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   Polyesters-Polyamide Fibres, Chemistry tutorial

Polyesters and Polyamide Fibres

Introduction

Nylon's 1st real success came by it's utilize in women's stockings, in about 1940. They were a big hit, but they became rigid to get, since a year later the United States entered World War II, and nylon was required to make war materials, like parachutes and ropes. Though, polyesters can be both plastics and fibres.

Definitions of Nylon and Polyester

Nylons are as well termed polyamides, since of the trait amide groups in the backbone chain. Polyesters are the polymers, in the form of fibres, which were utilized back in the seventies to build wonderful disco clothing.

Nylons

Nylons are one of the mainly general polymers employed as a fibre. Nylon is found in clothing all the time, but as well in other places, in the form of a thermoplastic67_Nylons.jpg

Fig: Nylons

Nylons are as well termed polyamides, since of the trait amide groups in the backbone chain.  Proteins, these as the silk nylon, are as well polyamides. Such amide groups are very polar, and can hydrogen bond through each other. Since of this and since the nylon backbone is so regular and symmetrical, nylons are frequently crystalline and make incredibly good fibres.

The nylon below is called nylon 6, 6, since each repeat chapter of the polymer chain has 2 stretches of carbon atoms, each being 6 carbon atoms long. Other nylons can have different numbers of carbon atoms in such stretches.

724_si x carbon atoms.jpg

Fig: six carbon atom

Nylons can be made from diacid chlorides and diamines. Nylon 6, 6 is made from the monomers adipoyl chloride and hexamethylene diamine

2227_nylon 6,6.jpg

Fig: nylon 6, 6

The industrial synthetic methods make utilize of the reaction of adipic acid by hexamethylene diamine;

1691_hexamethylene diamine.jpg

Fig: hexamethylene diamine

Another type of nylon is nylon 6. It is alike to nylon 6, 6 except that it only has 1 kind of carbon chain, which is 6 atoms long. It's made via a ring opening polymerization.

2092_caprolactam.jpg

Fig: caprolactam

Polyesters

Polyesters are the polymers, in the shape of fibres, that were utilized in the seventies to make wonderful clothing. But because then, the nations of the world have striven to extend more tasteful utilizes for polyesters, as those nifty shatterproof plastic bottles that hold our favorite refreshing beverages. An additional place we discover polyester is in balloons. The common ones employed to make water balloons are made of natural rubber. It's actually the fancy ones we use in the hospital. These are made of a polyester film made via DuPont termed Mylar. The balloons are made of a sandwich, composed of Mylar and aluminum foil. Materials like this, made of 2 kinds of substance are referred composites. Polyesters have hydrocarbon backbones that contain ester linkages, therefore the name.

2318_estar group.jpg

Fig: Estar group

The structure in termed poly (ethylene terephthalate), or PET for short, because it is made up of ethylene groups and terephthalate groups.

2058_ethylene group.jpg

Fig: ethylene group

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.

1801_naphthalate group.jpg

Fig: Naphthalate group

This permits the ester groups of nearby chains to line up through each other in crystal form that is why they can shape strong fibres. The inventor who 1st discovered how to build bottles from PET was Nathaniel Wyeth.

There is a new kind of polyester that is been utilized for jelly jars and burnable bottles. It is poly (ethylene naphthalate), or PEN. In the big industrial plants where polyester is generated, it is usual to begin off through a compound termed dimethyl terephthalate. This is reacted by ethylene glycol in a reaction termed transesterification. The result is bis- (2-hydroxyethyl) terephthalate and methanol. But if we heat the reaction to 210oC the methanol will boil away.

171_dimethyl terephthalate.jpg

Fig: dimethyl terephthalate

Then the bis-(2-hydroxyethyl)terephthalate is heated up to a balmy 270oC, which reacts  further to provide the poly(ethylene  terephthalate) and, oddly, ethylene glycol as a by product.

1281_poly(ethylene terepthalate).jpg

Fig: poly(ethylene terepthalate)

But in the laboratory, PET is made via other reactions. Terephthalic acid and ethylene glycol can polymerize to make PET when heated through an acid catalyst. It is as well possible to make PET from terephthoyl chloride and ethylene glycol. This reaction is easier, but terephthoyl chloride is more expensive than terephthalic acid, and even more dangerous.

1834_terephthalic acid.jpg

Fig: terephthalic acid

There are 2 more polyester in the market that is related to PET. There is poly (butylenes terephthalate) (PBT) and poly (trimethylene terephthalate) (PTT). They are generally employed for the similar kind of things as PET, but in several cases such perform better.

1918_poly(butylene terephthalate).jpg

Fig: poly (butylenes terephthalate)

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