JPS60252718A - Intermediate of high-performance composite material - Google Patents

Abstract

PURPOSE:An intermediate product that is obtained by using, as a reinforcing fiber, a high-elasticity carbon fiber and graphite fiber with an electric current in a specific range per unit area, when measured by the potential scanning method, thus showing high tenacity and flexural strength. CONSTITUTION:The objective intermediate product is obtained by using a high- elasticity carbon fiber such as PAN carbon fiber having 30-50t/mm.<2> of strand elasticity, more than 300kg/mm.<2> of strand strength and 0.100-0.400muA/cm<2> of electric current measured by the potential scanning method with a Poltum- metry analyzer or graphite fiber calcinating the above carbon fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a composite material intermediate having excellent tensile strength and bending strength using high-strength, high-modulus carbon fiber as a reinforcing material.

[Background technology]

The demand for improved performance of carbon fiber is getting stronger year by year.
Moreover, rather than focusing on the characteristic values of the fibers themselves, there is a strong focus on improving performance by enhancing the characteristics of the composite material molded product using them, specifically by increasing the elasticity and strength. .

Given these market demands, the elastic modulus is 30t/Ryu2
For PAN-based carbon fibers in the range from 50 t/ml to
00kl! /+t' or more are being developed.

However, even with these high-strength carbon fibers, the bending strength of the composite material differs from the elastic modulus, and is significantly lower than the value expected from the composite side. That is, there are cases where the fiber strength utilization rate decreases significantly, and it has become clear that this fiber strength utilization rate tends to decrease as the tensile strength increases.

This is because the bending strength of composite materials is influenced by the interfacial bonding force between the fibers and the matrix resin and the progress of the fracture at breakage, and the manner and degree of influence depends on the type of stress applied. It is thought that this is because the strength characteristics of the fibers are improved and this effect becomes stronger as the breaking energy increases.

On the other hand, it is necessary to tighten the surface treatment conditions after firing for highly elastic yarns fired at high temperatures. Therefore, surface treatments are currently carried out within a range that does not impair the strength characteristics of the fibers.

Therefore, in carbon fibers that have been surface-treated in this way, the optimal surface condition for strand strength is not necessarily optimal for the development of bending strength as a composite material, resulting in a decrease in the utilization rate of bending strength, etc. (This means that the benefits of improving strand strength cannot be achieved.

Furthermore, even if the surface treatment conditions are the same, the surface condition will vary depending on the raw material fibers used or the firing conditions (because they differ, so unless surface treatment is applied to accommodate these changes, the strength characteristics of the composite material cannot be controlled. I can't do it anymore.

In this way, the surface morphology of carbon fibers is a very important characteristic, especially for high strength and high elasticity yarns.

There have been many studies on the relationship between surface treatment conditions and composite material properties, but the results vary widely due to differences in raw material fibers, manufacturing conditions, etc. The optimal surface condition is not clear.

Therefore, we investigated the optimal surface conditions for high-strength, high-modulus carbon fibers that balance the strand strength and the bending strength of composite materials, and as a result, we arrived at the present invention.

[Purpose of the invention]

The present invention uses a composite material with excellent tensile strength and bending strength.
The purpose of the present invention is to provide an intermediate body made of high modulus carbon fiber.

[Structure of the invention]

That is, the gist of the present invention is that the strand elastic modulus is in the range of 30 t/ms' to 50 t/ryu2,
In addition, high elastic carbon fiber or graphite fiber with a strand strength of 300 kg/mu" or more has a current value per unit area of 0.100 as measured by the potential scanning method.
It is an intermediate of a composite material using high modulus carbon fiber or graphite fiber in the range of μA/α2 to 0.400 μA/cm” as a reinforcing fiber.

The potential scanning method referred to in the present invention generally refers to the
It is an analytical device called a metric analyzer, which consists of a potentiostat and a filter generator, and uses carbon fiber as one electrode to perform measurements.

In the present invention, the pH is set to 3.0 using a 5% sour/acid aqueous solution, and nitrogen is bubbled through to remove the influence of dissolved oxygen. An Ag/AgC1 standard electrode was used as the reference electrode,
A carbon fiber is immersed in an electrolytic solution as one electrode, and a platinum electrode with sufficient surface area is used as a counter electrode.

Any type of sample can be measured, such as tow, sheet, cloth, or tape, as long as it can be fixed as an electrode.Measurement is also possible even if the sample has resin components such as sizing agent or matrix resin attached. However, in this case, since the effective surface area is different, it is desirable to extract and remove the resin component in advance. Also, as a guideline for the sample size, the standard sample length is 12,000 filament tow with a sample length of 50 mm. However, there is no need to particularly limit the sample amount if it is converted to the current value tpa per unit area defined in the present invention.

The scanning range of the electric potential applied between the carbon fiber electrode and the platinum electrode must be set within a range that does not exceed the electrolytic voltage, and must be set at 5%.
For acid/acid aqueous solutions, the standard range is 10, 2, or +0.8v. Since the current value generated by potential scanning is dependent on the scanning speed, the scanning speed must always be kept constant, and in the present invention, 20 yriV/see is determined as the standard speed. Draw a current-voltage curve with an X-Y recorder, sweep it three times or more, and when the curve becomes stable, press A.
The current value number was read using the potential at +0.4 .mu.g/AgC1 as a reference potential with respect to the standard electrode, and the angular value a was calculated according to the following formula.

The apparent surface area was calculated from the sample weight and the sample density and basis weight determined by the method described in JIS-R7601, and the value was divided by the current value t to obtain the pa.

As is clear from the examples, the jpa obtained by the potential scanning method
corresponds well with the strength characteristics of the composite material, and it has become clear that the tensile strength and bending strength of the composite material can be maximized by controlling tpa within the range defined in the present invention.

Characteristic value tpa by potential scanning method is 0.100 tiA/c
Below a', the bending strength is small compared to the tensile strength, and %
If 0.400 μA/α2 is applied, the bending strength is 1.
1, back. 8, 3, a4. ．． 0,. −. Wow, -5 is inferior.

The high-modulus carbon fibers used in the present invention are not limited to PAN-based ones, but can also be applied to so-called pitch-based and cellulose-based carbon fibers, and there are no restrictions on the method for producing them. Further, graphite fibers fired at a high temperature may also be used.

In the present invention, the "intermediate" refers to carbon fibers impregnated with matrix resin in the form of tapes, sheets, cloths, or pellets, and includes all types of UD prepregs, cross prepregs, sleeves, SMC, and BMC intermediates. It also includes F RT, chops or pellets for P. When measuring the characteristic value jpa of these intermediates, it is preferable to sample them by extracting and removing the attached resin with a solvent.

[Although the potential scanning method is a well-known technique in the electrochemical industry, there has never been an example in which the characteristic value Lpa obtained from the potential scanning method has been studied in relation to the strength characteristics of a composite material. This is a mystery that was only revealed after our intensive investigation.

Although the details of ipa obtained by the potential scanning method are unknown, it probably reflects characteristics corresponding to the concentration of functional groups that participate in redox reactions on the carbon fiber surface and the physical surface area.

In the past, the surface condition of carbon fibers has been analyzed and evaluated using various methods, but none of these methods alone can fully grasp the strength characteristics of composite materials (practically effective characteristic values have not yet been clarified). Not yet.

The characteristic values referred to in the present invention relate to both physical characteristics and chemical characteristics, and since the observation field can be arbitrarily selected and it is a simple method, it is of great practical significance.

〔Example〕 The present invention will be described in detail below with reference to Examples.

Example 1 Elastic modulus of 30 obtained by firing acrylic precursor
The IPA of the non-sized carbon fiber of t/y+@' was measured using a Cyclic Pol Tam Metry Analyzer Model P-1100 manufactured by Yanagimoto Seisakusho. Potential scanning was performed using 6,000 carbon fiber filament tows with a sample length of 50 mm as electrodes in a 5% phosphoric acid aqueous solution at pH 3.
With the platinum electrode as the counter electrode, the scanning range of the potential applied between them was from 10.2V to +0.8V, and 20.2V to +0.8V. iV
Potential scanning was performed at a scanning speed of /see to detect current changes. Ag/AiCjl! Read the current value i at 10.4V with respect to the electrode, and the sample basis weight is 3.8 x 10 1/C1
jpB using sample density 1.750 P/cWL”
was calculated.

Evaluation of composite properties was performed using Pyrophil +: 5ZO (
Mitsubishi Ray 3F Co., Ltd. trademark) was used as the matrix resin, and the tensile test was performed using JIS-R760 instead of a flat coupon.
A strand test was conducted according to 1, and for the bending test, a unidirectional blip preg was exploded and cured at 130°C for 3 hours to obtain a flat plate composite with Vf = 60%, and a test piece of 10 mg x 100+stX:'+rtt was cut out. A three-point bending test was conducted.

Table 1 shows the results of the jpa', strand test, and composite bending test. rh1 to 6 are the cases where the surface treatment conditions were changed under the same firing conditions, and the optimum conditions for tensile strength and bending strength were different.
．． 40 ttA/cIIL' (Strength properties are best exhibited by controlling the D range.N7 to 11 are the results when the flame resistance conditions and surface treatment conditions in firing were changed, but even if the tensile strength is high, It can be seen that when ipa is not within the optimum range, the bending strength is not large and the strength utilization rate is significantly reduced.

Table 1 Example 2 The elastic modulus obtained by firing the acrylic precursor 24
The carbon fibers having an elastic modulus of 40 t/in' were further heat-treated at a high temperature to obtain graphite fibers having an elastic modulus of 40 t/in'.

IPA, strand test, and composite test were conducted in the same manner as in Example 1, changing the graphitization conditions and surface treatment conditions, and the results are shown in Table 2. Fiber basis weight is 7.3 x 10/
/m, the density is 1.81 P/an," and the number of filaments is 12,000. It can be seen that both the bending strength and the utilization rate become thick when the ipa is around 0.30.

Table 2 [Effects of the Invention] The composite material intermediate obtained by the present invention makes it possible to provide a composite material exhibiting excellent composite properties not seen before.

Procedural amendment (voluntary) 1. Display of incidents Patent Application No. 1983-104294 2. Name of the invention Intermediates for high-performance composite materials 3. Person who makes corrections Relationship to the case: Applicant 2-3-19 Kyobashi, Chuo-ku, Tokyo (603) Mitsubishi Rayon Co., Ltd. President and Director Akio Kawasaki 4. Agent 2-3-19 Kyobashi, Chuo-ku, Tokyo eyes Page 7, line 7 “1” → “From 1” that's all

Claims (1)

[Claims] Strand elastic modulus from 30 t/m" to 50 t/m"
and the strand strength is 300 to 9/y
m' or more, high elastic carbon fibers or graphite fibers with a voltage value per unit area measured by potential scanning method in the range of 0.100 μA/♂ to 0.400 μA/cm" A composite material intermediate using graphite fibers as reinforcing fibers.