Stock material or miscellaneous articles – Composite – Of epoxy ether
Patent
1994-08-24
1996-04-30
Krass, Frederick
Stock material or miscellaneous articles
Composite
Of epoxy ether
528 94, 528117, 528120, 525113, 525504, 525534, 525535, 427386, C08G 5944, C08G 5950, C08G 6500
Patent
active
055123724
DESCRIPTION:
BRIEF SUMMARY
The invention belongs to the field of epoxy resin compositions or formulations, more particularly intended for the impregnation of textile reinforcements or the production of films, applicable to the manufacture of composite structures.
It is well known in the art that epoxy resin compositions have a very valuable application in binding or impregnating various materials, such as fibrous textures, cellular materials, for example rigid, semi-rigid or flexible foams, as well as other semi-worked reinforcement materials, such as honeycombs. The manufacturing techniques for composite structures are also known. Often pre-impregnated materials are used with a resin of the same type as that used in the manufacture of the final composite structure. Practical conditions of molding are fairly varied. In fact, there are resin systems for high or low pressure molding, for example under partial vacuum, to improve the resin penetration into the reinforcement.
Other systems are used following the technique known as "contact stratification". In this case the successive reinforcement layers are impregnated as they are placed in the mold, and no pressure is necessary during polymerization. All these concepts are well known in the art, and thus need not be further described.
The person skilled in the art however knows that it is difficult to formulate epoxy resin compositions having all the properties desirable for the manufacture of composite structures. Among the parameters considered to be important, the first is the lifetime of the resin system. By lifetime should be understood the maximum time interval, guaranteed by the supplier of the resin or the reinforcement pre-impregnated with resin, during which the product is suitable for producing a composite structure, that is to say retains its handling properties and its mechanical performance after polymerization or hardening. This parameter is very important, in particular if very large articles requiring long handling periods are to be manufactured, above all if the temperature is relatively high, for example from 25.degree. to 30.degree. C.
Another parameter is the behavior in a humid environment of the composite structure after polymerization.
It is characterized by the quantity of water able to be absorbed by the composite and also by the thermomechanical properties of the latter (such as the glass transition temperature, for example) once the degree of saturation has been reached under the humidity conditions considered.
For the production of structures known as "sandwiches", the resin composition must also have good adhesion properties to the reinforcements, such as the synthetic foams and honeycombs which are often used in such structures.
It is also desirable that the epoxy resin composition is able to be molded under relatively mild conditions, that is at low pressure and moderate temperature.
To the knowledge of the applicant, none of the epoxy-based resin systems currently existing fulfills all the conditions stated above for the production of composite structures. The known systems for contact stratification have a very short lifetime (a few hours) and poor performance in a humid environment. The systems known as "Wet-Dregs" only have a lifetime of a few days and their properties under humid conditions are poor. Other existing epoxy resin-based compositions have a satisfactory lifetime but their polymerization or hardening must be carried out at relatively high temperatures (for example above 85.degree. C.). They only weakly adhere to reinforcements such as foams or honeycombs, and their performance in a humid environment remains poor.
Below are listed documents illustrating the prior art in the field of the invention.
U.S. Pat. No. 4.423.094 describes an epoxy resin composition intended to be applied to tools in order to give them an improved surface resistance. One such composition contains to this end a filler of very high hardness. Its hardening is achieved in the conventional way by carrying out successive reactions of an aliphatic amine at ambient tempera
REFERENCES:
patent: T869009 (1969-12-01), Frank
patent: 3489695 (1970-01-01), Green
patent: 3536654 (1970-10-01), Lantz et al.
patent: 4423094 (1983-12-01), Dearlove et al.
Chemical Abstracts, vol. 85, No. 6, abstract No. 34750q, "Powdered Epoxy Resin Compositions for Coating Materials".
Blanc Isabelle
Eyriey Fran.cedilla.oise
Gambert Xavier
Brochier S.A.
Krass Frederick
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