Do I need an adhesive additive for my polyester garments? What about for nylon substrates?
No, not for polyester. Plastisol ink will adhere to polyester substrates without the aid of a catalyst. In fact, introducing a catalyst will reduce the bleed-resistance of the ink.
For nylon, the answer is yes, in most cases. Here, the ink needs an additive to help form a mechanical bond with nylon. A good rule of thumb is: the less fabric texture, the more you need a catalyst.