Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1993-05-10
1999-03-30
Chen, Vivian
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
428323, 428325, 428327, 428328, 428329, 428330, 428331, 428364, 428367, 428413, 4284231, 4284735, 4284744, 428447, 4284259, 428482, 428524, 264442, 264443, 264 69, 4251742, B32B 502, B32B 2716, B29C 3508, B29C 4300
Patent
active
058886451
DESCRIPTION:
BRIEF SUMMARY
1. BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of fabricating an article made of a composite material by providing a compound material, producing a green body by forming and compacting the compound material into a desired compact form, producing the article by curing a curable matrix-forming binder in said green body, and, optionally, post-curing the matrix; and further relates to apparatus for use in carrying out the method, and articles of manufacture fabricated by the method.
Articles of manufacture of composite materials according to the present invention are useful in a multitude of applications particularly where in use the article must retain its shape and properties when subjected to temperatures above the melting point of usual thermoplastic materials, e.g. above 1000.degree. C. Typical examples of articles include friction pads, commutators, rubber parts, heat shields, electrical insulations, connectors, machinery parts, and magnets and bearings.
2. Prior Art Disclosure
GB Patent Application No. 2 012 204 discloses a composite friction assembly comprising at least one friction member and a support member, said friction member being formed from a mixture of a thermosettable phenol-aldehyde resin and filler material by heating a mould to a temperature of the resin, usually between about 160.degree. C. and about 180.degree. C., and exerting on the mixture a pressure, normally between about 2068 bars (approximately 30,000 psi) and about 3447 bars (approximately 50,000 psi) in a time between about 2 second and 10 second.
EP Patent Application No. 0 352 363 discloses an acrylic containing friction element manufactured by compressing a mixture comprising a thermosetting organic binder, a fibrous reinforcing material, and an effective amount of fibrillated acrylic polymer fibers to form a preform; pressing the preform at elevated temperatures; treating the pressed material at a temperature sufficient to effect curing and then forming a friction element such as disc brakes, friction pads, clutch linings from the cured material. The pressure to form the preform is in the range from 140 to 350 bars (approximately 2000 to 5000 psi), and the curing of the preform is accomplished by heating to a temperature in the range from 350.degree. to 600.degree. F. (175.degree.-315.degree. C.) for about 15 min., whereafter the preform is post-baked for several hours.
A disadvantage of these processes is that the compaction of the compound material has to be carried out at pressures as high as 200-500 bars, or more, for a satisfactory flow and compaction of the moulding material to occur which requires costly tooling and press equipment.
Further, for economically short forming and curing times, the cure of the curable matrix binder has to proceed at an elevated curing temperature typically in the range from about 135.degree. C. to about 250.degree. C., or more, to ensure that the curing temperature has been reached in all parts of the 30 article. Otherwise, if lower curing temperatures are applied, long forming and curing times are required which limits the production rate.
The curing time depend on the nature of the curable matrix binder and the dimensions of the article. For large articles, such as friction elements for brake pads, the curing time can be from about 15 min. to about 75 min., or more before sufficient mechanical stability Is obtained, and the article can be removed from the mould and transferred to an oven for post-cure.
Another disadvantage of these processes is that the heating is provided by conductive transfer of heat from the mould into the compound material the homogeneity of which heat transfer is difficult to control and results in a non-uniform polymerisation of the curable matrix-forming binder.
This deficiency of conductive heat transfer into moulds has been recognized, and methods of providing a homogeneous and accelerated transfer of energy-into the compound material have been disclosed.
EP Patent Application No. 0 347 299 discloses the use of cap
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patent: 4793954 (1988-12-01), Lee et al.
patent: 4866107 (1989-09-01), Doxsee et al.
patent: 4957668 (1990-09-01), Plackard et al.
patent: 5032327 (1991-07-01), Becheret
Lindgaard Torben
Thomas David Morgan
Chen Vivian
Obtec A/S
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