PCC 302 Test One – Flashcards

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Describe the 3 main stages of wet processing of textiles. 

 

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Preparation

Coloration

Finishing

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Describe the primary goals of wet processing. 

 

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Preparation

Dyeing

Finishing

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Describe what batch processes and continuous processes are. 

 

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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

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Describe the objective of slashing, which yarns are treated, and list three main properties of a well sized yarn. 

 

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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

 

 

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Recognize a diagram of a slashing machine. 

 

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[image]
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Describe at least three requirements of a good warp size. 

 

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Inexpensive, Recyclable, Water Soluble, good adhesion, form strong, flexible, and abrasion resistant films
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Draw the structure of amylose, a component of starch. 

 

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Recognize amylopectin and describe the different properties between amylose and amylopectin. 

 

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INSOLUBLE IN WATER

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Compare the differences in structure between amylose and cellulose. 

 

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The second half is flipped in Cellulose (shown is carboxymethylcellulose, which just has some added stuff to the cellulose)

 

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Recognize the repeat unit for PVA, and describe it’s properties. 

 

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Water SOLUBLE

More expensive than starch

Recyclable

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Describe what BOD is, and why it is important in textile wet processing. 

 

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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

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Describe what chemicals can be used to remove starch size. 

 

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*Alpha Amylase enzyme, mineral acids, or oxidizing agents
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Sketch a desizing range, and explain how a J box works. 

 

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THE J-BOX provides a dwelling time for the reaction to take place

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Describe how PVA can be removed from warp yarns and how it can be recycled. 

 

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It can be dissolved using hot water

It has a low BOD and therefore can be recycled

-by- using ultrafiltration

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Describe how ultrafiltration works. 

 

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Describe the purpose of scouring. 

 

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Process to remove impurities from fibers, yarns, fabrics, or garments
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List at least three impurities in cotton that should be removed during scouring. 

 

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Cellulose

Proteins and Pectins

Minerals

Waxes

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Describe the three main chemicals used in a scouring bath and explain why they are used. 

 

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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

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Define saponification and emulsification. 

 

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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

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Explain in detail, and with the aid of diagrams, what a surfactant is and how it can form a micelle 

 

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molecules with both hydrophobic and hydrophilic characteristics

[image]

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Draw the structure of sodium lauryl sulfate. 

 

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[image]
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Define what a chelate does. 

 

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solubilize the metal ions and prevent interactions with other chemical species
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List at least three impurities present in wool, and explain why NaOH cannot be used to scour this fiber. 

 

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Keratin, Dirt, Grease

NaOH will destroy wool

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Explain why synthetic fibers should be scoured. 

 

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Removes processing oils and waxes, residual warp sizes

 

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Explain, with the aid of sketches, the concept of cloud point of solutions of non-ionic surfactants 

 

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The temperature at which a 1% solution of a nonionicsurfactant becomes insoluble

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Explain why bleaching is sometimes performed on natural fibers. 

 

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because it remove natural color bodies from fibers, yarns, fabrics, or garments
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Draw the structure of hydrogen peroxide. 

 

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H2O2

lines divided underneath

 

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List the three main components of a peroxide bleach bath. 

 

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Sodium Hydroxide (activates peroxide)

Hydrogen Peroxide (bleaching agent)

Stabilizer (controls rate of bleaching reaction)

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Why are FBAs applied to cotton? Why are they NOT applied to wool or silk? 

 

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Increase whiteness in cotton by emitting in the blue range to offset the yellow

 

They will damage wool and silk through uv absorption

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Using sketches of absorption in the UV and emission in the visible spectrum, explain how an FBA works. 

 

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Using labels, sketch a reflectance curve for greige cotton, bleached cotton and bleached cotton treated with FBA. 

 

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State what chemical is used in mercerization and why the process is performed. 

 

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Treatment of cotton, or cotton blends, with a high concentration of NaOH prior to dyeing

 

  • Improved color yield in cotton
  • Improved appearance after dyeing
  • Improved strength
  • Improved luster
  • Increased absorbency

 

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Sketch the cross-sectional appearance of mercerized and non mercerized cotton 

 

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non-mercerized

[image]

mercerized

Large circles, like theyre swollen

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Explain how mercerization works (i.e. via breaking and reforming H-bonding….) 

 

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The bottom part is then taken out (the OHs)

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Recognize a mercerizing range. 

 

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Using a sketch define nanometer (nm) 

 

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Define the wavelength ranges of UV, visible and infra-red light, and explain the relationship of energy and wavelength. 

 

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Define the terms colorant, dye and pigment. 

 

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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

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List at least five factors that are considered when designing dyes for textiles 

 

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HUE

COLOR STRENGTH

LIGHT FASTNESS

WASH FASTNESS

TOXICITY

COST: inexpensive starting materials, inexpensive synthesis 

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Using sketches and formaldehyde as an example explain how light is absorbed at 185 nm (UV region) 

 

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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) 

 

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Give two examples of electron donating groups 

 

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NH2 (amino)

N(CH3)  (dimethylamino)

OH (hydroxy)

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Give two examples of electron withdrawing groups 

 

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NO2 (nitro)

CN (cyano)

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Define the term: auxochromes and give a structural example of electron donating auxochromes. 

 

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Auxochromes (color intensifier)

 

[image]

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Recognize the structure of a direct dye 

 

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[image]

 

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Explain what fiber can be dyed with direct dyes 

 

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Cotton, because the direct dyes form hydrogen bonds with the cellulose polymer

 

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With the aid of a sketch explain how direct dyes are attracted to cotton
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With the aid of a sketch, explain how direct dyes are attracted to cotton 

 

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Provide at least two advantages AND disadvantages to direct dyes 

 

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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

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Describe a typical dyeing procedure for direct dyes on cotton. 

 

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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

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Be able to recognize a typical structure of an azo based fiber reactive dye, and an anthraquinone based fiber reactive dye. 

 

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[image]6 member brain, chlorine

 

[image]

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Show how a covalent bond can be formed between a fiber- reactive dye and an OH group in cellulose 

 

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[image]
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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) 

 

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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

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Describe which fibers can be dyed with disperse dyes 

 

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Polyester, acetate, and nylon

because it has no affinity for cellulose

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Be able to recognize the structures of the three main chemical classes of dyes: azo, anthraquinone and nitrodiphenylamine 

 

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[image]
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Explain, with the aid of sketches, how disperse dyeing of fibers occurs 

 

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[image]

[image]

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List at least two benefits and disadvantages of using disperse dyes 

 

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+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

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Explain why high temperature (130 oC) is required to dye PET with disperse dyes without a carrier. 

 

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Provides energy for diffusion

 

Increases polymer chain mobility

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Explain why a reduction clear is sometimes necessary, and explain how it is performed (what chemicals, temp. and time). 

 

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Removes surface dyes to improve crockfastness

Chemically reduces the chromophores to water-soluble material

 

  1. Pad on disperse dye and antimigrant
  2. Predry; dry
  3. Heat to 400c for 45 seconds
  4. Cool on Cans
  5. Pad on caustic and hydro

 

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Explain what polyester trimer. 

 

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Polyester oligomer

Controlled with auxiliaries and procedures

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Describe, with the aid of a diagram, a typical continuous dyeing process of polyester (e.g. the Thermosol® process) 

 

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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

 

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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. 

 

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