JPS5910904B2 - Organic composite material consisting of fibers and stretchable matrix formed in situ - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to composite structural materials, in particular composite materials obtained from a fiber-reinforced 15 stretch resin system.

Fiber-reinforced composite systems are well known as structural materials, and the closest known analogs to the composites of the present invention include:
Although there are commercially available fiber-filled systems cut with a chopper, the incorporation of 20 such fibers into the curable resin results in a composite material whose mechanical properties are completely different from those of the composite material obtained according to the invention. Known fiber-filled composite materials exhibit high modulus, but often have reduced elongation and strength. Also, upon repeated loading, the properties of the known fiber-filled composite material 25 become completely different from those of the composite material obtained according to the invention. The present inventors investigated 30 types of materials with the aim of developing a reinforced composite structural material that exhibits almost no drawbacks of known composite material systems and has only the advantages of known composite material systems. We have now discovered a new fiber-filled composite material system containing a stretchable matrix.

That is, the composite material of the present invention is made of isotactic polypropylene, polyethylene, isotactic poly(4
- highly C-branched polyalkenes randomly arranged in all directions, formed from linear polyalkenes selected from the group consisting of methylpentene-1), isotactic poly(butene-1) and mixtures thereof; and a tight, isotropic, three-dimensional network of structurally connected polymeric fibers, and a curable urethane, silicone, aliphatic rubber, low melting temperature plastisol, and flexible material that fills and encloses the network. A composite material consisting of a stretchable resin matrix selected from the group consisting of polyester epoxides.

The composite material system of the present invention has unique properties in strength, flexibility and stretchability, and also increases in strength and toughness with repeated load cycling while retaining ultimate stretchability very well. It has the advantage of being

Composite materials formed according to the present invention can be used for flexible electrical components,
It is preferably used in structural fields such as the manufacture of mechanical power transmission belts, seals, O-rings, tires, and gaskets, and in fields that require strength as well as elasticity.

The composite material system of the present invention can be used in situ.
It consists of a stretchable resin filled with fibers formed and consisting of a three-dimensionally interconnected network.

Stretchable resin is fiber aggregates (Fibermasses)
It can be introduced into the fibers by polymerizing a monomeric solvent within the fiber assembly or by impregnating a prepolymer into the fiber assembly and then curing it. The inventors
A polymer fiber assembly formed in situ from a particular polymer solution and having an interconnected network can be impregnated with a stretchable curable resin, and the stretchable curable resin can be cured. It was discovered that the composite material obtained by this method has unique properties.

The unique advantages of the present invention obtained by combining fibers consisting of interconnected network fibers in an elastic matrix are listed below.

1. The flexibility of the matrix is maintained even when slightly deformed, ie the material is flexible and elastic.

2. If it is repeatedly deformed or stretched,
Increase in strength.

3. When subjected to repeated loading, the toughness increases, ie, it has a strain hardening effect or the opposite hysteresis effect.

4. The ultimate extensibility remains high, ie the elongation at ultimate strength is not reduced by fiber filling.

It is clear that the appearance of such unique behavior is based on the following two properties of the interconnected fiber network.

First, even if the original shape is significantly distorted, the mesh of the fibers can withstand this and work to return the distorted shape to its original shape without sustaining damage. Second
, the individual fibrils forming an interconnected network (
The fibrils may be deformed or stretched within the stretchable matrix to provide additional strength. Although it is well known that stretching increases fiber strength and is widely applied in the textile industry, applying tensioning in a reversible manner within a stretchable matrix is It belongs to new matters. Another significant advantage of the present invention is that, unlike conventional fiber-reinforced composite structures, it has excellent wettability and adhesion, so no forced compatibility between fibers and matrix is required. be.

The network structure of the fiber assembly maintains its geometric form even after repeated stretching and relaxation, allowing the load to be transferred to the matrix. The above-mentioned remarkable properties are imparted to the composite material of the present invention because the fiber aggregate obtained in situ contains materials such as urethane, silicone, aliphatic rubber, low melting temperature plastisol, and flexible epoxide. Based on the combination of flexible or elastic polymers.

The above flexible or elastic polymer preferably has the following properties. (a) It has a sufficiently low viscosity to allow pouring and impregnation of the fiber aggregate.

(b) have a curing temperature lower than the melting point of the fiber;

(c) have sufficient pot life to allow complete impregnation before curing; The fiber aggregate is formed from a solution containing a polymerizable solvent or an extractable solvent while applying vibration to the solution.

The stretchable matrix is introduced by polymerizing a monomeric solvent within the fiber assembly or by impregnating a prepolymer within the fiber assembly followed by curing. The above-mentioned composite material uses ScOtchcast (registered trademark) 28, which is a stretchable polymer, as a matrix.
0 and Sylgardl (registered trademark) 182
It was formed by a co-dipping method using polypropylene as the fiber aggregate.

FIG. 1 shows a comparison of the stress/strain curves of a single Scotchicast material and a polypropylene fiber aggregate/Scotchicast composite material. The curves in Figure 1 clearly show that composite materials have superior toughness (as determined by the area under the curve) and ultimate strength over single materials. However, the modulus (determined by the slope of the applied/strain curve) and elongation of the composite material remain almost unchanged compared to the single material. Scotchicast, a polar epoxy structure, provides some wettability to polypropylene fibers, but Sylgard, a silicone, does not. FIG. 2 shows a comparison of stress/strain curves for Sylgard single material and in-situ polypropylene fiber/Sylgard composite. Again, the overall toughness of the material is increased by incorporating in-situ formed fibers. And the growth rate is actually increasing. Also, the overall strength will be slightly affected simply because the non-wettable silicone matrix becomes brittle and begins to fail when stretched too hard; nevertheless, the composite material Compared to single materials, it exhibits high toughness against strains that do not reach the limits normally applied. Figures 3 and 4 show the cyclic stress/strain curves at a strain of O-0.5 for the Sylgard single material and composite material, respectively.

The figure shows that a single material has elasticity with little dissipation of energy, whereas a composite material has the ability to accept dissipated energy and increases its strength with repeated load cycling. produces substances that increase in amount. Figures 5 and 6 show the results of repeated loads applied to a single material and a composite material, respectively.

In the case of composites filled with commercially cut fibers, the modulus increases, but the strength, elongation and toughness decrease.

FIG. 1 is a comparison of the stress/strain curves of nascent Scotchicast 280, a composite made of in-situ polypropylene fibers, and a composite made of commercially available polypropylene fibers cut with a chopper. The strain properties vary significantly even at low elongation rates.

Commercially available fiber-reinforced elastomers show a decrease in elongation with stress when various loads are applied up to ultimate strength. The weight percentage of polypropylene fibers in the epoxy resin was the same in both cases (approximately 7%).

These results indicate that commercially available polypropylene fibers are 40,000
This becomes even more remarkable when one considers the fact that it is a highly tensile and strong material with a tensile strength on the order of psi.

Scotchicast 280 is a typical flexible bisphenol A-based epoxy polymer formed from bisphenol A copolymerized with glycerin and an anhydride hardener. This material is commercially available from 3M Company, St. Paul, Minn., USA. Also, Sylgard 182 is
It is typically a silicon rubber material consisting of vinyl-terminated dimethylsiloxane, a silane curing agent, and a platinum catalyst, and is commercially available from Dow Corning, Midland, Michigan, USA. Example 1 (Scotchicast 280/fiber composite material) A polymer solution was prepared by dissolving isotactic polypropylene in xylene solvent at 125°C, and the solution was vibrated while cooling to form a uniform fiber aggregate. I let it happen.

Next, xylene was removed from the fiber aggregate by extraction with acetone. The fiber assembly was dried under vacuum for 24 hours. In preparing the ingredients containing Scotchicast 280, first, 40 parts by weight of resin and 60 parts by weight of curing agent were mixed.

The mixture was then stirred and then heated at 150'P for 15
Heat for 1 minute to mix thoroughly. Furthermore, the generation of bubbles stopped,
Vacuum was maintained and the mixture was degassed until a pressure as low as 10-3 mmHg was reached. Impregnation of the polypropylene fiber aggregate with resin was carried out in a degassed flask.

The degassed resin was slowly introduced using a liquid separator. Each impregnation operation was carried out such that the resin began to impregnate the fiber mass at the bottom of the flask and eventually allowed excess resin to coat the fiber mass. Composite material is 160'
Cured at F for 48 hours under 80 psi positive pressure. Example 2 (Sylgard 182/Fiber Composite Material) A fiber aggregate was prepared in the same manner as in Example 1.

In preparing the Sylgard 182-containing component, 100 parts by weight of the resin and 10 parts by weight of the curing agent were first mixed, and then the mixture was thoroughly mixed and degassed. Impregnation of Sylgard was carried out in the same manner as for Scotchicast resin.
The Sylgard-containing composite was cured at 160'FS for 16 hours. In this case it was not necessary to apply positive pressure.

[Brief explanation of drawings]

FIG. 1 shows a comparison of the physical properties of the in-situ polypropylene fiber-Scotchicast resin-containing composite material of the present invention and the physical properties of a single Scotchicast resin material and a commercially available fiber-Scotchicast resin-containing composite material.

Claims (1)

[Claims] 1. Isotactic polypropylene, polyethylene,
Formed from a linear polyalkene selected from the group consisting of isotactic poly(4-methylpentene-1), isotactic poly(butene-1), and mixtures thereof, the highly A tight, isotropic, three-dimensional network of branched and structurally connected polymer fibers, and a curable urethane, silicone, aliphatic rubber, or low melting temperature plastisol that fills and encases the network. and a flexible epoxide. 2. The composite material according to claim 1, wherein the silicone comprises vinyl group-terminated dimethylsiloxane, a silane curing agent, and a platinum catalyst. 3. The composite material according to claim 1, wherein the flexible epoxy resin comprises a copolymer of bisphenol A and glycerin and an acid anhydride curing agent.