JPH0311603B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for reinforcing a whisker preform used as a fibrous skeleton when manufacturing a fiber-reinforced composite material by infiltrating or impregnating it with a matrix material. ``Prior art'' One method for manufacturing fiber-reinforced composite materials using silicon carbide whiskers, silicon nitride whiskers, etc. as reinforcing materials is to form a preform consisting of a whisker aggregate, and then apply a liquid matrix material to this preform. There is a method of press-fitting and solidifying. The composite material obtained by this method is influenced by the properties of the whisker preform, which is the fibrous skeleton.For example, the properties of the composite material are greatly influenced by the density of the whisker preform and the homogeneity of the tissue structure. . In particular, in order to obtain a high-performance composite material, it is important that the whisker preform has sufficient strength to maintain its original shape without being deformed when a liquid matrix material is press-fitted. The applicant first disperses the whisker product in water or an organic solvent as an effective means of forming a whisker preform for a composite material, and then passes this under normal pressure or pressurization to leave the remaining wet whisker cake as it is. Alternatively, he proposed a method of compressing to a predetermined density and then drying it (Japanese Patent Application No. 57-226545, No. 59
-12049 JP-A-59-121196, JP-A-60-
(See Publication No. 161400). Although these whisker preforms according to the prior art are aggregates of only whiskers, they have an extremely homogeneous and integral structure, but they are not strong enough, especially when forming a low-density preform. In this case, the strength properties deteriorate significantly. Therefore, there is a drawback that deformation often occurs during press-fitting of the matrix material, resulting in deterioration of the performance of the composite material. In order to overcome this drawback, the applicant has proposed a method in which the whiskers are dispersed in an aqueous solution containing an inorganic binder such as boric acid, an alkali metal borate or aluminate, or treated with a mixed aqueous solution of sodium alginate and acrylic acid. proposed a method of strengthening the preform, such as
58448, 59-65879, JP-A-60-210600, JP-A-60-204660). ``Problems to be Solved by the Invention'' However, when forming a reinforced whisker preform, it is necessary to not only have sufficient strength to withstand the press-fitting of the matrix material, but also to ensure good interfacial wettability with the matrix material. It is required to maintain a complex reinforcement function. The above methods were not sufficient in improving this interfacial wettability. The present invention provides a method for forming a reinforced whisker preform that satisfies the above-mentioned required characteristics. ``Means for Solving the Problems'' The present invention is based on repeated research into a binder component that provides sufficient strength to withstand press-fitting of a matrix material and has good interfacial wettability with the matrix material in the formation of whisker preforms. As a result, it was confirmed that a silane coupling agent was suitable for achieving this purpose, leading to its development. That is, in the present invention, after dispersing generated whiskers in a solution containing a silane coupling agent, the resulting wet whisker cake is dried as it is or compressed to a predetermined density. This is a method of forming a strengthened whisker preform with this structural feature. The whiskers used are silicon carbide whiskers and silicon nitride whiskers, which are substances consisting of fine short fiber-like single crystals with a diameter of 0.1 to 5.0 μm and a length of 10 to 500 μm. A silane coupling agent is a silane coupling agent that reacts with the organic phase and inorganic phase in the same molecule and chemically bonds them.
It has different types of reactive groups. That is,
Methoxy groups, epoxy groups, silanol groups, etc. that chemically bond with inorganic materials such as glass, metals, and silica sand, and vinyl groups, epoxy groups, methacrylic groups, amino groups, mercapto groups, etc. that chemically bond with organic materials such as various plastics. It has a reactive group. In this way, the silane coupling agent acts on the interface between the inorganic filler and the organic polymer matrix, chemically bonding them together or increasing their affinity, and exhibits an excellent function in improving the physical properties of composite materials. do. Therefore, the surface of the whisker is treated in advance with a silane coupling agent to form a preform.
When liquid plastic is press-fitted there, a strong composite structure is formed at the interface between the plastic and the whiskers via the silane coupling agent.
In order to provide this interfacial bonding function, it is sufficient to attach a silane coupling agent component to the surface of the whisker to form a thin film layer. By treating the whiskers in a solution of a silane coupling agent with a concentration of about 1% by weight, sufficient interfacial bonding function can be imparted to the plastic. It is said that it no longer contributes to the increase in Focusing on this effect of the silane coupling agent, the present invention improves the interfacial bonding function between the whiskers and the matrix by simply attaching the silane coupling agent component in an amount greater than that required for imparting the interfacial bonding function. This not only improves the performance of the silane coupling agent, but also creates a strong bond through mutual hydrolysis and chemical reaction between the silane coupling agents. This strong bond between the silane coupling agents results in a reinforced formation of the whisker preform. In this case, the concentration of the silane coupling agent is preferably used in the range of 3 to 5% by weight, and 5% by weight
Even if treated with a solution with a concentration exceeding this, no further effect will be observed. "Operation" As explained above, the present invention disperses the whisker product in a solution containing a relatively large amount of the silane coupling agent, so that the amount of the silane coupling agent present in the coating layer attached to the whisker surface is increases. Therefore, during the formation of the preform, the silane coupling agents react with each other to form a strong connective tissue and to strengthen the preform. On the other hand, the remaining silane coupling agent functions to promote and strengthen the interfacial bonding reaction with the plastic serving as the matrix. "Example" A silicon source material and a carbonaceous material were mixed and reacted at a temperature of 1600℃ in a non-oxidizing atmosphere, and the remaining carbonaceous component was removed by combustion to form a material with a diameter of 0.5 to 1.5μm and a length of 10mm.
~300 μm β-type silicon carbide whiskers were produced. The produced silicon carbide whiskers were mixed and dispersed in solutions of various concentrations using γ-aminopropyltriethoxysilane (KBE903, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent and toluene as a solvent. For the dispersion operation, charge 100 g of whiskers to 1 part solution in a screw-blade stirring tank, and incubate at 100℃ for 60 minutes.
Stir for a minute. After cooling to room temperature, this dispersion has a diameter of
It was injected into a 100 mm cylindrical sealed filtration device, and compressed air was injected into the upper sealed space to pass it under pressure. The cylindrical wet whisker preform formed in this way is compressed to a predetermined density and air-dried.
Dry at a temperature of 120°C. The compressive strength of this preform was measured and shown in Table 1.

[Table] From the results in Table 1, the compressive strength of the whisker preform formed by treatment with the silane coupling agent solution increases, and even in the case of a preform with a low Vf value (volume % of whiskers), the compressive strength is sufficient. It turns out that it has strong properties. The preform was then placed in an autoclave and set in a mold, impregnated with an epoxy resin solution at room temperature under a vacuum of 3 mmHg, and then press-fitted under a pressure of 10 kg/cm ² . It was then heat treated at 120°C to harden it. The compressive deformation rate and mechanical strength characteristics of the whisker preform in the pressurizing direction were measured for the fiber-reinforced resin composited in this way.
Shown in 2.

[Table] From these results, it is possible to strengthen the preform by treating the surface of the whiskers with a silane coupling agent, and as a result, it is possible to maintain almost the original shape even when the matrix resin is press-fitted. It has therefore been found that the composite material produced in this way has excellent homogeneity and also possesses high mechanical strength properties due to the interfacial bonding function of the silane coupling agent. "Effects of the Invention" As is clear from the above explanation, the present invention utilizes the interfacial bonding function of the silane coupling agent and the mutual hydrolysis and bonding action of the silane coupling agent to achieve interfacial bonding with the matrix resin. This makes it possible to maintain a good whisker preform and form a strengthened whisker preform. Therefore, a whisker-reinforced resin composite material with excellent mechanical strength properties can be efficiently produced.

Claims (1)

[Claims] 1. After dispersing the generated whiskers in a solution containing a silane coupling agent, the obtained wet whisker cake is filtered under normal pressure or pressurization, and the obtained wet whisker cake is left as it is or compressed to a predetermined density. A method for forming a strengthened whisker preform characterized by drying. 2 The concentration of the silane coupling agent is 3 to 5% by weight.
A method for forming a reinforced whisker preform according to claim 1.