The reason behind blending these two fibers is to improve the strength, durability, color, and texture.And also decrease the cost of making the before said fabric. One of the most useful blended fabric, which is used in the textile industry, is polyester- viscose (35/65, 25/75, 33/67) with polyester using in the highest percentage in the form of single-ply and two-ply yarn.The properties of this yarn to be mentioned are its high amount of moisture absorption, strength, rubbing resistance, and thermal resistance.Tergal fabrics are knitted with polyester-viscose yarns. Tergal fabrics are of two kinds; plain tergal which is called tergal and the other one is called twill.In tergal fabric, the warp yarn is polyester-viscose 30/2 and weft yarn is filament yarn 150 denier.The main differences between these two are their weight, pattern of weaving, and thickness. For instance, the tergal weight is about 240g and twill is about 290 g.