Polymer Coating Extends Tool Life
A new polymer sealant for chrome-plated metal surfaces is getting good reviews from plastic processors in application ranging from extruder screws and dies to injection molds and blow molding core rods. Called Micro Tuff™, the sealant fills in microcracks and porosity in the chrome plate, adding lubricity and improving wear resistance. Micro Tuff™ is supplied to both processors and tool makers by Plating Resources, Inc., Cocoa , FL.
Though originally intended for use on chrome plating, Micro Tuff™ gets similar results when applied to nickel-plated tools and even unplated stainless or carbon steels.
The lubrucity imparted by the sealant translates into higher extrusion rates or easier mold release. It also reduces mold deposits and wear. Plating Resources, Inc. says users may see a 14% rise in production rates, a 6% increase in machine uptime, and an 81% reduction in rechroming costs when Micro Tuff™ is applied to a new or reworked die.
Several major extrusion die makers are now offering Micro Tuff™ treatment. But Micro Tuff™ can be applied by a processor in his own shop, saving the time and expense of shipping a mold, die, or screw out for treatment. Users say they need only buffing tools, to apply the sealant themselves.
How It Works
Micro Tuff™ consists of a long-chain polymer combined with and an organic impregnating agent. The work piece is heated to 275 to 300F, and the sealant is brushed or rubbed on. A chemical reaction occurs, causing the polymer to crosslink and bond to the substrate.
Plating Resources, Inc. recommends that Micro Tuff™ be applied to either a new tool or one that has been stripped of previous plating and then cleaned and replated. A highly polished mirror finish or 1 to 3 roughness average (RA) gives best results. If the sealant is applied over metal surfaces that are not perfectly clean, performance may be somewhat reduced.
Tests conducted by Plating Resources, Inc. show that chrome plate sealed with Micro Tuff™ achieves 65 hrs of corrosion resistance before failing vs. 1 hr for unprotected plating in the ASTM B-368 “Cass” test. And in the ASTM B-117 salt-spray test, plating with Micro Tuff™ lasted 530 hrs vs. 5 hrs without the sealant.
Users say Micro Tuff™ minimizes polymer build-up, plate-out, and burning and reduces the frequency of tool cleaning by at least 50% with such resins as PVC, CPVC, PS, acrylic, PTFE, and PE. One producer of coextruded vinyl siding was able to process 5 million lb of a troublesome powder formulation without shutting down because there was only minor buildup on the die. The tool had been treated with Micro Tuff™ by the equipment supplier. In the same siding plant, a similar line without the sealant experienced frequent shutdowns due to burning. In another case, a CPVC pipemaker cut its chrome-plating costs from $37,000/yr to $7,000/yr after applying Micro Tuff™ to its pipe tooling and adapters.
Success In The Field
At least two flat-die makers offer Micro Tuff™ coating as an option on their dies.They have reported a 50% reduction in plate-out and die lines. Micro Tuff™’s lubricity acts as a “safety net” to protect tooling in the event of runaway extruder conditions.
A PVC sheet extruder reports 20% greater lb/hr output with Micro Tuff™ treatment on the coathanger section of its chrome-plated dies. “Clean-up is easier, there’s less burning, and die wear has been cut in half."
Another PVC sheet extruder applies Micro Tuff™ to the last five flights of an uncoated carbon-steel screw for better polymer release and reduced build-up of black specks.
A North American extruder of vinyl siding doubled the life of its extrusion tooling and increased productivity by 10% after applying Micro Tuff™.
A manufacturer of injection molded PP cups and PE lids applies Micro Tuff™ in-house to the cores and cavities of its chrome-plated molds for better release, they obtain at least 5% improvement in cycle time. Micro Tuff™ cuts both downtime and frequency of tool cleaning and rechroming in half. Since rechroming a mold costs the firm $400 to $500, the savings are substantial.