PCC 302 Test #3

Polyester, Acetate (Cellulose and Tri), Nylon

List which fibers can be dyed with disperse dyes.

Nylon, wool, and silk because acid dyes are negatively charged and these fibers all have amine groups that can take on positive charge; negative and positive charge form ionic bond

List which fibers can be dyed with acid dyes.

Positive charge on dye molecule (usually N) denotes a basic dye; only dye class with positive charge, ionic bond where dye is positive, and fiber is negative

Be able to recognize the structure of a basic dye and tell how it bonds to the fiber.

Disperse dyes are nonionic (no charge)

Be able to recognize the structure of a disperse dye and identify the three main types of chromophores for disperse dyes: azo, anthraquinone and nitrodiphenylamine.

Look for negative charge on the dye molecule (-SO3- groups); variety of chromophores; usually smaller and more compact than direct dyes; smaller and more compact; premetallized acid dye contains a Cr ion; negative charge on dye bonds to positively charged fiber to form ionic bond

Be able to recognize the structure of an acid dye (including a metal complexed azo) and tell how it bonds to the fiber.

Property of one object; when perceived color of one object color varies upon changing light source, color is inconstant Important bc determines if metamerism can occur

Clearly define color inconstancy and give an example of why it is important in the textile industry.

2 colored objects match in shade under one type of light but if the lighting changes the objects no longer match Example: Garment with different components dyed in different dye lots; match when leave the factory but no longer match under retail lighting

Clearly define metamerism and give an example of why it is important in the textile industry.

Different backgrounds affect perception of color in different ways

Clearly define simultaneous contrast.

Hue: quality of color described by word such as red, yellow, green, blue, etc. Value: quality of color we describe by the words light, dark, etc. (relates to gray similar lightness) Chroma: quality of color which describes the extent to which color differs from a gray of same value (color strength)

Define Munsell Hue, Value, and Chroma.

Pigment is an aggregation of colored molecules ground with anionic dispersants to a particle size of roughly 1 micron diameter or less; differs from dye because it is insoluble in water and other solvents, has no molecular interactions between the pigment and fiber and stays on the fiber surface through use of a binder; dyes are typically only used in textiles and paper where pigments are used in many different products

Define what a pigment is and how it is different from a dye.

Pad dye onto fiber surface; dye sublimes and fiber swells; dye diffuse into the fiber; retention by hydrophobic attraction

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

Because ionic bond is very strong, must control the rate at which dye goes onto fiber so dye does not go on all in one place because once ionic bond is formed, dye does not move around and level; 1. Temperature control - want to raise temp gradually so dye does not all go on at once 2. Incremental addition of acid - acid creates the dye sites on the fiber 3. Cationic leveling agent - leveling agent has positive charge (opposite charge to dye molecule); complexes with dye molecule and slows down the rate of the dye bonding with the fiber 4. Anionic leveling agent - leveling agent has the same charge as the dye; so leveling agent competes with dye for sites on the fiber; can temporarily block dye sites to let dye distribute more evenly before you get the ionic bond between dye and fiber

Describe, in detail, the four main approaches to controlling the rate of strike of acid dyes; i.e., be prepared to explain exactly how temperature is controlled, how pH is controlled, how a cationic leveling agent works, and how an anionic leveling agent works.

1. Temperature control above Tg of acrylic fiber; above Tg raise temperature gradually 2. Cationic retarders; if retarder has a positive charge, it will compete for the same dye sites as the dye on the fiber 3. Anionic leveling agents form complexes with cationic dye

Describe, in detail, the three main approaches to controlling the rate of strike of basic dyes on acrylic fiber; i.e., be prepared to explain exactly how temperature is controlled, how a retarder works, and how a leveling agent works.

Dye is slightly soluble in water, individual molecules dissolve from dye particles and exhaust to the fiber surface; heat or carrier used to diffuse dye into fiber; dye remains in fiber due to hydrophobic reactions

Explain and recognize a sketch of how disperse dyeing of fibers occurs in general (not the Thermosol® process).

Carriers are water insoluble organic chemicals that reduce fiber-fiber interactions and increase chain mobility by opening up space for dye; heat used without carrier to increase molecular motion to open fibers and allow dye to penetrate

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

Based on molecular weight of dye; sublimation energy increases from low to high energy; don't mix because different sublimation energies and rates of penetration into the fiber

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.

Low molecular weight polymer (polyester oligomer): made up of 3 PET units to form cyclic molecule; controlled with auxiliaries and procedures

Explain what polyester trimer is.

Reduction clear removes surface dyes to improve crock fastness; chemically reduces chromophores to water soluble material; done with "caustic" and "hydro"

Explain why a reduction clear is sometimes necessary, and tell what chemicals are used.

Cationic dyeable polyester is a copolymer (has 2 monomer types) and copolymer provides negative charges; regular polyester does not have negative charges; cationic polyester does have negative charges that allows ionic bond to form with positive dye; cationic dyeable polyester can also be dyed by disperse dyes

Explain why basic dyeable (same as cationic dyeable) polyester can be dyed with basic dyes and regular polyester cannot.

Adequate fastness; binder keeps pigment on fiber

Explain why pigments require a binder.

Add positive charge to (potentate) the amine group on the fiber; H+ indicates acid conditions; forms ionic bond with negatively charged dye

Explain, with the aid of sketches, how nylon can be dyed with acid dyes.

Washfastness, crockfastness, softness/stiffness of fabric

Give at least three physical properties of fibers that are affected by a pigment binder.

Padding and exhaust application

Give at least two methods by which pigments can be applied to fibers.

Rotary screen printing

Identify the major printing process (method) used in textiles today.

Advantages: economical and can be applied to any fiber/fiber blend Disadvantages: requires binders for adequate fastness and require softeners to overcome stiff hand

List at least two advantages and disadvantages of using pigments.

Roller printing, flatbed screen printing, rotary screen printing, transfer printing, ink jet printing

List five methods of textile printing.

Direct Printing: design is achieved by printing color directly on fabric Discharge Printing: design is achieved by printing a chemical that removes color from a previously dyed fabric Resist Printing: design is achieved by printing a chemical that prevents the printed areas from subsequent dyeing

List the three basic types or styles of printing and explain what they are.

Acrylic and cationic dyeable polyester

List which fibers can be dyed with basic dyes.

Simulated Daylight (Illuminant D65) Cool White Fluorescent (Illuminant F2) Tungsten Filament (Illuminant A) Triband Fluorescence (Illuminant F11)

Name four commonly-used light sources in textile shade matching.

1. Colorant (dye or pigment) 2. Thickener 3. Binder (if using pigments)

Name the three key ingredients in a print paste formulation.

1. Leveling - low molecular weight; exhaust under strong acid conditions; good leveling & poor washfastness 2. Milling - mid molecular weight; exhaust under moderate acid conditions; moderate leveling & washfastness 3. Super Milling (Neutral) - high molecular weight; exhaust under weak acid conditions; poor leveling & good washfastness

Name the three subclasses of acid dyes and explain their differences.

Blue, green, red

What are the three primary colors for additive mixing of light?

Cyan, yellow, magenta

What are the three primary colors for subtractive mixing of objects?

Visual and Colorimetric Visual: color difference between standard sample and trial (batch); must standardize viewing conditions Colorimetric: use spectrophotometers and color models to define color and color differences mathematically

What are the two main types of color assessment?

Using instrumentation and mathematical models to measure color

What is colorimetry?

The color difference in a pair of objects appears greatest when the background lightness is between the lightness of the 2 objects

What is lightness crispening?

Light source: actual emitter of radiation Illuminant: data set/graph that represent a real light source (used in calculations of L*a*b* data)

What is the difference between a light source and an illuminant?