| 摘要 |
1,174,341. Polymers containing glass microbubbles. MINNESOTA MINING & MFG. CO. 19 Jan., 1967 [20 Jan., 1966], No. 2977/67. Headings C3B and C3C. A rigid, light-weight, water-resistance syntactic foam comprises a high molecular weight polymeric composition matrix and waterresistant, hollow glass microbubbles uniformly distributed throughout the matrix material, the matrix being uniformly bonded to the surface of the microbubbles and essentially free of voids other than those contained in the microbubbles. The microbubbles have an average diameter of 5 to 300 microns, an average true particle density of 0À1 to 0À6 gms./c.c. and form between 55 and 90% of the volume of the foam; the foam has a density less than 42 1b./cu. foot, a uniaxial compression strength of at least 5000 p.s.i., and a one-inch cube of the foam does not absorb more than 2% of water when in direct contact with water under compression loads greater than 5000 p.s.i. for at least 1000 hours. The glass composition of the microbubbles preferably comprises at least 40% SiO 2 , and the microbubbles should withstand boiling water for at least 16 hours with weight losses of less than 4%. The polymeric matrix is preferably a highly crosslinked thermosetting polymer, e.g. an epoxy resin, polystyrene, a polyester or a polyurethane, in particular a polyglycidyl ether of a polyhydric phenol cross-linked with a polycarboxylic acid anhydride which composition is liquid at room temperature; the uncured epoxy resin is preferably pourable at temperatures below 200‹ F. When mixed with the microbubbles prior to curing, a curing agent, e.g. an amine catalyst, is preferably incorporated, also an anti-levitation agent, e.g. a finely divided clay with an amine surface active agent, so that the microbubbles can remain uniformly distributed throughout the resin for a period of days, the viscosity of the system being less than 100,000 c.p.s., preferably less than 50,000 c.p.s. at 200‹ F. The surfaces of the microbubbles are preferably coated with a primer which improves adhesion between the microbubbles and the resin, e.g. with an amino or an epoxysilane, or a chromium complex in alcohol especially methacrylatochromic chloride. |
