What is PVC coating ?
Polyvinyl chloride, a thermoplastic polymer commonly known as PVC, is the main alternative to plastisol for use in plastic or polymer coating. PVC has a number of valuable qualities, such as good water and chemical resistance. PVC is perhaps most highly valued for the fact that it is quite flexible; its resin, which is generally hard and inflexible, can become more flexible or softer when mixed with plasticizer additives, such as phthalates. This adaptability makes PVC a popular choice for use with dip molding and dip coating services. Usually, PVC coatings services have two main purposes: the protection of an object from environmental wear and tear, such as corrosion, and/or the achievement of altered aesthetic characteristics. Such characteristics include the alteration or addition of tints, colors, textures or scents. They may also be adjusted for rigidity. PVC coatings have applications in healthcare, textiles, transportation, construction, plumbing, recreation, sports and athletic equipment, food and beverage processing and hardware.
What are dip molding and dip coating? Dip molding, also called immersion molding, is a relatively low-cost and straightforward method of coating mandrels or molds. Almost identical, dip coating, also known as plastic coating, is a process used for coating products or objects. Both dipping processes are three-step processes that use dip molders. These stages are: immersion, dwelling and withdrawal. First, during immersion, an object or manufactured component like a mandrel is lowered and immersed into a vat of molten plastic, which, in this case, is PVC. Before this immersion, manufacturers have the choice of whether or not to apply a primer, such as a chromate or a phosphate, to the surface of the object, called a substrate, to increase the strength of the PVC’s adhesion to its surface. After the substrate has been immersed for a certain period of time, the substrate is then slowly lifted from the vat of molten PVC and allowed to cool. How soon a substrate is removed from the vat depends on its desired thickness. Dwell time, as this period is called, is longer for thicker coatings and shorter for thinner coatings. Note that the substrate must be removed slowly because, if it is removed too quickly, a manufacturer risks creating irregularities on its surface or achieving an improper or uneven coating thickness. Dip molding or coating can be conducted on any substrate that can fit into a vat. Of course, vats vary widely in capacity, so, really, just about any object, as long as it can stand the heat emitted by the molten PVC, can be dip molded or coated. In some cases, a substrate receives further heat treatment in order to complete the fusion of PVC to its surface. However, this only occurs if the substrate has undergone cold dip coating instead of hot dip coating. Cold dip coating is the less common of the two processes, performed by dipping a substrate into liquid PVC without preheating it, then finishing the fusion by placing the object in a heated chamber. Hot dip coating, on the other hand, involves the heating and possible priming of a substrate before it is dipped into a liquid polymer. This process does not involve post-coating heat treatment.
PVC coatings are wildly popular and useful. Manufacturers may choose to use PVC coatings for purely decorative reasons and/or protective reasons. Usually, though, the protective qualities of PVC supercede the value of the aesthetic elements of PVC. Because PVC coatings offer such a high degree of flexibility and water and chemical resistance, they may be used to coat a wide variety of products. These include: cords, wires, wire mesh, dishwasher baskets, chain link fences and frozen food shelving. The insulative quality of PVC coatings sets them up for roles as electrical and thermal insulators of electrical components subject to heavy usage and/or frequently exposed to the elements, such as extension cords and jumper cables. Additionally, manufacturers seeking to fabricate products for use in food processing can solidify the legitimacy of their product by acquiring FDA approval via the testing of their PVC coating. PVC coatings are also valued for their customizable nature. Because dip molding machines are mostly automatic in nature, objects can be molded, hardened and cool in a very short period of time. Thus, the turnaround rates of dip molding and coating are quite high. Furthermore, dip coating is a responsible choice. Because the molten PVC adheres to the surface of the object being dipped and nothing else, dip coating produces minimal material waste. Instead, leftover molten PVC may be left in the vat and reused. This reduces material costs, energy costs, time spent processing products as well as a manufacturer’s use of fossil fuels.