| 摘要 |
<p>902,747. Composite sheet material; laminates. MINNESOTA MINING & MANUFACTURING CO. July 10, 1958 [July 10, 1957], No. 22183/58. Class 140. A composite flexible sheet material comprises a room-temperature solid, heat-curable, rubber base/phenolic adhesive bonding layer characterized by being curable at elevated temperatures to a non-brittle thermoset condition, and a room-temperature solid and heat fluidizable, heat-curable, epoxy resin adhesive bonding layer characterized by being (a) flowable as a viscous liquid of high filletting action as it is elevated in temperature, and (b) curable from said flowable state to a solid thermoset state at higher elevated temperature, said epoxy resin layer comprising a roomtemperature solid epoxy resin initially softening at a temperature between about 100‹ and 200‹ F., and a heat-activatable curing agent for said epoxy resin. The solid epoxy resins suitable have on the average a 1,2-epoxy equivalency greater than 1.0; many are specified. The heat-curable elastomer/phenolic layer is formed from a blend including a dienetype rubbery elastomer, a heat-activatable curing agent, and between about 25 to 500 parts by weight of heat reacting, thermosetting, alcohol soluble phenol-aldehyde resin for every 100 parts of elastomer. The preferred elastomer is butadiene/acrylonitrile (buna N). The sheet material 10 is prepared by calendering the elastomer/phenolic blend to form a film 11, hot melt coating the epoxy resin 12 on to it and, if desired; placing preferably on the molten epoxy layer a porous, loosely woven, unbleached, unsized cotton cloth 13 (e.g. cotton scrim). Alternative materials may be woven or non-woven webs of materials such as cotton, glass fibres, metal wire or synthetic fibres. If desired, the scrim layer may be within the epoxy composition layer instead of on it, or as a network between the epoxy layer and the elastomer phenolic layer, or within the elastomer layer. Sandwich structures for aircraft construction may be made by placing the sheet 10 with its elastomer/phenolic layer 11 next to cleaned and etched aluminium skin panels 14 (Fig. 4), and with its scrim cloth layer 13 contacting a honeycomb structure of aluminium cell walls 15 and cells 16. The honeycomb structure is placed between two skin panels 14, as shown. On bonding by heat and pressure the epoxy resin fluidizes, passes through the pores of the scrim cloth and is drawn by capillary action along the sides of the cell walls (" filletting ") as shown in Fig. 4. Continued increase in temperature causes curing to a thermoset condition.</p> |
