Study On The Biodegradability Of Cellulose Fibers

As one kind of natural renewable macromolecule materials, cellulose massively exists in the green plants, which is the inexhaustible resource in nature. The cellulose fibers have a lot of excellent properties, such as good skin contact, wearing comfort, easy biodegradation and so on. The use, treatment and research of cellulose fibers are an important content of the current green textile. Today, the environmental load is increasingly aggravation, how to use the fibers'degradation characteristics to degrade fibers into low molecular substances through simple processing. It is very meaningful from the angle of waste utilization and environmental protection.The natural cellulose fibers and regenerated cellulose fibers were taken as the research objects, with the self-designed biodegradation device, the biodegradabilities of cellulose fibers in the river activated sludge and mulberry field soil were investigated. Effects of degradation time, temperature, whether enwrapping the nylon net or not on degradation of fibers were analyzed. The microorganisms'contents of the activated sludge used in the experiment respectively were:bacteria 1.9×107 CFU·g-1,fungi 5.1×103 CFU·g-1,actinomycete 8.8×104CFU·g-1. While the microorganisms'contents of the soil respectively are:bacteria 1.1×107 CFU·g-1,fungi 9.2×104CFU·g-1,actinomycete 1.5×105CFU·g-1.Biodegradability of cellulose fibers in activated sludge:Biodegradability of natural cellulose fibers and regenerated cellulose fibers was investigated by the activated sludge-burial test in condition of detest oxygen.The relations between the degradation rates, morphological structures, crystalline structures, thermal properties and mechanical properties of these fibers and the degradation time and temperature were analyzed. On the basis of it, the influence of enwraping the nylon net or not to biodegradabilities of these fibers were further analyzed. The results showed:The cellulose fibers were buried in activated sludge in 35℃. The degradation rates increased gradually as the degradation time developed, the degradation rates of regenerated cellulose fibers were higher than natural cellulose fibers. The fibers became yellow, displayed a lot of traces bited by microbes, even some tiny cavities and cracks. A new diffraction peak was appeared in 2θ=26.5°of the X-ray diffraction intensity of the fibers. The degrees of crystallinity and thermal stabilities of these fibers were fluctuated. The mechanical properties of the yarns dreased sharply after burying one week. The decreasing rate of breaking strength and initial module of yarns achieved 60%, the decreasing rate of breaking strength and breaking elongation of regenerated cellulose fibers achieved 90%; while bamboo pulp and Viloft could not obtain the suitable sample with the mechanical property test.After burying in activated sludge in 35℃, 40℃and 45℃, the regenerated cellulose fibers generally had more significant degeneration rate than the natural cellulose fibers. With the increase of the temperature, the fiber became yellow. The hole and crack number and breakage appeared in the fiber surface in 35℃and 45℃than that in 40℃.Accordingly, the decreasing degree of mechanical properties was greater. The change of fiber's crystal structure is not obvious, the degree of crystallinity of natural cellulose fibers increased, while the degree of crystallinity of regenerated cellulose fibers decreased.Whether enwrapping the fiber with nylon net or not has certain influence to its degradability. Compared with enwrapping the fiber with nylon net, the degradability of the sample which was not enwrapped the nylon net was fierce, yarns became yellow, fiber's surface appeared holes and ruptures. After burying two weeks, the new diffraction peak was appeared in 2θ=26.5°, the degrees of crystallinity of these fibers were lower, the decreasing rate of mechanical properties of the yarns was higher.Biodegradability of cellulose fibers in soil:Biodegradability of natural cellulose fibers and regenerated cellulose fibers was investigated by the soil-burial test, and effects of degradation time and temperature on degradation rates, morphological structures, crystal structures and mechanical properties of these fibers were analyzed. The results showed:The yarns were buried in soil of 35℃. As a function of the degradation time, the degradation rates increased gradually; the fibers became brown and displayed a lot of tiny cavities and cracks. Two new diffraction peaks were appeared in 2θ=26.5°and 29.4°, the degrees of crystallinity of the fibers and the degradation time have no clear regularity. The mechanical properties of the yarns dreased sharply.With the increasing of the buried temperature, the degradation rates of the fibers decreased at first, and then increased. After buring in soil in 35℃, 40℃and 45℃four weeks, the fibers respectively became brown, tan, light yellow and displayed a lot of tiny cavities and holes. When the temperature was 40℃, the fiber's damages were less, the samples which could be tested the mechanical properties were obtained. The changes of aggregation structure of the fibers in 35℃are bigger than 40℃and 45℃.