Investigation On Separated Process Of Micro/Nano Fibrillated Cellulose And Its Properties Of Composites

In this paper, the poplar fiber selected as the main research object to preparemicro/nanofibrillated cellulose, it was pretreated by lye and then the fiber was separated withoptimizing process by synergister treatment of cellulase hydrolysis and mechanical processing.The micro/nanofibrillated cellulose were characterized as X-ray diffraction analysis, scanningelectron microscopy (SEM) analysis, infrared spectroscopy (IR) analysis and etc. The propertyof micro/nanofibrillated cellulose composites were investigated, including the optial andelectrical property of micro/nanofibrillated cellulose film, micro/nano fibrillated celluloseenhanced urea-formaldehyde, the composite film of micro/nanofibrillated cellulose andhemicelluloses and its fratures. The conclusions are listed as follows:(1) The optimal values of cellulase hydrolyzed poplar fiber are as follows: cellulaseenzyme activity is46.74FPU/g, processing time for48h,50FPU of cellulase, the ratio of solidto liquid of1:30. The cellulase hydrolyzation can get42.5%, the cellulose content is95.26%and crystallinity of fibers is89.2%after cellulase hydrolysis. The surface of micro/nanofibrilsemerge tiny fibers and fibrillation, the micro/nanofibrils are exposured on the central layer ofsecondary wall (S2) which generate mircofibrils after mechanical treatment.(2) The light transmittance is weaking as the thickness increasing of micro/nanofibrillatedcellulose film. MFC film’s transmissivity is higher than MFC’ film. The surface resistance isincreasing with the thickness of the micro/nanofibrillated cellulose film added. There is noobvious difference among micro/nanofibrillated cellulose film, rubber and PTFE etc. Thethinner of the film, the greater of the dielectric loss factor; The dielectric loss factor of MFCfilm is higher than MFC’ film; The dielectric loss factor of micro/nanofibrillated cellulose filmis highger than rubber and PTFE, but it has an equivalent factor with PVA,besides that, itsthickness is thinner than PVA. The permittivity of MFC film is higher than MFC’ film, thepermittivity of micro/nanofibrillated cellulose film could reach synthetic polymer materials’.(3) The content of hemicellulose is larger, the stronger of the composite film ofmicro/nanofibrillated cellulose. The hygroscopicity of the composite film tend to keep stabilityas the micro/nanofibrillated cellulose added to a certain amount. The composite film hasobviously change with the elongation at break as the elongation at break is less than5%, theelongation at break is laeger, the tensile strength is larger; When of the elongation at break ismore than5%, though the tensile strength is proportional to the change, the change is smaller;when the addition of micro/nanofibrillated cellulose is0.2~0.6%, the composite film’s tensilestrength and elongation at break have distinct change. When the addition ofmicro/nanofibrillated cellulose is more than0.6%, the tensile strength of the composite filmdidn’t alter significantly, the elongation at break is still rising. The elongation at break of thecomposite film got7.12%and the tensile strength decreased at54.66MPa (fell by2.7%) whenthe addition of micro/nanofibrillated cellulose is more than1%, the composite film has higher rigidity and lower plasticity.(4)The modified urea-formaldehyde viscosity has a downward trend as the increasingcontent of micro/nanofibrillated cellulose. When the fibrils reach1%of urea-formaldehyde (UF)solid content, the viscosity of the two kinds of the modified UF resin are down significantly.With self-made micro/nanofibrillated cellulose (MFC) and purchased micro/nanofibrillatedcellulose (MFC’) keep adding, the formaldehyde emission of plywood is smaller and smaller,when the fibrils reach1%, the emission meet for E1grade; The formaldehyde emission hasbroad difference as adding the same amount of MFC and MFC’. The bond strength of plywoodis gradually rising which used modified UF with the incresing of fibrils; But as fibril contentreaches1%, the bond strength is less obviously rising. The bond strength of MFC enhanced UFis better than MFC’ enhanced UF. The system of UF has C-O stretching vibration absorptionpeak after micro/nanofibrillated cellulose added, it is a new characteristic Peak, this shows thatmicro/nanofibrillated cellulose have been introduced into the UF system.