Transcript hydrophilic
Introduction to Fibers II Measuring Properties – Moisture Terms • • • • hydrophilic (Gr.: hydros = water + philos = love)-fibers with an 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. Also hydrophilic fibers may either absorb or adsorb water. • • Absorb – moisture penetrates into the fiber Adsorb – moisture bound on the fiber’s surface Regain & Moisture Content Super Sc ale Compa ny W 100 grams Hot & Ready Oven Co. Regain = (W – w)/w x 100% Super Scale Company Moisture Content = (W – w)/W x 100% W gram s 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. s trong material weak material tenacity = strength/λ Mechanical Properties - Elongation ext en s ion 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 Electro nic Lo ad Cell Gauge Le ngth Fiber Vide o Monitor Compute r I nterface Pen Recorder Pull Apart Co., I nc Measurement of Mechanical Properties Initial modulus (stiffness) – resistance to deformation 2. Ultimate tenacity and strain 3. Specific work of rupture – energy (stored or released) at time of rupture 1. Tenacity 2 u 1 3 u Strai n Natural Fibers Cellulosic H CH OH 2 H O O H H OH H OH HO H H OH H O H H O glycoside linkages CH OH 2 D-glucose unit Cotton Seed hair fiber • Hydrophilic – affinity between the hydroxyl groups (OH-) and water (H—OH) • Adsorbs • cuticle (outer waxy layer) primary wall lumen s econdary wall convolution Wool • 18 different amino acids all with the structure shown to the right R H2 N C O C OH H General amino acid Polypeptide chain R1 N C H H O C R2 N C H H amide linkage O C Crosslinking-cystine O=C C=O CH•CH 2•S•S•CH •HC 2 cystine link H—N N—H Wool • • • • Depending upon the source, wool fibers range in length from 38-375 mm round, and have a diameter of about 25 µm. The fibers can be identified by the scales on the surface Felting Cortex Scales Wool ortho 2 types of cortical cells • Natural waviness • Because each amino acid has different properties • • Hydrophilic • para • absorbs Amphoteric – behaves like both acid and base Silk • • • • • Protein fiber 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 Very few cystine crosslinks Not amphoteric. Silk • • • 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 cocoon of the silkworm contains about 800-1200 meters of fiber (two strands); each fiber is about 10 µm thick sericin fibroin Asbestos • • • • 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 Vast majority of textile fibers are chrysotile asbestos, hydrated magnesium silicate, [Mg3Si2O5(OH)4] Flame resistant chrysotile Next • • Monday: Short reports Tuesday: Manufactured Fibers