Study On Properties Of Maltodextrin/1,3-dimethylol-4,5-dihydroxyethyleneurea Impregnation Modified Poplar Wood

Poplar wood(Populus adenopoda Maxim)is a low-quality,high-yield,and fast-growing material,which is of great significance for its high value-added functional improvement.The chemical modification of wood mainly involves the reaction of the chemicals with the polymer molecules in the wood cell wall to block the hydroxyl groups,thereby invigorating the cell wall or filling the cell cavity,which improving the corresponding performance of the wood.As global environmental problems become more serious,it is imperative to explore environmentally friendly modifications.This study proposes an environmentally friendly,inexpensive and renewable modifier—maltodextrin(MA),and combined with 1,3-dimethylol-4,5-dihydroxyethyleneurea(DM)to modify poplar wood,systematic evaluation and analysis.The performance of the modified material,the drying characteristics during the drying process and the optimization effect of the modified formula were systematic evaluated and analysised.And the results reached the following conclusions:(1)The modification treatment was carried out by vacuum pressure impregnation,the cheaper and environmentally friendly MA was used as a modifier,and the poplar was modified with MA and DM resin for the first time,which compared with 10%sucrose(SU).The results showed that the composite modifier was impregnated into the wood cell cavity by scanning electron microscopy(SEM)and the change of weight percent gain;the anti-swelling efficiency(ASE)was also improved,but the MA treatment was slightly lower than SU;the flexural strength modulus as well as compressive strength perpendicular to the grain increased with increasing MA concentration,but the compressive modulus and impact strength were reduced.The change of infrared spectroscopy(FTIR)also proved that MA can slow down DM and cross-linking reaction of cell wall,but also to some extent reduce the crystallinity of the crystalline region of cellulose;(2)In order to optimize the modified formula,the effect of curing agent ZnCl2 combined with 103℃ and 120℃ on the fixing rate of modified materials was discussed for the first time(103℃ curing,ZnCl2+103℃ curing,120 curing,and ZnCl2+120℃ curing were denoted as group A,B,C,and D,respectively).The results showed that group B had the highest fixation rate,but its weight leaching ratio was higher than group C;FTIR spectroscopy showed that ZnCl2 would not affect the functional groups of modified chemicals;Furthermore,the flexural strength and modulus of the group B and the compressive strength perpendicular to the grain were higher than other groups,but the compressive modulus and impact strength were slightly reduced.Meanwhile,the thermal stability and surface hydrophobicity of group B were optimized through thermogravimetric and surface wettability analysis.(3)Using 10%DM and 5%MA as the main agent,the effect of impregnation treatment on the conventional drying characteristics of poplar wood(300 mm×150 mm×25 mm)was systematically studied.Untreated materials,impregnated materials with 10%initial moisture content(MC),and impregnated materials with 20%initial MC—denoted as T1,T2,and T3,respectively.The results showed Relative to that of T1,the average drying rate of T2 was reduced by 46%,compared with T1,and that of T3 was reduced by 37%.The anti-swelling efficiency of T2 sharply increased,whereas that of T3 only slightly increased in width and thickness.The drying defects of T2 were markedly less than those of T1 and T3,attributed to the reduced residual stress and fixation of the modifier.SEM indicated that large amounts of modifiers were deposited inside the cell cavity of T2,whereas small amounts of modifiers were deposited in the cell cavity of T3.The impregnation treatment generally reduced the average drying rate and MC uniformity and delayed the decrease in residual stress;however,it reduced the number of defects in the wood and considerably improved the dimensional stability of the wood.In summary,the study demonstrated the feasibility of MA combined with DM resin to enhance poplar,which achieved similar or even better results with the same concentration of SU.Group B has the highest effective fixation rate,which acted as a curing agent for ZnCl2,and increased the interfacial properties between the modifier and the cell wall,while increasing the probability of polycondensation between the modifier and the cell wall materials.Meanwhile,the immersion treatment would reduce the average drying speed and MC uniformity,and the residual stress index also slowed down slower than the untreated material,whereas the immersion treatment could reduce the wood defects and greatly improve the dimensional stability of the wood;while the higher initial MC immersion treatment were prone to occur drying defects during the drying process.