VINYL ESTER-BASED COMPOSITE DESIGNED FOR USE IN MOLDS

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Lenox Polymers Ltd. in Port Huron, Mich., introduced a resin-based composite mold material for the automotive, recreational, agricultural, aerospace, packaging, marine and building industries.

According to Lenox, the molds have been production-proven and are adaptable for such processes as reaction injection molding, compression molding, resin transfer molding, thermoforming and contact molding.

The vinyl ester-based, composite molds are capable of molding parts in polyurethane, ABS, polyolefin, nylon and fiberglass materials for a variety of applications such as automotive doors, hoods, interior panels, spoilers and bumpers.

President Kenneth Kurple explained that using the vinyl ester-based composite makes it possible to build tooling without the high-heat limitations of composite materials.

``Other composite materials can't take the heat, but ours have good heat resistance so they can function at higher heat levels to fill that void between metal molds and composite molds,'' he said.

Dann Deavers helped Lenox develop the unique tooling system. He is president of Polymer Systems International LC, and his Matrix Tooling Systems division in Chesterfield Township, Mich., near Detroit, makes molds using the composite materials.

Deavers said he developed some of the first expoxy molds used in automotive applications back in 1964. He said the vinyl ester material provides excellence heat-transfer capability in excess of 600 F.

``We developed this system with the production of tools for RIM materials in mind,'' Deavers said.

Those materials, he explained, have extremely high exothermic properties and corrosive qualities.

Deavers said they have ``successfully used the material for injection molding'' molds, however the firms are still performing tests to see what kind of life the mold has under the higher heats and pressures injection molding demands.

Because the turnaround time from art to part is so fast, the mold system offers opportunities in rapid prototyping applications. In one automobile door application, Deavers was able to take the computerized math data to generate a medium density fiberboard model, then produce the mold and make parts in three weeks.

Also, the system can make molds for very large parts. Deavers said the molds can be sprayed up, laid up or mask-cast in four or five days.

The composite material incorporates a high-percentage of nickle particulate, which is not corrosive, and produces good thermal conductivity. Kurple said molds made using the new Lenox system also offers a ``significant cost advantage compared to aluminum tooling.''

Deavers added that, since a highly polished surface is achievable on the mold, it is ideal for applications requiring asthetic finishes.

Lenox began delivery of the new mold materials in November. A major automobile supplier has funded a $100,000 mold program to manufacture plastic car door interiors.

Lenox Polymers also makes a variety of high-performance polymers using lignin, a byproduct of paper mills. The nontoxic substance acts as the glue that holds the cellulose fibers of wood together, and makes up about 25 percent of most woods. The new polymers made from lignin can serve as alternatives to epoxy, phenolic and polyurethane. More than 16 tons of lignin now is incinerated annually in the United States, Lenox said.