Abstract:

Objective Compared with the tenacity, specific work of rupture can specify the resistance of yarn to breakage more accurately. The specific work of rupture for blended yarn is strongly connected with blended ratio in blended yarn, but little attention has been concentrated on this field. Therefore, in order to predict the specific work of rupture for two-component blended yarn with various blended ratios and guide the reasonable selection of blended ratio in production, the law of varying specific work of rupture for two-component blended yarn with blended ratio was investigated.

Method Based on the analysis of rupture process for two-component blended yarn, some special points on the stress-strain curve of blended yarn were predicted using the stress-strain curves of pure spun yarns. By linearly connecting these points, a simple model of stress-strain curve for blended yarn was obtained. According to this model, expression of specific work of rupture was obtained. Cotton/viscose blended yarns were then spun and its tensile properties were tested so as to verify the established relationship in this paper. The data from previous literature were also used to further verification of the relationship's accuracy and applicability.

Results The predicted and experimental values of specific work of rupture for cotton/viscose, cotton/bamboo pulp fiber, cotton/modacrylic, cotton/soybean protein fiber, cotton/high strength polyamide, hemp/polyamide, cashmere/wool and polyester/soybean protein fiber yarns were considered in this research (Fig.7, Fig. 9-15). The predicted relations of specific work of rupture with blended ratio are essentially consistent according to the experimental results. The prediction error of specific work of rupture by this expression was acceptable and similar to that of tenacity and breaking extension by predecessors' expression. There are two main reasons for the prediction error of specific work of rupture, which are the simplification of tensile curve and the prediction error of tenacity and breaking extension. The actual stress-strain curves of blended yarns are often smooth and convex, while the predicted curve is simplified as straight or broken line (Fig. 4 and Fig. 5). When the actual curve is convex, such as cotton/viscose blended yarn (Fig. 7 and Fig. 8), cotton/bamboo pulp fiber blended yarn (Fig. 9) and polyester/soybean protein fiber blend yarn (Fig. 15), the predicted value of the specific work of rupture will be smaller than the experimental. On the contrary, when the actual curve is concave, such as high proportion of modacrylic blended yarn and high proportion of wool blended yarn, the predicted values of specific work of rupture will be larger than the experimental values. On the other hand, if the predicted value of tenacity or breaking extension is larger than the experimental, the predicted value of specific work of rupture would also be larger than the experimental. On the contrary, the predicted values of tenacity or breaking extension was smaller than the experimental, such as cotton/soybean protein fiber (Fig. 11), cotton/high strength polyamide(Fig. 12) and hemp/polyamide blended yarns (Fig. 13), the predicted values of specific work of rupture would also be smaller than the experimental.

Conclusion The relationship between specific work of rupture and blended ratio of two-component blended yarn is established in this paper. Then the applicability and reliability of the relationship are verified by the experimental data. It was found that, similar to the tenacity and breaking extension, the trend of specific work of rupture for blended yarn with the blended ratio varies around the critical blended ratio. This work provides a simple method for predicting the specific rupture work of blended yarn, and the prediction error is similar to that of existing expressions of tenacity or breaking extension and is within the acceptable range. Therefore, this study can provide guidance for blended yarn manufacture.

Key words: two-component yarn, blended ratio, specific work of rupture, tenacity, breaking extension, property prediction