Week 2 Lecture Notes
Week 2 Lecture Notes TXC 006
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This 7 page Class Notes was uploaded by Demi Chang on Wednesday October 7, 2015. The Class Notes belongs to TXC 006 at University of California - Davis taught by Sun, Gang in Fall 2015. Since its upload, it has received 47 views. For similar materials see Introduction to Textiles in Textile and Apparel Management at University of California - Davis.
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Date Created: 10/07/15
TXC 006 Introduction to Textiles lecture Notes lecture 4 3 Hberformation Fiber Spinning is a process where synthetic bers are made by forcing a molten liquid polymer through a spinneret with a thousand holes A spinneret is similar to a faucet head with the tiny holes for water to lter through though ber is produced instead of water Three common spinning processes include EgtMelt Spinning The molten polymer is extruded through the spinneret to create brous forms of polymer that solidify in cool air Melt spinning is used for thermoplastic polymers which can be melted from solid to liquid and vice versa making it an easily processed material Textiles formed through melt spinning include nylon polyester and ole n ber Fiber spinning is a relatively simple ber spinning process that requires to solvent produces no water pollution and its product can be recycled Egt Dry Spinning The polymer dissolves into an organic solvent to become a polymer solution This solution is forced through a spinneret into a circulating current that evaporates the solvent from the polymer to cause the bers to harden The solvent can then be reused recycled Dry Spinning creates textiles like acrylic ber and Spandex It does not contribute directly to water pollution and is ideal for polymers that can molecularly separate at low temperatures Egt Wet Spinning The polymer dissolves into a water solution solvent and is forced through ajet into a liquid bath where the laments thicken Wet spinning can create rayon acetate and aramid bers Acrylic which can be created through dry spinning is also able to be created through wet spinning as well Wet spinning is the most problematic process because it produces water pollution and toxic chemicals 3 Otherfxtrusion ProcessesThese processes include EgtGel Spinning A diluted syrupy solution of high molecular weight polymer is pushed through ajet in uid form at the extrusion temperature The gel form of the bers is cooled and processed after Gel spinning is often used for nonapparel bers such as for textiles in bulletproof vests and seat belts or textiles requiring the strongest ber High MW Molecular Weight polyethylene ber a textile used in body armor and parachutes also uses gel spinning Egt Reaction Spinning This process causes the polymers to form together as it39s being pushed out of the spinneret 3 Fiber Properties include Mechanical Sorptive Thermal Chemical and Miscellaneous properties EgtMechanica Properties refer to a ber s response to applied forces and how the ber recovers from those forces The overarching mechanical property is Durability or a ber39s ability to retain its physical shape under mechanical stress for a reasonable time period Properties under durability include 1 Stress a ber s resistance to deformation as it is being subjected to a pullingtensile force This resistance creates a change in the ber39s length Stress is measured in units of N newtonstex or g gramsden 2 Strain The deformation of a ber that is caused by applying the pullingtensile force Deformation refers to the lengthening or extension of the ber similar to a stretched and elongated rubber band Strain is measured as a percentage which is calculated by Change in lengthoriginal unstretched length100 Tenacity at Ereahjl a m E quot E quot quot quotquotquotquot quotquot quotquotquotT T quotquot L 39 quotl The polymer chains begin tn straighten The chain molecue aleng the ber anis beins tn straighten its arrangement as it stretches 2 chain molecules begin to slip causing the fiber tn became Inngen as the E w 7 pnlymeir deferms Ann fiber pullledl pass Area Em I ma Z w the yield nint will fall bath e last39c I T t W w h a p necesery me After the yield paint the E A i I if if can walk f imaterial begins tn nae tn the force and w p 39 TEE TEE J I Rupture I more defnir mation accurs even though I 139 3 m3 ma 3 v 2 the force is being applied at the same g a if Hecnaered Wench Area lincpgaginy rate 3 a 39 nnj in at Brea f I ll Lg bl quot i Elongation 1 Strain liii Initial E Yigld Hardening lD Rupture Stness5train Enrae Modulus Pint paint Pint ElemRemains 3 Tenacity The stress expressed as force per linear density can be measured in gramsforce per denier or Newtons per tex Breaking tenacity or tenacity at breakquot in graph above is the level of tenacity in which the ber ruptures The higher the orientation degree of polymerization and crystallinity the higher the breaking tenacity For example ax and ole n have high breaking tenacity while wool and acetate have low breaking tenacity 4 Elongation The ber39s ability to extend lengthen which is expressed as a percentage of its original length change in lengthoriginal unstretched length 100 Breaking elongation or elongation at breakquot in graph above refers to the elongation when the ber ruptures The higher the crystallinity the lower the break elongation While wool and nylon have high elongation cotton and ax has low elongation 5 Initial Modulus The rst segment of the stressstrain curve is the straight line Aquot in graph above where stress is proportional to strain as the force is being applied at a steady positive rate the strain of the ber increases at a steady positive rate as well The line39s slope stress strain measures the ber39s initial modulus or Young39s modulus The higher the modulus the harder it is to elongate For example cotton has a high modulus making it a dif cult textile to elongate while rayon has a low modulus making it easier to elongate Higher modulus textiles tend to be higher in crystallinity and molecules while lower modulus textiles are more exible and softer 6 Work of Rupture Toughness A ber39s ability to endure large deformation without rupturing This is measured by the area under the stressstrain curve areas XYZ in graph above Polyester and nylon are tough bers therefore their work of rupture encompasses a larger area underneath the stressstrain curve 7 Yield Point The point where the stressstrain curve attens and the molecules permanently deform Bquot in graph above If a textile is stretched before the yield point 1quot in graph above then the textile will return to the initial modulus However if it is stretched beyond the yield point 2quot in graph above then the textile will fall to the elastic recovery curve lecture 5 8 Elastic Recovery A ber39s ability to return to its initial length after being stressed elongated Spiraledfolded polymer chains tend to create a springlike property Textiles with more hydrogen and ionic bonds may reduce the elastic recovery For one Nylon as good elastic recovery while rayon does not 9 Resilience work recovery A ber39s ability to spring back after being extended It is expressed as the ratio of recovered work X to total work XY in graph above needed to deform and release the ber Crimped bers are more resilient than smooth bers Hydrogen bonds lower the level of resilience The higher level of resilience the more wrinkle resistant the textile is For example polyester nylon and wool have the highest degree of resilience which is why nylon and wool are used for carpeting completely wrinkleprintfree Cotton and rayon which have the lowest degree of resilience would be easy to make imprints in if they were made into carpeting 10 Stiffness exural rigidity A ber39s resistance to bending or its ability to carry loads without deforming lengthening Fibers3929 in terms of dentex and crosssectional shape can affect the ber39s stiffness The bigger the size in dentex the coarser the ber is The coarser the ber the stiffer it is The smaller the size the ner and less stiff it becomes Spectra ole n ber has the highest stiffness while Spandex has the lowest stiffness 11 Abrasion Resistance A ber39s ability not to break crack or wear away under a rubbing force or friction Textiles like nylon has the highest abrasion resistance making it ideal for making backpacks Textiles like Acetate has very low abrasion resistance which is why it is made to create women39s delicates night gowns 12 Flexibility The number of times a ber can be bent without rupturing The higher a ber39s crystallinity the less exible it is Polyester has high exibility while carbon has the lowest exibility gt Sorptive Properties 1 Moisture RegainVaporous Water Absorption The percentage of moisture a ber contains when placed an environment This is calculated by its dry weight or the weight of the ber when it contains no water at all If W1 is the ber39s weight in a humid environment and W0 is the ber39s dry weight then the change can be calculated by W1W0 W1 Sorptive properties affect the textile products weight and its commercial use The more polar hydrogen bonds the higher the moisture regain natural bers have high moisture regain while synthetic bers have low moisture regain A Hydrophilic water loving textiles like cotton have more polar and hydrogen bonds B Hydrophobic water avoiding textiles like polyester do not absorb water well C Hygroscopic textiles that absorb moisture in large amounts without feeling wet to the touch such as wool and sports clothing eg the synthetic ber Coolmax 2 Swelling Liquid Water Absorption The increase in a ber39s size crosssectional area or length when it is immersed in water It is measured as a percent increase in diameter or length The wetmoa uus is when the ber is at maximum water absorbance While rayon has a high swelling effect which is why it can not be washed like other apparel textiles nylon as the least swelling effect A wet ber can often have different tenacity mechanical properties than the dry ber While linen and cotton have higher wet tenacity textiles like silk wool and nylon are weaker when wet 3 Heat of Wetting The heat produced when a ber absorbs water when a ber absorbs water heat is created from the attractive force between the ber and the water molecules Hydrophilic bers have higher heat of wetting Wool for example has the highest heat of wetting it is often used to make hiking socks because the sweat will make the skin feel warmer even in extremely cold weather 4 Oil Absorption Amount of oil adsorbed held as a thin lm on the outside surface or absorbed by a ber Oil can refer to oils from food the body cosmetics or soil Oleophilicity refers to a ber39s ability to release oily soil when placed in a solution of detergent Cotton a hydrophilic textile has the highest oil absorption and easiest oil release Polyester a hydrophobic textile has the lowest oil absorption and hardest oil release gtTherma Properties 1 Thermal Conductivity the rate of heat ow that occurs along the ber 2 Heat Resistance Heat Durability The ber39s temperature as it begins to degrade break apart 3 Glass Transition Temperature Tg The ber39s temperature when it changes from glass to a rubber state 4 Softening Melting Temperature The temperature that thermoplastic ber softens and changes from a solid state to a liquid state 5 Decomposition Temperature The temperature where a ber39s polymer structure loses its chemical identity a higher temperature than Heat Resistance Thermoplastic bers are soft when heated and hard when cooled lecture 6 6 Combustibility a ber39s ability or inability to ignite making it either combustible or noncombustible Naturally ame resistant bers include Nomex and Modacrylic while modi ed ame resistant bers include wood cotton and polyester 7 Resistance to Chemicals A ber39s stability in regards to its interaction with acids bases and organic solvents For example rayon ax and cotton are very vulnerable to acids like sulfuric acid and hydrochloric acid 0n the other hand wool and silk are extremely vulnerable to bases like alkaline Exposure to these solvents can reduce breaking tenacity and other mechanical properties gt Miscellaneous Properties 1 Resistance to UV Light short or high energy wavelengths in sunlight uorescent lights can break covalent bonds in polymers Manmade bers can be altered in its size crosssectional shape and delustrant amount to resist degradation by UV light 2 Resistance to Microorganisms Natural bers are the most likely to face deterioration from biological organisms especially in warm humid areas while synthetic bers are less likely to face deterioration Geotextiles which are often associated with soil and used in drains and roads also face this problem as well 3 Electrical Resistance Fibers with higher moisture content have lower electrical resistivity or lack of a static charge This is becoming more important today with the presence of wearable technology where clothing are being used as ways of conducting or generating energy and connecting it to mobile devices 4 Speci c Gravity density The ratio of the ber39s mass to the mass of water at equal volume and at 392 degrees Fahrenheit m mass v volume Speci c gravity ranges in value between 09 to 151 3 Textile Labeling EgtThe Three Major Laws in textile labeling are 1 WPL Wool Products Labeling wool textile products both 100 wool or wool blends must be labeled 2 TFPIA Textile Fiber Products Identi cation Act Fibers other than wool that are made into apparel interior household consumer and industrial products or sold overthecounter must have labels 3 Care Label Rule This rule only applies to apparel or certain piece goods Things like upholstery sewing threads apparel paddings and surgical dressings are exempt from this rule gt The Standard Terminology and Labeling on all apparel and piece good labels include these ve items names of ber content ber composition in terms of percent of total fabric the manu rcturer39sname country of origin and the care instructions 1 Generic names manu rctureo bers and common names natural bers are the only names allowed to be used to de ne the ber content Some examples of generic bers include acetate acrylic aramid Kevlar Nomex glass metallic modacrylic nylon ole n polyester rayon rubber and spandex 2 The percent composition only has to be listed by its common generic name if the ber more than 5 of the weight Fiber content is listed from highest to lowest eg 55 cotton 35 polyester 10 acrylic 3 The manurbcturerlsname RN registered number or WPL number Wool Product Labeling should be labeled so the customer has the ability to contact the producer Numbers can be applied at the FTC Federal Trade Commission 4 The country oforgin can only have two countries at most be disclosed on all textile products in the US The four forms of country of origin include A Made in XOffshore Country The last country involved in substantially transforming the product before being imported to the US is the country name labeled on it For some products the country of origin is the last country to nish the manufacturing For cutandassembled it is the country that sews and assembles the textile For knitwear it is the country that produces the parts For dyeing it the country that produces the fabric B Made in the USA textile products are made completely in the US C Made in the USA of Imported Components The textile and product was made in the USA but the ber was from another country For example Made in the USA of silk ber imported from Chinaquot D Partially Manufactured in the USA and Partially Offshore The product may have been made in the USA but the ber and textile parts are from another country For example Imported fabric from Italy sewn in the USAquot Additional Chapter 7 Reading Highlights 3 Polymer Synthesis Polymerization for Synthetic Fibers EgtStep Growth or Step Reaction Where the formation of every covalent bond in the polymer is accompanied by a small byproduct molecule that is liberated often times water This occurs in the creation of nylon and polyester EgtChain Growth or Chain Reaction Addition Polymerization unreacted monomers are approached by a reactive initiator molecule A free radical is then produced which will most likely strike another monomer to create a polymer chain of identical monomer units 3 Drawing and Heat Setting EgtDrawing When polymers are extruded they are unoriented or undrawn meaning that they have a low degree of orientation crystallinity Filaments are drawn or elongated under heat to move them closer together EgtHeat Setting The heat stabilizes the synthetic bers and lowers the stress within the ber Modifying Manufactured bers can be achieved by changing the crosssectional shape surface contour degree of polymerization crystallinity incorporating chemicals in polymer chains adding monomers adding reactive groups and making biocomponents two polymers that are chemically physically different
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