Pressure-sensitive elastic resistor compositions

Claim 1

A pressure-sensitive composition adaptable for use as an elastic resistor which comprises i. metallic-conductive particles having Knoop microhardness at 100 grams applied load (K 100 ) of at least 500 Kg/mm 2 , and electrical resistivity of less than 1000 microohm-cm, and being from 0.01 to 50 microns in their largest dimension, said particles being selected from at least one member of the group consisting of (a) the electrically conductive borides, carbides, nitrides, silicides and germanides of a transition metal selected from Periodic Groups III through VIII, and (b) the alloy of metal A, metal B, silicon and, optionally, chromium, metal A being cobalt, nickel or iron present at 50 to 78 atomic percent, metal B being molybdenum or tungsten present at 18 to 34 atomic percent, Si being present at 4 to 22 atomic percent, and chromium being present at 0 to 28 atomic percent, and ii. elastomer having an interaction parameter, Z, with said particles of from 1.5 to 1.75, said particles being distributed in the elastomer to form a volume fraction, φ F , of the composition that provides a first relatively high resistance in the uncompressed state and a second relatively low resistance in the compressed state; the value for Z being determined by the equation ##EQU2## wherein E c ' is the elastic modulus of the particle-filled elastomer composition and E o ' is the elastic modulus of the unfilled elastomer.