Frontiers in Science 2013, 3(1): 14-21 DOI: 10.5923/j.fs.20130301.03 Fiber Crimp Distribution in Nonwoven Structure Kunal Singha 1,* , Mrinal Singha 2 1 Department of Textile Technology, Panipat Institute of Engineering & Technology, Harayana, India 2 Department of Pharmaceutical Chemistry, CU Shah College of Pharmacy & Research, Gujarat, India Abstract The crimp of the textile fibers is very critical to determine its properties and voluminisity. The microscopic characteristic of the nonwoven fabric is totally depends on the linearity and length of the crimp and the amplitude of the crimp. In this review paper we have discussed about the crimp calculation, measurement techniques and the standards used for the textile nonwoven substrates. The crimp frequency (orientation distribution function; ODF) which is being measured by Textechno FAVIMAT instrument and by modern image processing techniques is also been discussed here. Keywords Crimp, Voluminisity, Nonwoven Fabric, Crimp Calculation, Crimps Frequency, Orientation Distribution Function 1. Introduction Crimp in a textile strand is defined as the undulations or succession of waves or curls in the strand, induced either naturally during fiber growth, mechanically, or chemically. Crimp in a fiber is thus considered as the degree of deviation from linearity of a non straight fiber. Fiber crimp is the waviness of a fiber expressed as waves or crimps per unit length (figure 1) or as the difference between the lengths of the straightened and crimped fiber (expressed as a percentage of the straightened length)[1-3]. Fiber crimp characteristics have a big influence on the processing performance of the fibers. Crimp also contributes essentially to the properties of intermediate fiber assemblies, yarn and finished fabrics. Fiber crimp imparted to synthetic fibers, which are initially straight, makes it possible to process these fibers with existing machinery designed for natural fibers. Straight, slick synthetic fibers would not have sufficient cohesion for carding, combing, drawing, roving, and spinning. In nonwoven processes, crimp and crimp retention during processing are major contributors to processing efficiency, cohesion, fabric bulk and bulk stability. 1.1. Wave Length, Crimp Frequency and Crimp Length The wave length λ of fiber crimp is twice the distance between two crossings of the fiber with the zero axis. It cannot be measured directly, since fiber crimp is by far too irregular and the small measuring quantities- wavelengths in the order of 1-3 mm - cause problems. Therefore, the crimp * Corresponding author: kunalsingha28@gmail.com (Kunal Singha) Published online at http://journal.sapub.org/fs Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved length lc, as the average length of fiber in one crimp, is sometimes used to describe crimp which can be measured as equation (1); (1) More commonly used is the crimp frequency C f may be calculated from the equation (2) of a fiber, defined as twice the average of the inverse of the wavelength. It is also called crimp number or crimp count, and characterizes the number of crimp bows or waves C n per unit length of straightened fiber L 0 . The unit length L 0 is taken as 1 inch in the US, whereas in Europe, 100 mm or 1 cm is used[2-6]. (2) 1.2. Crimp Angle The angle α between the leg of a crimp wave and the zero line may be used to characterize crimp geometry. The crimp angle φ is the angle between the two legs of a crimp bow, as shown in Figure 2; Φ indicates the sharpness of a crimp[2]. 1.3. Crimp Amplitude and Crimp Index The crimp amplitude A is the maximum distance of a crimp bow from the zero axes. Since the measurement of the amplitude of single crimp bows is practically impossible, average crimp amplitude of the fiber is derived geometrically with Pythagoras from length measurements of the crimped and the uncrimped fiber. The crimp index C i is an indirect measure of the crimp amplitude. It is also called crimp ratio, crimp percentage, crimp contraction or crimp retraction and is the ratio of the difference of extended length L 0 and crimped length Lc of a fiber, in percent of the extended length of the fiber L 0 as shown in by the equation (3). C i