Plastic bottles can be made from a variety of thermoplastic resins. Each resin contains properties which complement its end use. The popular resins from which bottles are molded are: the Polyolefins (LDPE, HDPE, PP, etc.); Vinyl (PVC); Polyester (PET and PETG); and Styrenics (PS and SAN).
The untreated surface of bottles manufactured from Polyolefins does not attract and hold inks, adhesives, decorative, or protective coatings. The surface must be altered to make it receptive to labeling or decorating.
The surface can be altered to obtain bonding of adhesive or other decorative materials by treating it with a flame or electronically via Corona-Discharge. The treatment methods only modify an extremely thin layer of the surface. Non-Polyolefins (PVC, PET, PETG, PS, and SAN) do not need to be treated for bonding or adhesion.
Flame Treating is the most commonly used means of rendering a molded bottle surface receptive to suitable inks, paints, etc. In this method, a hot oxidizing flame (2000 degrees to 5000 degrees) is applied directly to the intended label or decorated area. Both exposure time and burner set up are important to insure good label and decorating adhesion.
Electronic Corona-Discharge Surface Treating may be utilized to make a Polyolefin bottle surface conducive to labeling and decorating. In this method, the bottles are moved through a high-frequency "bombardment" of high voltage sparks.
Fluoro Prep surface enhancement that increases adhesion properties and wetability of plastic, is an application that improves paint and ink adhesion on items ranging from small containers such as mascara tubes to large handle ware packages. The dyne level resulting from this surface enhancement application is as good as or better than that of flame treatment and Corona Discharge methods.