Preparation And Performance Control Of Degradable Mulch Film Based On Tea Residu

The long-term overuse of traditional plastic mulch has brought serious problems to environmental protection and agricultural production.In order to solve the above problems,the eco-friendly degradable mulch has attracted wide attention.In this paper,a variety of degradable materials such as tea waste,polyvinyl alcohol(PVA),cellulose and its derivatives were used as raw materials for the preparation of mulching film.The effect of the concentration of each component on the properties of the prepared mulching film was studied by modifying methods such as blending,dipping and crosslinking,and the degradable mulching film with excellent mechanical properties,good water resistance,strong UV resistance and stable performance was prepared.This thesis mainly research contents are as follows:Firstly,the tea waste was divided into two parts through a certain pretreatment process:filtrate and filter residue.The filtrate was mixed with PVA/ polyvinyl oxide(PEO)solution and sprayed to get liquid mulching film(LMF).By studying the influence of tea waste concentration during pretreatment and PVA concentration on the viscosity,mechanical properties,thickness,water content and water solubility of LMF,the optimum conditions for preparation of LMF were determined.The light transmittance,water resistance,degradation and aging resistance of LMF were studied.The results showed that the integrated performance of LMF was the best when the concentration of tea waste was 5%,the composition of LMF was5% PVA,50% tea residue filtrate and 0.02% PEO.At this time,the viscosity of the filmforming solution was 42.533 m Pa·s,and the thickness,water content and water solubility of LMF were 0.321 mm,25.14% and 4.04%,respectively.The tensile strength and elongation at break of LMF in dry state reached 9.46 MPa and 297.25%,and the tensile strength and elongation at break of LMF in wet state reached 7.68 MPa and 314.66%.The light transmittance of LMF was less than 3%,and the weight loss rate reached 71.3% in 100 days.In addition,transmission polarization microscopy showed that the components of LMF had good compatibility,and there were no obvious defects in LMF.According to other relevant tests and characterization,LMF had excellent thermal stability,UV resistance and water resistance.The liquid mulching film prepared with tea waste and PVA as raw materials has wonderful comprehensive performance,which is conducive to promoting the application of biomass materials in agriculture.Secondly,the tea waste filter residue was evenly dispersed in the cellulose solution,the base film(TBF)was prepared by phase transformation method,TBF was impregnated with sodium alginate/agar/glycerol mixture and then transferred into calcium chloride solution to get solid mulching film(SMF).The effect of the concentration of each component on the thickness,water content,water solubility and mechanical properties of SMF were discussed.The light transmittance,degradation and artificial aging of SMF were studied.The SMF was characterized by SEM,FTIR,contact angle,TG and XRD.When the composition conditions of SMF were 2% tea waste filter residue,3% cellulose,1% sodium alginate,0.2% agar and 1.5%glycerol,the thickness of SMF was 0.089 mm,the water content was 6.5%,and the water solubility was 0.85%.The tensile strength and elongation at break of SMF under dry condition were 56.47 MPa and 3.85%,and under wet condition were 10.49 MPa and 5.41%.In this case,the comprehensive performance of SMF was the best.SMF had good UV resistance,water resistance,heat stability,aging resistance and degradation performance,100 days weight loss rate reached 87.6%.Solid mulching film made from natural polysaccharide polymers such as tea waste and cellulose has the advantages of no pollution,easy biodegradation,and has important environmental protection significance.Thirdly,the tea waste was made into slurry by alkalization and bleaching.Tea waste slurry was reinforcement,sodium carboxymethyl cellulose(CMC)was crosslinked with glutaraldehyde and borax,and the degradable mulching film(DMF)was prepared by pouring method.The optimal crosslinking time and temperature were determined by orthogonal experiment as 60 min and 60℃,respectively.The effect of the concentration of each component on the mechanical properties,thickness,water content and water solubility of DMF were discussed.The properties of DMF,such as light transmission,aging resistance,degradation,FTIR,SEM,contact angle,TG and XRD were tested and chemically characterized.The mechanical properties of DMF was the best when the concentration of DMF components was0.5% CMC,50% tea waste slurry,3% glutaraldehyde and 1.5% borax.The tensile strength and elongation at break of DMF reached 16.77 MPa and 11.34%(dry)and 15.41 MPa and 15.66%(wet),respectively.The thickness,water content and water solubility of DMF were 0.215 mm,18.34% and 2.57%,respectively.The transmittance of DMF in UV band was less than 2.64%,and the anti-UV performance was good.The contact angle of DMF was 80.62°,and the weight loss rate reached 69.4% after 100 days of degradation.The degradable mulching film prepared from tea waste and CMC has excellent comprehensive performance,which not only makes full use of biomass materials,but also provides a new way for its development and application.The degradable mulch prepared by the three methods has good comprehensive performance,and realizes the high-value utilization of biomass materials and the replacement of traditional mulch.