Highly durable and cost-effective, liquid clearcoats have long been the norm in the automotive industry. But with increasing energy costs and the specter of tightening solvent and carbon dioxide emissions looming on the horizon, forward-thinking manufacturers have begun searching for alternatives. One solution that offers both high durability and substantial environmental benefits is a new generation of powder clearcoats.
The BMW Group was the first automaker to embrace powder clearcoat technology. Through a collaboration with PPG Industries and other suppliers, the company installed its original powder application equipment at its Dingolfing, Germany facility, where its premier 5, 6 and 7 series automobiles are produced. For more than 10 years, this line has consistently delivered high quality, durable finishes.
The use of a powder clearcoat has yielded many advantages for the BMW Group. The plant has enjoyed a respectable 90% first run capability (FRC) while being able to reclaim and reuse its powder overspray, which allows for more than 95% product utilization. The powder clearcoat booth is also energy-efficient; it uses 85 to 90% recirculated air, compared to less efficient liquid systems that might also require incineration of the solvent-laden air for emissions compliance.
Formulating a powder clearcoat with the smooth, flawless properties required by the automotive industry can be quite a challenge. There is a constant battle to achieve low molecular weight resins for appearance that are still high enough so that the end result is in solid form.
These obstacles notwithstanding, PPG and BMW won several awards for their innovative collaboration, including the R&D100 and the prestigious Automotive News PACE Award. And due to the great success of powder technology at Dingolfing, the BMW Group converted its Regensburg and Leipzig plants to powder clearcoat, as well.
In recent years, BMW challenged PPG to develop an even better powder clearcoat. While existing formulations had scratch resistance comparable to many liquid clearcoats of the time, BMW wanted this aspect of the coating raised to a higher level.
Increased DurabilityTo equal the excellent scratch resistance of the industry’s “superior” liquid clearcoats - such as CeramiClear® and carbamate liquid - the team at PPG Industries had to drastically narrow the gap. Their efforts led to the development of new flow additives for improved appearance, alternate additive packages to improve humidity resistance and the use of mar enhancement additives (MEA) for substantially improved scratch resistance.
These improvements mean that consumers will enjoy the look of their new BMW even longer than before. Scratches inevitably happen over time; however, if a scratch does mar the surface of the new powder clearcoat, there will be less visual damage. This effect occurs because the MEA acts like a small layer of ball bearings partially sticking up from the coating surface. Instead of a child sliding a backpack against the car and scratching the clearcoat, for instance, the child’s backpack is actually rubbing against the ball bearings, which keeps the clearcoat well protected.
Continued DevelopmentsThe newest generation of powder clears was successfully implemented in BMW’s Regensburg and Dingolfing plants by mid-2006. According to a company spokesperson, the new products “completely met BMW’s expectations.” In addition to the main target of improved scratch resistance, significant improvements in processability (e.g., fluidization) have been achieved.
But the research and development efforts have not stopped there. Additional advances in most of the materials that make up the clearcoat, from the resins to the additives, continue to be made. Researchers are close to equaling the liquid CeramiClear® specification for scratch resistance, and the technology fits into the “best in show” category for automotive clearcoat performance in both the liquid and powder forms.
A major barrier to the adoption of powder coatings in the past has been the fear associated with running a powder booth. Manufacturers have worried that the application equipment would not be easy to maintain or robust enough to be used day in and day out in an automotive setting.
The growing success of both powder primer surfacer and powder clearcoat has alleviated these concerns to a great extent. Nearly four million units using powder coatings will hit dealerships globally this year. The environmental benefits - use of overspray, recirculation of booth air, and reduced energy costs hazardous waste - have all been proven. As the comfort level of running a powder booth rises, so does the performance of the powder clearcoats being developed.
As environmental regulations change and energy prices increase, automotive manufacturers worldwide will need to investigate alternative technologies. With the many improvements taking place, powder clearcoats offer a smart, efficient and eco-friendly alternative to liquid systems.
PPG’s website is at www.ppg.com.
Editor’s note: In addition to PPG products, BMW also uses powder clearcoats from DuPont (www.dupont.com). BMW’s website is at www.bmw.com.