DIP UNIT

What is “dipping”?

“Dipping” of nylon fabric is done to ensure the adhesiveness to the rubber. If
uncoated nylon cords are calendared with rubber, then the rubber may not adhere to the
fabric.

The main function of the dipping process is to coat the fabric with resorcinol
based solution so as to make it more adhesive to the rubber under stringent conditions of
tension and temperature.

What happens during “dipping”?

The fabric that is used for dipping is made of high quality nylon and polyester
yarns through the process of polymerization, spinning, drawing and weaving. Fabric cord
quality is based on its strength, stretch, elasticity and shrinkage. The yarn used is first
twisted and then two or more spools of yarn are twisted into a cord.

Why are the tension and temperature conditions important during “impregnating”?

The tension, temperature and humidity are critical before the fabric cords are
calendared with the rubber compound. That is why the fabric cord is kept in a
temperature – and – humidity controlled room once it arrives in shop floor.

Heat setting studies of RFL dipped cords in the temperature range of 180 – 210
degrees show a loss in tensile properties.

But the loss in tensile strength is minimal if the cords were given pretension load.

Another factor taken into account is the shrinkage of the dipped cords, which
increases with increase in the temperature of heat setting. More shrinkage in relaxed
conditions influences the rubber – fabric matrix (rubber gets more fabric surface) leading
to more adhesion. More shrinkage also results from more pretension load.
After dipping, the dipped fabric is heat treated for dimensional stability of tire
cord fabrics.