Rong Zhou,a, Mingxia Yang,b and Haixia Zhang,c Textile College, Henan Institute of Engineering, Zhengzhou 450007, P.R. China Received: 7 April 04, Accepted: 6 May 04 Summary In this study, chemical degumming was applied to corn husks, and the optimal degumming procedure and pretreatment method were determined. Through orthogonal experiments, it was determined the optimal pretreatment parameters are: of 8 g/l, urea of 8 g/l, pretreatment temperature of 0 C and pretreatment time of 0 min. The effectiveness of this combination of parameters was validated by its resultant glial removal rate of 85.%. Keywords: Corn husks; Degumming; with hydrogen peroxide and urea; Orthogonal experiment. Introduction In recent years, along with social progress advancement, economic development, and the improvement of people s level of consumption and standard of living, consumers are pursuing more natural and healthy lifestyle, and are focusing more on green and environmental friendly clothing. A new trend in the textile industry is green products produced from natural fibers, as this kind of products are gaining more and more favors of consumers. Corn is the most commonly harvested crop in north China. Corn husks, the external skin of corn ears, are not efficiently re-utilized. Lacking a better way to dispose them, corn husks are usually burned in the field, which causes environmental pollution and is a significant waste of biomass resources. Corn husks have a high cellulose content of 60%, and the composition is to a certain extent similar to that of bast plants. The spinnability of corn husks has become a hot topic of textile research. The degumming of corn husks was a hnfzzr@6.com, b ymming@6.com, c zhanghaixia800@6.com Smithers Information Ltd., 04 investigated in this study, and it may help obtain a new type of fiber that can be used in the textile industry.. Degumming Design. Main Components of Corn Husks Literature shows that currently the raw materials of the commonly used natural plant fibers in textile production contain mainly cellulose, hemicelluloses, lignin, pectin, waxy, etc. The components of corn husks have been tested by the Henan Institute of Agriculture and compared with those of other plant fibers, with results as shown in Table. As apparent in Table, the chemical compositions of corn husks and other plant phloem are substantially the same and they basically all contain cellulose, hemicelluloses, lignin, pectin, waxy fat, water-soluble substances, etc. Corn husks have a cellulose content of about 54-58%, a lignin content of about 0% and a hemicelluloses content of about 0%. The contents of cellulose, ash, fat and wax in corn husks are similar to those in hemp, the lignin content is similar to that in cotton bast, and the hemicelluloses content is close to that in flax. Therefore, the degumming treatment to corn husks can be done in a similar way to the degumming of bamboo, hemp and cotton bast.. Degumming Design As corn husks has a high lignin content, the main objective of the degumming process is to remove lignin. Studies have shown that lignin is highly stable in acid, and using inorganic acid to treat lignin will not result in lowmolecular-weight compound, and in addition may cause reverse reaction, namely further polycondensation of lignin. Therefore, acid-free process should be considered when designing the degumming treatment. On the basis of extensive literature 4-7, as well as thorough experimental exploration and research, the corn husk degumming process was designed as follows: Sample preparation Washing Scouring Washing Playing fiber Pickling Washing Dehydration Oiling Dehydration Natural drying. Polymers & Polymer Composites, Vol., No. 8, 04 687
Rong Zhou, Mingxia Yang and Haixia Zhang Table. Major chemical components of some plant fiber materials (%) Materials Cellulose Hemicelluloses Lignin Pectin Water soluble Waxy fat Ash matter Bamboo 45-55 0-5 0-0 0.5-.5 7.5-.5 Ramie 65-75 4-6 0.8-.5 4-5 4-8 0.5-.0-5 Hemp 55-67 6-8.5 6.-9..8-6.8 0- -..6-4.6 Flax 70-80 8-.5-7 -4 - -4 0.5-.5 Jute 50-60 -8 0-5 0.5-.5-.5 0.- 0.5- Sisal 7...0 0.9. 0. Mulberry.48 8.5 7.04 6.7.47 4.49 Cotton bast 4.7 8. 8.95 6.94 9.60 4. Corn husks 54-58 8-8- -- -- < - The pretreatment before scouring can remove part of the glial, and the remaining glial may be hydrolyzed into low-molecular-weight substances that can be easily removed during scouring. Therefore, the pretreatment can reduce the work load in the souring process, improve the scouring effect, and shorten the scouring time, thereby reducing material consumption and saving energy. Through comparative tests, two relatively superior pretreatment methods were selected, the pretreatment with oxygen and the pretreatment with hydrogen peroxide and urea. To eliminate the differences caused by the different distribution of fibers in the husks, the corn husks used in the experiment were from the same origin (produced in Hebei, China), of the same species, and harvested in the same batch. In addition, all the husks were mid-layer husks with about mm bottom and mm tip cut off. In the experiment, the solutions were prepared using distilled water and tap water was used for other processes. All comparative tests were completed on the same day in order to reduce experimental error. Each group of experiments included three equal-precision repeated experiments, and the results were averaged as the experiment results. The bath ratio in the small-specimen experiments was :00, and the dry weight of the sample was g. The degumming effect can be represented by the glial removal rate. With the weight of sample before degumming denoted by W, and the weight of the degummed sample, washed to neutral, naturally dried and weighed in dry environment, denoted by W, the glial removal rate can be calculated by the following equation: Glial removal rate = W -W W 00%. for Degumming With the two selected pretreatment methods, the pretreatment with oxygen and the pretreatment with hydrogen peroxide and urea, comparative tests were conducted. The two methods are detailed as follows: The pretreatment with oxygen had the following parameters: the was 6 g/l, the temperature was 40 C, and the preprocessing time was 0 min. The pretreatment with hydrogen peroxide and urea was carried out with of 6 g/l, urea of 0 g/l, temperature of 40 C, and preprocessing time of 0 min. The scouring after both types of pretreatment was done with NaOH of g/l, temperature of 90 C, and scouring time of 0 min, with appropriate amounts of sodium polyphosphate, anhydrous sodium sulfite, ammonium oxalate, and penetrant JFC as scouring additives. The degumming results of the equalprecision repeated experiments with the two different pretreatment methods are shown in Table. It can be seen in Table that with the pretreatment with hydrogen peroxide and urea more glial can be removed from corn husks. In addition, it was observed that the obtained fibers through this pretreatment had better dispersion and whiteness than the fibers obtained through the pretreatment with oxygen. Urea is an hygroscopic organic compound with great hydration capacity, it allows the gaps between microfibers to expand during treatment, thereby further penetrating and swelling the fibers. Meanwhile, urea also reacts with the organic acids produced by fiber oxidation, neutralizing them and promoting the pretreatment process. In addition, urea can be decomposed into cyanate, which can be converted into cyanuric acid. Cyanuric acid reacts with lignin alcohol type hydroxyl and generate water-soluble isocyanates, thereby removing lignin 7. Based on above analysis, it was finally decided to adopt the method of pretreatment with hydrogen peroxide 688 Polymers & Polymer Composites, Vol., No. 8, 04
and urea for the degumming of corn husks..4 Process Optimization.4. Orthogonal Experiments The main factors of the pretreatment with hydrogen peroxide and urea that have significant influences on the corn husk degumming effect are Table. Results of experiments with different pretreatment methods methods Degumming results / glial removal rates (%) with oxygen hydrogen peroxide, urea, pretreatment temperature, and pretreatment time. With these four factors as the test factors, and three different values selected for each factor, L 9 ( 4 ) orthogonal experiments was conducted to optimize the process parameters of the pretreatment. In order to exclude the influence of other factors, all scouring processes were done with NaOH with hydrogen peroxide and urea 65. 7.68 69. 70.90 65.64 7.74 Average glial removal rate (%) 66.76 7.44 of g/l, temperature of 90 C, and scouring time of 0 min. During the design of the factor levels in the orthogonal experiments, the degumming processes of bamboo, hemp and other plants were referenced, and the feasibility and cost of production were also considered. The determined values of the parameters shown in Table. The experiments were divided into nine groups. To ensure that accuracy of experiment results, two equal-precision repeated experiments were performed for each group, and the results were averaged as the experiment results. The experimental design and the obtained results are presented in Table 4. In Table 4, ki is the arithmetic mean of the glial removal rates when all levels of one factor are i. R is the range, and R= -MAX{k,k,k}-MIN{k, k,k}. Table. Factor levels for the orthogonal experiments Factors Levels A /g L - B Urea /g L - C temperature / C 4 6 8 8 0 0 0 40 D time/min 0 0 0.5 Data Analysis The tests data in Table 4 were analyzed and the analysis is detailed as follows: Range analysis determines the significance of the influence of each factor on the degumming effect. Larger range indicates Table 4. Retreatment test scheme and results Test No. A /g L - B Urea /g L - 4 5 6 7 8 9 k k k (4) (6) (8) 76.4 76.96 77.4 (8) (0) () 77.96 77.6 74.85 C temperature / C (0) (0) (40) 8.0 76.4 7.99 D time /min (0) (0) (0) 75.90 76.75 77.80 Range R.00. 8.04.90 Main Secondary CBDA Optimal scheme ABCD Glial removal rate /% 80.69 76.59 7.44 78.70 7.0 79.5 74.50 8.5 7.97 Polymers & Polymer Composites, Vol., No. 8, 04 689
Rong Zhou, Mingxia Yang and Haixia Zhang that the factor s variation in the tested scope will result in a greater variation of the index value. As the data in Table 4 show, the influencing factors of the corn husk degumming can be arranged in descending order of their influences as C B D A, which means the pretreatment temperature is the primary influencing factor. The effect of each factor was also analyzed. Figure presents the glial removal rate of each experiment, and Figure illustrates the trends of each factor s influence on the glial removal rate. Figure. Glial removal rates of the experiments Figure. Trends of factors influences on glial removal rate Combining range analysis with the diagrams in Figures and, it was determined that the combination of factor levels with the highest glial removal rate is A B C D, whereas the combination with the lowest glial removal rate is A B C D. Increasing the hydrogen peroxide in the pretreatment will result in better whiteness of the fibers and higher glial removal rate, yet overly high hydrogen peroxide will reduce the fibers tolerance to the chemicals in the subsequent processes. Likewise, reducing the urea appropriately will result in higher strength of the fibers, yet overly low urea will cause poor dispersibility of the fibers as well as lower glial removal rate. Temperature has the greatest influence on glial removal rate, and lower temperature leads to higher glial removal rate. The nine groups of orthogonal experiments did not include the test with the optimal factor level combination of A B C D, thus three equal-precision experiments were performed and the obtained average glial removal rate was 85.%, which is superior to those of the nine groups of experiments. Therefore, it was confirmed that the optimal technical parameters for the pretreatment with hydrogen peroxide and urea are: of 8 g/l, urea of 8 g/l, pretreatment temperature of 0 C and pretreatment time of 0 min.. Conclusions The chemical composition of corn husks is substantially the same with those of other plant phloem. They basically all contain cellulose, hemicelluloses, lignin, pectin, waxy fat, water-soluble substances, etc., where the cellulose content in corn husks is about 54-58%. The degumming of corn husks is mainly to remove the lignin. Through experimental study, it was concluded that using pretreatment with hydrogen peroxide and urea can help remove more glial, while resulting in better whiteness and dispersion of the fibers. The optimal pretreatment parameters are: of 8 g/l, urea of 8 g/l, pretreatment temperature of 0 C and pretreatment time of 0 min. Acknowledgment This work is supported by Henan Engineering Laboratory of New Textile Product Development, Henan Collaborative Innovation Center of Textile and Garment Industry and Henan Scientific and Technological Fund Project, and the paper is one of the achievements of the above projects. References. Zhengfeng Zhu and Xinlei Dong, Zhongyuan University of Technology master's degree thesis, In Chinese. 50 (008) 9-8.. Mingxia Yang and Rong Zhou, Advanced Materials Research, 7 (0) 4-47.. Xiaofeng Song, Yali Wang, and Yan Jiang, Changchun University Of Technology. In Chinese. 6 (005) -. 690 Polymers & Polymer Composites, Vol., No. 8, 04
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Rong Zhou, Mingxia Yang and Haixia Zhang 69 Polymers & Polymer Composites, Vol., No. 8, 04