Advanced composites are high strength, high modulus materials which have found extensive use as structural components in the aerospace, automotive, electronics, and sporting goods industries. Typically they are comprised of structural filaments such as carbon (graphite), glass, boron and the like, in the form of bundles (fibers) or non-woven mats, or woven fibers (fabric), embedded in a thermosetting resin matrix.
A common method of preparing composite structures is hot melt prepregging. This process is characterized by impregnating bundles or fabrics of continuous fiber with a thermosetting resin composition in molten form to yield a prepreg, which is then layed up and cured to provide a composite of fiber and thermoset resin. In the prepreg stage the resin may be either uncured or partially cured. Resin systems containing a polyepoxide resin and an aromatic amine hardener are often used in prepregging since they possess the balance of properties required for this composite fabrication process.
Other processing techniques have been used to form fiber reinforced composites. For example, filament winding, solvent prepregging, and pultrusion are typical processing techniques in which an uncured epoxy resin composition can be used.
These composites have been made using a wide range of epoxy resin compositions. U.S. Pat. Nos. 4,331,582; 4,447,512; 4,521,583; 4,636,535; and 4,656,207 exemplify this. The matrix resins are frequently required to possess high glass transition temperatures (T.sub.g) upon curing in order to maintain the structural properties and integrity of the composite at the elevated temperatures frequently encountered during manufacturing, testing, or operation.
Epoxy resins containing 9,9-bis[4-(2,3-epoxypropoxy)phenyl]fluorene have been investigated with regard to their thermal stability, heat resistance, and flammability in the following disclosures: Korshak et al., Vysokomol. Soedin, Ser. A 13(1), 150-155 (1971); Chen et al., J. Appl. Poly. Sci., 27 , 3289-3312 (1982); and Holloway, M.S. Thesis, San Jose State, San Jose, California, August 1984, pp. ii, iii, iv, 5, 6, 14, 18-20, 22, 23. None of the above references disclose the use of 9,9-bis[4-(2,3-epoxypropoxy)phenyl]fluorene as a component of a matrix resin in fiber reinforced composites.
Compositions containing ortho-substituted 9,9-bis[4-(2,3-epoxypropoxy)phenyl]fluorenes and the impregnation of substrates with these compositions is disclosed in U.S. Pat. No. 4,707,534.
Fiber reinforced composites which include 9,9-bis[4-(2,3-epoxypropoxy)phenyl]fluorene in the matrix resin are described by Keck in NASA Contract NAS2-10130 (Report 166501)(1983), and in U.S. Pat. No. 4,684,678. Keck reports low T.sub.g values (&lt;110.degree. C) for resin systems cured with trimethoxyboroxine or a novolac phenolic. U.S. Pat. No. 4,684,678 claims high T.sub.g matrix resins by virtue of using fluorene amine curing agents. It is not disclosed or suggested how resins having a high T.sub.g can be obtained without the use of a fluorene amine curative.
USPTO Backgrounds
USPTO Backgrounds