Viscoelastic Properties of Polyethylene Syntactic foam with Polymer Microballoons

Syntactic foam products are most often made from glass microballoons embedded in a thermosetting polymer matrix, and they have good mechanical and thermal properties. However, the glass microballoons easily break in shear and are therefore very difficult to use for manufacturing methods that cause shearing of the material. Polymer microballoons are an alternative by which it is possible to produce a foamed product using unmodified commercial extruders or injection moulding machines. The present study deals with the viscoelastic properties of extruded polyethylene (PE) and a foam made from PE and approximately 40 volume percent of polymer microballoons. Results are shown from creep tests carried out at three temperatures and with three force levels, and from stress relaxation tests carried out at room temperature and with five deformation levels. The overall conclusion was that for some applications the foam will be the best choice, whereas for others it is more advantageous to use bulk polyethylene.