GB1477650A - Strips for use in or as transmission belts - Google Patents

Abstract

1477650 -Laminated belting PNEUMATIQUES CAOUTCHOUC MANUFACTURE ET PLASTIQUES KLEBER-COLOMBES 29 Nov 1974 51907/74 Heading B5N [Also in Division F2] In a driving belt, a tensile member is formed of at least two superimposed and interconnected layers 1, 2, which are each composed of a flexible elastomer or plastomer -material as a matrix, reinforced with discontinuous elongated fibrils dispersed through the matrix, with their predominant orientation in the longitudinal direction of the tensile member providing an elasticity such that a tensile stress of 15 kg/cm<SP>2</SP> in the tensile member gives rise to an elongation not exceeding 1%. The matrix material preferably receives not less than 5% by weight of elongated fibrils, which are composed of a crystalline polyolefin having a molecular weight exceeding 500,000. Dispersion of the fibrils is achieved by subjecting the matrix to a mixing operation, which may be carried out at a temperature close to or higher than the melting point of the polyolefin, so that the polyolefin particles become broken up and drawn out into elongated fibrils during the course of the mixing operation, when the matrix material becomes subjected to shear forces. At the same time, or subsequently, the matrix material is also subjected to a drawing-out operation, between the rolls of a rolling mill or a calender, thereby causing the fibrils to become oriented generally in a direction parallel to the direction of drawing. The resulting flat sheet material provides two or more layer strips 1, 2, Fig. 1, each cut at an angle relatively to the predominant fibril direction, so that the assembled pair of superimposed strips 1, 2, have symmetrically differing predominant directions, 3, 4, forming angles less than 10 degrees with the belt centreline. The strips 1, 2, may be secured together directly, Fig. 1, by vulcanization or hot welding, or alternatively they may be similarly secured, Fig. 2, on either side of an interposed layer 5, composed of similar matrix material without fibrils. The flat belts of Figs. 1, 2, may be used on cylindrical or cambered pulleys, or in other embodiments either of these belt constructions may serve as a tensile member in a composite belt having a facing of trapezoidal, multiple-V, Fig. 4, transversely toothed or corrugated form. Typical compositions of elastomer and plastomer matrix materials are described.