Polyester

Polyester Presentation

1. Polyester Presented by: M Faisal Waqas, Shahid Ul Rehman, M Umer Farooq

2. Introduction Polyesters are one of the most important and most used polycondensation polymers and are derived from dicarboxylic acids and diols. Polyester is a polymer class containing ester functional group on polymeric main chain. Polyester term is usually used for polyethylene terephthalate (PET), despite the numerous polyester forms are present. Polyester  is a synthetic fabric that's usually derived from petroleum. This fabric is one of the world's most popular textiles, and it is used in thousands of different consumer and industrial applications. 

3. History 1926:  American scientist Wallace Carothers first discovered that alcohols and carboxyl acids could be mixed to create synthetic fibers. Unfortunately, his work on polyester was temporarily shelved to focus on nylon. 1939:  British scientists John Winfield and James Dickson continued Carother’s work. By 1941, they patented polyethylene terephthalate (PET), which would form the basis for synthetic fibers.   1951:  Polyester was first introduced to the public as a miracle fabric that could be worn, pulled, and washed without any wrinkling or signs of wear-and-tear.

4. Classifications of Polyester Polyester can be classified into two types 1.Saturated polyesters. 2.Unsaturated polyesters. Saturated polyesters refer to that family of polyesters in which the polyester backbones are saturated. They are thus not as reactive as unsaturated polyesters. They consist of low molecular weight liquids used as plasticizers. Unsaturated polyesters refer to that family of polyesters in which the backbone consists of alkyl thermosetting resins characterized by vinyl unsaturation. They are mostly used in reinforced plastics.

5. Structure of Polyester (PET) The structure in the picture is called poly(ethylene terephthalate), or PET for short, because it is made up of ethylene groups and terephthalate groups. The ester groups in the polyester chain are polar, with the carbonyl oxygen atom having a somewhat negative charge and the carbonyl carbon atom having a somewhat positive charge. The positive and negative charges of different ester groups are attracted to each other. This allows the ester groups of nearby chains to line up with each other in crystal form, which is why they can form strong  fibers .

6. Making Polyester In condensation polymerisation, when the monomers join together a small molecule gets lost. A Polyester is made by a reaction involving an acid with two –COOH groups, and an alcohol with two –OH groups. The acid is benzene-1,4-dicarboxylic acid (old name: terephthalic acid).
The alcohol is ethane-1,2-diol (old name: ethylene glycol).

7. Cont… Now imagine lining these up alternately and making esters with each acid group and each alcohol group, losing a molecule of water every time an ester linkage is made.

8. Manufacturing of Polyester Polyesters are generally manufactured from petroleum from which the constituent acids and alcohols are derived. There are three steps in the synthesizing of polyester, Polymerization Condensation  polymerization  occurs when the acid and alcohol are reacted in a vacuum at high temperatures. The polymerized material is extruded in the form of a ribbon onto a casting trough or  cooling wheel . After the ribbon hardens, it is cut into chips.

9. Cont… Spinning The chips are dried and then put into hopper reservoirs for melting. Polyester is a "melt spun" fiber, which means that it is heated, extruded through the spinnerets, and cools upon hitting the air. From there it is loosely wound around cylinders. 3) Drawing The fibers are then hot stretched until they are about five times their original length in order to decrease their width. The fiber is then wound onto cones as filaments or is crimped and then is cut into staple lengths.

10. Characteristics Polyester fabrics and fibers are extremely strong. It is durable ,resistant to most chemicals, stretching and shrinking . It is also wrinkle resistant and abrasion resistant. Polyester is hydrophobic in nature and quick drying. Polyester retains it's shape and hence is good for making outdoor clothing for harsh climates. It is easily washed and dried. Cotton is comfortable to wear. It has natural cellulosic fiber. Cotton is made from the cotton ball. It absorbs water, slow in drying, resists static electricity build up. Cotton wrinkles easily, can withstand heat, detergents and bleach.

11. Cont…. Very high heat can "melt" the fabric . Easy to wash ,dry and wear . Does not absorb water (can be uncomfortable when worn next to the skin in warm weather unless loosely woven) but it can be produced in such a way (as in polypropylene and microfibers) as to "wick" water away from the skin . Attracts static electricity which also attracts dirt and lint . Although they do NOT absorb water, they DO absorb oil and grease. Resist soiling, but once an oil based stain soaks in, it can be difficult to clean. Strong fiber (but nylon is stronger) . Often blended with cotton or even wool to add crease resistance.

12. Uses of Polyester in Garments Polyester is used in the manufacturing of all kinds of clothes and home furnishings like bedspreads, sheets, pillows, furniture, carpets and even curtains. Hydrophobic nature: High tenacity and good durability makes polyester the choice of fabric for high stress outdoors use. Polyester is also a strong fiber that is hydrophobic in nature. It is thus ideal for clothing to be used in wet and damp environments. The fabric is also coated with a water-resistant finish and further intensifies the hydrophobic nature.

13. Cont…. Creating insulation : By creating hollow fibers it is also possible to build insulation into the polyester fiber. Air is trapped inside the fiber, which is then warmed by the heat of the body. This keeps the body warm in cold weather. Another method to build insulation is to use crimped polyester in a fiberfill. Wrinkle resistant: Polyester is also wrinkle resistant and is used very often in everyday clothing like pants, shirts, tops, skirts and suits. Used either by itself or as a blend, it is also stain resistant and hence is very popular.

14. Industrial uses of Polyester The most common use of polyester today is to make the plastic bottles that store our much beloved beverages. An unusual and little known use of polyester is in the of balloons. These are made of Mylar – a kind of polyester film and aluminum foil. Polyester is also used to manufacture high strength ropes (Due to its strength and tenacity ) thread, hoses, sails, floppy disk liners, power belting and much more in industries.