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Carver Non-Woven Technologies, Fremont, Indiana, US, will shortly begin commercial production of pre-impregnated, pre-consolidated glass mat thermoplastic (GMT)-type composite products using its nonwoven mat technology.
The company is finishing installation of a double-belt laminator/press from Sandvik TPS Composite Solutions. The new equipment will begin commercial production in mid-August and will enable Carver to supply pre-consolidated continuous roll goods and pre-cut sheets to the half of its customer base using infrared (IR) heaters prior to moulding nonwovens with thermoplastic matrices into 3D shapes.
Double-belt laminators are widely used to produce prepregs and unidirectional tapes with glass or carbon fibre reinforcement. Such equipment is also used to consolidate glass fibre and carbon fibre mats, webs, or cross-ply reinforcements (including fabrics and nonwovens using commingled polymer-based fibres) with thermoplastic or thermoset matrices. When older IR ovens are used with traditional nonwovens, fibres 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. This can prove problematic for unconsolidated nonwovens – especially thermally sensitive formulations containing natural fibres (which can burn/carbonise) or thermoplastic fibres like polypropylene (which can shrink, sag, or even melt) during the preheating cycle. In cases where moulders cannot justify the capital expense of installing contact heating systems, changing to pre-impregnated and pre-consolidated nonwovens provides several benefits, according to Carver. First, thermoplastic fibres experience less shrinkage, so moulders need not buy as wide a roll or sheet of product, thereby saving money. Second, the pre-consolidated products heat faster, which reduces both time and energy requirements during preheating and moulding while reducing risk of damage to the materials.
As supplied, conventional nonwovens feature fibre layers that are needle punched to mechanically intertwine and interlock fibres, 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 fibres into a single resin-impregnated, pre-consolidated sheet where all layers are thermally and chemically interlocked and ready to be moulded (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). 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-fibre products since they are much lighter and more damage tolerant, and will not absorb moisture or rot. Furthermore, unlike wood-fibre products, Carver’s pre-consolidated composites are low in volatile organic compounds (VOCs) and free of formaldehyde, and unlike sheet moulding compound (SMC) composites, they contain no styrene.
“Our decision to start offering pre-consolidated nonwovens means that moulders 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 moulder 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 nonwovens production to be carried out continuously in a single short cycle, including heating, reaction, pressing, and cooling. This has 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 nonwovens made on low-cost laminators can be so high that customers end up having to purchase rolls that are 6-8 inches [15-20 cm] 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 moulder’s productivity.”
The Sandvik system will allow Carver to produce roll goods or flat sheet products as thin as 0.6 mm (0.02 inches) and in five blank widths as wide as 3.2 m (10.5 ft) with a 2.92 m (9.58 ft) post-trim finish. Sheet stock can be supplied in custom lengths to 17 m (55 ft); for product that is flexible enough to roll, cut lengths can extend to 183 m (600 ft).
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 fibre), allowing carbon fibre-based products to be run through the new laminator.
Image provided by Carver Non-Woven / R3 Composites
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