Fibre Analysis Flashcards

Question

man made fibres

Answer 1

Either synthetic or semi-synthetic - The former is derived from petrochemicals – e.g polyamides (nylons), polyesters, acrylics and polyurethanes - The latter are derived from natural materials but are ‘regenerated’ to produce novel properties – e.g viscose, rayon and acetate

Answer 2

- The aim is to produce something that replicates natural fibres, a cheaper version or improves limitations of natural fibre - Improvements may include greater tolerance to chemical action, heat, shrinkage, greater strength, greater absorbency or less practically, improved appearance, texture or the greater ability to be permanently coloured

Answer 3

Regenerated fibres from one of two sources  Biological sources: Most commonly cellulose which is used in the manufacture of viscose, rayon and various cellulose ester or alternatively a protein source such as casein or seaweeds!  Mineral Source: Glass fibres and metallised yarns ``` Cellulosic fibres  By far the most common class of regenerated fibres  Various sub-classes of regenerated cellulosic fibre each with very different mechanical and structural properties  Despite this cellulosic fibres appear very similar with uniform diameter, longitudinal striations and irregular cross section ```

Answer 4

Semi-Synthetic Fibres – Rayon Viscose Rayon - The most important regenerated fibre in terms of volume - Inexpensive to manufacture and versatile producing fibres of silk, wool or cotton like feel, lustre or appearance! - A very soft, comfortable fibre ideal for warm climates - The cheapest man-made fibre and therefore often used in clothing made to a budget or commonly seen in furnishings and medical and hygiene products due to absorptiveness – Weak with poor abrasion resistance and low wet strength (50% dry) meaning dry cleaning is a necessity

Answer 5

* The process begins with cellulose material in the form of wood pulp * This is treated with sodium hydroxide which causes a chemical change * The material is then treated with CS2 forming Sodium Cellulose Xanthate! * This when a little water and sodium hydroxide is added, will form a viscous liquid of honey like consistency and this is then extruded in a hardening bath * Hardening bath consists of H2SO4 (which converts Xanthate to cellulose), sodium and zinc sulphates (which precipitate the xanthate and add structural strength

Answer 6

A modern variant of viscose with superior properties (1991) - Performs well with a soft, strong, wrinkle resistant fibre with strong water absorption properties - Similar applications to viscose rayon including medical and personal products, clothing, conveyor belts and cigarette filters! - Novel manufacture process in which the fibre is obtained direct from a solvent without derivative formation - Raw bleached cellulose dissolved in N-methylmorpholine N-oxide - This material is then extruded and drawn in air after which they are set in dilute amine oxide which hardens the fibres - From this point they can be washed and dried and undergo any post-processing

Answer 7

- semi-synthetic fibre type derived from cellulose - Soft smooth fibres, which dries quickly and has a lustrous appearance and is colourfast under most circumstances - distorts and wrinkles very easily, has poor thermal properties and is a comparatively weak fibre especially when wet making it dry clean only - Raw bleached cellulose reacts with acetic anhydride, acetic acid and sulphuric acid which acetylates the hydroxyl groups - This then undergoes controlled hydrolysis to produce diacetate or triacetate - This is then dissolved in acetone or other solvent and extruded into fibres

Answer 8

- All are organic polymeric fibres - Manufactured by chemical synthesis - The first example (Nylon) was developed in about 1935 by Wallace Carothers - Most polymers are manufactured from simple precursors generally by one of two methods of polymerisation - Condensation polymerisation - Chemical condensation reaction in which water or acid is produced as a by-product - Addition polymerisation - Produced by joining molecules using a double bond or free radical reaction

Answer 9

- Soft, smooth fibres, with controllable lustre characteristics and able to be set allowing early non-iron - High strength fibres with good abrasion resistance and elastic recovery - used for manufacture of seatbelts, tirecord, ropes and other high strength materials including gun parts! - Resists attack by some chemicals, molds and mildew - A fibre derived from simple pre-cursor organic materials - Produced in two forms: Nylon 6,6 and Nylon 6 - Nylon 6 is slightly inferior in its properties particularly in regard to its melting point - Nylon 6,6 is produced from a condensation reaction between adipic acid and hexamethylene diamine - The 6,6 comes from the use of two 6C precursors - The reaction is a simple condensation - Nylon 6 is produced from a ring opening reaction between molecules of caprolactam - The 6 comes from the use of a single 6C precursor - The reaction is a ring opening forming a linear chain polymeric molecule

Answer 10

- Aromatic polyamides having at least 85% of their amide linkage directly attached to two aromatic rings - By comparison to traditional fibres, aramids lack the properties required to produce soft, comfortable fashionable clothing - Both fibres are extremely strong with good abrasion resistance - Nomex has excellent thermal resistance properties and is used in flame retardant clothing for pilots, firefighters and racing drivers - Kevlar has incredible strength being on a weight for weight basis five times stronger than steel! - It is used far ballistic protection, stab resistance gloves, tyre ply and for top end racing sails - Nomex is produced from a condensation reaction between meta-phenylenediamine and isophthaloyl chloride producing HCl condensate - Kevlar is produced from para-phenylenediamine and terphthaloyl chloride producing very linear polymer chain of high strength

Answer 11

- Smooth, soft warm fibres comparable to wool - Moderate strength fibres with fair abrasion resistance - May be seen in jumpers, hats rugs, curtains and various plastic items such as garden furniture - Light and chemical resistant but flammable and ‘staticky’ - A fibre derived from acrylonitrile (>85%) and a copolymer (such as methyl acrylate) which are polymerised and dissolved in a solvent - The material produced then undergoes dry spinning or wet spinning in a bath of dilute solvent

Answer 12

- Many of the same properties as acrylic and similar uses - modacrylic is somewhat flame retardant and will self extinguish - Modacrylic is as the name suggests a modified acrylic fibre where between 35% and 85% of the fibre consists of polyacrlonitrile monomer units and the remainder consists of some other sub-unit - This is normally vinyl chloride, vinylidene chloride or vinyl bromide - Once polymerised, the fibre is dissolved in solvent and dry spun

Answer 13

- Both semi and synthetic fibres are produced using similar principles - Polymer prepared in conc. Viscous form in solvent or in molten state - This is the extruded through tiny holes in a spinneret - The spinneret can produce fibres of various shapes

Answer 14

- Wet spinning - Dry spinning - Melt spinning

Answer 15

- may be used for polymers which need to be dissolved in a solvent for spinning such as acrylic, rayon, aramid and modacrylic - The spinneret is submerged in a bath containing a solution with causes the emerging fibres to precipitate and solidify to strands - The strands are then taken up and are normally drawn to increase their strength and align the polymers chain in the same direction thereby increasing fibre tenacity - Setting solution varies according to the fibre being manufactured and is normally sulphuric acid for rayon and DMF or thiocyanate for acrylic

Answer 16

- used for polymers which need to be dissolved in a solvent for spinning such as acetate and triacetate and acrylic - Instead of the spinneret being submerged in a chemical bath, it lies at the top of a warmed chamber - As the material emerges from the spinneret, the solvent evaporates causing the polymer to coagulate and form individual fibres - Hot air of warmed inert gases carry the solvent away where it can be recovered and reused - The strands are then taken up and are normally drawn

Answer 17

- used for polymers which can be melted such as nylons, polyester and various others - The polymer, normally in pellet form is melted in an inert atmosphere and then forced through the spinneret into a cooling chamber - The strands are then taken up and are normally drawn to increase overall strength - Cross sectional shape is easily controlled using melt spinning which is a very useful point for fibre identification

Answer 18

- Fibre cross sectional shape may be a result of the spinning process - With melt spun fibres it is possible to engineer the fibre cross section to produce certain specific properties such as greater softness of wicking Examples - Round – No major longitudinal striations uniform diameter - Bilobal – Kidney or dog-bone shaped single or double striation - Trilobal – Parallel striations that appear to move - Hollow – Single continuous hollow forming a black core - Complex – Multiple striation appearing irregular - Natural fibre may have their own distinct shape… e.g. silk

Answer 19

for many applications, lustre within man-made fibre can be problematic - Engineering fibre shape and cross section can help to alleviate the problem to some extent but may not always lead to favourable ‘hand’ - In such cases, it is possible to include materials that help dampen the lustre of fibres and in most cases this is Anatase (Titanium Dioxide) - Not only does Anatase help prevent light reflection, but its inclusion may also roughen the fibre surface dampening reflectivity - Delustrant appears as dark coloured ‘dots’ (0.1-1μm) within the fibre matrix and the size, shape, appearance, abundance and general distribution are useful for comparative purposes - Although the presence of delustrant does not serve to identify a specific fibre type, it is a useful indicator of man-made fibre and may be use as a comparison tool

Answer 20

• The dyeing process can be completed after spinning or part of the spinning process • dyes and pigments all can be designated by one or all of the following: • CI number – All dyes are given a 5 digit colour index number or CI number – Dyes which comes as multiple salts may include a sixth • Generic Name – All dyes are also given a generic name which may indicate use • Commercial Name

Answer 21

- Acid Dyes – Polyamides, wools, silk and polypropylene - Azo Dyes – Cellulosic fibres - Basic Dyes – Acrylics, polyester and polypropylene - Direct Dyes e.g Dylon – Cellulosic fibres - Disperse Dyes – Commonly polyester and acetate - Metallized Dyes – Wool - Sulphur Dyes – Cellulosic fibres - Vat Dyes – Cellulosic fibres – Principally denim - Pigment – Polypropylene, viscose, acrylic, polyamide and polyester (pigments are different to dyes as they are insoluable)