GATE (TF) Textile 2012 Question Paper Solution | GATE/2012/TF/25

A softener, also known as a fabric softener, is a type of laundry additive that is used to make fabrics feel softer and smoother. Softeners work by depositing a thin layer of chemicals on the surface of the fabric, which helps to reduce friction between fibers and make the fabric feel smoother and more pliable.
Softeners are typically used in the rinse cycle of the washing machine, although some products can also be added directly to the dryer. They are commonly used on fabrics made from natural fibers, such as cotton, linen, and wool, which can sometimes feel rough or scratchy after washing.
Softeners can come in liquid or sheet form and may contain a variety of ingredients, including fatty acids, quaternary ammonium compounds, and silicones. Some softeners may also contain fragrances or other additives that provide a pleasant scent or other benefits, such as antibacterial properties or color protection.
While softeners can make fabrics feel softer and more comfortable, some people may be sensitive to the chemicals in these products or may prefer the natural feel of untreated fabrics. Softeners can also leave a residue on fabrics, which can reduce their absorbency or cause staining or discoloration over time.

The bending rigidity of a fabric refers to its resistance to bending or flexing when subjected to external forces. It is a measure of the fabric’s stiffness or rigidity, which is determined by the fabric’s inherent physical properties, such as its fiber type, yarn construction, and weave structure.
Bending rigidity is often measured using a device called a cantilever bending tester, which measures the force required to bend a fabric sample to a certain degree. The results of this test can be used to calculate the bending rigidity of the fabric, which is typically reported in units of millinewtons (mN) or grams-centimeters (g.cm).
The bending rigidity of a fabric can affect its drape, or the way it hangs or falls when draped over a surface. Fabrics with high bending rigidity tend to have a stiff or structured drape, while fabrics with low bending rigidity tend to have a more fluid or flexible drape. The bending rigidity of a fabric can also affect its comfort and wearability, as stiff or rigid fabrics may be less comfortable to wear than softer, more flexible fabrics.
Bending rigidity can be affected by various factors, including the fiber content of the fabric, the yarn construction, and the weave structure. For example, fabrics made from stiffer fibers, such as polyester or nylon, may have higher bending rigidity than fabrics made from softer fibers, such as cotton or silk. Similarly, fabrics with tighter weaves or thicker yarns may be more rigid than fabrics with looser weaves or finer yarns.