Published 01/28/2026

New Take on Extrusion Creates ‘First’ Long-Glass Composite Siding

A customer request for a new class of thermoplastic siding leads GaMra into market-creating territory.

Editorial Director, Plastics Technology

The new patent-pending technology consists of 40% (by weight) long-glass fiber extruded with 60% PP copolymer, which is foamed using a chemical blowing agent to reduce its density. Whereas most profiles for siding are extruded flat then post-formed while hot right after the die, GaMra’s product is formed right in the die. GaMra runs a pelletized compound of long-glass fiber PP, and its tests to date show the new siding outperforms existing products.

In business for more than 25 years, GaMra runs 12 extrusion lines utilizing 20 extruders from a 60,000-square-foot plant in Hudson, Wisconsin. The profile extrusion company runs a wide range of materials, including high- and low-density polyethylene, polypropylene (PP), thermoplastic elastomers (TPEs) ABS, polycarbonate (PS), nylon, polystyrene (PS) and more.

The processor produces tooling in-house, utilizing a variety of advanced machinery, including three Makino five-axis wire EDMs and three vertical machining centers from Haas. GaMra was co-founded in 2000 in Baldwin, Wisconsin, by its current CEO Greg Mitsch, who spent the previous 18 years at Intek Plastics, a custom extrusion firm in Minnesota.

GaMra’s nail-ready siding product is being developed in many weatherable colors. Source: GaMra Composites

Development of this product began in 2023, when a customer approached the company to look at developing a new class of siding. GaMra was already exploring market expansion when Michael Deaner, the holder of what Mitsch describes as a “wall full of patents” from his 30-year stint at Andersen Windows, joined GaMra as principal engineer. Their objective was to develop a thermoplastic-based siding that could compete with the likes of fiber cement and oriented strand board.

As they envisioned it, the product needed to be able to be “hard nailed,” available in 16-foot long boards, light in weight (easily installed/moved by one installer), feature good impact properties, heat deflection temperature above 200°F, good weathering and be fit for ground-contact situations where existing materials cannot be used. The siding also, of course, had to be manufactured at a reasonable cost.

In-House Tooling Expedites Development

GaMra started out with a small strip die to begin the screening process and ran a variety of resins during trials before settling on the glass-filled PP compound. The company’s in-house tooling capabilities expedited the product- and process-development process, Mitsch says. “I’m not aware of anyone who is extruding long-glass composites,” he states. “Most applications for long-glass are injection- or compression-molded. We developed a proprietary extrusion process to make our unique siding.”

GaMra coextrudes the siding with a weatherable polyolefin cap layer at a thickness of about 0.015 in., which Mitsch says provides a superior finish that’s weatherable and far superior to painting. “Over a year ago, we initiated outdoor exposures to examine the effects of both direct and reflected sunlight on our product,” he explains. “In addition, we measured product temperature at various locations on these exposures on a minute-by-minute basis. We believe it’s important to expose our product not only to direct southern sunlight but also to indirect heating sources like adjoining windows and garage roofs.” GaMra conducts outdoor exposure testing in Hudson, and Cave Creek, Arizona.

GaMra is currently working with a siding processor to commercialize new products, and Mitsch believes the technology will also be advantageous to those that extrude dark-colored fencing and window lineals. As such, the company is open to exploring licensing this technology to other processors in these and other markets.