The company is finishing installation of a new double-belt laminator/press from Sandvik TPS Composite Solutions division of Sandvik AB (Sandviken, Sweden) at its production facilities. The new equipment will begin commercial production in mid-August and will enable Carver to supply preconsolidated continuous roll goods and precut sheets to the half of its customer base using infrared (IR) heaters prior to molding non-wovens with thermoplastic matrices into three-dimensional (3D) shapes.
Double-belt laminators are widely used to produce prepregs and unidirectional tapes with fiberglass or carbon fiber reinforcement. Such equipment also is used to consolidate glass fiber and carbon fiber mats, webs, or cross-ply reinforcements (including fabrics and non-wovens using commingled polymer-based fibers) with thermoplastic or thermoset matrices.
When older IR ovens are used with traditional non-wovens, fibers are exposed to heat throughout the thickness of the web (not just on top and bottom surfaces) and for a longer duration than typically is seen with contact heating, the preferred method. This can prove problematic for unconsolidated non-wovens – especially thermally sensitive formulations containing natural fibers (which can burn/carbonize) or thermoplastic fibers like polypropylene (which can shrink, sag, or even melt) during the preheating cycle. In cases where molders cannot justify the capital expense of installing contact heating systems, changing to pre-impregnated and preconsolidated non-wovens provides several benefits. First, thermoplastic fibers experience less shrinkage, so molders need not buy as wide a roll or sheet of product, thereby saving money. Second, the preconsolidated products heat faster, which reduces both time and energy requirements during preheating and molding while reducing risk of damage to the materials.
As supplied, conventional non-wovens feature fiber layers that are needle punched to mechanically intertwine and interlock fibers, resulting in a fluffy, air-filled mat that is hard to heat efficiently. Carver’s twin-belt lamination line will initially start with the ability to combine up to six layers of different fibers into a single resin-impregnated, preconsolidated sheet where all layers are thermally and chemically interlocked and ready to be molded (the preferred method for interior trim panels, headliners, and underbody shields in the automotive market) or cut and used as is (the preferred method for sidewalls, flooring, and roofing systems in the recreational vehicle (RV) market). In fact, Carver expects to focus a significant amount of production of these new materials on the RV market, where GMT-type composites are an excellent alternative to wood-fiber products since they are much lighter and more damage tolerant, and will not absorb moisture or rot.
Furthermore, unlike wood-fiber products, Carver’s preconsolidated composites are low in volatile organic compounds (VOCs) and free of formaldehyde, and unlike sheet-molding compound (SMC) composites, they contain no styrene.
“Our decision to start offering preconsolidated non-wovens means that molders can use our high-quality Carver products without having to make the capital investment to add contact heaters,” explains Mark Glidden, president, R3 Composites and Carver Non-Woven. “By broadening our offering, no matter which heating mechanism a molder is using, we now have a product that should work in that facility. The new system we’re installing will give us high throughput while also providing very accurate control of temperature and pressure. That way, there aren’t a lot of residual mechanical or thermal stresses on the material, so we maintain excellent product quality and consistency.”
Sandvik’s high-capacity and highly automated TPS double-belt laminator/press systems are designed to enable all stages of non-wovens production to be carried out continuously in a single short cycle, including heating, reaction, pressing, and cooling. This has obvious benefits in terms of productivity as well as in accurate control and adjustment of process parameters to provide a high-quality, consistent end-product. Additionally, the high quality and precision control of the Sandvik laminator will allow Carver to take shrinkage (residual stresses) out of the web as it is being produced.
“Shrinkage of non-wovens made on low-cost laminators can be so high that customers end up having to purchase rolls that are 6-8 inches [15-20 centimeters] wider than they need just to compensate for the dimensional changes,” adds Glidden. “With the type of laminator we purchased, customers have reported seeing a 50-60% decrease in product shrinkage, which can really make a difference in a molder’s productivity.”
The Sandvik system Carver has installed will allow the company to produce roll goods or flat sheet products as thin as 0.6mm (0.02 inches) and in five blank widths as wide as 3.2 meters (10.5 feet) with a 2.92-meter (9.58-foot) post-trim finish. Sheet stock can be supplied in custom lengths to 17 meters (55 feet); for product that is flexible enough to roll, cut lengths can extend to 183 meters (600 feet).
To prepare for the installation, Carver converted the entire facility’s electrical system to be compliant with IP65 Ingress Protection/International Protection ratings. This means that electrical equipment is protected from dust (especially electrically conductive dust that is produced when running carbon fiber), allowing carbon fiber-based products to be run through the new laminator.
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