Carbon fiber and method for producing same

Abstract

The present invention addresses the problem of providing a carbon fiber for a carbon fiber reinforced composite material which is not easily damaged during a molding process and exhibits an excellentelastic modulus. The carbon fiber has a strand elastic modulus of at least 360 GPa, a strand strength of at least 3.5 GPa, and a single fiber diameter of at least 6.0 [mu]m, and satisfies one or moreof the requirements below. (A) When one end is a fixed end and the other end is a free end that can rotate about the axis of a fiber bundle, the remaining twist number is at least 2 turns/m. (B) The total fineness, which is the product of the single fiber fineness (g/km) as a carbon fiber and the number of filaments (counts), is at least 740 g/km. In addition, the single fiber elastic modulus Es (Gpa) and the loop breaking load A (N) of the carbon fiber satisfy the relationship of expression (1). (1): A>=-0.0017*Es+1.02. Furthermore, the single fiber diameter of the carbon fiber is at least 6.0 [mu]m, the relationship between the strand elastic modulus E (GPa) of the carbon fiber and the knot strength B (MPa) of the carbon fiber as evaluated at a heating loss rate of 0.15% or less at 450 DEG C satisfies expression (2), and the twist number of the carbon fiber is 20-80 turns/m. (2): B>= 6.7*109*E-2.85.

Description

technical field [0001] The present invention relates to carbon fibers and methods for their manufacture. Background technique [0002] Carbon fiber is an indispensable material for achieving high energy efficiency in society because it has excellent specific strength and specific elastic modulus, and by using it as a reinforcing fiber for carbon fiber-reinforced composite materials, it can greatly reduce the weight of parts One of them is widely used in various fields. In recent years, it has been used in fields where there is a strong demand for cost reduction, such as automobiles and electronic equipment housings, and there is a strong demand for cost reduction of final parts including molding costs. [0003] In order to effectively reduce the cost of the final part, not only the cost reduction of carbon fiber itself is important, but also a comprehensive approach such as reducing the required amount by improving the performance of carbon fiber, and reducing molding cost ...

AI Technical Summary

Problems solved by technology

The graphitization process can effectively improve the tensile elastic modulus of carbon fibers, but on the other hand, it is easy to need equipment for high temperature, and it is easy to promote the crystal growth in carbon fibers so that the tensile strength and compressive strength of the obtained carbon fibers are relatively low. Low

In addition, such high elastic modulus carbon fibers tend to be low in productivity as carbon fibers as described above and low in molding processability when obtaining carbon fiber reinforced composite materials, and when used as discontinuous fibers, the fiber length tends to be shortened

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