Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-07-28
2000-01-11
Sellers, Robert E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
523428, 525119, 428290, 428413, 428417, C08L 902, C08L 6300, C08L 6302, B32B 2704
Patent
active
060137304
DESCRIPTION:
BRIEF SUMMARY
This invention relates to curable compositions.
The use of curable compositions such as epoxy, cyanate, phenolic and like resins, both reinforced and unreinforced, has been known for a long time in a wide variety of commercial and military applications. Of particular importance is the use of such resins reinforced with continuous fibres, both unidirectional and woven, for structural applications such as aerospace vehicle parts such as aircraft tail assemblies and wing structures. Many such applications involve the use of multifunctional epoxy resins such as tetraglycidyl compounds cured using diamine hardeners.
However, whilst composite materials made from these resins have a relatively high modulus and Tg, they are usually brittle. A number of approaches have been used to improve the mechanical properties of the resin systems both in the bulk resin system and in the interlaminar regions in laminated fibre-reinforced composite materials. Typically, to improve toughness, for example, these include the addition of rubbers, thermoplastics, particulate fillers, interlaminar tougheners etc, often in combination.
Examples of toughened resin systems are to be found in U.S. Pat. No. 4,482,660, U.S. Pat. No. 4,500,660, U.S. Pat. No. 4,680,076, U.S. Pat. No. 4,783,506, U.S. Pat. No. 4,863,787, U.S. Pat. No. 4,977,215, U.S. Pat. No. 4,977,218, EP-A-71197 and EP-A-559437. Brief details of the disclosures of these documents is given below.
U.S. Pat. No. 4,482,660 and U.S. Pat. No. 4,500,660 both disclose epoxy resin systems which are derived from epoxy resins, a reaction product of an epoxy resin and a butadiene/acrylonitrile copolymer having carboxylic groups and a curing agent such as dicyandiamide or 4,4-diaminodipnenylsulphone. Whilst there are no specific details disclosed, both documents suggest that using a reaction product of an epoxy resin and a solid rubber does not give rise to useful properties either in the curable composition or in the cured articles made therefrom. It is suggested that the viscosity of the curable composition can be adjusted by the addition of solid rubber particles, eg nitrile rubbers having carboxylic groups, thereto.
U.S. Pat. No. 4,680,076 discloses a tough cured resin system having a phase-inverted morphology derived from a polyepoxy resin, an aromatic oligomer (ie thermoplastic), an aromatic diamine hardener and a reactive liquid rubber.
U.S. Pat. No. 4,783,506 and U.S. Pat. No. 4,863,787 disclose a curable composition based on a polyepoxy resin, an aromatic oligomer, a diamine hardener for the epoxy resin and a reactive (eg carboxyl functionality) solid rubber, the latter being present as infusible particles having a median size between 10 .mu. and 75 .mu.. The conversion of the rubber into infusible particles is preferably achieved in situ by removing solvent from the epoxy/oligomer/rubber mixture whilst heating it. In using the composition to form fibre-reinforced composite materials, a large proportion of the particles are filtered by the fibres and remain on the prepreg surface to act as interlaminar toughening agents. Alternatively, the particles, presumably preformed, may be applied directly to the surface of the prepregs.
U.S. Pat. No. 4,977,215 and U.S. Pat. No. 4,977,218 disclose similar resin systems to U.S. Pat. No. 4,783,506 and U.S. Pat. No. 4,863,787 but in which the infusible rubber particles are preformed, have a Tg above 15.degree. C., a size in the range 1 to 75 .mu. and comprise cross-linked carboxylated diene rubbers or carboxylated acrylic rubbers. Again, in using the composition to form fibre-reinforced composite materials, a large proportion, if not all, of the particles remain on the prepreg surface to act as interlaminar toughening agents.
EP-A-71197 is primarily concerned with novel diamine hardeners for curable compositions but again discloses the use of what is termed flexibilizing agents or elastomeric compounds such as rubbers and thermoplastics.
EP-A-559437 is concerned with a particular problem arising when fabricating honeycomb reinforcing structur
REFERENCES:
patent: 4500660 (1985-02-01), Minamisawa et al.
patent: 4550129 (1985-10-01), Nir et al.
Carter Jeffrey T.
Ciriscioli Peter R.
Jenkins Stephen D.
Lucas Scott D.
Maskell Robin K.
Fiberite Inc.
Kleinsmith David F.
Reiter Stephen E.
Sellers Robert E.
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