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ABSTRACT
Test Method 58 was established by the International Wool Textile Organization in 2000 to analyze textile products made from specialty fibers, sheep's wool, and their blends using the scanning electron microscope. This part of the series critically examines the design of the analytical approach for quantitative analysis of binary blends specified in IWTO-58. The 95% confidence range is established as a suitable measure for the precision and accuracy of the method. The most critical, legal, and technical issue of quantitative analyses of binary wool/specialty fiber blends is the requirement of 3 weight-% accuracy. This accuracy is not consistently reached with the current analytical protocol, that is, for 50:50 blends, though the course of the analysis already operates at its feasible technical and economical limits. Extended analysis protocols are investigated showing the requirements for meeting this pre-set accuracy. The results show that a substantially higher number of diameter measurements for the fiber components and a substantial increase in the number of identified fibers are required for routine analysis, which is beyond the reach of the current operator-based and thus rather tedious methodology.
To analyze blends of specialty fibers with sheep's wool, the International Wool Textile Organization (IWTO) established Test Method 58 [12] in 2000. The method specifies the use of the scanning electron microscope (SEM) for distinguishing sheep's wool on the one hand from all specialty fibers on the other. Corroborating a previous paper [32], our current objective is to elucidate in some detail the technical and economic possibilities and limitations of the methodology for quantitative analyses of binary blends, that is, by addressing issues related to the precision and accuracy parameter implemented in IWTO-58. Furthermore, some current and future practical and legal consequences are considered.
Principles of IWTO-58
Analysis of a textile consisting in total or in part of specialty fibers according to IWTO-58 is based on the following principles: Short fiber snippets (0.4 mm) are obtained from the material according, for example, to IWTO-8 [9]. These samples are length-biased [23], in that longer fibers in the sample have a proportionally higher chance to be represented as snippets than shorter fibers. These snippets are the basis for SEM analysis of the sample according to IWTO-58 [12].
Wool fibers can be differentiated in the...