporation of water will lead to wood dry shrinkage and wet expansion,resulting in cracking,warping and deformation.In order to overcome the inherent defects of wood and prolong the service life of wood,scholars have prepared hydrophobic wood through various technical methods,and give it multiple functions according to the needs.Many organisms in nature exhibit special surface wettability,and the bionic wettability surfaces can be prepared according to the structural characteristics.The construction of multifunctional special wettability wood surface can not only make up for the inherent defects of wood,improve the dimensional stability and antibacterial properties of wood,but also broaden the application field of wood.Zinc oxide(Zn O)is a cheap and environmentally friendly material with antibacterial and photocatalytic properties.When combined with the wood,the roughness of wood will increase and the hydrophobic property will be obtained.Nevertheless,there are still some problems which need to be solved in the current research on superhydrophobic wood,such as weak interface between the hydrophobic layer and the substrate,poor weatherability and durability of the hydrophobic layer,and high cost of hydrophobic treatment.In this paper,nanometer Zn O was deposited on the surface of larch by hydrothermal method,and the wettability of Zn O wood was studied.In the preparation of superhydrophobic wood surface and reversible wettability surface,the influence of pretreatment methods on wettability and durability of Zn O wood were mainly discussed.In the construction of wood surface with hydrophilic and hydrophobic uneven wettability,the optimum hydrothermal reaction conditions for achieving uneven wettability were probed.In the preparation of superhydrophobic antibacterial wood,the effect of nano-Zn O morphology on antibacterial properties and antibacterial mechanism were explored.Specific research methods and results in this paper include:(1)The superhydrophobic wood was prepared by pretreating wood preferentially and then growing nanometer zinc oxide on the surface of pretreated wood by hydrothermal method.The durability and self-cleaning ability of its hydrophobic surface were tested.The test results exhibited that the surface contact angle of the pretreated Zn O wood was greater than 150°,showing superhydrophobic property.SEM images showed that compared with the untreated wood,the surface roughness of the pretreated wood increased and the distribution of nanometer zinc oxide was more dense.The Zn O on the surface of the hydrothermal pretreated wood was arranged in rod-like structure.The results of wear test and light test indicated that the surface wear resistance and light aging resistance of wood treated by hydrothermal method were the optimum.In addition,it was found that the superhydrophobic Zn O wood not only has excellent self-cleaning ability,but also its surface wettability can be reversibly changed under the switching of light and heat.After exposure to light for 6 h,the surface wettability of superhydrophobic wood changed to superhydrophilic,and recovered to superhydrophobic state after heating at 150~oC for 30 min.This wettability transformation process was repeated for five times,and the wood surface remain had satisfactory reversible wettability.(2)Based on the unique structural difference between early wood and late wood,the wood surface with hydrophilic and hydrophobic uneven wettability was prepared by deposition of nanometer Zn O particles on wood surface by hydrothermal method.Through the single control variable method,the optimum growth conditions of Zn O were selected by taking hydrothermal temperature(80~oC,90~oC,100~oC,110~oC)and time(1 h,4 h,6 h,10 h)as control variables.SEM images showed that the structure of nano-Zn O was affected by hydrothermal temperature and time,and there were differences in the distribution of early wood and late wood.Under the same hydrothermal reaction condition,Zn O was more distributed in early wood.Moreover,the distribution difference of Zn O particles on early wood and late wood was the most obvious when the hydrothermal temperature was 90~oC and the time was 4 h.The results of XRD and FTIR tests revealed that the surface of wood was successfully loaded with Zn O particles.The distribution of zinc on early wood and late wood was observed by EDS,and the distribution of zinc on early wood was significantly more than that on late wood.The surface wettability test indicated that the contact angle of early wood was(129.3±5.5)°,showing hydrophobicity,while the contact angle of late wood was(57.0±8.0)°,showing hydrophilicity,which displayed obvious wettability difference between early wood and late wood.(3)The superhydrophobic antibacterial wood was prepared by adding polyethylenimide(PEI)with different concentration in the process of hydroheat treatment of pretreated wood.The influence of PEI concentration on the morphology of nano-zno particles was investigated.The contact angle,self-cleaning and durability of the surface of zinc oxide wood were tested,and the antibacterial ability of zinc oxide wood was observed by bacteriostatic zone method.SEM images showed that the Zn O structure without PEI was hexagonal prism,and the particle size of Zn O decreased with the increase of PEI concentration.When 6 mmol/L PEI was added,the Zn O changed into a conical structure.Contact angle test results indicated that the contact angle of zinc oxide wood was greater than 150°,and it had superhydrophobicity.In the meantime,superhydrophobic wood also qualified with self-cleaning ability and good durability.The antibacterial performance test results revealed that the superhydrophobic Zn O wood prepared with 6 mmol/L PEI had better antibacterial performance.In addition,the antibacterial activity of Zn O against gram-positive bacteria(S.aureus)was better than that of gram-negative bacteria(E.coli).