Research On Microcosmic Mechanism Of Cellulose Structure In Cotton And Baster Fiber Based On Molecular Simulation

With the rapid development of global economy, there is a growing preference for natural fibers with excellent wear abilities. The natural fibers of cotton and flax have a lot of advantages, such as comfort and good moisture absorption, but defects such as wrinkling and shrinking have restricted the development of cotton and fiber products. After anhydrous ammonia treatment, natural curl can been totally eliminated, section become rounder, inner cavity is smaller, and surfaces are smoother and brighter. However, different temperatures and pressures have a great influence on the behavior of ammonia in cellulose. Therefore, based on the microstructure of cotton and baster fiber, changes of lattice structure after ammonia treatment are analyzed under different temperatures and pressures. And then interaction mechanism between ammonia and cellulose can be revealed, guiding the production practice well.Although many scholars has revealed the related changes after ammonia treatment from the experimental point of view, the microscopic mechanism between ammonia and cellulose has not yet been clearly explained. With the improvement of the level of computer technology, the development of molecular dynamics simulation techniques provides a new research ideas and methods.In this article, interaction mechanisms between ammonia and cellulose1β are studied using molecular dynamics simulation. The main contents are as follows:1. To analyze the structure and properties of cellulose1β, the model of cellulose1β is established in Chapter3. It has been verified by thermal expansion and X-ray diffraction diagram, which also prove that the force field PCFF and the step1fs are reasonable. The Mulliken population is computed at room temperature; hydrogen bonds and movement of center chain were studied over the range300-550K using PCFF force field by Materials Studio.2. To study the interaction between ammonia and cellulose1β, the system of cellulose non-ammonia and system of cellulose with ammonia are built in Chapter3. After obtaining the optimal model, the simulation has been done under different temperatures and pressures in these two systems. The changes of supple performance, diffusion behaviors and hydrogen bonds are researched.3. To explain the role of ammonia molecules on cellulose from macro view, the flax fibers has been treated by ammonia in Chapter5, obtaining the modified flax fiber. Then the X-ray diffraction patterns, infrared spectra, physical and mechanical properties of the flax fibers are got respectively.