Four major classes of inks can be used for screenprinting on packaging and similar products: solvent-based, water-based, plastisols, and UV. The selection of ink for a printing application largely depends on the end use of the product, although environmental concerns increasingly are a factor. Solvent-based inks are the traditional ink of choice used by many manufacturers because such inks are versatile and can be employed in a wide variety of applications. Unfortunately, in recent years it has become clear that solvent-based inks emit volatile organic compounds (VOCs), which may harm employees’ health in an industrial setting and can contribute to atmospheric pollution. Water-based inks are preferable to solvent-based inks, but increase drying time and may cause the shape of a product to change slightly as it dries. Plastisol inks contain polyvinyl chloride resins dispersed in a plasticizer that fuse with whatever ink is applied to when the ink is heated to approximately 320°F. Owing to the high temperatures involved, plastisol inks are not suitable for use on plastic foodservice products. They are generally used on textiles.

Dart chooses to use UV inks for our polystyrene products for several reasons. First, UV inks are well suited for plastic, vinyl, metal and paper products because they adhere to surfaces smoothly and evenly. Moreover, they contain no VOCs. As an added bonus, they will not dry on a press or screen, thereby substantially reducing the need for cleaning solvents. Finally, UV inks generally do not contain heavy metals that may harm human health or the natural environment. In short, the company believes that the use of UV inks on our products is the best choice considering all relevant factors, especially the suitability of the application and the environmental consequences.