Types of Rayon
There are two types of rayons- viscose rayon and high-wet-modulus (HWM) rayon, categorized on the basis of two principal methods of making rayon. Whatever the method used for making rayons, they are essentially made from cotton linter or wood pulp usually obtained from pine, spruce, or hemlock trees. Cotton linter is the residue cotton fiber which cling to cotton seed after the ginning process.
Wood chips or cotton fibers are used to make viscose solution, which is forced through a spinneret into sulfuric acid to produce cellulose filaments. After extrusion from spinneret, the viscose rayon fibers are processed to make filament or spun staple yarns through various spinning processes, such as Pot Spinning, Spool Spinning, and Continuous Spinning. Different varieties of yarns such as monofilament yarns, multifilament yarns, spun yarns etc. are made that are further woven into a wide variety of fabrics. Spun rayon yarns can be used for making fabrics similar to cotton, linen or wool. Rayon filament yarns can make fabrics like silk. Various finishes are also applied to these fabrics that give numerous properties to viscose rayon
Properties of Rayon- A Comparison with Other Fabrics
Strength: The tensile strength of viscose rayon is greater than wool but only about half as great as that of silk.
Elasticity: Viscose rayon has greater elasticity than cotton or linen but less than wool or silk.
Resilience: Viscose rayon lack the resilience like that of wool and silk and creases readily. However, resistance to creasing depends on the kind of yarn, weave and finishing process. For instance, extremely fine filaments used in multifilament rayons and any crepe surface produced by tightly twisted yarns have greater resistance to creasing.
Drapability: Viscose rayon have a good quality of drapability as it is a relatively heavyweight fabric.
Heat Conductivity: Viscose rayon is a good conductor of heat and thus is appropriate for summer clothing.
Absorbency: Viscose rayon is one of the most absorbent fabrics, more absorbent than cotton or linen. Only wool and silk exceed rayon in absorbency.
Shrinkage: Viscose rayon fabrics tend to shrink more than cotton fabrics of similar construction. Spun Viscose rayon fabrics shrink more with repeated laundering than fabrics made of the filament yarns.
Washability: Viscose rayon fiber, due to its smoothness, produces such fabric that sheds dirt. Some of them wash easily. Finishes given to them decides whether they'll become yellow on washing or dry cleaning. Since viscose rayon temporarily loses strength when wet, it must be handled with care when washed.