Extra-low density plastic syntactic foam - consists of mass of hollow polyhedric particles plus binder with very few intermediate gussets of adhesive

摘要

Moulded microspheres type syntactic foam has its particles bonded in a matrix of adhesive; the hollow microspheres used are polyhedra held together in sheets by the matrix adhesive with much reduction in the gusset wedges of adhesive. The microspheres are pref. polyvinylidene chloride, polyvinyldiene fluoride, polymethylmethacrylate. Pref., the figure shows the structure obtained, in which the individual particles are polyhedra (1). They are pressed together with their adhesive (2) which prevents relaxation into the other structures. To produce the foam concerned the microspheres (1) and adhesive (2) are mixed together and then tumbled. This is followed by a curing phase. Many types of adhesive can be used e.g. polyurethane, urea-formaldehyde, polyester, epoxy, acrylic, etc. Foams with glass microspheres are less favourable because they are less easy to mould and they contain gussets of adhesive. ADVANTAGE - The prod has significantly lower density than such materials hitherto (e.g. 25-300 kg/m3 instead of 450 kg/m3). The foam concerned is closed-cell, water-tight, solvent-resistant and fine-pored. Use of the pref. polymers enables the products to have thin walls and good elasticity. The process if very versatile.