Study Of The Preparation And Application Of Cellulose Nanofibers

Cellulose nanofibers (CNFs) are a kind of nanoscale polymer materials extracted from natural cellulose, having wider availability, low-cost, non-toxic, biodegradation, and good biocompatibility. CNFs have drawn increased attention because of their unique characteristics, such as large surface to volume ratio, high crystallinity, high reactivity, small size effect, quantum tunnel effect and excellent mechanical properties including high tensile strength and high Young’s modulus.In this paper, we combined high pressure homogeneous technology and chemical treatment to prepare cellulose nanofibers from sugar beet pulp. Then, the performance of the CNFs were investigated. The results indicated chemical treatments can effectively remove the pentin, hemicellulose and lignin contents from the amorphous area, lignin content was completely removed, hemicellulose content was reduced from25.40%to7.01%, and cellulose content was increased from44.96%to82.83%. High pressure treatment destroyed the cell wall, and cellulose nanofibers were released. The diameter of CNFs ranged from<10nm to70nm. The crystallinity of the cellulose nanofibers increased from39.96%to77.89%, the thermal degradation temperature of cellulose nanofibers was increased from224.4℃to.272.7℃.The plastic starch/cellulose nanofibers composite films (PS/CNFs) were prepared using solution casting method. The morphology, crystallinity, hydrophilic, water permeability, opcity and thermal stability of the PS/CNFs films were investigated. The results indicated no large aggregates and a homogeneous distribution of the CNFs in the starch matrix were observed when the CNFs content was less than15%, this is due to the good affinity between CNFs and plastic starch matrix (starch and plasticizer). The distribution of CNFs in the composite films containing20%CNFs was worse than their distribution in films containing15%or less of CNFs. This can be attributed to the agglomeration of CNFs. CNFs increased the crystallinity and Tg (from39.56℃to57.35℃), and CNFs significantly decreased the hydrophilic (contact angle increased from49.46°to88.57°), water permeability (WPVT value decaresed from4.734×10-7g. Pa-1.h-1.m-1to3.001×10-7g. Pa-1. h-1.m-1) and opcity (opacity values increased from101.25AU. nm to218.71AU. nm).We used DMA to investige the storage modulus (G’) and loss modulus (G"), creep and creep-recovery behavior of the PS/CNFs nanocomposite films. The results indicated the stoage modulus increased with the increase of the CNFs content, and the creep deformation, creep compliance, and irreversible deformation decreased with the increase of the CNFs content until the CNFs content reached15%. Power law and Burgers model were capable (R2>0.981) of fitting experimental G’ versus angular frequency and creep strain versus time data, respectively.Cellulose fibers were obtained from corncob by using microwave-assisted chemical treatments. The morphology, chemical structure, degree of crystallinity and thermal degradation characteristics of the resultant cellulose fibers were studied by using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results indicated the diameter of the cellulose fibers ranged from10μm to20μm. Hemicellulose content was reduced from42.25%to10.68%, lignin content was reduced from10.78%to2.21%, and cellulose content was increased from40.16%to86.18%. The crystallinity of the corncob cellulose fibers increased from32.7%to73%, and the thermal degradation temperature of cellulose fibers was increased from235℃to262℃.