Do I need an adhesive additive for nylon substrates?

In most cases, the answer is YES. In order for ink to adhere to Nylon, the ink must form a mechanical bond with the fabric. A good "rule of thumb" is; "The less fabric texture, the more you need catalyst" (and visa-versa).

Nylon Garments with little texture to the fabric, such as Satin jackets, require an addition of catalyst to create ink with greater tensile strength. In the case of woven nylon bags, most ink companies offer a single-part Nylon ink. This line of inks does not require a catalyst when printed on nylon substrates with a heavy texture. However, these materials may be treated for waterproofing, in which case the coating must be removed and a catalyst added to the ink. 

Be sure to check the label on the garment before you proceed with the print. Nylon micromesh athletic jerseys require an ink specifically designed to cure harder which will adhere to that type of fabric, it does not need catalyst. Many substrates look similar but require different print parameters. Nylon Dazzle cloth and Polyester Dazzle cloth look identical, so you must test the material for bleed propensity.