关键词: 棉型化, 汉麻, RSM法, 柔软性, 活泼率

Abstract: The single fiber length of hemp is short, and the content of hemicellulose and lignin is higher than that of other hemp fibers. There are problems such as difficulty in degumming and poor fiber quality after degumming. The produced hemp yarn has a low count, and the hemp fabric has a rough and hard feel. Due to the rich resources of hemp in Northeast China, the single fiber length and fineness of hemp are similar to those of cotton, and there is no itching sensation compared to other hemp types. In order to make full use of hemp, improve the softness of hemp fabrics, and increase product added value, we conducted optimization research on the processing conditions of cotton shaped hemp fabric.
Firstly, single factor experiment was conducted to investigate the effects of the sodium periodate dosage, oxidation time, and oxidation temperature on fabric softness. Based on this investigation, representative sodium periodate dosage, oxidation time, and oxidation temperature experimental conditions were selected from comprehensive experiments according to orthogonality (evenly dispersed, and comparable in integrity) for orthogonal test analysis at three factors and one level. Because response surface methodology is an optimization method that integrates experimental design and mathematical modeling, it can provide intuitive contour maps and three-dimensional stereograms, and can examine the interaction between influencing factors. This method not only establishes a prediction model, but also tests the adaptability of the model, the significance of the model and coefficients, and the mismatched terms. We further performed analysis of variance and model diagnosis. However, the premise of response surface optimization requires that the experimental points designed should contain the optimal experimental conditions. In order to obtain the optimal results and compensate for this limitation of response surface optimization, we adopted the experimental analysis method of response surface design and orthogonal experimental design using the activity rate as the response value, verifing that the selected experimental conditions are the parameters containing the optimal experimental points orthogonal experimental optimization. Additionally, we used response surface optimization to screen the optimal process parameters for sodium periodate dosage, oxidation time, and oxidation temperature, improving the reliability of the experimental optimization results.
Through comprehensive consideration of the results of single factor tests on fabric softness at three factors: sodium periodate dosage, oxidation time, and oxidation temperature, and three levels of optimal design for orthogonal tests: a sodium periodate dosage of 6 g/L, 13 g/L, and 20 g/L were selected; oxidation time: 0.5 h, 1.5 h, 2.5 h; oxidation temperature: 40 ℃, 50 ℃, 60 ℃. Using the L9 (34) orthogonal table and the activity rate as the response index, it can be seen that the order of influence of various factors is sodium periodate dosage>oxidation temperature>oxidation time. The optimal level requires a sodium periodate dosage of 13 g/L, oxidation temperature of 50 ℃, and a oxidation time of 1.5 h. A response surface design experiment was conducted on the basis of orthogonal experiments. With Design Expert 11 software, response surface analysis was conducted on the experimental results and variance analysis was conducted on the levels of various influencing factors. It can be seen that the model is significant; the significant degree of influence of various factors on the activity rate is sodium periodate dosage>oxidation temperature>oxidation time, which is consistent with the results of orthogonal experiments. The probability value P of the mismatch test is between 0.05-0.10, being 0.0537, and the mismatch analysis result is not significant. Therefore, the quadratic model can accurately describe the actual activity rate. Analysis of factor contour plots and response surface plots showes that the amount of sodium periodate and oxidation time has a strong interaction on the reactivity of response values; there is a certain interaction between the amount of sodium periodate and oxidation temperature on the response value activity, but the interaction between oxidation time and temperature is not obvious. Through comparison, it is found that the analysis results are consistent with the optimal prediction chart. On this basis, it is found by comparing the reactivity, strength retention, and wicking height of hemp fabrics before and after process optimization that except for slightly lower strength, both the feel and water absorption of the fabrics are improved. The design optimization model has certain significance for improving the added value of hemp fabrics.

Key words: cotton type, hemp, RSM method, softness, lively rate