Preparation And Environmental Assessment Of Ammonium Lignosulfonate/Corn Stalk Composite Boards

The production of straw-based panel has some difficult problems,such as poor compatibility between straw and adhesive,poor environmental protection of adhesive,high cost and high energy consumption in hot-pressing molding process,which seriously affect the wide range of promotion and application of straw based on panel.The research mainly focuses on the preparation and modification technology of straw wood-based panel,and the research on its preparation,modification and binding mechanism needs to be further explained.Because of its complex structure,the compound mechanism of environmental friendly ammonium lignosulfonate-based binder applied to straw-based panel is still unclear.This study for corn stalk substrate,through pretreatment and activation of modified collaborative processing corn stalk(CS),compound with oxidation modified ammonium lignosulphonate(OMLA),preparation of oxidation modified ammonium lignosulphonate/corn stover(OMLA/CS)composite boards,combination of sol-gel and UV curing technology hydrophobic modified composite boards material surface,and the environment effect of the optimized composite boards was analyzed.The pretreatment conditions on the treatment effect of wax layer and ash content of corn stalk was studied.The influence of activation modification on the chemical composition,surface elements,the microstructure of corn stalk and composite boards was compared.The effects of hydrolysis time,photocatalyst,additives added on surface hydrophobic properties of the composite boards were discussed.The mechanism of ammonium lignosulfonate and corn stalk was revealed.It provided the theoretical basis for the low carbon development and application of straw-based composite boards.The main conclusions are as follows:(1)Pretreatment reduced the wax layer and ash content on the surface of corn stalk.The effects of oxalic acid+ultrasonic pretreatment on corn stalk(CSEUS)were better and provide more reaction sites for subsequent activation treatment.Under the condition of laccase system,it effectively oxided in the maize straw lignin of aromatic ring groups.Polyethyleneimine(PEI)under the effect of glutaraldehyde crosslinking agent will amine and aldehyde group into the surface of corn stalk.The activated corn stalk has high O/C atomic ratio by laccase system(LCSEUS),and it showed that low lignin content in the sample,and after the PEI activation treatment of samples(PCSEUS),had lower O/C atomic ratio,its activation in maize straw lignin oxidation polymerization played a leading role.PEI activation effectively reduced the SiO2 content of corn stalk surface,with increasing the N content.With the increase of concentration of laccase,crystallinity,first the trend of rise and fall,and with the increase of the dosage of PEI,the crystallinity of a downward trend.The cellulose molecules of LCSEUS were naked,and cell porosity was clearly visible.Under the PEI activation treatment,corn stalk surface crosslinking material was growing.The morphology fuzzy laccase system activation treatment on the surface of corn stalk hydrophilic had a role in promoting,and PEI activation treatment only low dosage had a promoting effect,the hydrophobicity was increased with the increase amount of the PEI.(2)The suggested optimal conditions of OMLA/PCSEUS composite boards were about 160℃ for hot press temperature,5 min for hot press time and 16.0 wt.%for OMLA dosage.The mechanical properties of the composite boards can meet the requirements of particleboard under dry condition.The amino reaction of quinones or ketones in OMLA with PEI-activated corn stalk can improve water resistance and binding strength.The surface of the PEI-treated corn stalk was cross-linked with OMLA to block the water entering,which could improve the dimensional stability of the material.The surface activity of PEI-activated corn stalk was good,which was beneficial to the improvement of physicochemical properties of the composite boards.OMLA/PCSEUS composite boards had higher stiffness and stronger deformation resistance than OMLA/LCSEUS composite boards.The micromorphological results showed that PEI promoted the formation of "glue layer",and the interaction between CSEUS and OMLA molecules treated by PEI was strong,which improved the bonding performance of the interface between corn straw fibers.(3)3-(trimethoxy silicyl)propylmethacrylate(MEMO)as the precursor,was hydrolyzed in polyvinyl alcohol(PVA)solution,added different photoinitiators(1173/184),formed hydrophobic film under UV light to modify the surface of OMLA/PCSEUS composite boards.C-MEMO1173/PVA surface hydrophobicity treatment can significantly improve the surface hydrophobicity of OMLA/PCSEUS composite boards.Two different photoinitiators formed MEMO/PVA film on the surface of OMLA/PCSEUS composite boards.The hydrolysis time of 30 min and the addition of the additive chitosan promoted the cross-linking of MEMO/PVA on the surface of the composite boards The ordered interaction between MEMO and PVA molecular chains improves the relative crystallinity,but excessive hydrolysis or introduction of chitosan results in different degrees of entanglement between the molecular chains,which destroyed the degree of crystallization.MEMO in photoinitiator 1173 under the action of light initiator and composite boards surface hydroxyl and formed a solid polymer network film on its surface,after the introduction of chitosan,further reduce OMLA/PCSEUS composite boards of polymerization on the surface of the hydrophilic group and hydrophobic polymer film network structure of the hydroxyl of moisture absorption sites to keep the hydrophobic effect.The SEM of OMLA/PCSEUS composite boards after C-MEMO1173/PVA processing was better.In addition,the mechanical properties of the hydrophobic modified OMLA/PCSEUS composite boards met the requirements of using furniture particleboard in the humid state of GB/T 4897-2015,which could be applied in public humid environment such as bath furniture and toilet partition.(4)OMLA/PCSEUS composite boards had a small environmental effect.Taking OMLA/PCSEUS composite boards and traditional corn stalk-based composite boards as the research object,the environmental impact in the whole process of manufacturing of the two products was analyzed.Gabi 6.0 software was used to establish the model,and the life cycle evaluation comparison of the two products was investigated based on the ReCiPe method.The results showed that the contribution of raw material preparation and hot press molding to the environmental impact index of all end points was large,but the contribution of the late processing stage to the environmental impact index was small.As an environmentally friendly product,compared with the traditional corn stalk-based composite boards,the environmental impact index of the three types of terminals of OMLA/PCSEUS composite boards was smaller,indicating that the production of OMLA/PCSEUS composite boards was more environmentally friendly.It can replace the traditional corn straw-based composite boards.