Using the Geometric Model to Explain the Longitudinal and Cross–Sectional Reflection Behaviors of Acrylic yarns

In the present work the reflection behavior and the color appearance of acrylic yarns, as pile yarns used in carpet and pilled fabrics, are considered along their lengths as well as their cross- sections. Differences between longitudinal and cross-sectional reflection behaviors of yarns are measured in different yarn densities and hues and explained by the geometric model. The results of experimental work show that the average of reflectance and lightness values along yarns' length, with identical hue, are higher than values obtained from their cross-section. Besides, the lightness values of cross-sectional of samples, with identical hue, increase when the density of yarns in holder cell increases. The metric chromas as well as the hue angles of samples, dyed with the same dyestuff are different in two directions and lead to color difference values between 3.35 and 27.84 under D65 Illumination and CIE 1964 standard observer in CIELAB color difference formula. The reflection differences between two directions are analyzed using the geometric model and it is found that they originated from different optical passes through the fibers in the mentioned modes. Keywords: Reflection behavior, Geometric model, Acrylic yarn