SURFACE-CHARGES IN BLENDING SHORT FIBERS WITH POLYETHYLENE POWDER

Short fibres and ultra-high molecular weight polyethylene (UHMWPE) pow der were mixed by swirling in a glass jar with compressed nitrogen. It was found that a kind of attraction between the fibres and UHMWPE par ticles is crucial for making a composite with a proper fibre distribut ion. If aramid and UHMWPE fibres are mixed with UHMWPE powder, electri c charges are generated by triboelectrification. The electrostatic att raction is responsible for the coherence of the two components. Howeve r, if PET fibres are used, hardly any charges are formed, leading to a n inhomogeneous composite. This problem can be solved in two ways: (i) by charging the components before the mixing step with corona or(ii) by using oxidized UHMWPE powder. In this case, hydrogen bonds are form ed between the PET fibres and as a result the UHMWPE particles and a c omposite with a proper fibre distribution and better mechanical proper ties could be obtained. (C) 1998 Elsevier Science B.V. All rights rese rved.