Objective evaluation of sizing morphology of E-glass filament yarn

In spinning, sizing agent makes originally rigid glass filament yarn soft, smooth, reduces mechanical wear, and alleviates static electricity. In order to produce “stronger, thinner, and more uniform” E(Electronic) fiberglass cloth, the sized filament yarn is required to have good strand integrity and uniform belt-like shape. Currently, the sizing effect can only be evaluated artificially according to the image of cross section or longitudinal section of yarns. The goal of the paper is to find an objective evaluation method for sizing effects on strand integrity and performance of belt-forming of E-glass filament yarn. The image of cross section of yarn is captured by Keyence VK-X110 and analyzed by Image-Pro Plus to obtain the central position and diameter of each filament. The threshold of fiber spacing is set to determine whether filaments are clustered in group. The area of outer enveloping convex polygon containing all the clustered filaments is calculated and fiber-filling rate is calculated accordingly. By using the least square method, the minimum rectangle containing all groups of filaments is obtained to describe the basic contour of yarn cross section. The outer envelope polygon is divided into several equal parts to calculate the coefficient variation of thickness distribution and yarn distribution. These objective values well reflect the strand integrity and feature of belt-forming of yarn, and are consistent with the subjective evaluation. Rank order method is used to compare the sizing morphology of the yarns based on the values. A standard is also suggested for objective grade assessment of sized E-Glass yarns.