PVC-Cu composites with chemically deposited ultrafine copper particles

Abstract

PVC-Cu composites with chemically deposited ultrafine (0.1 to 0.3 μm diameter) copper particles were prepared by hot-pressing copper-coated PVC powder (−106, +150 μm) at 120° C. Metallic copper in fine-particle form was deposited on the PVC particles by reducing an ammoniacal cupric acetate solution with hydrazine at 85° C. The electrical resistivity (d.c.) and transverse rupture strength of these composites were measured. Measurement of electrical resistivity indicated that in these composites copper particle network formation was initiated at a copper content of about 0.2 vol%; with further increase of copper content the resistivity dropped sharply from about 10¹⁴ (for pure PVC) to about 10⁵ MN m⁻² Ωcm at a copper content of about 0.5 vol%. Increase of copper loading beyond 0.5 vol% did not decrease resistivity significantly whereas the rupture strength increased continuously from 120 MN m⁻² (for pure PVC) to a value of about 300 MN m⁻² with 4 vol% copper loading. This high value of resistivity even after copper particle chain formation and the continuous increase of rupture strength, is thought to be due to formation of a thin layer of polymer film between the copper particles introducing a “quasi-random” character to the otherwise segregated network of copper particles.