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  • Topic: Cellulose, Rayon, Synthetic fiber
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  • Published : January 30, 2013
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CHemistry project .....

CHEMISTRY INVESTIGATORY PROJECT

TOPIC:

RAYON FIBRE

BY:-
VIKRAM RAO
XII – B
OBJECTIVE OF THE PROJECT

This project is aimed at preparation of rayon thread from filter paper employing cuprammonium process

INTRODUCTION

Rayon is the oldest commercial manmade fiber. The U. S. Trade Commission defines rayon as "manmade textile fibers and filaments composed of regenerated cellulose". The process of making viscose was discovered by C.F.Cross and E.J.Bevan in 1891. The process used to make viscose can either be a continuous or batch process. The batch process is flexible in producing a wide variety of rayons, with broad versatility. Rayon's versatility is the result of the fiber being chemically and structurally engineered by making use of the properties of cellulose from which it is made. However, it is somewhat difficult to control uniformity between batches and it also requires high labor involvement. The continuous process is the main method for producing rayon. Three methods of production lead to distinctly different rayon fibers: viscose rayon, cuprammonium rayon and saponified cellulose acetate. Of the methods mentioned, the viscose method is relatively inexpensive and of particular significance in the production of nonwoven fabrics.

For a very long period of human history, man depended on natural elements to make fibers for clothing. These were natural fibers. However, with the technological advances many manmade synthetic fibers were developed. Man-made fibers have two main categories: One that are made from natural products (cellulosic fibers) and the other that are synthesized from chemical compounds (non cellulosic polymer fibers). Rayon fiber is a natural-based material made from the cellulose of wood pulp or cotton fiber. In fact, they are made from reformed or regenerated cellulose. As such, they are identified as regenerated cellulose fibers.

MANUFACTURING PROCESS

While there are many variations in the manufacturing process that exploit the versatility of the fiber, the following is a description of the procedure that is used in making regular or viscose rayon.

Regardless of whether wood pulp or cotton linters are used, the basic raw material for making rayon must be processed in order to extract and purify the cellulose. The resulting sheets of white, purified cellulose are then treated to form regenerated cellulose filaments. In turn, these filaments are spun into yarns and eventually made into the desired fabric.

Processing Purified Cellulose:

• 1. Sheets of purified cellulose are steeped in sodium hydroxide (caustic soda), which produces sheets of alkali cellulose. These sheets are dried, shredded into crumbs, and then aged in metal containers for 2 to 3 days. The temperature and humidity in the metal containers are carefully controlled. •

• 2. After ageing, the crumbs are combined and churned with liquid carbon disulfide, which turns the mix into orange-colored crumbs known as sodium cellulose xanthate. The cellulose xanthate is bathed in caustic soda, resulting in a viscose solution that looks and feels much like honey. Any dyes or delusterants in the design are then added. The syrupy solution is filtered for impurities and stored in vats to age, this time between 4 and 5 days. •

Producing Filaments:

• 3. The viscose solution is next turned into strings of fibers. This is done by forcing the liquid through a spinneret, which works like a shower-head, into an acid bath. If staple fiber is to be produced, a large spinneret with large holes is used. If filament fiber is being produced, then a spinneret with smaller holes is used. In the acid bath, the acid coagulates and solidifies the filaments, now known as regenerated cellulose...
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