Yarn: mass measurement with 1-mm length samples

In textile production, measurement of yarn mass in the 1-mm range is of utmost importance to properly evaluate evenness, as several irregularities occur in 1—4-mm yarn Iength. Direct measurements in the 1-mm range are not available in commercial equipment. One of the most common, from Uster, is based on yarn samples of 8 mm. This paper presents a direct mass measurement in the 1-mm range system based on parallel capacitive sensors and signal-processing techniques for detection of periodical errors. Results point out that evaluation of yarn mass, with this approach, is feasible in the 1-mm range, allowing online measurement (1-mm yarn mass) in a spinning frame for real-time control. Despite low signal-to-noise ratio, it is possible to measure small variations of yarn mass (typical capacity variation of 2.08 x 10-17 F for 57 tex—O.057 g/m of yarn). As a spin-off of this project, a new low-cost control system is being prepared for detection of yarn break and bobbin end in knitting flat machines. Online quality classification is also feasible with the developed system.Fundação para a Ciencia e a Tecnologia (FCT)Universidade do Minho (UM

Synthesis of starch-based derivatives and their application in processes of yarn sizing

The intention of this study was to check the feasibility of the implementation of the newly synthesized biopolymeric materials for sizing of cotton yarn, based on the basic principles of chemical modification and practical verification in industrial conditions. The paper includes acid hydrolysis of corn and potato starch up to the controlled molecular weight with graft–polymerization of acrylamide, acrylic acid, 2-hydroxyethyl methacrylate and methacrylic acid on hydrolyzed starch for improving the hydrophilicity and solubility, capability of forming the film, increasing the potential of the adhesive potential, avoidance of retrogradation phenomena, etc. The objectives of the research were primarily related to the establishment of appropriate, environmentally–friendly and productive systems for sizing cotton yarns through the analysis and systematization of a large number of synthesis methods in conjunction with the characterization and properties of the graft copolymer. The results showed the following: (a) benzoyl peroxide initiator was very successful in grafting of acrylamide, azobisisobutyronitrile initiator in grafting of acrylic acid and 2-hydroxyethyl methacrylate, while the initiator potassium persulfate was the best in the grafting of methacrylic acid on size; (b) contribution of hydrolysis and grafting, the percentage of grafting and grafting efficiency, the conversion of monomers to polymer, molar mass as well as FTIR analysis confirmed that this is a new product made of starch and vinyl monomers; (c) after impregnation of single yarn and double yarn (type of yarn), it was found that coarse single yarn as well as double yarn absorb or bind to themselves more size in all cases compared to the finer yarns, which is associated with a higher volume in scope, looser structure, as well as a smaller number of turns; (d) after sizing, warp becomes more uniform in thickness, which is the effect of size deposit mass to yarn when different types of deformity along the length of the yarn are "fixed"; (e) mechanical properties change during the impregnation with various sizes, tensile strength of analyzed yarns is increased and partial elongation is decreased; (f) values for the abrasion in cycles go beyond the raw yarn in all cases; (g) yarn hairiness decreases with sizing, which increases the smoothness and reduces friction; (h) micrographs of yarn processed with new sizes have smoother structure with fibers stuck together to each other, and a large degree of parallelism in the direction of the longitudinal axis of the yarn; (i) with desizing in conventional washing there is a significant removal of the applied starch copolymer, while the use of ultrasound in washing caused the greatest degree of size removal from yarns; (j) recycling of applied sizes after desizing is possible because those are water–soluble compounds, similar products for sizing must first be decomposed in order to perform the desizing and therefore they cannot be recycled; (k) using a statistical one–way Anova analysis and multiple linear regression, the advantage of the new derivatives of starch as potential means for the sizing of cotton yarn of different fineness and string was confirmed, what stands out is the copolymer of starch and 2-hydroxyethyl methacrylate as a potential and highly efficient size; (l) practical assessment of sized warp in weaving proved usability and potential of new size