TXA quiz

Fibers, yarn intermediates, yarns, fabrics, and products made from fabrics which retain more or less completely the strength, flexibility, and other typical properties of the original fibers or filaments

a long chain molecule (macromolecule)

unit of matter having an extremely small diameter and a length at least 100 times the diameter

a continuous strand of textile fibers, and filaments

a thin sheet that is formed by interlaced, interloped, or knotted yarns, or by distributed fibers that are held together mechanically or chemically

thermal, moisture, specific gravity

resistance to acid, alkali, oxidizing

hydrochloric, sulfuric, nitric acids, acetic acids

sodium, potassium, and ammonium hydroxides

stress-strain, resilience, flexibility

Carbon, Hydrogen, Nitrogen, and Sulfur

• a large molecule commonly created by some form of polymerization
• Four conventional biopolymers: nucleic acids, proteins, carbs, and lipids

• Monomer --> polymer
• Ex: ethylene --> polyethylene
• 
• Ex: Propylene --> polypropylene
• Ex: Styrene --> polystyrene (styrofoam)
• No by-products are produced

individual units in polymer

• carbon atoms covalently bonded to each other or oxygen or nitrogen
• -C-C-C- , -C-O-C- , -C-N-C-

• Hydrogen (-H)
• Methyl (-CH₃)--Hydrophobic
• Hydroxyl (-OH)--Hydrophilic

• compound of C and H
• (R)

direct coupling of two identical monomers, unstable bonds (double bond)

breaks a double bond

breaks more double bonds (in addition to initiator)

• thermoplastic polymer, made by the chemical industry and used in a wide variety of applications
• An addition polymer, made from the monomer propylene, is rugged and unusually resistant to many chemical solvents, bases, and acids

thermoplastic substance, which is in solid (glassy) state at room temperature, but flows if heated above its glass transition temperature (for molding or extrusion), and becomes solid again when cooled

• used as an emulsion polymerization aid, as protective colloid, to make polyvinyl acetate dispersions
• One of the largest market applications in China

• thermoplastic vinyl polymer constructed of repeating vinyl groups (ethenyls) having one of their hydrogens replaced with a chloride group
• third most widely produced plastic, after polyethylene and polypropylene
• Widely used in construction because it's cheap, durable, and easy to assemble

By addition of plasticizers, the most widely used being phthalates

• Step-growth
• directly coupling two different monomers (reactive groups)
• the formation of covalent bonds in polymer chains produces by-products

the number of monomer units present in a polymer

[], O represent two different monomers

one monomer -[]-[]-[]-[]-

two monomers -[]-O-[]-O-

two or more homopolymers -([])_n-(O)_m-

forcing or pumping the spinning solution through the tiny holes of a spinneret

extruding a liquid polymer solution through one or thousands of holes in a spinneret

• Melt spinning
• Dry spinning
• Wet spinning

• a reservoir and a metering pump
• spinning jet (spinneret)
• take-up device to draw filaments and wind them onto a package

• thermoplastic polymers
• resin solids are melted in autoclave
• fiber is spun out into the air
• fiber solidifies
• least expensive
• Ex: nylon, polyester
• 

• while extruded fibers are solidifying, or in some cases after they have hardened, the filaments may be drawn to impart strength
• Drawing pulls the molecular chains together and orients them along the fiber axis, creating a considerably stronger yarn

• polymer is dissolved in solvent
• extruded into a hot gas where filaments are hardened
• solvent evaporates and is recycled
• Ex: acrylics, acetate
• 

• polymer is dissolved in suitable solvent
• extruded into a liquid bath, where filaments coagulate
• Ex: viscose, rayon, acrylics
• 

extrusion

forcing a thick, viscous liquid through the tiny holes of a device called a spinneret to form continuous filaments of semi-solid polymer

thermoplastic synthetics

Non-thermoplastic cellulosics

• consists of two polymers that are chemically and/or physically different
• Ex: side by side; matrix fibril; sheath core

• polymers are tightly packed, ordered
• Mechanical properties such as strength, stiffness, etc.
• (Rc)

loose, disordered

dyeability, absorbancy, etc. (Ra)

• the property of crystalline to amorphous regions
• C = Rc / (Rc + Ra)

• directions of polymer chains relative to the longitudinal axis of the fiber
• 

the stronger, stiffer, less stretchable, less absorbent

neutral molecular attractions due to very weak electrostatic forces

• positive end of one polar molecule to the negative end of another polar molecule
• Ex: the attraction occurring between hydrogen atoms on one molecule with strongly electronegative atoms on another molecule (chlorine, fluorine)

a strong dipole-dipole attraction occurring between hydrogen on one molecule and oxygen and nitrogen on another molecule

• an atom on one polymer chain and an atom on the adjacent polymer chain due to the sharing of electrons
• Ex: disulfide bonds in wool polymers

behaviors under a pulling force along the fiber axis

resistance to deformation developed within a fiber being subjected to a tensile force (gram or Newton)

1 kgf = 9.8N

stress expressed as a force per linear density (gram/denier or Newton/tex)

coarseness/fineness of fibers or yarns

• Tex = grams / 1000 m
• Tex = 9 x denier

• Denier = grams / 9000 m
• Denier = Tex / 9

• deformation (elongation) by a tensile force
• strain is the percent of elongation vs original length (%)

• Strain = E / L₀ x 100%
• 

• the initial portion of the stress-strain curve is straight
• the slope of the line is called initial (Young's) modulus
• IM indicates how easily the fiber extends under small stress

the stiffer and less extendible

• the point at which the stress-strain curve flattens
• Permanent change in fiber structure and permanent deformation occurs

Catastrophic change in structure (polymers massively either slip or rupture)

the maximum stress

the maximum strain

• a strained fiber contracts as the applied stress decreases
• Before the yield point, the fiber acts like a spring, 100% recovery
• Beyond the yield point partial recovery through a different path

• the amount of moisture the fiber contains when placed in an environment at a certain temperature and relative humidity
• MR = (W - W_b) / W_d x 100%
• W=weight at standard condition
• W_d=weight in the dry condition

70^oF and 65% RH

15~16%

12%

8.5%

6.5%

4%

1.5%

0.4%

0%

Wool

Polypropylene

a percent increase in diameter

shrinkage in length

• hydrophilic fibers except cotton and flax become weaker
• hydrophobic fibers are not or less affected by water

decreases with water absorption

• the amount of heat that evolves in water absorption
• It influences comfort
• When a person goes from an environment of low relative humidity into one of higher relative humidity, he/she will receive that heat

a measure of the amount of heat require to change the temperature of a unit mass of the fiber by 1^oC

a measure of the rate of heat flow through the fibers

bonds in the amorphous regions are broken up

bonds in the crystalline regions are broken up