Applications of Polycarbonates

Electronic components

Polycarbonate is mainly used for electronic applications that capitalize on its collective safety features. Being a good electrical insulator and having heat resistant and flame retardant properties, it is used in various products associated with electrical and telecommunications hardware. It also serves as dielectric in high stability capacitors.

Pros and Cones of Polycarbonates (Advantages and Disadvantages)

Pros (Advantages)

1. Excellent impact resistance and strength at low and high temperatures.
2. Available in visually clear grades.
3. Good heat strength, flame retardant, RoHS compliant, mould release, good lubricated, dimensional stability, good impact resistance, good process ability, good heat resistance and high viscosity.

Properties of Polycarbonates

• High Durability: Polycarbonate plastic is an extremely durable material. This makes it the material of choice where long product life and reliable performance are critical.
• Shatter Resistance: Polycarbonate is virtually unbreakable.

Synthesis of Polycarbonates

PC is most often synthesized from Bisphenol A and phosgene by a step-growth polymerization in which Cl- ions are eliminated every time the monomers react.

History of Polycarbonate Polymers

The discovery of Polycarbonate dates back to 1898 when Alfred Einhorn, a German chemist, observed the formation of an insoluble, infusible solid, while endeavouring to prepare cyclic carbonates by reacting hydroquinone with phosgene.

Advantages of Sanforization

• By applying the process of sanforization, a cloth is produced which does not shrink significantly during clothes production such as washing, cutting, ironing, sewing, hence decreasing the production cost.

Sanforizing Machine and Process

The machine used for the sanforizing process is called "Sanforizing Machine". Sanforizing Machine means a machine consisting of a large steam-heated cylinder, an endless, thick, woolen felt blanket which is in close contact with the cylinder for most of its perimeter, and an electrically heated shoe which presses the cloth against the blanket while the latter is in a stretched condition as it curves around feed-in roll.

Shrinkage of Fabrics… Why Fabrics Shrink?

Woven and knitted goods are 3-dimensional arrays of crimped yarns. Fabric forming processes take straight lengths of yarns and force them into 2-dimensional crimped lengths. The degree of crimp is a function of the yarn size and fabric construction. When fabric is completely relaxed, the crossing yarns will move around in relation to each other until a stable configuration is reached.

History of Sanforization

Sanforizing is a method that was produced in the 30s to prevent denim from shrinking. Having spent his youth wrangling alligators in Florida, learning the Seminole language and working in the engineer corps for the Spanish-American War, the process of sanforizing was invented by Sanford Lockwood Cluett (1874–1968) in 1930.

Sanforization

Sanforizing or Sanforization is the process of pre-shrinking fabric, which is a controlled compressive shrinkage process, which is applied on woven fabric to achieve shrinkage before making the garments. The process of sanforizing limits the post-wash fabric shrinkage to less than 1%.

Application of Space Dyeing

• Space dyed yarns produced from variety of dyes are used to produce a variegated weave when used for knitting or crocheting which give a very lively look.
• Space dyed yarns are commonly used in the manufacture of tufted carpets to make them appealing and beautiful.

Space Dyeing Techniques

Space dyeing can be achieved through several methods:

1. Knit-De-Knit Process
2. Warp Yarn Printing/Dyeing Process
3. Pot Skein Dyeing Process
4. Package Form Dyeing Process
5. Hank Form Dyeing Process
6. Continuous Dyeing Process
7. Spraying of colors onto the skeins of yarn.

Mechanism of Space Dyeing

In space dyeing, mordant is mostly used to chemically fix the dyestuff to substrate and the fixation of dyestuff is permanent type. There are three different ways to apply a mordant but mechanism of mordant stays same for all types of applications

Mordant in Space Dyeing

The secret to space dyeing yarn involves the use of a special chemical called a mordant. Dye in the space dyeing is fixed on yarn with the help of mordant.

What is Space Dyeing?

"Space dyeing is a process of dyeing of yarn in which multiple colors are applied along the length of each strand of yarn which may or may not repeat after a fixed interval."

Application areas of Stabilizers

1. Hydrogen peroxide bleach stabilizers are most widely used in the bleaching of cellulosic fibres [cotton, flax, linen, jute etc.] and wool, silk, nylon and acrylics with hydrogen peroxide.

Working Mechanism of Stabilizers

The basic mechanism of stabilizer involves the stabilization of chemical reactions by inhibiting the reaction or slowing down the reaction.

Anti-oxidants

Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When the chain reaction occurs in a cell, it can cause damage or death

Chemistry of Stabilizers

Hydrogen Peroxide Bleach Stabilizer

Stabilizers must be added to the bleach solution to control the decomposition of hydrogen peroxide. Stabilizers function by providing buffering action to control the pH at the optimum level and to complex with trace metals which catalyze the degradation of the fibres. Stabilizers include sodium silicate, organic compounds and phosphates.

Types of Stabilizers

Antioxidants

Antioxidants are substances which prevent the unwanted oxidation of materials. They inhibit oxidation reactions by free radicals in the human body before they can do any harm.

Stabilizers or Stabilizing Agents

Stabilizer is basically something that stabilizes something such as a substance added to another substance to prevent an unwanted alteration of physical state of that substance.

Manufacturing of Viscose Rayon – Viscose Process

Viscose Process

It is the worldwide manufacturing process of "Viscose Rayon".

Raw Materials

• Wood Pulp
• Cotton Waste
• Cotton Linters

Viscose Process is as follows:

History of Viscose Rayon

• Viscose Rayon is the very first viable manufactured fiber and artificial silk fiber.
• In 1664, English naturalist Robert Hooke gave a theory that artificial silk filaments can be spun from a substance similar to that which silkworms utilize to make silk.

Relationship between Properties and Structure of Viscose Rayon

In general, the fiber structures of various viscose fibers depend on the properties such as conditions of viscose, acid bath, stretching, regeneration and so forth. In the case of ordinary rayon, in which an acid bath offering high coagulative and regenerative powers is used, the major portion of fiber structure is determined in acid bath. For viscose fibers, however, in which a weak acid bath is employed, the regeneration and crystallization of fibers in acid bath are only carried out to a small extent and the fiber structure is not only dependent on acid bath conditions but also on the stretching and regeneration conditions. Consequently, a wide choice of fiber structures and properties is available by combining such factors such as viscose, acid bath, stretching and regeneration.

Structure of Viscose Rayon

The structure of rayon fiber is generally that of smooth, inelastic filaments like glass rods. However, different processes, additives and finishes can vary the physical appearance and structure of viscose rayon.

Properties of Viscose Rayon

Rayon as a fabric is soft and comfortable. It drapes well which is why it is highly sought after as an apparel fabric. Most characteristics are variable depending on processing, additives and other finishing treatments and fabric construction.

Preparation of Viscose Rayon

Rayon fiber made from "viscose process" is called Viscose Rayon. Viscose Rayon is the oldest commercial manmade fiber. Viscose Rayon is a manufactured fiber composed of regenerated cellulose. Out of all the fibers produced, rayon is the most perplexing to consumers. It can be found in cotton-like end uses as well as silk-like end uses. It may function successfully in absorbent hygiene and incontinence pads and equally well providing strength in tire cords. Unlike most man-made fibers, rayon is not synthetic. It is generally made from wood pulp which is a cellulose-based raw material. Hence, properties of rayon are more like natural cellulosic fibers, such as lint or cotton, than those of synthetic fibers.

What is Fiber Science?

Fiber science is a very important and fundamental field in textile. Fiber science deals with the physical, chemical and engineering properties of fibrous materials and their applications but mainly it deals with physical properties of fibers. Fiber science helps determine the properties and structure of fibers. It is detrimental in identifying all kinds of fibers through physical and chemical methods and telling those fibers apart from each other. Popular methods for the identification of fibers in a fabric are absorption of infrared radiation, Raman scattering of light, X-ray diffraction studies and optical microscopy.

Major Woolen Yarn Manufacturing Stages

The fleece coming from the sheep is put under many processes to make a woolen yarn that are described below:

Scouring

Previous to scouring, the wool as it comes from the sorter is in the majority cases passed through a machine known as duster. The object of dusting grease wools is, as far as possible, to remove before scouring such foreign impurities as lumps of dirt, dust, shives etc.
The operation that follows the dusting of wool is known as wool scouring or washing, and has for its object the cleansing of the wool from the natural and foreign

Raw Materials for Woolen Industry

Wool is the animal fiber forming the protective covering, or fleece, of sheep or of other hairy mammals, such as goats and camels. Prehistoric man, clothing himself with sheepskins, eventually learned to make yarn and fabric from their fiber covering. Selective sheep breeding eliminated most of the long, coarse hairs forming a protective outer coat, leaving the insulating fleecy undercoat of soft and fine fiber.

Impurities Present in Raw Wool

The proportions of the different components of unwashed or greasy wool are:

• Moisture = 4 – 24 %
• Yolk = 12 – 22 %
• Dirt = 3 – 9 %
• Wool Fibers = 60 – 70 %

Raw wool contains three main impurities

Woolen Yarn Manufacturing

Introduction

Wool fiber and hair fiber are the natural hair growth of certain animals and are composed of protein. Protein consists of complex organic compounds containing amino acids.
The Great Britain comes first into the story of wool as producer of raw material. The other chief producing countries are Australia, The USSR, New Zealand, Argentina, South Africa, Uruguay and The United States.
The Wool Fiber is obtained from sheep. The breeding of sheep and the production of wool fiber are more costly processes than the cultivation of plant fibers. Consequently, wool fabrics are more expensive than cotton and linen.
Hair fibers have all the qualities of wool and, in general, are more expensive than wool. The hair fibers obtained from the certain animals are;

Differences between Woolen and Worsted Yarn Manufacturing Systems

There is a large difference between the spinning and manufacturing process of both woolen and worsted yarn. These are the two different systems through which different grades of yarns are produced from the wool taken from different animals like sheep, alpaca, rabbits, goats and llama.

Worsted Yarn Manufacturing

A fine smooth yarn spun from combed long staple wool. Worsted yarns are more tightly twisted than the bulkier woolen yarns. The soft, heavy yarn is strong and durable and is often used for sweaters. Worsted yarns are also used for fine dress fabrics and suit materials.