Dip coating is an increasingly popular method as it adds functionally, color, texture, electrical insulation and comfort to plastic parts for companies in a variety of different industries. Despite the prevalence of this coating process, many people are not aware that they use dip coated products every day.
This definitive guide to dip coating will explain the history, procedure, applications, and advantages of dip coating.
Dip coating and dip molding have been around for about 100 years. During the early part of the 20th century, there was a shortage of natural rubber as demand began to outpace the available materials. PVC was created as a response to this shortage. While PVC went on to become well known for its use in plumbing pipes and fittings, it was also discovered that adding a plasticizer to PVC would make it remain permanently flexible. This discovery paved the way for the processes known as dip coating and dip molding. Vinyl plastisol became available for non-military use following World War II, and quickly became a popular coating for tool handles.
Dip Coating vs. Dip Molding
Dip coating and dip molding are essentially the same process. Both techniques make use of a plastisol dip to form a skin around a mandrel.
Dip molding creates an entirely new product from plastisol. In dip molding, a pre-formed mandrel or mold is dipped into plastisol and then extracted. Once the mold is extracted from the dip tank, it goes through post-heat and cooling processes. Finally, the dip molded item is stripped from the mold.
Dip coating improves an existing product by coating it in a plastisol skin. In dip coating, the item is dipped into plastisol to form a plastic skin around the surface. There are many products that are coated using this technique, but one of the most common examples is tool handles.
Dip Coating Procedure
Dip coating is a process that involves several steps. These steps include pre-treatment of the item to be coated, preheat, immersion in plastisol, dwelling in the plastisol dip, withdrawal, post heat and cooling.
Pre-treatment – This preparatory step involves cleaning oils off of the surface of the item to prepare it for coating. Another pre-processing technique used is priming. Priming makes the vinyl adhere to the parts and forms an incredible tight bond.
Preheat – During the preheat stage, the ovens put thermal energy into the mandrels so that it can be released into the plastisol during the dip.
Dip – Once the product is ready to be coated, there are three stages to the dipping process, which includes immersing the product into the coating material, dwelling it and withdrawing it:
- Immersion – This step is the actual “dip” in the dip coating process. During immersion, the item is dipped into the coating material, usually plastisol, at controlled speeds.
- Dwelling – Once the item has been immersed, it is kept in the plastisol for precise amount of time. The length of time the item dwells in the plastisol affects the thickness of the coating.
- Withdrawal – Following immersion and dwelling, the item is withdrawn from the plastisol dip tank at a controlled velocity.
Post heat – During post heat, the oven adds energy to the gelled plastisol and enables it to fuse and become a solid when the molded and coated part is cool. Plastisol is liquid at room temperature, but fuses into vinyl when it is heated. Plastisol is a thermoplastic and can be reprocessed in some cases.
Cool – As the plastisol cools, it becomes a solid protective, colorful and comfortable coating on the outside of the original part. The dip coating process takes place very quickly but it has a big impact on the overall form and function of the product!
Dip coating is a widely used technique across many different industries. In fact, dip coating is so popular in manufacturing that most people use dip coated items many times each day.
If you open your toolbox, you will find pliers, wrenches and other specialty tools whose handles have plastisol coating for a better, more comfortable grip. Other common examples include bumpers, toys, medical instruments, plumbing fittings and electrical connectors which are all dip coated for a protective, insulating and resilient final product.
Advantages of Dip Coating
Dip coating offers numerous advantages. A partial list of the benefits of dip coating follows:
- Corrosion resistant
- Chemically resistant to detergents, oils, acids, alkalis, and even some solvents
- Resilient and durable
- Available for a wide variety of part sizes from small to large
- Thickness can vary from 0.25” up to 0.5”
- Available in all colors (including metallic, luminescent, and phosphorescent)
- Available in a variety of textures (including matte and high gloss)
- Available in a variety of durometers (hardness) from 35A – 95A
- Provides insulation against electrical currents, cold, and heat
- UV resistant chemicals
- Sound damping
Dip coating performs well at a wide range of temperatures, with standard formulations being functional from -35 F up to 200 F. A high temperature formula is available that will function up to 300 F.
It is also an economical alternative to injection molding the plastic coating and then fitting it to the device. Dip coating results in a superior finished product without seams and with better fit and adherence than is possible with injection molding.
Dip coating is also particularly useful for products that have a difficult shape. When dipping a product into plastisol, every nook and cranny will be covered.
Dip coating is a valuable process that provides outstanding results at a reasonable cost. The many advantages of this process have helped to make it such a popular coating option.
Piper Plastics Corp. has been a leader in the dip coating and molding industry for more than 50 years. We operate 19 fully automatic top-of-the line plastisol dipping machines and utilize customizable techniques to control each step of the process to meet your specific needs. Contact us online or call us at 631-842-6889 to learn how dip coating can benefit your business!