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The use of coated products in prepreg production is expanding rapidly, which has prompted Coatema Coating Machinery GmbH to develop new and highly innovative machinery concepts in prepreg impregnation and coating.
(Published on July-August 2008 – JEC Magazine #42)
1- ANDREA GLAWE, PROJECTSMANAGER
2- KARIN TIMMERMANNS, PROJECTS EXECUTIVE
3- REGINA REUSCHER, DIRECTOR OF PROJECTS COATEMA COATINGMACHINERY GMBH
The worldwide trend in prepreg machinery is towards flexible, multifunctional systems for the production of a variety of products made from rovings, textiles and multiaxial structures. The use of fibres like carbon, glass and Kevlar® in combination with epoxy resins to produce reinforced plastics for lightweight products in the aerospace, sports and automotive industries is becoming more widespread. There are a number of mechanical engineering challenges when it comes to the design of specialized coating technologies and of effective treatments for the fibre materials used in prepreg products. Generally speaking, prepregs are temperatureactivated intermediate products with tailormade properties that offer a number of application advantages, such as: superior stiffness; high tensile strength; low density; corrosion resistance; high vibration resistance; low heat elongation; low weight; extraordinary fatigue resistance; easy installation; and low maintenance costs in use. Finding a machinery solution usually requires 1) testing the chemistry of epoxy or phenolic resins on substrates made of different types of material and 2) assessing potential product-handling problems for winding, material guiding, coating and drying processes. Each piece of equipment proposed for coating and impregnating lines must be assessed in detail as a function of the substrate, coating chemistry and end product.
Material types and product design
Coatema has considerable experience in handling prepreg fibre materials, mainly carbon, glass, Kevlar®, graphite and other man-made fibres. Different types of fibre products are available, such as woven fabrics, uni-, bi- and multidirectional fibre constructions, and products with more than one orientation depending on the desired strength direction.
The material structure determines the specific creel- or roll-winding handling technology used. Different creel sizes are used to wind off the rovings in parallel and feed them to the coating process, as a function of the number of rovings to be coated. Tensile strength control is essential, as rovings can cause problems if they are too tight or if they sag. The result can be an 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.
Coatema's top ten ideas for prepreg manufacturing systems