| Lignocellulosic fiber is a kind of abundant resource in nature,which has been widely concerned and applied because of its low density,low cost and biodegradation.As an important basic property of fibers,the fiber deformability affects the bonding properties between fibers and the physical properties of paper products.In this paper,the chemical components in cell wall of lignocellulosic fibers were controlled to study the fiber deformation and the related response mechanism of the deformation behavior of lignocellulosic fibers to the interfiber bonding properties.Firstly,chemical(sodium chlorite)and biological(laccase/mediator system)techniques were used to control three fiber models with different lignin contents at about 20%,10%,5%,respectively.The lignin distribution in cell walls was determined based on the "enzymatic peeling method" and the SEM-EDS analysis.Results showed that the lignin concentrations in fiber cell walls prepared from the combined chemical and biological techniques were lower in the outer region and higher in the inner region than those from the chemical treatment only,which was due to the fact that laccase-induced lignin degradation was only limited to the outer region and not able to get into the inner region.The characteristics of the fiber model were analyzed.With the deepening of delignification,the fiber coarseness decreased significantly and the water retention value increased sharply.The lignin concentration on the fiber surface decreased,and the surface pore size increased gradually.Secondly,different methods were used to characterize the deformation properties of fiber models with different chemical components,including the fiber flexibility and the fiber collapsibility(aspect ratio of the cross section of the fiber),and the different characterization methods were compared and evaluated.The result showed that the deformability of fibers increased gradually after delignification,and the deformability of fibers from chemical treatment changed more,indicating that the lignin distribution in the cell wall has influence on the fiber deformability.Finally,the response mechanism of the deformability of fiber models with different chemical components to the bonding properties of fiber network was described.Based on the analysis of the deformability of fibers,the relationship between the chemical components,their distribution and the deformability with bonding properties of fibers is discussed.The results showed that with the improvement of the fiber deformability,there were more bonding points,and the shear bonding strength(b)increased by 11.93 MPa and 13.00 MPa,respectively.At the same time,the relative bonded area(RBA)increased by 33%and 28%,resulting in the increase of the bonding strength index(B).And the tensile index showed an upward trend,while the bulk of fiber network(hand sheets)decreased significantly.Therefore,the deformability of lignocellulosic fibers can be changed by adjusting the proportion and distribution of chemical components to meet the demand of different fiber-based products. |
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