Preparation And Performance Regulation Of Dust-proof And Sand-fixing Environment-friendly Liquid Mulch Film

Traditional plastic films have offered undeniable benefits for agriculture production.Nevertheless,non-degradable plastic films caused serious white pollution,which has become a threat to human health and environmental quality.Recently,the eco-friendly and biodegradable liquid mulching film as an alternative to the traditional plastic film has aroused human extensive attention.The biggest advantage of liquid mulching film is that it can form a film on irregular surfaces in comparison with the traditional plastic film,which can be used in desertification environment and dust areas.At present,the liquid mulching film had some defects in mechanical properties,water resistance and sources,which restricted the development of liquid mulching film.In this paper,natural polymer materials such as starch,lignin etc were used as raw materials.Through blending and grafting modification methods,the performances of the liquid mulching films were regulated.Preparation of liquid mulching film which are easy to produce and apply,are biodegradable,reduce PM2.5,are anti-erosive,dust suppression,and sand fixating.The main content of this paper is as follows:Firstly,the starch/lignin based liquid mulching film(CLS film)was prepared by blending cationic starch(CS)and sodium lignosulfonate(LS)with glycerol as plasticizer.The effects of regulating CS,LS and glycerol concentration on the mechanical properties and viscosity of the CLS film were investigated.The CLS films were characterized and regulation in terms of contact angle,light transmittance,degradation performance,erosion resistance performance,SEM,TG,ATR-FTIR and transmitted polarized microscope.The results showed that the optimal composition of CLS films was as follows: 3%(CS),0.6%(LS),1%(glycerol).At this point,the CLS film had a tensile strength of 2.46 MPa,an elongation at break of 14.66%,a viscosity of 63.5m Pa·s,and a contact angle of 48.024°.The degradation rate of CLS film after 90 days was 81.34%.Transmission polarized microscope could observe that the sand particles were closely adhered to each other and the surface of the sand particles formed a similar network structure.The CLS film had good UV resistance,thermal stability,and anti-erosion,could achieve the effect of dust suppression and sand fixation.Secondly,the dust suppression and sand-fixation liquid mulching film was prepared via a facile secondary spraying process.Water polyurethane(WPU)was blended with dissolved humic acid(HA),and then the blend solutions(HWPU)were sprayed on the surface of CLS film to prepare starch/lignin-HA/WPU liquid mulching film(CLS-HWPU film).The effects of regulating the composition of liquid mulching film on the mechanical properties under dry and wet states of the CLS-HWPU film were studied.The CLS-HWPU films were characterized in terms of contact angle,light transmittance,degradation performance,erosion resistance performance,SEM,TG,ATR-FTIR and transmitted polarized microscope.The results showed that the optimal composition of CLS-HWPU film was: 3%(CS),0.9%(LS),1.5%(glycerol),2%(HA),and 30%(WPU).At this point,the tensile strength of CLS-HWPU films under dry and wet states was 8.76 MPa,4.31 MPa,elongation at break was 147%,124.2%.The contact angle of CLS-HWPU film was48.024°,and the degradation rate of film after 90 days was 76.35%.SEM results showed that the addition of HWPU solution could make the surface of the film smoother and improved the water resistance of the film.Transmission polarized microscope could observe that the sand particles were more closely bonded to each other,with almost no gaps and stronger stability.The CLS-HWPU film had good UV resistance and thermal stability.Compared with CLS film,the mechanical properties,surface hydrophobicity and erosion resistance performance of CLS-HWPU film were significantly improved.Thirdly,LS and acrylic acid(AA)were grafted copolymerized by using ammonium persulfate as initiator to obtain the graft product LS-AA.The effects of regulating reaction time,reaction temperature,monomer dosage and initiator dosage on the grafting rate and grafting efficiency were investigated.The optimal grafting conditions were determined as follows: 2.5h(reaction time),80℃(reaction temperature),5/5(mass ratio of AA to LS),initiator dosage 1% of monomer dosage.Under these conditions,grafting rate and grafting efficiency were 24.24% and 30.30%.The CLS-AA film were prepared by blending CS and LS-AA with glycerol as plasticizer.Then WPU was blended with dissolved HA,and the blend solutions were sprayed on the surface of CLS-AA film to prepare starch/modified lignin-HA/WPU liquid mulching film(CLS-AA-HWPU film).The effects of regulating LS-AA concentration on the mechanical properties,viscosity and contact angle of the CLS-AA-HWPU film were studied.The CLS-AA-HWPU films were characterized in terms of light transmittance,degradation performance,erosion resistance performance,SEM,TG,ATR-FTIR and XRD.The results showed that the optimal concentration of LS-AA was 0.9%.At this point,the tensile strength and elongation at break of CLS-AA-HWPU film were 4.14 MPa,15.34%,the viscosity of CLS-AA film was 25 m Pa·s,the contact angle value was 44.105°.The degradation rate of CLS-AA-HWPU film after90 days was 64.75%.FTIR indicated that LS and AA were grafted successfully.XRD showed that the crystal structure of LS-AA has changed.CLS-AA-HWPU film had good UV resistance,biodegradation,thermal stability,and anti-erosion.After graft modification,the viscosity and anti-erosion resistance of CLS-AA-HWPU film were further improved.The viscosity and anti-erosion resistance of liquid mulching film are important factors to evaluate the liquid mulching film.Considered the viscosity and anti-erosion resistance of liquid mulching film,CLS-AA-HWPU film had the optimal performance.