PCC Test 3

Dyes

Soluble in water or made soluble during dyeing process

Fixed in fiber

Primarily used in textiles and paper

Pigments

Insoluble in water and other solvents due to big molecules

No interactions between pigment and fiber, remains on fiber surface

Used in textiles and other stuff

Strcuture of Pigments

Aggregation of colored molecules ground with anionic dispersants

1 micron diameter or less

Variety of chromophores

Binders for Pigments

Leads to durability

Polymeric film formers that adhere to the fiber surface

Determine wash fastness, crock fastness, abrasion resistance, softness/stiffness of the fabric

Pigments Pros and Cons

**Pros:**

Can be applied to any fiber or fiber blend

Economical

Wide color range

Good lightfastness

**Cons:**

Requires binders

Requires softeners

Application of Pigments

Padding

Exhausting

Add to fiber melt before extrusion (polymers)

Printing

Padding Pigments

Pigment, binder, antimigrant, softener

Pad, dry, cure

Exhausting pigments to garments

Apply exhaustible cationic polymer

Exhaust pigment

Apply exhaustible binder

Printing

Localized coloration of textiles

Includes chemical to limit movement of colorant

Solid shade (*Blotches*)

Repeating patterns

Random

Printing Styles

Direct

Discharge

Resist

Direct Printing

Printing color directly on fabric

Discharge Printing

Printing a chemical that removes color from a previously dyed fabric

Resist Printing

Printing a chemical that prevents the printed areas from subsequent dyeing

Factors Influencing Printing Process

Fiber type (absorbent or nonabsorbent)

Fabric construction (loose or tight)

Colorant type (dye or pigment)

Printing style

Printing method

Printing paste

Fixation of colorant

Printing Methods

Roller

Screen (flatbed and rotary)

Transfer

Ink Jet

Roller Printing

Chrome coated engraved copper rolls (one color per roll)

Paste transferred by pressing fabric onto engraved roll by second larger roll and backing fabric

Ideal for high-volume and low cost printing

High cost for engraving and setting up machine

Long runs are essential

Expensive inventory of rolls

Roller Printing Pros and Cons

**Pros:**

Finest quality printing

Intricate designs

**Cons:**

Long development time for new designs

Design repeats limited to circumference of roll

Expensive inventory of rollers

Short runs not economical

Screen Printing

Negative image of design

Print paste is forced through screen onto fabric to form design

Flatbed screen printing

Clean screen is coated to the photosensitive material

Light source illuminates the coating through a positive image of the design

Coating hardens where exposed to light

Unhardened coating is washed away, leaving a negative image

Screens made with woven monofilament yarns

One screen for each color

Flatbed screen printing pros and cons

**Pros:**

Inexpensive

Large designs

Large number of colors possible

**Cons:**

Slow

Potential for problems with registration of colors

Less precise designs

Rotary screen printing

Overcome lack of continuity of flatbed screen printing

Hollow cylindrical screens

__High production speeds__

Max 20 colors

Screens are made from nickel

Fabric moves continuously beneath screens, one screen per color

Print paste is continuously applied to fabric

Rotary screen printing pros and cons

**Pros:**

High process speed

Inexpensive screen preparation

Large number of colors possible

**Cons:**

Design repeats limited to screen diameter

Not capable of intricate designs

Print Paste Ingredients

Colorant (dye or pigment)

Thickener

Binder if pigment

Auxiliaries if needed

Colorants for Printing

Mostly pigments, reactive dyes, then disperse dyes

Paste Thickeners

__High viscosity in water__ due to high molecular weight polymers

__Proper rheology__ so it’s thin under pressure

__Keep colorant uniformly dispersed__

__Easily removed after printing__

__Inexpensive__

Natural (starch, guar gum, or sodium alginate for reactive dyes)

Synthetic (acrylic copolymers)

Oil in water emulsions like varsol, gives a soft hand

Binders for pigment printing

__Clear and colorless__

__Form tough, flexible film__

__Durable on fabric__

__Easily removed from screens and rollers__

**Acrylic copolymers**

Print Paste Auxiliaries

__Antiwicking agents__ (slow wicking of the paste)

__Dispersants__ (keeps the screens unclogged)

__Humectants__ (slow the drying of the paste, *urea, glycerin*)

__Crosslinkers__ (improve the durability of print, *melamine resin*)

__Softeners__ (improve fabric hand, *silicone, and mineral oils*)

__Defoamers__ (prevent foam formation in paste)

Fixation of Printed Colorants

Continuous or batch

__Dyes__ - pad, steam, wash

__Pigments__ - heat to film forming temp of binders, wash

Transfer Printing

Design roller printed with disperse dyes on specially traded paper

Design transferred by sublimation to thermoplastic fibers

Polyester, nylon, acrylic, cellulose acetate

Transfer Printing Pros and Cons

**Pros:**

Intricate designs possible

Dry fabric process

Suited for short production runs

**Cons:**

Limited to disperse dyes

Limited fiber choices

Printed paper inventory

Ink Jet Printing

Computer controlled deposition of colorants on fabric for carpets and flat goods

Dye or pigments

Instantaneous pattern changes possible

Ink Jet Printing pros and cons

**Pros:**

Unlimited design potential

Allows for mass customization

Ideal for samples

**Cons:**

Very slow process speed

Ink jet samples must match traditional printing production

High ink and equipment costs

Fabric pretreatment is usually necessary

Color Control Goal

Ensure that the customer sees what the product designer intended

Key Factors in the Textile Supply Chain

Concept/Design

Human factors

Manufacturing

Color quality control

Point of saleF

Fishbone diagram

Understand a process in detail for a given variable

ID potential problem areas

Consumer frustrations with laundry

Visible set-in stains

Color fading

Pills on fabrics

Dull whites and colors

Shrinkage

Water out/fall apart

Colors bleeding

Key players in supply chain

Designer

Buyer/retailer

Color standard developer

Production dyer/printer

Product manufacturer

Consumer

Metamerism

When 2 colored objects match under one set of conditions but not another (illuminant, observer, etc.)

Color inconstancy

When perceived color of 1 object color varies upon changing light source (illuminant)

Simultaneous Contrast

Different backgrounds affect colors in different ways

Crispening Effects

If the lightness of the samples straddle the lightness of the surround we see the most color difference

Makes the choice of surround critical to determining color

Color Assessment

**Visual** - color different between standard sample and trial (batch)

**Colorimetric** - use spectrophotometers and color models to define color and color differences mathematically

Types of Light Sources

Artificial Sources - simulated daylight (illuminant D65), cool white fluorescent (illuminant F2), Tungsten filament (Illuminant A), tribune fluorescence (illuminant F11)

Light Source

Actual emitter of radiation

Illuminant

Data set that represent a real light source used in calculations of L**A*B data*

NOT a light source

Additive color mixing

TV or computer monitors

Red, green, and blue

Makes white

Subtractive

Dyes and paints

Absorb specific colors from white light

Cyan, yellow, magenta

Makes black

Munsell Hue

Quality of color which we describe by the words red, yellow, green, blue, etc.

Munsell Value

Quality of color we describe by the words light and dark

Munsell Chroma

Quality of color which describes the extent to which a color differs from a gray of same value

**Color strength**

Munsell Circle

Arranged with 100 hue notations

Issues with physical samples

Age over time

Color will vary depending on observer and lighting

Color gamut limited by dyes/pigments used

Cannot easily communicate color and color differences electronically

Color Measurement Issues

Different spectrophotometers produce slightly different color data (calibrate it accurately, temp and humidity controlled)

Sample presentation important (number of layers, 2-4 measurements, UV included or not)

Tristimulus Values, XYZ

CIE created a mathematical method of describing the color of any sample as viewed by a standard observer

XYZ are primaries

X = red, Y = green, Z = blue

Now L\*A\*B\*

L\*

Light is positive and negative is dark

A\*

Negative is green and positive is red

B\*

Negative is blue and positive is yellow

Pass/Fail Tolerance Boundaries

A tolerance boundary would be a sphere

Euclidean color space

DE\* ab

= \[(Delta L\*)^2 + (Delta A\*)^2 + (Delta B\*)^2\]^(1/2)

DECMC

Color difference formula

More recommended

Need for Repellency

Aesthetic for carpets and upholstery

Functional for water repellent fabrics

Safety for medical textiles and bullet proof vests

Mechanism of repellency

__Static contact angle and surface energies determine repellency__

Strong fiber/liquid interaction means high energy surface - **Absorption**

Weak fiber/liquid interaction means low energy surface - **repels**

Above 150 degrees is super hydrophobic

30 erg/cm2

Water repellency

18 erg/cm2

Oil repellency

Water repellent finishes

__Waxes__ (applied with DP finishes)

__Melamine resins__ (pad and exhausting)

__Silicones__ (padding, silicone fluids or cross linked silicones)

Melamine resin water repellents

Covalent bonds

Excellent durability (N-methylol reactivity)

Apply by pad and exhaust

Used with fluorocarbons as extenders

Adverse effect on fabric physical properties

Formaldehyde release issues

Silicone Water Repllent

Polydimethylsiloxane

High level of effectiveness at low addons

Moderate cost

Soft, resilient fabric hand

Increased pilling and seam slippage

Moderate laundering and dry cleaning durability

Fluorochemicals

Pad applied with DP resin

Oil and water repellent

Fluoropolymer

Must cure finish to form a surface film

P-FOA - Carbon

P-FOS - sulfate

High level of effectiveness at low add-ons

High level of water repellency

Dry soil repellency

High cost

Bad for environment

Poor soil redeposition when laundered

Stain blocking agents

Nylon carpet treatment combined with fluorocarbon repellent

Prevents staining of fibers from food coloring

Acts as colorless dyes to tie up accessible dye sites in fiber

Anionic polymers that ring dye fibers

Soil release

Finish applied to apparel fabric to overcome certain fiber deficiencies

Oily soil release

Moisture absorbency

Applied to polyester, polyester/cotton, and DP-treated cotton

Influenced by fiber surface energies

Factors Affecting Soil Release

__Nature of soil__ (dry or oily)

__Fiber type__ (natural or synthetic)

__Fabric construction__ (loose or tight)

__Residual chemical__

__Other chemical finishes__

Fiber surface energy for soil release

Fiber-water interaction should be stronger than the fiber-oil interaction

Desired Fiber Surface Characteristics

Hydrophilic

Oleophobic

Cotton is good for these and polyester and DP cotton are not

Requirements of soil release finish

Hydrophilic

Oleophobic

Durable to multiple laundering

Not affecting fabric physical properties or colorfastness

Economical

Mechanism of soil release finish

Exhaustible hydrophilic block copolymers applied to 100% polyester textures filament fabric during dyeing

Polyester blocks align with fiber during heat setting leaving hydrophilic surface (sits on top of fiber)

1-2% add-on required

Acrylic copolymers

pad applied to cotton and polyester/cotton blends

Combined with DP finish

Finish absorbs water during laundering

Squeezes oil out of fabric

Dual-Action fluorocarbon block co polymers

Pad applied with DP finish to cotton and polyester/cotton fabrics

Water/oil repellent in air and hydrophilic in water releasing oily oil

1-2% add-on required

Evaluating soil release

__AATCC 130__ - washing it

1-5, 5 being perfect release

__AATCC 79__ - water drop on fabric

__Prevention of soil re-deposition__ - “graying” of fabric during laundering

__Antistatic effects / AATCC 76__ - measure the electrical resistance of fabric

Finishing

Last manufacturing step in textile production

__Physical properties__ - dimensional stability, softness, raised fibers, brushed fibers, etc.

__Chemical properties__ - durable press, flame retardant, water/soil repellent, antimicrobial, etc.

Durable Press

Finish applied to cellulose and cellulose blend fabric to overcome certain fiber deficiencies

How do wrinkles form?

Polymer chain degrades and slides/breaks, creates lint and wrinkles and decreases strength

Requirements of durable press finish

Wrinkle resistant fabrics and apparel

Low residual shrinkage

Smooth drying

Permanent shape retention

Use cross linkers (covalent bonds) to hold polymer chains in place

Types of durable press finishes

Urea formaldehyde

Melamine formaldehyde (problems with yellowing and formaldehyde)

Trying DMDHEU based DP finishes to combat

DMDHEU

Major chemical in use for durable press

Moderate conditions

Formaldehyde release

With catalyst and heat, it creates crosslinks

DMDHEU plus Glycols (ULF finishes)

Lower formaldehyde release than DMDHEU alone

Harder to react

Fabric properties with DP finishes

**Pros:**

shrinkage and garment shape retention

Wet and dry wrinkle recovery

Surface appearance

Pressed crease retention

**Cons:**

tensile and tear strength

Abrasion resistance

Color changes

Ingredients of DP finish

Crosslinker (connects cellulose polymer chains)

Catalyst (catalyzes the cross linking reaction)

Softener (improves fabric hand and processing, reduces loss in tear strength and needle cuts when sewing)

Pad-dry-cure (pre-cure) application of DP finish

Pad, dry, cure

Crosslinker (DMDHEU), catalyst, and softener

Cure for 3 minutes at 320 F or 30 seconds at 400 F

Post cure application of DP finish

Pad-dry with delayed cure

Pad chemicals

Dry only at mill

Cut and sew garment

Smooth wrinkles and forms creases, pleats, etc.

Cure

Garment application of DP finishes

Dip or spray garment with finishing bath

Dry

Form creases and smooth out wrinkles

Cure in oven for 15 minutes at 310 F

Types of DP finish applications

**Pre-cure** - suitable for sheeting, shirting, and dress goods. Best for wrinkle resistance and smoothness

**Post-cure** - suitable for slacks and skirts with creases and pleats. Best for crease retention

**Garment** - suitable for wet processed garments. Best for hand

Issues with DP finishes

Better DP performance leads to poor physical properties

Formaldehyde regulation

Flame retardant finishes

Applied to textile products to reduce flammability

Consumer protection

Occupational safety

Military applications

Factors that affect flammability

Fiber type

Fabric construction

Flame retardant finish

Flame retardancy mechanisms

__Condensed Phase__ - removal of heat, elevating TP, reducing flammable volatiles, enhancing char formation

__Vapor phase__ - elevate TC, interfere with flame chemistry

Vapor phase

Generates free radicals that interfere with combustion reactions

Nonspecific flame retardants

Nondurable - Al203 with 3H2O and H3BO3 for condensed phase OR NH4Br for vapor phase

Durable - decabromodipehnyl oxide (DBDPO) with antimony oxide (Db2O3) for vapor phase, binder required

Flame retardant finishes for cellulose

Nondurable salts - DAP

Durable products (contain phosphorous) - THP with urea (pad, dry, cure, oxidize, wash) OR THP-OH with ammonia (pad, dry, NH3, oxidize, wash), gives very soft hand, very durable

Flame retardant for wool

__Zirpro process__

Potassium hexafluorozirconate

Exhaust applied at pH < 3

Durable

Flame retardant for polyester and nylon

Proprietary phosphorous and halogen compounds

Exhaust and pad applied