Introduction

Fibers are substances used to make textiles and materials including cables, wires, clothing, drapes, and bedsheets. Generally speaking, they are long, thin, and flexible, which makes them ideal for producing strong, bending materials. Cotton, silk, jute, linen, nylon, rayon, and other common fibers are only a few of the most popular varieties.[1]

Some of the most popular uses include the production of furniture, automobiles, packaging, military equipment, aerospace goods, and other items used in daily life. Fibers are ubiquitous and play a significant role in modern life.[1]

Both plants and animals can serve as a source of natural fibers. Chemical synthesis is used to produce artificial fibers, commonly referred to as man-made or synthetic fibers. The nineteenth century saw the first development of synthetic fibres.[1]

In this article we will study the naturally obtained Spider Silk and American chemist Stephanie Kwolek creation of Kevlar:

Naturally obtained Spider silk.

A protein fiber called “spider silk” is spun by spiders.[2] Silk is used by spiders in nature for a variety of purposes, including the construction of webs, the wrapping of prey, the safeguarding of offspring, and as a lifeline for safe escape from predators. Compared to insects like silkworms,

which frequently use their silk for the production of cocoons, spiders use silk for a much broader range of purposes. [3]

Silks are produced by all spiders, and a single spider can produce up to seven distinct kinds of silk for various applications. In contrast, an individual rarely produces more than one type of insect silk. There are numerous ecological applications for spider silks, each with properties that complement the purpose of the silk. From primitive tube webs 300–400 million years ago to complex orb webs 110 million years ago, spiders’ silks have become more complex and used for a variety of purposes as they have evolved.[2]

The Structure of Spider Silk

Schematic representation of the hierarchical structure of a spider MA silk filament. At the macroscopic level, the thermonuclear structure can be identified, and at the submicroscopic level, the presence of aligned fibrils is shown. The nanoscopic structure is represented by poly-Ala β-sheet crystals aligned along the fiber axis and embedded in an amorphous phase containing GPGXX and GGX cluster

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Presently, there are a number of recombinant spider silk proteins being researched, which are generated in sufficient quantities by a variety of host species to allow for the study of possible material applications. The physical features of spider silk emphasize the possibility of thread

acting as high performance fibers. The key challenge in this field is the development of adequate spinning technologies to generate threads with qualities close to those of the natural material in a reproducible manner.

Spidroins have also been found to be adaptable proteins that can be processed into a variety of non-fibrous morphologies. They are useful for biological applications due to their innate biocompatibility and minimal immunological response. Cell culture and drug delivery uses of these materials are currently being researched. Furthermore, knowing the molecular structure of silks has sparked a slew of studies that use the repeating modules of silk in conjunction with other chemical patterns to create innovative materials.[5]

Kevlar created by American chemist Stephanie Kwolek

Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber that is linked to Nomex and Technora. Stephanie Kwolek developed the high-strength material at DuPont in 1965, and it was initially utilised commercially in the early 1970s as a substitute for steel in racing tyres. It is often spun into ropes or fabric sheets that may be utilised on their own or as a component in composite materials.[6]

Kevlar has a wide range of applications, from bicycle tyres and racing sails to bulletproof jackets, because of its high tensile strength-to-weight ratio; it is five times stronger than steel by this metric. It’s also utilised to manufacture high-impact marching drumheads, as well as mooring lines and other underwater applications.[6]

The Structure of Kevlar

Kevlar is made in solution by combining the monomers 1,4-phenylene-diamine (para- phenylenediamine) with terephthaloyl chloride in a condensation process that produces hydrochloric acid as a byproduct. Mechanical drawing orients the polymer chains in the direction of the fiber, resulting in liquid-crystalline behavior. The solvent first used for polymerization was hexamethylphosphoramide (HMPA), but for safety considerations, DuPont replaced it with a solution of N-methyl-pyrrolidone and calcium chloride. Because Akzo (see above) had patented this procedure in the manufacturing of Twaron, a patent dispute began.

Kevlar fiber type	Density (g/cm3)	Tensile strength (MPa)	Young’s modulus (GPa)	Elongation at break
Kevlar 29	1.44	3600	60	3.6
Kevlar 49	1.45	3600–4100	120	1.9
Kevlar 149	1.47	3400	160	1.5

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Since Kevlar is used in numerous structural operations, NDT plays an important part in determining the integrity of the structure. One of the styles used to check the integrity of structures made from Kevlar is CT. CT is generally used in the examination of essence. Still, this system is now being used for mixes. Fidan employed micro-computerized tomography to fantasize the internal damage impact on glass fiber – corroborated and glass fiber aramid fiber – corroborated polyester mixes. Low- haste impacts were tested at 80 J energy.

From the disquisition, themicro-CT showed that the 3D- delamination pattern disfigurement in glass- corroborated mixes is more visible due to the nature of the glass fiber. still, the delamination pattern lost its effectiveness when aramid fiber was added to the glass fiber. Another system used to descry blights is the eddy current system. still, in the work of Grimberg and Savin, the eddy current system used is for   mixes made from synthetic fiber, which are carbon and Kevlar. Eddy current microscopy, involving a micro-focus transducer, was used to probe the individual fiber breakage in the instance after it was impacted by a7.62- mm- quality pellet.[8]

Conclusion

Kevlar is one of the strongest man- made fibers which is used to create many different design structures. From 1965 there has been many research conducts and different levels of Kevlar are being created. Also spider silk which was seen 300 – 400 million times ago to complex sphere webs 110 million times. Spiders’ silk are useful for biological applications due to their innate biocompatibility and minimal immunological response. Kevlar fiber which is strong for safety at the same time spider silk is biologically useful

By Khyati Sutarii,Pass out Student of S. N. D. T Women University