ADHESION AND AUTOHESION OF RUBBER COMPOUNDS - EFFECT OF SURFACE-ROUGHNESS

Sheets of various rubber compounds were pre-molded using different mol d surfaces: Mylar film, smooth steel, and roughened steel. Two sheets of the same compound were then bonded together by crosslinking them in contact. Measurements of peel strength were carried out over a range of temperatures from -40 degrees C to +130 degrees C. When an uncured sheet was crosslinked in contact with a smooth fully-cured sheet, the peel strength was generally lower than the tear strength of either she et and the degree of interlinking was inferred to be only about one-ha lf of the degree of crosslinking. On the other hand, when a sheet was cured in contact with a rough surface the strength of adhesion was 2X to 3X higher than with a smooth surface, probably because of increased area for bonding. Thus, when a rubber compound was cured in contact w ith a fully-cured sheet having a roughened surface, the two effects la rgely cancelled out and the resultant bond was about as strong as the material itself. Examples are given for carbon-black-filled and unfill ed compounds based on polybutadiene, a styrene-butadiene copolymer, an d natural rubber.