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researh design > dyeing & dyestuff > Flashcards

dyeing & dyestuff Flashcards

1
Q

What is dyeing?

A

The application of color to a textile material with a degree of fastness.

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2
Q

What is the difference between dyeing and printing?

A

Dyeing applies a uniform single color, while printing creates multicolored patterns.

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3
Q

What are the two main types of colorants used in textiles?

A

Dyes and pigments.

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4
Q

How do dyes impart color?

A

By penetrating the fiber’s internal structure on a molecular level.

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5
Q

How do pigments impart color?

A

By attaching to the fiber’s outer surface, held by a binder.

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6
Q

Name three historical natural dyes.

A

Indigo, madder, cochineal.

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7
Q

Why are synthetic dyes more prevalent than natural dyes today?

A

Superior color depth, brightness, and colorfastness; lower cost and higher volume production.

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8
Q

What was the first synthetic dye?

A

Mauveine, discovered by William Henry Perkin in 1856.

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9
Q

What are the four forms in which textiles can be dyed?

A

Fiber, yarn, fabric, garment.

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10
Q

What is another term for fabric dyeing?

A

Piece dyeing.

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11
Q

Name two methods of dyeing fibers.

A

Stock dyeing and dope dyeing (solution dyeing).

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12
Q

Describe stock dyeing.

A

Dyeing fibers in loose form, requiring special equipment.

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13
Q

Describe dope dyeing.

A

Incorporating colored pigments into the polymer before fiber extrusion.

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14
Q

What is a benefit of dope dyeing?

A

Excellent fastness properties.

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15
Q

What is a drawback of dope dyeing?

A

Increased cost and reduced flexibility for color changes.

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16
Q

What is a heather style fabric?

A

A fabric with a mixed color effect created by blending differently colored fibers.

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17
Q

Name three methods of dyeing yarns.

A

Skein dyeing, package dyeing, beam dyeing.

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18
Q

When is skein dyeing used?

A

For bulky yarns that shouldn’t be wound under tension.

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19
Q

What is a key advantage of yarn dyeing over printing?

A

Typically produces higher color quality.

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20
Q

What are dye tubes used for?

A

Winding yarn for package dyeing.

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21
Q

What is critical for high-quality package dyeing?

A

Accurate control of yarn tension and package density.

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22
Q

What type of dyeing is advantageous for fabrics that crease easily?

A

Beam dyeing.

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23
Q

What is the most widely used dyeing technique?

A

Fabric dyeing.

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24
Q

Name three fabric printing methods.

A

Engraved roller, flat screen, rotary screen.

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25
Q

Describe tie-dyeing.

A

A technique involving knotting fabric and dipping it in dye baths to create patterns.

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26
Q

What is a benefit of garment dyeing?

A

Faster response time to market color changes.

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27
Q

What is a drawback of garment dyeing?

A

Lower color quality and reproducibility compared to fabric dyeing.

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28
Q

What must be considered when garment dyeing?

A

Thread, buttons, zippers, and seams must withstand the process.

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29
Q

List the three primary objectives of the dyeing process in order of importance.

A

Shade matching, colorfastness, cost-effectiveness.

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30
Q

What is the largest cause of textile seconds?

A

Off-shade (failure to match the shade standard).

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31
Q

What organization publishes test methods for textile fastness?

A

AATCC (American Association of Textile Chemists and Colorists).

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32
Q

What three components are necessary for color perception?

A

Light source, observer, object (and its surroundings).

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33
Q

What standard light source is typically used for shade evaluation?

A

D-65 (artificial daylight).

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34
Q

What is ring dyeing?

A

Incomplete dye penetration resulting in uneven color and potential for white areas with wear.

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35
Q

What is a crucial step for good-quality dyeing?

A

Good fabric preparation (scouring and bleaching).

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36
Q

How should knit fabrics be handled during wet processing?

A

Minimize tension to reduce shrinkage.

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37
Q

What is chemical barré?

A

Uneven dye uptake due to varying crystalline/amorphous regions in fibers.

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38
Q

What is mechanical barré?

A

Streakiness in knitted fabrics caused by factors other than dyeing.

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39
Q

Name two classifications of dyeing processes based on fabric amount.

A

Exhaustion (batch) dyeing and continuous dyeing.

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40
Q

Describe exhaustion dyeing.

A

Dyeing a fixed amount of material in a bath, requiring time and agitation.

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41
Q

What is fractional exhaustion?

A

The ratio of dye in the fabric to the initial dye in the bath.

42
Q

What is percent dye owf?

A

Percentage of dye based on the initial weight of the fiber/fabric.

43
Q

What is liquor ratio?

A

The ratio of bath weight to fabric weight.

44
Q

What is a benefit of a higher liquor ratio?

A

More level dyeing.

45
Q

Describe continuous dyeing.

A

Dyeing a continuously moving width of fabric using a padder.

46
Q

What is wet pickup in continuous dyeing?

A

The amount of dye solution absorbed by the fabric.

47
Q

What can cause uneven dyeing in continuous dyeing?

A

Uneven drying after padding.

48
Q

What is an advantage of continuous dyeing?

A

Higher production efficiency and lower water/energy use per yard.

49
Q

What is a disadvantage of continuous dyeing?

A

High initial cost and large space requirements.

50
Q

What promotes levelness and uniformity in dyeing?

A

Good preparation, agitation, high liquor ratio, gradual temperature increase.

51
Q

Name three factors that can cause non-level dyeing.

A

Inadequate agitation, low liquor ratio, rapid temperature increase.

52
Q

Why are dye classes fiber-specific?

A

Different fibers have different chemical structures and affinities for different dyes.

53
Q

Name four common dye classes.

A

Direct, reactive, acid, disperse.

54
Q

What is a key consideration when choosing dyes besides shade and fastness?

A

Toxicity to workers and the environment.

55
Q

Where can information on dyestuffs be found?

A

AATCC Buyer’s Guide and Colour Index International online.

56
Q

What is a fishbone diagram used for?

A

Identifying causes of problems in a manufacturing process.

57
Q

What are the four ‘M’s in a typical manufacturing process?

A

Materials, Machines, Manpower, Methods.

58
Q

What are the main categories in the shade reproduction fishbone diagram?

A

Materials, Equipment, Human Factors, Processes, Controls, Logistics.

59
Q

How many dye classes are used to dye cotton and other cellulosics?

A

Five: Direct, Naphthols, Reactives, Sulfurs, Vats.

60
Q

What is the most widely used dye class for cellulosics?

A

Reactive dyes.

61
Q

Which fibers are typically dyed with disperse dyes?

A

Almost all synthetic fibers, particularly polyester.

62
Q

Which fibers are primarily dyed with acid dyes?

A

Nylon, wool, silk.

63
Q

Which fibers are dyed with basic dyes?

A

Acrylic fibers and cationic-dyeable polyester.

64
Q

How are polypropylene and polyethylene fibers dyed?

A

Solution dyeing or pigment/binder systems.

65
Q

Describe mechanical entrapment in dye retention.

A

Dye molecules are physically trapped inside the fiber.

66
Q

Describe ionic bonding in dye retention.

A

Oppositely charged dye and fiber form a strong bond.

67
Q

Describe covalent bonding in dye retention.

A

Dye chemically reacts with the fiber to form a bond.

68
Q

Describe preferential absorption in dye retention.

A

Dye is attracted to the fiber due to chemical similarities.

69
Q

Name three commercially important dye classes for cellulosics.

A

Direct, reactive, vat.

70
Q

Describe the dye retention mechanism of direct dyes on cellulose.

A

Preferential absorption via hydrogen bonding and Van der Waals forces.

71
Q

Why is salt added to direct dye baths?

A

To neutralize the negative charge on the fiber and overcome dye repulsion.

72
Q

How can washfastness of direct dyes be improved?

A

Aftertreatments like cationic fixing agents or formaldehyde.

73
Q

Describe the dye retention mechanism of reactive dyes on cellulose.

A

Covalent bonding through chemical reaction.

74
Q

What is a problem with reactive dyes?

A

Competing reaction with water, leading to dye inactivation and loss.

75
Q

Describe the dye retention mechanism of vat dyes on cellulose.

A

Mechanical entrapment after solubilization, application, and insolubilization.

76
Q

What chemical are most vat dyes based on?

A

Anthraquinone.

77
Q

Describe the application of disperse dyes on polyester.

A

Dispersed in water with a surfactant, penetration enhanced by carriers or pressure dyeing.

78
Q

What is a carrier in disperse dyeing?

A

An organic chemical that swells the fiber to allow dye penetration.

79
Q

What is the Thermosol process?

A

A continuous dyeing process using disperse dye sublimation at high temperatures.

80
Q

Describe the dye retention mechanism of acid dyes.

A

Strong ionic bonding with amines in the fiber.

81
Q

What are pre-metallized acid dyes?

A

Acid dyes containing chrome or cobalt to improve fastness.

82
Q

Name three classes of acid dyes.

A

Leveling, milling, neutral (super milling).

83
Q

What is a retarder in dyeing?

A

A chemical that slows the dyeing rate to promote levelness.

84
Q

Describe the dye retention mechanism of basic dyes.

A

Strong ionic bonding with negatively charged fibers.

85
Q

What is the glass transition temperature of acrylic fibers?

A

Approximately 180°F.

86
Q

How are basic dyes categorized?

A

By exhaustion rate (K values).

87
Q

What is a general relationship between ease of application and washfastness of dyes?

A

Easy-on, easy-off; easy application often means poor washfastness.

88
Q

What are the advantages of pigment coloration?

A

Economical, applicable to all fibers, extensive color range, high lightfastness, satisfactory washfastness.

89
Q

What are the disadvantages of pigment coloration?

A

Poor crockfastness (especially heavy shades), binder stiffness, potential for pad roll build-up, migration issues.

90
Q

What is union dyeing?

A

Achieving a uniform shade on a blended fabric.

91
Q

What is cross-dyeing?

A

Dyeing each fiber component of a blend a different shade.

92
Q

What is reserve dyeing?

A

Leaving at least one fiber component undyed.

93
Q

What is tone-on-tone dyeing?

A

Dyeing fibers in a blend with the same dye class but to different shade depths.

94
Q

What is multi-level dyeing?

A

Dyeing multifilament yarns with different filament types having different dye uptake capabilities.

95
Q

What is staining in blend dyeing?

A

One fiber being stained by the dye intended for the other fiber, resulting in poor fastness.

96
Q

What is the purpose of dyeing machinery in batch dyeing?

A

To move dye liquor through the goods, or goods through the dye liquor, promoting level dyeing.

97
Q

What is the purpose of dyeing machinery in continuous dyeing?

A

Even, uniform dye application with thorough penetration.

98
Q

What is a key feature of jet dyeing machines?

A

Fabric propelled by pressurized jets of dye bath liquid.

99
Q

Describe a dye jig.

A

A machine with rollers holding fabric in open width, moving it back and forth through the dye bath.

100
Q

Describe a dye beck.

A

An atmospheric machine with an elliptical roller propelling fabric in rope form through the dye bath.

researh design (12 decks)

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