The Role of Permanent Adhesivesin Fabric Printing

Modern fabric printing technique has almost exclusively come to rely on the use of permanent adhesives to fix fabrics onto the usual working surfaces (plasticized cloths, rubber blankets) of printing tables, automatic flatbed and rotary machines. Usage of water soluble glues is restricted to those particular cases where the use of permanent adhesives proves to be inconvenient (e.g. pigment dye printing with plenty of dye coming in contact with the adhesive, printing of very hairy fabrics; permanent adhesive activity is neutralized in a short time).If employment of a water soluble glue becomes necessary for the abovementioned reasons, it may be applied onto the permanent adhesive film suitably neutralized with a barrier resin.

Theoretical Background
In order to simplify the understanding of physico-chemical characteristics of adhesives in general, let us remember some definitions:

Molecule: the smallest constituent of a substance featuring the same propertie s as the substance itself
Molecular interaction: forces active between molecules
Cohesion: force that holds together identical molecules of one substance, preventing the breakup of the substance itself
Adhesion: force that holds together molecules of different substances, also the attractive force active between two surfaces in contact
Polymers: chemical compounds resulting from the union of a very large number of identical molecules (monomers)
Copolymers: chemical compounds resulting from the union of a very large number of molecules belonging to two or more different substances


Adhesives have the property of causing the adhesion of the surface of different materials.
The employment of adhesives for fabric printing rests on the same physical principles which regulate adhesion phenomena in general.
Fabric printing adhesives, however, must show quite different properties from usual adhesives.

E.g., consider the following system:

In the normal coupling of two materials an adhesive must guaranteee a strong and durable bond. In order to separate one element from the other, one has to apply a force proportional to the strength of the bond, often damaging the material. In our case (fabric - working surface), requirements are different. Here the adhesive must allow successive cycles of adhesion and smooth separation between the elements, without any damage to them and to its own structure.Therefore it is defined as permanent.

Theoretically the two surfaces of a permanent adhesive film (one facing the fabric, the other the working surface) should feature different properties to meet different requirements. The first surface has to hold the fabric in place during printing operations and allow its release afterwards, with a light peeling action, so that no damage occurs to the fabric.The second surface must yield a firm bond with the working surface. It is obviously impossible to impart different and conflicting properties to the same substance.

The purpose of our formulation development work with our VISTASOL permanent adhesives aims at the design of products which offer optimal reliability regarding the bond with the working surface, while showing a good versatility in fixing different fabrics. If we observe this system:

T (fabric)
A (adesive)
S (working surface)

we conclude that to obtain the desired performance molecular interactions should be as follows:

1. TA < AA
2. TA < AS

TA - molecular interaction between fabric and adhesive (adhesion
AA - molecular interaction within the adhesive (cohesion
AS - molecular interaction between adhesive and working surface (adhesion)

Tack is determined by the nature of the polymer (tight molecular structure: relatively hard adhesive film with lower tack; loose molecular structure: relatively soft film with higher tack) and the addition (or not) of plasticizers.Excessive plasticizer contents may weaken AA interactions (product cohesion), causing the film to be disrupted and tacky residues to be left on theabric.
Villa Industrie Chimiche - Theoretical background - Technical features - Vistasol line - Italian version
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