The Role of Auxiliaries in Textiles (4.SIZING)
by : Rahul Sharma
4. SIZING
Sizing is the process in which the sheet of yarn containing the requisite number of warp threads is prepared or "sized" for the weaving operation by giving it the necessary characteristics to stand up to the conditions prevailing during weaving. The main ingredient needed for this purpose is a film forming agent. From the point of economy and ready availability, the most common film forming agent used is natural or modified starch. When starch used, it is usually used in the concentration range of 5-15%, and in this range of concentration it imparts to the yarn the required strength necessary for weaving alsong with desired film farmation so necessary to prevent abrasion due to chaffing during the shedding operation on the loom.
However the yarn is more brittle and inflexible and non-elastic than it was before sizing and, for is reason the use of softening agents becomes necessary. The best known example of a suitable softener is mutton tallow which is ideal from many points of consideration. Recently there has been a phenomenal growth in the development of alternatives or substitutes for mutton tallow has held its ground firmly. The other ingredients which play specific roles in the operation of sizing are :
(i) Wetting agent : for instant wetting of the rey yarn to be sized for greater penetration of e size.
(ii) Fillers : Weighting agents to give greater weight to the sized yarn, especially in sized yarn, especially in sizing for added weight as in "Heavy Sizing"
(iii) Hygroscopic Agents : The main purpose is to add weight without being visible; however in many cases they are used as emolints e.g. glycerine.
(iv) Gums : Where necessary they serve to give firmness and body to the yarns.
(v) Lustering Agents : These serve to increase the lustre of the yarn especially in heavy sizing.
(vi) Preservatives : Since many of the ingredients used in sizing are food materials, their storage life after sizing in limited and hence the use of suitable preservatives becomes essential.
All these ingedients or sizing auxiliaries as they may be called, serve to enhance the effect of sizing and in the hands of an experienced size aided by an intelligent chemist, they can make all the difference between efficient and bad weaving.
