纤维素辐照改性及其应用

Radiochemical upgrading of cellulose and its application

辐照技术利用电离辐射诱发物理化学反应(例如交联、聚合、接枝、降解等)对材料进行加工或改性,与常规加工方法相比,具有节能、无环境污染等特点。将辐照技术应用于纤维素改性过程近年已成为非动力核技术应用领域研究的热点之一。本工作对目前纤维素的辐照技术及其基本反应机理进行了概述,其中包括纤维素膜材料、纤维素水凝胶、纤维素微晶/纳米材料,并对纤维素辐照改性过程的辐照环境,包括溶剂、敏化剂、温度、辐照剂量、环境氛围、结晶度等进行了总结。要点:(1)分析了纤维素辐照改性的研究背景及其意义。(2)阐明了纤维素辐照聚合、交联、降解的原理。(3)对纤维素辐照改性的反应条件进行了总结。

Cellulose irradiation technology uses high-energy ionizing rays as the energy source, such asα-rays,β-rays, γ-rays, X-rays, electron beams, etc., by which, cellulose is radiated so that it produces free radicals and further initiates a series of reactions such as polymerization, cleavage, crosslinking, grafting, and so on, followed by cellulose degradation or modification. The extent of cellulose polymerization, cleavage, grafting, crosslinking can be adjusted by changing the irradiation dose and reaction conditions. Unlike traditional chemical modification methods such as thermal cross-linking and polymerization, cellulose irradiation modification technology can accomplish the modification task that is difficult to achieve by traditional methods without the addition of other catalysts or chemical reagents. The modification of cellulose using irradiation technology has the advantages of easy pretreatment and post-treatment, energy-saving, and little waste. The application of irradiation technology in cellulose modification has become a hot spot in the field of nuclear technology in recent years. Irradiation technology utilizes physical or chemical reaction induced by ionizing radiation(such as crosslinking, polymerization, grafting, degradation, etc.) to produce or modify materials, and irradiation technology is different from traditional chemical methods, which utilize the radiation of high-energy electrons or rays into the interior of matter so that they generate free radicals and initiate a series of irreversible changes that alter material properties at the molecular level. By this physical means, reactions such as cellulose polymerization, cleavage, or graft crosslinking can be achieved without the use of catalysts. More critically, the series of chemical reactions evoked under an irradiation environment is expected to provide cellulose products that are difficult to synthesize by other methods, providing opportunities for the improvement of natural cellulose with the development of new products from downstream derivatives. In this work, an overview of current irradiation techniques for cellulose and their underlying reaction mechanisms is given, which includes cellulose film materials, cellulose hydrogels, cellulose crystallites/nanomaterials, and the irradiation environment for the irradiation modification process of cellulose, including solvents, sensitizers, temperature, irradiation dose, ambient atmosphere,crystallinity, etc., is summarized.Key learning points:(1) The background and significance of irradiation modification of cellulose were analyzed.(2) The principle of irradiation polymerization, crosslinking and degradation of cellulose was expounded.(3) The reaction conditions of irradiation modification of cellulose were summarized.