Fusetex Ltd have developed a range of cross-linkable thermoplastic powders for use in various applications for the composites sector.
These novel hot melt adhesives have an initial melting range of 100 – 110°C and on additional heating the melt viscosity increases to a point of immobility. The ideal temperature for cross-linking the product is 165 – 170°C for 25 - 60 seconds. Depending on temperature/time, the fully reacted bond has been tested to 250°C (Aramid to PTFE coated non woven) with no delamination and the adhesive is excellent at bonding low energy surfaces such as glass, carbon fiber, Aramid and metal. It also exhibits excellent adhesion to substrates with difficult finishes such as fluorocarbon.
The polymer chain has a large proportion of polar chemical groups offering true specific/chemical adhesion. These high molecular weight polymers offer excellent cohesive strength both before and after curing making them suitable for impregnation of composite materials in addition to laminating and coating.
They particularly lend themselves to deep draw moulding applications for the automotive sector or applications where post curing is required and have the ability to cross-link with time and temperature only, requiring no external catalyst, UV or moisture for reaction. Unlike PUR systems, the reaction is "stop-go", which means that the cross-linking is fully controllable and can be halted by removing the heat and re-started later by further application of heat. This readily facilitates the ability to coat in one process and then laminate in a subsequent one. Shelf life is in excess of one year in powder form and coated or bonded material which has been processed below 150°C and therefore not cross-linked can be stored for at least 6 months without any reduction in its reactive properties. This makes it ideal and easy to control for multi-process operations where storage between processes is important.