New Technologies Combine to Improve SMC
An OEM-led research collaboration is developing new interrelated technologies that allow sheet molding composite (SMC) parts to be powder-primed without sacrificing the quality of the SMC Class A surface. Key technology participants include General Motors Research and Development, Tier One supplier Meridian Automotive Systems, resin supplier AOC and coatings supplier Red Spot Paint & Varnish..jpg)
Powder primers help improve the workplace and environment by reducing volatile organic compound (VOC) emissions and overspray waste. OEM facilities want to apply powder primers to steel and SMC body parts that are sent side-by-side through E-coat and paint coating cycles.
When powder primed, conventional SMC develops a leather-like surface appearance during the powder primer high-temperature cure cycle. At General Motors R&D, the issue came under the full technical scrutiny of Hamid Kia, Principal Researcher and world renowned automotive SMC authority.
Jeff Robbins, Director R&D for SMC supplier Meridian Automotive Systems, says, "GM research concluded that the failure mechanism was a combination of air and moisture that is released when a common low profile additive (LPA) is used. After defining the problem and determining the thresholds, Hamid Kia challenged companies in the automotive supplier value chain to work together toward a synergistic solution."
Solution by Teamwork
To evaluate different SMCs, Meridian Automotive provided tooling and molding equipment that are used in regular production. Full-size parts molded with different SMCs were sent to GM assembly plants for standard powder primer application and cure. These production-scale trials validated laboratory data and ensured that the solution could be implemented without changing process or equipment parameters.
AOC’s role was to develop a special, low-moisture content formulation, which incorporated new LPAs in a synergistic fashion. The new additives continue to provide the traditional LPA function of contributing to reduced shrinkage and improved surface finish.
"All our new low moisture content SMCs are based on high performance Atryl®TCA resins," points out Ed Kleese, Technical Services Manager for AOC. "SMCs made with Atryl TCA are bringing increased toughness, reduced surface waviness and superior Class A finishes to a host of car and truck applications."
To achieve even greater surface quality in powder primed parts, Hamid Kia encouraged automotive plastics coating leader Red Spot to develop a new SMC primer. The Red Spot primer is applied by Meridian before SMC parts are shipped to the GM facility. The Red Spot primer is conductive so that the electrostatically-charged solid particles of the OEM powder coating process will be attracted to the SMC part surface.
"Red Spot research led by Dr. Keith Cannon results in a conductive powder- capable SMC primer with a unique patent-pending technology, says Marilyn Bara, New Product Marketing Director for Red Spot. "In essence, the new low-permeability coating technology forms a layer that significantly controls the release of moisture from the SMC into the powder primer. Combining our proprietary primer with low moisture composite takes the surface quality of powder-primed SMC to extraordinary levels."
About Meridian Automotive
Headquartered in Allen Park, MI, Meridian Automotive Systems, Inc., is a leading supplier of technologically advanced components, modules and systems to automobile and truck manufacturers. Meridian is also a leader supplier of sheet molding composite (SMC) for cars and trucks.
About Red Spot
With headquarters in Evansville, IN, and a Coatings Application Center in metropolitan Detroit, Red Spot Paint & Varnish Co., Inc., is first in high performance automotive coatings. Red Spot pioneered the development of paints for application to plastics and continues to be the technological leader in coatings for automotive plastics and composites, including SMC.
About AOC
AOC is a leading global supplier of resins, gel coats, colorants, additives and synergistic systems for composites and cast polymers. AOC products are manufactured in facilities strategically located in North America, Europe and Asia. AOC-owned manufacturing plants are ISO 9001:2000-certified, use proprietary technology to ensure resin batch-to-batch consistency, and follow Six Sigma-Lean principles for improved efficiency.
SMC is a priority at AOC. For more information, e-mail Mike Dettre at mdettre@aoc-resins.com, phone him at (901) 854-2800, or visit www.aoc-resins.com on the Internet.