Study On Acetylation And Application Of Ramie Fiber

Cellulose, the most abundant in nature, is a cheap and regenerative amylase resource. The yield of cellulose is about 1×10¹² tons formed by photosynthesis every year. The major superiority of cellulose lies in its reproducible, biodegradable, biocompatible and derivable. However, the application of the natural cellulose is far less than that of the synthesized cellulose. The environmental problem, such as greenhouse effect, air pollution, water pollution, has been got more and more attention at 21 century. In recent years, the developed countries harness the environmental problem from passiveness to empolder new production process and technology, reduce headstream and manufacture friendly environmental production. The green technology is considered the hotspot and important technological distillate of chemical engineering technique and chemical research.Ramie is a member of bast family mainly grown in temperate and tropical areas. Ramie produces one of the strongest and longest plant fibers, lustrous with an almost silky appearance. Ramie fibers are used for clothing fabrics, industrial packaging, twines, cordages, canvas, car outfits, etc. As one of the most important nature fibers, the content of celluloses in ramie is higher than the other bast fibers such as hemp, flax and jute. However, the further exploitation and utilization of ramie products are restricted by their high degree of crystallization and orientation. Therefore, modification is essential to overcome these disadvantages. The resource of ramie is abundant in China, therefore, how to utilize it efficiently and profitably is of great importance. The interest toward natural-fiber-reinforced polymers has considerably grown in recent years, and the modification of ramie fibers is proved to be feasible. The main contents of this thesis are as follows:1. In this study, the cellulose acetate (CA) was prepared by reacting ramie fiber with acetic anhydride under mild reaction conditions. The CA was characterized with transmission Fourier transform infrared spectroscopy (FT-IR) and the degree of substitution (DS) was tested. The relationship between DS and swollen conditions, reaction time, reaction temperature, the mode of precipitation was also discussed. The optimum technique conditions for preparation of CA by reacting ramie with acetic anhydride under acidic condition were determined. Reaction was carried out under the ratio of ramie to acetic anhydride and acetic acid of 1∶2.5∶4 (w/w) at 60℃for 1 h. The highest DS of 2.50 for CA was achieved under the optimum conditions.2. The CA sol-gel was added directly to the mixture of water and acetone at a room temperature. A turbid solution of CA was obtained. Then the CA panicles were separated from the turbid solution by centrifugal separator and washed to neutral with water or aqueous sodium bicarbonate. Finally, CA panicles having different shapes and diameters were obtained. The CA panicles were synthesized and characterized with transmission Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), TGA, DSC, SEM and grain size analysis. The synthesized CA panicles showed a well-distribution diameter. The property, structure and adsorption ability of CA panicles were also studied by chemical and spectroscopic techniques in this work.3. The optimum technique conditions for preparation of cellulose acetate membrane by ramie fiber and acetic anhydride under acidic conditions were determined. The reaction was carried out under the ratio of ramie to acetic anhydride and acetic acid of 1∶2.5∶4 (w/w) at 60℃for 1 h. In order to prepare membranes with improved properties, modification of cellulose acetate with polyethelene glycol (PEG Mw 600), and tributyl citrate (TBC) has been attempted. The effects of CA composition and additives concentration given by a mixture design of experiments on membrane compaction, pure water flux and water content have been studied. The thermal stability and hydrophobicity/hydrophilicity of the developed membranes prepared with PEG 600 and TBC additives have also been investigated in this paper.