PCC 302 Test One – Flashcards
Unlock all answers in this set
Unlock answers
Describe the 3 main stages of wet processing of textiles.
|
Preparation Coloration Finishing |
Describe the primary goals of wet processing.
|
Preparation Dyeing Finishing |
Describe what batch processes and continuous processes are.
|
Batch= entire batch of dry fabric contacts the entire amount of the solution
Continuous= Process where the dry fabric only contacts a portion of the solution |
Describe the objective of slashing, which yarns are treated, and list three main properties of a well sized yarn.
|
To improve the weaving efficiency of the yarn by making the yarn stronger.
Warp yarns are treated
Higher tensile strength, Lower Elongation, Higher abrasion resistance, more rigid, less flexible
|
Recognize a diagram of a slashing machine.
|
| [image] |
Describe at least three requirements of a good warp size.
|
| Inexpensive, Recyclable, Water Soluble, good adhesion, form strong, flexible, and abrasion resistant films |
Draw the structure of amylose, a component of starch.
|
| [image] |
Recognize amylopectin and describe the different properties between amylose and amylopectin.
|
[image] INSOLUBLE IN WATER |
Compare the differences in structure between amylose and cellulose.
|
[image] The second half is flipped in Cellulose (shown is carboxymethylcellulose, which just has some added stuff to the cellulose)
|
Recognize the repeat unit for PVA, and describe it’s properties.
|
[image] Water SOLUBLE More expensive than starch Recyclable |
Describe what BOD is, and why it is important in textile wet processing.
|
BIOLOGICAL OXYGEN DEMAND For a given material, the amount of oxygen that will be consumed by biological processes
It is important because too much BOD can cause pollution |
Describe what chemicals can be used to remove starch size.
|
| *Alpha Amylase enzyme, mineral acids, or oxidizing agents |
Sketch a desizing range, and explain how a J box works.
|
[image]
THE J-BOX provides a dwelling time for the reaction to take place |
Describe how PVA can be removed from warp yarns and how it can be recycled.
|
It can be dissolved using hot water It has a low BOD and therefore can be recycled -by- using ultrafiltration |
Describe how ultrafiltration works.
|
| [image] |
Describe the purpose of scouring.
|
| Process to remove impurities from fibers, yarns, fabrics, or garments |
List at least three impurities in cotton that should be removed during scouring.
|
Cellulose Proteins and Pectins Minerals Waxes |
Describe the three main chemicals used in a scouring bath and explain why they are used.
|
NaOH (Caustic Soda) -- Swell Motes(seed coat fragments), dissolve pectins and degrade proteins
Surfactant -- Reduces surface tension, disperse insoluble particles
Chelate -- form water-soluble complexes with metal ions |
Define saponification and emulsification.
|
Chemical process that converts insoluble fatty esters to soluble alcohols and fatty acid salts
Physical process that disperses water insoluble waxes and oils in water |
Explain in detail, and with the aid of diagrams, what a surfactant is and how it can form a micelle
|
molecules with both hydrophobic and hydrophilic characteristics [image] [image] |
Draw the structure of sodium lauryl sulfate.
|
| [image] |
Define what a chelate does.
|
| solubilize the metal ions and prevent interactions with other chemical species |
List at least three impurities present in wool, and explain why NaOH cannot be used to scour this fiber.
|
Keratin, Dirt, Grease NaOH will destroy wool |
Explain why synthetic fibers should be scoured.
|
Removes processing oils and waxes, residual warp sizes
|
Explain, with the aid of sketches, the concept of cloud point of solutions of non-ionic surfactants
|
The temperature at which a 1% solution of a nonionicsurfactant becomes insoluble [image] |
Explain why bleaching is sometimes performed on natural fibers.
|
| because it remove natural color bodies from fibers, yarns, fabrics, or garments |
Draw the structure of hydrogen peroxide.
|
H2O2 lines divided underneath
|
List the three main components of a peroxide bleach bath.
|
Sodium Hydroxide (activates peroxide) Hydrogen Peroxide (bleaching agent) Stabilizer (controls rate of bleaching reaction) |
Why are FBAs applied to cotton? Why are they NOT applied to wool or silk?
|
Increase whiteness in cotton by emitting in the blue range to offset the yellow
They will damage wool and silk through uv absorption |
Using sketches of absorption in the UV and emission in the visible spectrum, explain how an FBA works.
|
| [image] |
Using labels, sketch a reflectance curve for greige cotton, bleached cotton and bleached cotton treated with FBA.
|
| [image] |
State what chemical is used in mercerization and why the process is performed.
|
Treatment of cotton, or cotton blends, with a high concentration of NaOH prior to dyeing
|
Sketch the cross-sectional appearance of mercerized and non mercerized cotton
|
non-mercerized [image] mercerized Large circles, like theyre swollen |
Explain how mercerization works (i.e. via breaking and reforming H-bonding….)
|
[image] The bottom part is then taken out (the OHs) |
Recognize a mercerizing range.
|
| [image] |
Using a sketch define nanometer (nm)
|
| [image] |
Define the wavelength ranges of UV, visible and infra-red light, and explain the relationship of energy and wavelength.
|
| [image] |
Define the terms colorant, dye and pigment.
|
Colorant -- any material imparting color to another material Dye -- soluble in the medium in which it is applied Pigment -- insoluble, particulate: fixed by a binder, or mechanically entrapped in the fiber |
List at least five factors that are considered when designing dyes for textiles
|
HUE COLOR STRENGTH LIGHT FASTNESS WASH FASTNESS TOXICITY COST: inexpensive starting materials, inexpensive synthesis |
Using sketches and formaldehyde as an example explain how light is absorbed at 185 nm (UV region)
|
| [image] |
Using chemical structures as examples, explain how we get organic molecules to absorb light in the visible region (hint: Increasing the number of alternating single and double bonds)
|
| [image] |
Give two examples of electron donating groups
|
NH2 (amino) N(CH3) (dimethylamino) OH (hydroxy) |
Give two examples of electron withdrawing groups
|
NO2 (nitro) CN (cyano) |
Define the term: auxochromes and give a structural example of electron donating auxochromes.
|
Auxochromes (color intensifier)
[image] |
Recognize the structure of a direct dye
|
[image]
|
Explain what fiber can be dyed with direct dyes
|
Cotton, because the direct dyes form hydrogen bonds with the cellulose polymer
|
| With the aid of a sketch explain how direct dyes are attracted to cotton |
| [image] |
With the aid of a sketch, explain how direct dyes are attracted to cotton
|
| [image] |
Provide at least two advantages AND disadvantages to direct dyes
|
Economical process Easy to apply wide range of shades available
poor chlorine fastness limited brightness must be aftertreated with fixatives to achieve acceptable wetfastness properties |
Describe a typical dyeing procedure for direct dyes on cotton.
|
Load well prepared fabric into dyeing machine; fill to proper running level
Add wetting agent and diluted dye at room temperature
Heat to dyeing temperature: hold 20 minutes
add salt in three increments over 45 minutes, run additional 10 minutes
cool and rinse several times with salt solution
aftertreat with cationic fixative if required |
Be able to recognize a typical structure of an azo based fiber reactive dye, and an anthraquinone based fiber reactive dye.
|
[image]6 member brain, chlorine
[image] |
Show how a covalent bond can be formed between a fiber- reactive dye and an OH group in cellulose
|
| [image] |
Explain why alkali (OH-) is needed to fix the dye to the fibre, and why a precise amount of alkali is needed (typically, to give pH 11) (slide 7)
|
Alkali is used to get a desired pH around 11 Too much OH- gives greater hydrolysis of dye Too little OH- gives lower fixation rate to fiber |
Describe which fibers can be dyed with disperse dyes
|
Polyester, acetate, and nylon because it has no affinity for cellulose |
Be able to recognize the structures of the three main chemical classes of dyes: azo, anthraquinone and nitrodiphenylamine
|
| [image] |
Explain, with the aid of sketches, how disperse dyeing of fibers occurs
|
[image] [image] |
List at least two benefits and disadvantages of using disperse dyes
|
+Good fastness properties +Wide range of shades available +unique application properties
-thermal migration to fiber surface during drying can cause crocking or staining problems -Polyester dyeing requires carriers or high temperature |
Explain why high temperature (130 oC) is required to dye PET with disperse dyes without a carrier.
|
Provides energy for diffusion
Increases polymer chain mobility |
Explain why a reduction clear is sometimes necessary, and explain how it is performed (what chemicals, temp. and time).
|
Removes surface dyes to improve crockfastness Chemically reduces the chromophores to water-soluble material
|
Explain what polyester trimer.
|
Polyester oligomer Controlled with auxiliaries and procedures |
Describe, with the aid of a diagram, a typical continuous dyeing process of polyester (e.g. the Thermosol® process)
|
pad on disperse dye and antimigrant predry; dry heat to 400c for 45seconds
draw a circle with dots around it, and then dots in it
|
Explain the difference between low, medium and high energy disperse dyes and explain why the different energy classes should not be used in the same dyebath.
|
| [image] |
