STEPS  IN  PRINTING  PROCESS

1. PREPARATION  OF  PRINT  PASTE

2.  PRINTING  OF  FABRIC

3.  DRYING

4.  FIXATION  OF  DYESTUFF

5.  WASHING-OFF

Preparation of printing

Type  of specific farmulation used depeds on fiber, the  colorant system  usd and,  to some  extent,  the type of  printing machines

Typical ingredients used include:

Dyes or pigment

Thickeners

Binders, cross-linking agents

Sequestrants

Adhension promoters

Defoamers

Catalysts

Hand modifiers

Thickeners

viscosity – the resistance of fluid to flow-(ie.the thickness of the fluid)

-one of the most important variables in a print paste formulation

-can be controlled by choosing from a wide range of possible thickener products, modified by changes in temperature,ph,and electrolyte concentration.

Thickener system-

              Natural gums

              Synthetic polymers

              Emulsions-(oil –in-water,water-in-oil)

              Foam

Dymanics of Print pastes

             Viscosity-laminar flow(fluids )

                     Turbulent flow

             Important factors for print paste:

                      Shear stress

                      Shear rate

             Newtonian Fluids-those fulids which possess a constant ficosity over a broad shear rate(stress) range at a given temperature.

             Non-newtonian fluids-those fluids which exhibit a changing viscosity with a changing shear rate(stress)

             -Pseudoplastic

             -plastic

             -Thixopropic

Effect of Electrolytes

Effect of concerntration

THICKENING AGENTS

Msut have psedoplastic flow behavior

Low shear=high viscosity

High shear=low viscosity

Pseudoplastic hehavior