Textile Science

Cars need fuel to run. Likewise, everything requires fuel to be sustained. Cows need to chew and regurgitate grass endlessly to sustain their huge bodies. Human beings eat food three times a day in order to secure enough energy for living. This fuel is glucose, a type of sugar. It is a common source of energy for all animals and plants.

Everything starts from the sun. Carbon, hydrogen, oxygen, and 92 other key elements all originate from the sun. It provides energy to Earth from 150 million kilometers away with energy generated from nuclear fusion reactions. These happen when 597 million tons of hydrogen is combined to create 593 million tons of helium. The difference in masses converts into energy. This is the energy source for 50 millions of species on Earth. It was not until the 20th century that mankind attempted to harness the solar energy to generate electricity. Plants, however, have been already converting the solar energy 3,600 million years ago through a chemical process called photosynthesis.

Countless plants depend on the energy from the sun. Plants produce 180 grams of glucose from 688 Kcal of solar energy. 6 moles of carbon dioxide and 6 moles of water and 6 moles of oxygen are also produced. A mole is Avogadro’s number, 6×1023. Glucose that consists of carbon, hydrogen, and oxygen is called carbohydrate. Plants convert some glucose to starch for immediate use. The rest is stored in insoluble state. In this process, glucose becomes a linear-chained molecule called polymer. This is also called fiber. Polymer goes through a chemical reaction that joins chains of polymers called polymerization. The human DNA is a type of polymer with four types of protein: adenine, thymine, guanine and cytosine. Protein is made of 20 kinds of polymerized amino acids.

The polymer which plants change into glucose is called cellulose, the source of plants structure. The fuel for animals is also glucose. Animals, however, cannot photosynthesize. Therefore, they either gain it from plants or other animals. As the result of evolution of plants’ defense mechanism, animals cannot digest cellulous. Starch, the form of sugar stored in plants, is fortunately digestible. Starch is turned into disaccharide (two glucose units) by ptyalin, an enzyme in saliva that unchains the polymers. Fully digested glucose in stomach is turned into monosaccharide. Cellulose is a polysaccharide containing 2,500 to 10,000 glucose molecules. Polysaccharide is a form of sugar but its taste is not sweet. Reducing the number of glucose molecules to about 2 makes sweet tasting sugar types called fructose and sucrose.

Cellulose and starch are glucose polymers. The cellulose structure of natural fibers plays an important role in determining their properties. Cotton is 99% cellulose made of 3 basic elements: carbon, hydrogen, and oxygen. Burning cotton smells like paper and it is turned into black ash. Cellulose becomes partially crystallized during polymerization. Its amorphous portion makes it become wrinkled. Synthetic fabric like polyester does not become creased easily because the fiber is mostly crystalline in structure.

Hemp is a polymer made of cellulose and pectin which contains about 36,000 glucose molecules. It is tougher than cotton but becomes easily wrinkled because its cellulose structure is more amorphous than that of cotton. Hemp is characterized by its high thermal conductivity, which makes it feel cool. It is good for making summer clothes.

Based on the notion that plants are generally made of cellulose, there has been an attempt to obtain cotton from wood in England. It is true that wood pulp mostly consists of cellulose. Wood cellulose, however, is too entangled to be made into fibers. Its proper use is making paper through grinding and flattening cellulose.

If cellulose is melted, it can be made into fibers by passing the liquid through a nozzle. This method was developed by Courtaulds, a mill in England. Cellulose was turned into sticky brown syrup by adding sodium hydroxide and carbon disulfide. The yarn that came out of the nozzle was viscose rayon. Making the solution into a thin paper-like shape makes it cellophane. If it is shaped into a ball, it becomes a ping-pong ball. Viscose is the same with cotton in composition as we can check by the smell that both smells same when burning. But the former is likely to crease more and less strong than cotton due to less crystallization portion.

Viscose was once popular because it felt and looked like silk. Its popularity declined due to pollution caused by toxic solvents used in its production. The next cellulose based fiber was modal, developed by Lenzing in Austria. It was better than rayon with more strength that allowed additional finishing effects like sandwash. The new cellulose based fiber, however, still did not completely solve the pollution problem. This defect would eventually lead to the development of Tencel fibers.

Rayon must be the most well-known artificial fiber that is made from cellulose. It is also called bemberg, which is also the name of the company that developed it. The fiber is spun from lint solvent, not wood pulp. Copper ammonia is used to melt the lints. Rayon is also called cupra-ammonium rayon after this chemical.

Viscose and rayon are mixed sometimes. Viscose rayon is actually closer to viscose because it retains more of the cellulose characteristic similar to viscose. Rayon is mixed with acetate to be made into acetate rayon, which behaves more like a synthetic fiber. It also burns like polyester, producing black smoke. Viscose rayon and acetate rayon are both made with acetic acid solvent. Occasionally, acetate rayon accidently changes to viscose through the process of saponification. This is explained in more detail in "Acetate and Viscose."

Where as cellulose is made of glucose polymers, protein is polymerized with tiny molecules called amino acids. There are 20 different types of amino acids that make up this building block of life. Some names of amino acids are glycine, glutamine, and lysine. These may all sound familiar to the fanatic readers of Jurassic Park. Protein is truly the building block of animal cells. Hemoglobin that transfers oxygen in human body is a type of protein made with 580 amino acid. Wool and silk are made of protein as well. Because amino acids that make up protein contain sulfur and nitrogen, burning animal cells smells like sulfur.

As cellulose based fiber has been artificially created in the lab as rayon, protein fiber also has gone through this development. Human desire to mimic nature's power just seems endless. Wallace Hume Carothers synthesized a high polymer with two molecules, adipic acid and hexamethylenediamine. This is nylon, which has a similar chemical structure as that of the peptide bond in protein. For this reason, rayon is called amide or poly amide. The proto type of nylon is 66 nylon made of two molecules, adipic acid and hexamethylenediamine with 6 carbons. Nylon 6 comes after, with its production simplified by requiring polymerization of only one type of molecule called caprolactam. Nylon is similar to animal fiber because it has nitrogen and amine groups of amino acid which are not found in cellulose based fibers. Due to its high thermal conductivity that makes it lose heat fast, different types of nylon has been developed by blending the fiber with cotton.

Polyester taking up 65% of synthetic fiber production is a high polymer created from ethylene glycol and terephthalic acid. Its name comes from esterification, the reaction between alcohol and acid. Polyester is more popular than nylon because it is easy to print on and is weight reducible. Polyester is a compound of carbon, hydrogen, and oxygen like cotton. Although the chemical composition is similar, polyester does not decompose like cotton. It takes 500 years to become fully decomposed.

Unlike other synthetic fibers that have been made to be like silk, acrylic is an alternative to wool. Acrylic is made in fibers rather than filaments. It is made by vinyl polymerization, similar to the way PVC and PVA are produced. As it contains nitrogen, its behavior is like that of an animal fiber. Because of this nitrogen in its chemical structure, another name for acrylic is acrylonitrile. Ironically, acrylic belongs to the chemical family of potassium cyanide that Wallace Hume Carothers put into his orange juice to commit suicide.