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July 18, 1999

3 Min Read
Secret to surface appeal

Beauty may be only skin deep, but when it comes to molded plastic parts with stringent appearance requirements, beauty is all that matters. Cosmetic flaws on parts that have no structural duties still spell scrap for molders. Painting may hide some imperfections, but the costs can be prohibitive. Reworking a tool, scrapping and reprocessing, or tweaking the process may or may not be feasible. There is another option. Several molders (who shall remain anonymous) let us in on a low-cost secret for ensuring uniform surface appearance—they use a patented flaw-repair coating called Per-Fix.

According to manufacturer Chem-Pak (Winchester, VA), Per-Fix is a micro-thin coating that is applied directly to the molded part, not to the mold. It bonds permanently with the plastic and remains intact for the life of the part. Developed and patented in 1985, the coating alters the way light reflects off of the part surface. In essence, it makes the flaws invisible. If you were able to remove the coating (you can’t), the flaw would still be there, but since it is rendered invisible, it has, in effect, been eliminated. Because it is transparent and does not alter color, there is no color matching involved. Costs average 10¢/sq ft.

Automotive interiors are perhaps the largest application area for Per-Fix. Chem-Pak has obtained specs from Ford and Chrysler for its coating, and is working on acceptance from GM. Chem-Pak says Per-Fix is used extensively both by U.S. automotive molders and those supplying Japanese transplants. According to Chem-Pak, if an automobile company is assembling in North America, Per-Fix is being used on some of its parts.

A compelling reason for using the coating, according to customers, includes the fact that the molder saves time and money and is able to stay on schedule. The customers benefit from the molder’s lower costs. As downward price pressures increase, the molder is better able to meet the customer’s demands while still delivering perfect parts. And the consumer benefits, because the final product is picture perfect, every time.

Lou Jones of Matlab (Asheboro, NC), a coating applicator, uses Per-Fix to achieve low-gloss requirements for his customer, a custom molder. “The material cannot achieve lower gloss levels by itself, so we use the coating to produce a uniform surface appearance. It has high repeatability and produces parts with uniform gloss levels.”

A few limitations apply. Per-Fix is only for parts that are going to be used in interior settings. It is also a matte finish coating, so it is suitable only with matte finished parts, although it is offered in several different gloss levels to match the gloss of the parts being coated. It will eliminate knit lines, glossy spots, flow lines, mild rib print-through, and other cosmetic flaws. Chem-Pak has developed five different systems compatible with a wide range of polymers, including polypropylene.

Why is it a secret? Apparently, injection molders (like most people) don’t relish admitting there are problems they can’t fix. For some, problems stem from an older mold that was inherited. Others are trying to mold parts that weren’t designed either with moldability or with an eye toward the potential to create defects.

Bryan Biddle, director of marketing for Chem-Pak, offers an example. “I recently had a new customer call out of the blue and put in a very large order. Since we had never sold anything to this customer, or, for that matter, even heard of this molder, it aroused our interest. We eventually found out that the molding manager had, until recently, worked for another molder who is a very big customer. When he went to his new job and was charged with fixing new problems, he came to us for a solution. When asked if we could quote him, we got a polite ‘no.’ He really didn’t want to advertise his solution. In other words, Per-Fix is his secret weapon.”

Contact information
Chem-Pak Inc.
Winchester, VA
Bryan Biddle
Phone: (800) 336-9828
Fax: (540) 722-3993
Web: www.chem-pak.com

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