Development and evaluation of a video microscopic technique for fiber surface energy measurement

Natural cellulosic fibers, like flax, cotton or hemp, are traditionally used in the textile industry for the production of yams and fabrics. Currently, researchers are interested in utilizing these fibers as reinforcing agents in composite materials. Knowledge of the surface properties of natural fibers is essential to understanding the interaction of these fibers with polymer matrices. Therefore, fiber scientists, textile and material science technologists need to understand and measure the surface free energy of natural fibers.; This research was designed to develop and evaluate a system (instrumentation, methodologies and algorithms) for automated fiber surface energy determination based on video microscopic techniques. The study was organized into three interrelated components. In the first component, a video microscopic technique for fiber contact angle analysis is presented. Liquid - solid contact angle analysis was developed to measure the surface energy of fibers using Neumann's equation, Owens - Wendt method, and acid-based method. The conventional Whilhelmy balance method for measuring contact angle was difficult to apply to flax fibers because of the non-rigid nature and fine diameters involved. In this paper, a video microscopic technique which utilizes precision optics and a CCD camera in conjunction with advanced image processing algorithms is presented. The system is an instrument with fully automated image processing capabilities to aid in the determination of the surface energy of fibers from contact angle measurement.; In the second component, an active contour model is applied for tracking the liquid droplet boundaries for fiber dynamic contact angle measurements. We address the problem of modeling and extracting the changing contours from noisy images acquired with a video microscope. We explore the technique based on an active contour model commonly called "snake". We used this technique to track the boundaries of a liquid droplet being absorbed by a flax fiber. This paper demonstrates the usefulness of the snake model, under some constraints, in solving simultaneously both the segmentation and tracking problems of changing liquid droplet contours.; In the third component, an evaluation of our technique was carried out by determining fiber surface energy from contact angle measurements obtained with a video microscopic based system. Measurements of the contact angle using water and glycerol as testing liquids on flax fibers were made. Using results obtained and a "geometric mean" approach, the dispersion and non-dispersion components of the surface energy of flax fiber were determined and compared with other methods. Synthetic fibers were also tested to evaluate the performance of the method. Based on the measurements and calculations, it was found that the surface energy of the flax fiber depends largely on the degree of retting. Raw flax fibers, which have high wax and pectin contents, possess low surface energy while over-retted flax fibers, which contain mainly cellulose, have high surface energy. (Abstract shortened by UMI.)...