JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008 - 26

BUSINESS Trends g…/… Coatema expertise: coating and materials handling technologies for prepregs Plant concepts Specialized coating plant layouts must take into account important prepreg-handling parameters such as: - various winding technologies with perfect tension control, - various coating technologies determined by the coating’s weight, chemistry, viscosity and delivery, - drying technology determined by coating chemistry (water- or solvent-based), - appropriate exhaust technology. End users choose composite materials based on their weight, strength and cost characteristics. The extreme differences between individual products means that the production machines must be very Installed coating plant for prepreg products versatile. Click&CoatTM concept as flexible layout for prepreg production uneven coat, rendering the products unusable due to poor quality. Handling woven or multiaxial substrates can be a problem if the slippage resistance is too low. The tension must be finely adjusted, because any out-of-place fibre affects the resulting force distribution in the structural component part. Chemical solutions and coating technologies The resins (matrix) used as coating materials can include solvent- or waterbased epoxy resins, powder materials, hotmelt resins, phenolic systems, and polyester/vinyl ester/acrylic resin systems; this use of chemical solutions imposes a further requirement in the special handling of products for prepreg materials. The choice of coating system must be based on the chemistry, the application weight and the viscosity of the coating material, among other factors, for example whether the substrate is to be impregnated fully or only coated on one side. fibre bundles, so the substrate has to be guided very carefully into the coating process by guiding rollers with very smooth surfaces. A variety of technologies is available for filament coating, with dipping technology and heated-knife coating generally being the preferred solutions. Roller systems, slot die technologies, powder scattering and hotmelt technologies are also used. Most product-handling problems are due to: - breakable fibres, - the need for complete fibre coverage when coating single rovings or closed substrates, - critical damps during the drying process, like formaldehyde or phenolic chemistry compounds. Drying technology The drying stage after the coating step is a very important feature of a prepreg coating line. Two techniques are currently available: hot air drying and infrared (IR) drying. Obtaining a high-quality end product depends upon precise adjustments of the drying or curing process. The drying technique used will depend on the coating material and the thickness of the layer. Convective dryers are used with solventbased raw materials and when very consistent air control is necessary. With IR technology, the radiation heats the substrate from the inside out. This accelerates the drying process, making IR the ideal drying method for high rates of output and for water-based coating materials. Meeting prepreg manufacturers’ expectations Driven by the need for fuel savings, demand for advanced composite materials is taking off, literally and figuratively, in the transportation industry. Airplane, automotive, bus and even passenger train designers are looking to composites for energy-saving weight reductions without sacrificing durability, safety and production costs. Prepreg manufacturers are looking to companies like Coatema Coating Machinery, Dormagen, Germany, for possible solutions to problems created by the burgeoning demand for more, newer and cheaper products. Coatema's design and manufacturing team has responded with a combination of traditional and innovative coating, laminating and handling technology. More information: www.coatema.de Contact: coatema@coatema.de Drying/Curing via IR Before coating, guiding systems are used to position the substrates optimally and feed them into the coating system and subsequent drying process without displacing fibres in the rovings or woven fabrics. The slippage resistance of woven substrates is very low and very often causes problems, as mentioned above. There is nearly no physical adhesion between the Hot air drying JEC Composites Magazine / No42 July-August 2008

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JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008