Screen Printing on Polyester T-shirts
by: Christy Leville

Problems Printing on Nylon

Getting inks to properly adhere to nylon is tricky. In the process, two main problems are likely to occur: shrinkage and bonding problems. First, nylon is highly prone to shrinkage when flash cured. Secondly, some nylon products, such as nylon jackets, are treated with waterproofing chemicals. These chemicals prevent the ink from bonding to the nylon.

1.) To deal with curing problems:

a. Shorten your curing times.
or
b. Preshrink the material before printing on it. Use this method if a shorter curing time does not allow the ik to properly adhere to the material.

2.) To prevent problems due to waterproofing:

a. Remove the coating prior to printing. One method to remove the coating is wiping the fabric with rubbing alchohol. However, the alcohol may create shade variation on the fabric.
or
b. Modify your ink to enhance their ability to adhere by introducing an adhesion promoter. Use this method if shade variation is a problem with the particular fabric you are using.

Problems Printing on Polyester

Many screen printers choose to print only on printing on 50/50 cotton/polyester t-shirt fabrics. This fabric tends not to be problematic when good bleed-resistant inks are used. Problems mainly occur with 100% polyester. Problems that occur include the fabric’s potential for shrinkage when exposed to heat, the fabric’s potential for dye migration and sublimation, the ink’s inability to bond to the fabric, and matching the ink’s elongation characteristics to the fabric’s elongation characteristics.

1.) To prevent shrinkage problems:

a. Use a low-temperature when curing.
or
b. Use fast-fusing plastisols in order to reduce the total heat to which the material is subjected. These inks typically will fuse in the 280°F range, as opposed to the 320°F range commonly used for standard inks.

2.) To prevent the fabric's potential for dye migration and sublimation:

a. Select 100%-polyester fabrics that are dyed with cationic polyester colorants. These dyes are locked into the polyester fibers and resist migration.
b. Perform a number of ink-adhesion tests to test the fabric's receptivity to your inks such as wash testing.
c. Produce test prints at least a week in advance of the planned production run because bleeding may take a week or more to appear.

3.) To match the ink’s elongation characteristics to the fabric elongation characteristics:

a. Use a bleed-resistant, high-elongation ink. Many woven 100%-polyester materials have a high elongation factor. This type of ink is more resilient and resistant to cracking than conventional plastisols and can help prints remain intact on stretchable fabrics.
b. Match the ink’s elongation characteristics to the fabric’s elongation characteristics. Test the ink/fabric combination beforehand because not all athletic polyester fabrics stretch to the same degrees.

For both nylon and polyester it is essential that you experiment with different fabrics, inks, and curing methods to choose the best overall process.