Introduction to Fibers II

Measuring Properties – Moisture Terms hydrophilic (Gr.: hydros = water + philos = love)-fibers with an affinity to water hydrophilic (Gr.: hydros = water + philos = love)-fibers with an affinity to water hydrophobic (Gr.: hydros = water +phobos = loathe)-fibers with no affinity to water hydrophobic (Gr.: hydros = water +phobos = loathe)-fibers with no affinity to water The moisture properties of a fiber is determined, in large measure, by its chemical composition; does it have an affinity for water. The moisture properties of a fiber is determined, in large measure, by its chemical composition; does it have an affinity for water. Also hydrophilic fibers may either absorb or adsorb water. Also hydrophilic fibers may either absorb or adsorb water. Absorb – moisture penetrates into the fiber Absorb – moisture penetrates into the fiber Adsorb – moisture bound on the fiber’s surface Adsorb – moisture bound on the fiber’s surface

Regain & Moisture Content Regain = (W – w)/w x 100% Moisture Content = (W – w)/W x 100%

Mechanical Properties - Tenacity A fiber that is made from a less strong material may be able to carry more load than one made from a stronger material if the former is greater in size. tenacity = strength/λ

Mechanical Properties - Elongation Similarly, a long fiber will extend further when stretched than a short fiber, even if they are of the same material. elongation = “stretched length” – original length strain = elongation/original length Often these are multiplied by 100% to give percent elongation and percent strain

Measurement of Mechanical Properties

1. Initial modulus (stiffness) – resistance to deformation 2. Ultimate tenacity and strain 3. Specific work of rupture – energy (stored or released) at time of rupture 2 3 1

Natural Fibers

Cellulosic

Cotton Seed hair fiber Seed hair fiber Hydrophilic – affinity between the hydroxyl groups (OH - ) and water (H—OH) Hydrophilic – affinity between the hydroxyl groups (OH - ) and water (H—OH) Adsorbs Adsorbs

Wool 18 different amino acids all with the structure shown to the right 18 different amino acids all with the structure shown to the right General amino acid

Polypeptide chain

Crosslinking-cystine

Wool Depending upon the source, wool fibers range in length from mm Depending upon the source, wool fibers range in length from mm round, and have a diameter of about 25 µm. round, and have a diameter of about 25 µm. The fibers can be identified by the scales on the surface The fibers can be identified by the scales on the surface Felting Felting

Wool 2 types of cortical cells 2 types of cortical cells Natural waviness Natural waviness Because each amino acid has different properties Because each amino acid has different properties Hydrophilic Hydrophilic absorbs absorbs Amphoteric – behaves like both acid and base Amphoteric – behaves like both acid and base

Silk Protein fiber Protein fiber The secretion of the larva of the Bombyx mori moth, used to form its cocoon The secretion of the larva of the Bombyx mori moth, used to form its cocoon The major fiber protein is fibroin, which is composed of 15 amino acids in a polypeptide chain The major fiber protein is fibroin, which is composed of 15 amino acids in a polypeptide chain Very few cystine cross- links Very few cystine cross- links Not amphoteric. Not amphoteric.

Silk The larva secretes two 'D' shaped filaments (called brins) simultaneously, held together by the protein gum sericin. The larva secretes two 'D' shaped filaments (called brins) simultaneously, held together by the protein gum sericin. The fibers are highly regular and very lustrous. The fibers are highly regular and very lustrous. The cocoon of the silkworm contains about meters of fiber (two strands); each fiber is about 10 µm thick The cocoon of the silkworm contains about meters of fiber (two strands); each fiber is about 10 µm thick fibroin sericin

Asbestos Asbestos is the only naturally occurring mineral fiber Asbestos is the only naturally occurring mineral fiber There are 6 forms of asbestos: Six minerals are defined as "asbestos" including, chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite There are 6 forms of asbestos: Six minerals are defined as "asbestos" including, chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolitechrysotile amositecrocidolitetremolite anthophylliteactinolitechrysotile amositecrocidolitetremolite anthophylliteactinolite Vast majority of textile fibers are chrysotile asbestos, hydrated magnesium silicate, [Mg 3 Si 2 O 5 (OH) 4 ] Vast majority of textile fibers are chrysotile asbestos, hydrated magnesium silicate, [Mg 3 Si 2 O 5 (OH) 4 ] Flame resistant Flame resistant chrysotile

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