For over 30 years, Estron additives and resins have been used to produce billions of pounds of smooth, defect free powder coatings. Resiflow ®, Isocryl ®, Epomatt™, Escat™, and Oxymelt ® products are the industry standards for quality. Read more...

Lumicryl ® energy cured acrylic macromers are at the forefront of UV/EB technology providing unique product properties and formulating latitude for 100% solids or solventborne systems. Read more...

Resiflow® additives for liquid coatings afford: superior flow and leveling, excellent recoat properties, stain resistance, pigment flooding / floating resistance, synergism with silicone additives, mar and slip resistance, air release, increased surface hardness, elimination of solvent popping, and reduced edge pull and sagging. Read more...

Estron provides Polyester (Polynex™), Tosylamide Epoxy (Polytex™) and Tosylamide Formaldehyde (Sulfonex™) Resins for the nail varnish industry. Read more...

8/20/2008 - A SMOOTH FINISH by C. David Green, Ph.D. - Estron Chemical Inc. -Powder coating manufacturing companies are often presented with the opportunity to obtain new business if a formulation can be developed to match either a competitor’s product or a standard panel that defines the color and appearance properties that the customer wants. The desired performance properties will roughly dictate the particular powder coating binder that will be used, and there will of course be a manufactured cost ceiling above which the potential new business will not meet profitability requirements. Armed with this information, the project will be assigned to an appropriate formulator whose task it will be to develop a product that will meet all of the above criteria. A common pathway for a formulator assigned such a task is to first decide on a binder (or in some cases binders) that, based on his/her judgment and experience, will allow the new product to meet the performance and cost criteria. Using the selected binder system, the formulator will then proceed to develop the pigment system (including the chroma pigment that will match the color and provide the appropriate hiding) and select inert pigments that will aid in reducing costs. All of the above can usually be accomplished in a relatively short period of time (even less than a day) if the color matching is not unusually difficult. Once these steps have been completed, the fine-tuning of the formula begins. The purpose of this article is to address one of the pitfalls that formulators often fall into during the fine-tuning phase of the product development. At some point in the fine-tuning process, the appearance of the product must be addressed. Usually, the most critical appearance property other than color is smoothness. It is at this point that Estron is often consulted, since a significant portion of our business is the sale of additives that affect the flow and leveling of powder coatings. When our best product recommendations fail to provide the formulator with the desired smoothness, we then must dig deeper for other methods to achieve the same smoothness as the competitor’s product or the submitted standard. Before any ingredient changes are made to the formula, we suggest that the formulator look at three important factors that will affect smoothness. The first of these is film thickness; panels should be sprayed at varying film thicknesses in increments of 0.2 mil around a center film thickness defined by the competitive product or standard panel. If a smoothness match is achieved, but at a different film thickness than the standard, then adjustments other than composition may bring the product into the desired range. Another technique for improving smoothness in the laboratory is particle size adjustment. Extraordinary efforts must often be made to produce a mean particle size and particle size distribution in the laboratory to match that achieved in production equipment. Nonetheless, it is not uncommon to successfully achieve the same smoothness with a simple laboratory mill and single sieving as that of a panel or part coated with plant-produced material. Not all laboratories have the luxury of particle size measuring equipment, however, so some simple sieving experiments with plant versus laboratory material can provide a rough guideline as to how the mean particle size and particle size distribution of laboratory-produced powder compares to that from the manufacturing facility. With this knowledge, the formulator can develop laboratory procedures that will more closely match those of material produced in production equipment. The third non-formulation factor to address is cure schedule; there is a cure schedule for each formulation that will provide the highest smoothness for that formulation. Elements of this cure schedule include the heat-up rate, (i.e. the time from ambient temperature to peak metal temperature), the peak metal temperature (PMT), time at PMT and finally the cool-down temperature. When evaluating a formulation for smoothness, the laboratory cure profile should approximate the profile of the customer’s oven as closely as possible. Laboratory ovens in general have a much shorter heat-up time than commercial ovens, so if it is not possible to match the commercial oven’s profile in the laboratory, perhaps a test panel or part can be cured in the customer’s plant to evaluate smoothness. Finally, the substrate should not be overlooked; the preferred method for evaluating smoothness is on the actual metal that is to be coated. Differences in mass, surface treatment and surface profile can have a significant effect on the coating smoothness. It stands to reason that coatings on a 22 gauge metal panel will have significantly different smoothness than on a half-inch metal casting. The pH of the metal surface can also affect cure rate by either catalyzing or inhibiting the curing mechanism. Powder coatings (especially those in decorative applications) tend to show the profile of the substrate--one must therefore be cautious not to compare two coatings for smoothness if there is a significant difference in the surface profile of the substrates. If attention to the above does not provide the desired smoothness, then adjustments to the formulation will have to made. These will include modifying the gel time, viscosity of the binder, pigment-to-binder ratio, type of inerts used, and change of flow control agent.