U.S. patent application number 15/389690 was filed with the patent office on 2018-06-28 for carbon fiber manufacturing method.
The applicant listed for this patent is UHT UNITECH CO., LTD. Invention is credited to CHIH-YUNG WANG.
Application Number | 20180179696 15/389690 |
Document ID | / |
Family ID | 62625523 |
Filed Date | 2018-06-28 |
United States Patent
Application |
20180179696 |
Kind Code |
A1 |
WANG; CHIH-YUNG |
June 28, 2018 |
CARBON FIBER MANUFACTURING METHOD
Abstract
A carbon fiber manufacturing method is provided. A carbon fiber
precursor fiber bundle is performed with a high-temperature
carbonization step to form a carbon fiber, and then the carbon
fiber is performed with a plasma surface treatment so that the
surface of the carbon fiber is formed with a plasma-modified
configuration which is relatively rougher. Finally, the surface of
the carbon fiber is coated with a resin oiling agent to obtain the
carbon fiber having the resin oiling agent thereon. Particularly,
through a plasma surface treatment step, the surface of the carbon
fiber is roughened and provided with functional groups, which is
beneficial to enhance the interface bonding of the resin oiling
agent and the carbon fiber. The structure of the carbon fiber is
more stable and reliable. The cost of the carbon fiber production
equipment and the working time can be reduced effectively.
Inventors: |
WANG; CHIH-YUNG; (Taoyuan,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UHT UNITECH CO., LTD |
Taoyuan |
|
TW |
|
|
Family ID: |
62625523 |
Appl. No.: |
15/389690 |
Filed: |
December 23, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D06M 2101/40 20130101;
D10B 2321/10 20130101; D10B 2101/12 20130101; D06M 10/003 20130101;
D01F 11/16 20130101; D01F 11/14 20130101 |
International
Class: |
D06M 10/02 20060101
D06M010/02; D01F 9/22 20060101 D01F009/22; D01F 9/32 20060101
D01F009/32; D06M 15/55 20060101 D06M015/55 |
Claims
1. A carbon fiber manufacturing method, comprising: providing a raw
material step, providing a carbon fiber precursor fiber bundle;
performing a high-temperature carbonization step, the carbon fiber
precursor fiber bundle being heated to form a carbon fiber having a
predetermined carbon content; performing a plasma surface treatment
step, a plasma gas flow with a predetermined power being provided
to act on the carbon fiber at a predetermined time so that a
surface of the carbon fiber is formed with a plasma-modified
configuration; performing a sizing step, the plasma-modified
configuration being coated with a resin oiling agent; and
performing a drying step, the resin oiling agent coated on the
plasma-modified configuration being processed with drying so that
the resin oiling agent is firmly adhered to the surface of the
carbon fiber.
2. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the high-temperature carbonization step, the carbon
fiber precursor fiber bundle is guided into a chamber, the chamber
is formed with at least one microwave field concentration area
therein, and is provided with a gas supply module to supply an
inert gas and a microwave generating module to supply a
high-frequency microwave, under the protection of the inert gas
atmosphere, an electric field of the high-frequency microwave
produces a sensing current to heat up and produce a high
temperature quickly with the carbon fiber precursor fiber bundle
passing through the microwave field concentration area.
3. The carbon fiber manufacturing method as claimed in claim 2,
wherein the chamber is provided with at least one pair of
microwave-sensitive materials.
4. The carbon fiber manufacturing method as claimed in claim 3,
wherein the microwave-sensitive materials are one of graphite,
carbide, magnetic compound, nitride, and ionic compound or a
combination thereof.
5. The carbon fiber manufacturing method as claimed in claim 2,
wherein the inert gas is nitrogen, argon, helium, or a combination
thereof.
6. The carbon fiber manufacturing method as claimed in claim 2,
wherein the frequency of the high-frequency microwave is in the
range of 300-30,000 MHz, and its microwave power density is in the
range of 1-1000 kW/m3.
7. The carbon fiber manufacturing method as claimed in claim 2,
wherein the chamber is an elliptic chamber.
8. The carbon fiber manufacturing method as claimed in claim 2,
wherein the chamber is a flat panel chamber.
9. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the plasma surface treatment step, the plasma gas flow
with a power of 100-10000 watts acts on the carbon fiber for
10-1000 milliseconds.
10. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the plasma surface treatment step, an atmospheric plasma
gas flow with a power of 100-10000 watts acts on the carbon fiber
for 10-1000 milliseconds.
11. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the plasma surface treatment step, a low-pressure plasma
gas flow with a power of 100-10000 watts acts on the carbon fiber
for 10-1000 milliseconds.
12. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the plasma surface treatment step, a microwave plasma
gas flow with a power of 100-10000 watts acts on the carbon fiber
for 10-1000 milliseconds.
13. The carbon fiber manufacturing method as claimed in claim 1,
wherein in the plasma surface treatment step, a glow plasma gas
flow with a power of 100-10000 watts acts on the carbon fiber for
10-1000 milliseconds.
14. The carbon fiber manufacturing method as claimed in claim 1,
wherein the carbon fiber precursor fiber bundle has a surface not
processed with a pre-oxidation treatment.
15. The carbon fiber manufacturing method as claimed in claim 1,
wherein the carbon fiber precursor fiber bundle has a surface
processed with a pre-oxidation treatment in advance.
16. The carbon fiber manufacturing method as claimed in claim 1,
wherein the resin oiling agent is a thermosetting resin oiling
agent.
17. The carbon fiber manufacturing method as claimed in claim 1,
wherein the resin oiling agent is a thermoplastic resin oiling
agent.
18. The carbon fiber manufacturing method as claimed in claim 1,
wherein the carbon content of the carbon fiber is in the range of
80%-90%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a carbon fiber
manufacturing technique, and more particularly to a carbon fiber
manufacturing method which can greatly improve the sizing quality
of a carbon fiber and effectively reduce the cost of the carbon
fiber production equipment and the working time.
BACKGROUND OF THE INVENTION
[0002] Carbon fibers are classified into carbon fibers or graphite
fibers according to their carbon contents, which have excellent
mechanical properties and electrical properties and can be widely
used in various applications. A conventional carbon fiber is
achieved by bundling precursor fibers, such as polyacrylonitrile
fibers, to form a carbon fiber precursor fiber bundle, and then the
carbon fiber precursor fiber bundle is calcined (high-temperature
carbonization) to form the carbon fiber.
[0003] There are various precursor fibers of carbon fibers on the
market, such as rayon, poly vinyl alcohol, vinylidene chloride,
polyacrylonitrile (PAN), pitch, and the like. In general,
polyacrylonitrile (PAN) is used as the raw material of carbon
fibers. The manufacturing steps are generally as follows: PAN raw
material (precursor
fiber).fwdarw.pre-oxidation.fwdarw.high-temperature
carbonization.fwdarw.surface treatment.fwdarw.sizing.
[0004] In the carbonization step, the carbon fiber precursor fiber
bundles are heated to form carbon fibers or graphite fibers by
different heating apparatuses according to the application of the
carbon fibers. In principle, the carbon content of the fibers of
graphite fibers is 90% or more, forming a two-dimensional
carbocyclic planar net structure and a graphite layer structure
having parallel layers. The results show that the crystalline
region of a high-strength carbon fiber is composed of 5-6 graphite
layers, and the crystalline region of a high-strength and
high-modulus carbon fiber is composed of 10-20 graphite layers.
Theoretically and practically, it is pointed out that the larger
the crystalline thickness of the graphite layer is, the higher the
tensile modulus of the carbon fiber is.
[0005] On the other hand, the surface of the carbon fiber after the
high-temperature carbonization step is usually coated with a layer
of oiling agent (a resin oiling agent is generally used, it is
called as a sizing step) before it leaves the factory. The layer of
oiling agent is used to protect the fiber from breakage due to
friction in the subsequent step to affect the overall quality of
the carbon fiber. The surfaces of untreated carbon fibers adsorb
impurities thereon. Since these impurities are present between the
surface of the carbon fiber and the resin oiling agent, the
adhesion between the carbon fiber and the resin oiling agent is
insufficient, and the purpose of protecting the fiber cannot be
achieved
[0006] Furthermore, in the high-temperature carbonization step, the
surface of the carbon fiber is excessively finely formed due to
high-temperature sintering, and there are few functional groups on
the surface. As a result, the fiber and the resin oiling agent
cannot be bonded fully in the sizing step. It is known that a heat
treatment or electrolysis technique can be applied to the surface
treatment of the fiber after the high-temperature carbonization
step, and then the sizing step is performed in order to improve the
bonding of the fiber and the resin oiling agent.
[0007] However, when the surface treatment of the carbon fiber is
performed by means of heat treatment, the carbon fiber is treated
at a temperature in the range of 500.degree. C. to 800.degree. C.
for 1-10 minutes. A relatively long period of time is required.
Besides, the heat treatment is always performed with a large number
of fibers at a time, so it is difficult to control the processing
quality. When the surface treatment of the carbon fiber is
performed by means of electrolysis, at least one drying process is
required before the surface of the fiber is coated with the oiling
agent. This also takes more time. Moreover, a change of the
electrolyte may affect the processing quality. Even the surface of
the fiber may have depositions.
[0008] Accordingly, the inventor of the present invention has
devoted himself based on his many years of practical experiences to
solve these problems.
SUMMARY OF THE INVENTION
[0009] In view of the problems of the prior art, the primary object
of the present invention is to provide a carbon fiber manufacturing
method which can greatly improve the sizing quality of a carbon
fiber and effectively reduce the cost of the carbon fiber
production equipment and the working time.
[0010] In order to achieve the forgoing object, the carbon fiber
manufacturing method of the present invention comprises providing a
raw material step, providing a carbon fiber precursor fiber bundle;
performing a high-temperature carbonization step, the carbon fiber
precursor fiber bundle being heated to form a carbon fiber having a
predetermined carbon content; performing a plasma surface treatment
step, a plasma gas flow with a predetermined power being provided
to act on the carbon fiber at a predetermined time so that a
surface of the carbon fiber is formed with a plasma-modified
configuration; performing a sizing step, the plasma-modified
configuration being coated with a resin oiling agent; and
performing a drying step, the resin oiling agent coated on the
plasma-modified configuration being processed with drying so that
the resin oiling agent is firmly adhered to the surface of the
carbon fiber.
[0011] In the carbon fiber manufacturing method of the present
invention, through the plasma surface treatment step, the surface
of the carbon fiber is roughened and provided with functional
groups, which is beneficial to enhance the interface bonding of the
resin oiling agent and the carbon fiber in the subsequent sizing
step so as to improve the sizing quality of the carbon fiber
greatly. The structure of the carbon fiber is more stable and
reliable. The plasma surface treatment belongs to a dry-type and
fast surface treatment technique to effectively reduce the cost of
the carbon fiber production equipment and the working time.
[0012] Preferably, in the high-temperature carbonization step, the
carbon fiber precursor fiber bundle is guided into a chamber. The
chamber is formed with at least one microwave field concentration
area therein, and is provided with a gas supply module to supply an
inert gas and a microwave generating module to supply a
high-frequency microwave. Under the protection of the inert gas
atmosphere, the electric field of the high-frequency microwave
produces a sensing current to heat up and produce a high
temperature quickly with the carbon fiber precursor fiber bundle
passing through the microwave field concentration area.
[0013] Preferably, the chamber is provided with at least one pair
of microwave-sensitive materials.
[0014] Preferably, the microwave-sensitive materials are one of
graphite, carbide, magnetic compound, nitride, and ionic compound
or a combination thereof.
[0015] Preferably, the inert gas is nitrogen, argon, helium, or a
combination thereof.
[0016] Preferably, the frequency of the high-frequency microwave is
in the range of 300-30,000 MHz, and its microwave power density is
in the range of 1-1000 kW/m3.
[0017] Preferably, the chamber is an elliptic chamber.
[0018] Alternatively, the chamber is a flat panel chamber.
[0019] Preferably, in the plasma surface treatment step, the plasma
gas flow with a power of 100-10000 watts acts on the carbon fiber
for 10-1000 milliseconds.
[0020] Alternatively, in the plasma surface treatment step, an
atmospheric plasma gas flow with a power of 100-10000 watts acts on
the carbon fiber for 10-1000 milliseconds.
[0021] Alternatively, in the plasma surface treatment step, a
low-pressure plasma gas flow with a power of 100-10000 watts acts
on the carbon fiber for 10-1000 milliseconds.
[0022] Alternatively, in the plasma surface treatment step, a
microwave plasma gas flow with a power of 100-10000 watts acts on
the carbon fiber for 10-1000 milliseconds.
[0023] Alternatively, in the plasma surface treatment step, a glow
plasma gas flow with a power of 100-10000 watts acts on the carbon
fiber for 10-1000 milliseconds.
[0024] Preferably, the carbon fiber precursor fiber bundle has a
surface not processed with a pre-oxidation treatment.
[0025] Alternatively, the carbon fiber precursor fiber bundle has a
surface processed with a pre-oxidation treatment in advance.
[0026] Preferably, the resin oiling agent is a thermosetting resin
oiling agent.
[0027] Alternatively, the resin oiling agent is a thermoplastic
resin oiling agent.
[0028] Preferably, the carbon content of the carbon fiber is in the
range of 80%-90%.
[0029] Specifically, through plasma surface treatment, the surface
of the carbon fiber can be roughened and provided with the
functional groups, which is beneficial to enhance the interface
bonding of the resin oiling agent and the carbon fiber in the
subsequent sizing step. The structure of the carbon fiber is more
stable and reliable. By the microwave focusing heating way, the
same apparatus can be applied to a carbon fiber precursor fiber
bundle whose surface has not been processed with a pre-oxidation
treatment or a carbon fiber precursor fiber bundle whose surface
has been processed with a pre-oxidation treatment in advance. By
simply adjusting the microwave power, the apparatus can be used to
produce general carbon fibers or high modulus carbon fibers
(graphite fibers) so as reduce the cost of the carbon fiber
production equipment and the working time effectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a flow diagram of a carbon fiber manufacturing
method of the present invention;
[0031] FIG. 2 is a structural schematic view of a chamber in
accordance with an embodiment of the present invention;
[0032] FIG. 3 is a sectional schematic view of a carbon fiber after
finishing a plasma surface treatment step in accordance with the
carbon fiber manufacturing method of the present invention;
[0033] FIG. 4 is a sectional schematic view of a carbon fiber after
finishing a sizing step in accordance with the carbon fiber
manufacturing method of the present invention;
[0034] FIG. 5 is a structural schematic view of a chamber in
accordance with another embodiment of the present invention;
[0035] FIG. 6a illustrates a SEM image of an object to be tested
without plasma treatment; and
[0036] FIG. 6b illustrates a SEM image of an object to be tested
with the plasma treatment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] Embodiments of the present invention will now be described,
by way of example only, with reference to the accompanying
drawings.
[0038] The present invention discloses a carbon fiber manufacturing
method which can greatly improve the sizing quality of carbon
fibers and effectively reduce the cost of the carbon fiber
production equipment and the working time. As shown in FIG. 1, the
carbon fiber manufacturing method of the present invention
comprises providing a raw material step, performing a
high-temperature carbonization step, performing a plasma surface
treatment step, and performing a sizing step. The carbon fiber
manufacturing method further comprises performing a drying step
after the sizing step. Referring to FIG. 1 through FIG. 5, the
steps are described in details as below.
[0039] In the step of providing the raw material, a carbon fiber
precursor fiber bundle 10A is provided to be processed to form a
carbon fiber 10B. In practice, the carbon fiber precursor fiber
bundle 10A may be formed of rayon, poly vinyl alcohol, vinylidene
chloride, polyacrylonitrile (PAN), pitch, and the like. The surface
of the carbon fiber precursor fiber bundle 10A may have not been
processed with a pre-oxidation treatment or have been processed
with a pre-oxidation treatment in advance.
[0040] In the high-temperature carbonization step, the carbon fiber
precursor fiber bundle 10A is heated to form the carbon fiber 10B
having a predetermined carbon content. In practice, as shown in
FIG. 2, the carbon fiber precursor fiber bundle 10A is guided into
a chamber 30. The chamber 30 is formed with at least one microwave
field concentration area 31 therein, and is provided with a gas
supply module 32 to supply an inert gas and a microwave generating
module 33 to supply a high-frequency microwave. Under the
protection of the inert gas atmosphere, the electric field of the
high-frequency microwave produces a sensing current to heat up and
produce a high temperature quickly with the carbon fiber precursor
fiber bundle 10A passing through the microwave field concentration
area 31, enabling the carbon fiber precursor fiber bundle 10A to
form the carbon fiber 10B having a predetermined carbon content.
The carbon content of the carbon fiber 10B is in the range of
80%-90%.
[0041] In the plasma surface treatment step, a plasma gas flow with
a predetermined power is provided to act on the carbon fiber 10B at
a predetermined time, such that the surface of the carbon fiber 10B
is formed with a plasma-modified configuration 11 (shown in FIG. 3)
which is rougher or has more functional groups relative to the
carbon fiber precursor fiber bundle 10A.
[0042] In the sizing step, the plasma-modified configuration 11 on
the surface of the carbon fiber 10B is coated with a resin oiling
agent 20, so that the surface of the carbon fiber 10B has the resin
oiling agent 20, as shown in FIG. 4. In practice, the resin oiling
agent 20 is coated on the surface of the carbon fiber 10B by
soaking or immersing. The resin oiling agent 20 may be a
thermosetting resin oiling agent or a thermoplastic resin oiling
agent.
[0043] In the drying step, a drying treatment is applied to the
resin oiling agent 20 coated on the plasma-modified configuration
11 so that the resin oiling agent 10 is firmly adhered to the
surface of the carbon fiber 10B. In practice, the drying treatment
is carried out by ultraviolet irradiation, cooling, drying or
air-drying for the resin oiling agent to be bonded to the surface
of the carbon fiber.
[0044] In the plasma surface treatment step, an atmospheric plasma
gas flow, a low-pressure plasma gas flow, a microwave plasma gas
flow, or a glow plasma gas flow with a power of 100-10000 watts may
be used to act on the carbon fiber 10B for 10-1000 milliseconds.
Since the plasma gas flow contains particles having energy, the
impurities that originally adhere to the surface of the carbon
fiber 10B can be broken to form small molecules by the impact of
the plasma gas flow through the physical reaction (collision) of
the plasma gas flow, and then the small molecules are blown away
from the surface of the carbon fiber 10B by the air flow, so that
the surface of the carbon fiber 10B is clean. In the sizing step,
the resin oiling agent 20 can be completely in contact with the
carbon fiber 10B to increase the bonding effect. In addition, the
impact of the plasma gas flow will also form the plasma-modified
configuration 11 on the surface of the carbon fiber 10B. The
plasma-modified configuration 11 is rougher relative to the carbon
fiber precursor fiber bundle 10A, and is further formed with pores.
The surface of the carbon fiber 10B is roughened or formed with the
pores, which is beneficial to increase the contact area between the
resin oiling agent 20 and the carbon fiber 10B in the subsequent
sizing step. The resin oiling agent 20 penetrates into the pores,
and the resin oiling agent 20 is anchored between the pores to form
an anchor effect to enhance the bonding effect of the resin oiling
agent 20 and the carbon fiber 10B.
[0045] The plasma gas flow also makes the surface of the carbon
fiber 10B generate a chemical reaction at the same time, so that at
least one functional group (such as --OH, --N, etc.) is added to
the surface of the carbon fiber 10B. In the sizing step, the
surface tension of the surface of the carbon fiber 10B is increased
due to the presence of the functional group, which is beneficial to
improve the wetting effect for the resin oiling agent to be coated
on the carbon fiber 10B. That is, the contact angle of the resin
oiling agent 20 to the carbon fiber 10B becomes small, so that the
resin oiling agent 20 can be quickly or instantaneously coated on
the carbon fiber 10B, and the speed of the sizing step is
increased, thereby accelerating the overall production speed of the
carbon fiber 10B. The presence of the functional group such as the
OH group reacts with the resin oiling agent 20, such as epoxy resin
(Epoxy), to generate hydrogen bonding, thereby increasing the
bonding effect.
[0046] Thereby, in the carbon fiber manufacturing method of the
present invention, through the plasma surface treatment step, the
surface of the carbon fiber 10B is roughened and provided with
functional groups, which is beneficial to enhance the interface
bonding of the resin oiling agent 20 and the carbon fiber 10B in
the subsequent sizing step so as to improve the sizing quality of
the carbon fiber 10B greatly. The structure of the carbon fiber is
more stable and reliable. The plasma surface treatment belongs to a
dry-type and fast surface treatment technique to effectively reduce
the cost of the carbon fiber production equipment and the working
time.
[0047] Furthermore, the foregoing inert gas may be nitrogen, argon,
helium, or a combination thereof. The frequency of the
high-frequency microwave may be in the range of 300-30,000 MHz, and
its microwave power density may be in the range of 1-1000
kW/m3.
[0048] In the embodiment as shown in FIG. 2, the chamber 30 may be
an elliptic chamber, or the chamber 30 may be a flat plate chamber
as shown in FIG. 5. As shown in FIG. 5, whatever the chamber 30 is,
the chamber 30 is provided with a pair of microwave-sensitive
materials 34 therein, thereby enhancing the focusing effect on the
microwave field in order to further accelerate the high-temperature
carbonization process. In practice, the microwave-sensitive
materials 34 may be one of graphite, carbide, magnetic compound,
nitride, and ionic compound or a combination thereof.
[0049] Due to the resonant effect of microwave heating, the
carbonization of the carbon fiber is enhanced rapidly and more
crystalline carbons are formed and stacked, which leads to the
formation of larger graphite crystalline molecules, namely, larger
graphite crystalline thickness, while deriving a higher microwave
induction heating effect is derived. Such a cycle generates an
autocatalytic reaction, enabling the carbon fiber to be rapidly
heated to the graphitization temperature (1500-3000.degree. C.),
and carbon atoms are reconstructed and rearranged more rapidly to
form a graphite layer.
[0050] In other words, the same apparatus can be applied to a
carbon fiber precursor fiber bundle whose surface has not been
processed with a pre-oxidation treatment or a carbon fiber
precursor fiber bundle whose surface has been processed with a
pre-oxidation treatment in advance. It is only necessary to adjust
the microwave power for the production, the apparatus can be used
to produce general carbon fibers (1000-1500.degree. C.) or high
modulus carbon fibers (graphite fibers).
[0051] In a preferred embodiment, an article to be tested that the
resin oiling agent 20 after the drying step is firmly adhered to
the surface of the carbon fiber 10B, and the treatment conditions
in the plasma surface treatment step are shown in Table 1
below:
TABLE-US-00001 TABLE 1 the conditions of the plasma surface
treatment plasma gas consumption N.sub.2 200 L/min CDA 0.4 L/min
plasma gas amount 200.4 L/min plasma power 0~1000 W plasma surface
treatment time 0.025~0.100 sec. carbon fiber yarn width 7 mm yarn
per unit time receiving 0.28 J/s capacity distance 1 mm
[0052] The ILSS strength (interlayer bonding force) was measured
for an object to be tested in an environment of a temperature of
23.degree. C. and a humidity of 50% RH by using an INSTRON
measuring machine according to ASTM 2344, and the results are shown
in Table 2 below:
TABLE-US-00002 TABLE 2 the relationship between the plasma surface
treatment power (W), the processing time (sec.) and the interlayer
bonding force (MPa) (epoxy resin used as the resin oiling agent) of
PAN carbon fiber 12K plasma power (W) of surface interlayer bonding
force (ILSS)(MPa) treatment 0.025 sec. 0.075 sec. 0.100 sec.
0(untreated) 70 70 70 250 71 73 75 500 73 76 81 750 75 81 85 900 79
86 88 1000 83 89 91
[0053] As can be seen from Table 2, the carbon fiber without the
plasma surface treatment, the interlayer bonding force of the
object to be tested is only 70 MPa. With an increase of the plasma
power, for example, the processing time is 0.075 seconds and the
plasma power is increased from the untreated (0 W, without plasma
power) to 10000 W, the interlayer bonding force is increased from
70 MPa to 89 MPa. That is, the interlayer bonding force is
increased to 127%.
[0054] In the sizing step, the epoxy resin is used as the resin
oiling agent 20, and the carbon fiber is used as the carbon fiber
10B. FIG. 6a shows a SEM image of the object to be tested without
the plasma treatment. FIG. 6b shows a SEM image of the object to be
tested with the plasma treatment. As shown in FIG. 6a, the SEM
image of the object to be tested without the plasma surface
treatment illustrates a void H between the resin oiling agent 20
and the carbon fiber 10B because the surface of the carbon fiber
10B is smooth and doesn't have functional groups. The void H causes
a decrease in the strength of the object to be tested. That is to
say, the bonding force between the carbon fiber and the resin
oiling agent is insufficient for protecting the fiber.
[0055] As shown in FIG. 6b, the SEM image of the object to be
tested with the plasma surface treatment illustrates that there is
no void between the resin oiling agent 20 and the carbon fiber 10B
because the surface of the carbon fiber 10B is rough and has
functional groups (such as --OH, --N, etc.). The resin oiling agent
20 and the carbon fiber 10B are bonded tightly, so that the
strength of the object to be tested is enhanced. That is, the
adhesion between the carbon fiber and the resin oiling agent is
enhanced, so that the purpose of protecting the fiber can be
achieved.
[0056] Compared to the prior art, through the carbon fiber
manufacturing method of the present invention, the surface of the
carbon fiber can be roughened and provided with the functional
groups by the plasma surface treatment step, which is beneficial to
enhance the interface bonding of the resin oiling agent and the
carbon fiber in the subsequent sizing step. The structure of the
carbon fiber is more stable and reliable to improve the quality of
the carbon fiber, thereby accelerating the overall production speed
of the carbon fiber. By the microwave focusing heating way, the
same apparatus can be applied to a carbon fiber precursor fiber
bundle whose surface has not been processed with a pre-oxidation
treatment or a carbon fiber precursor fiber bundle whose surface
has been processed with a pre-oxidation treatment in advance. By
simply adjusting the microwave power, the apparatus can be used to
produce general carbon fibers or high modulus carbon fibers
(graphite fibers) so as reduce the cost of the carbon fiber
production equipment and the working time effectively.
[0057] Although particular embodiments of the present invention
have been described in detail for purposes of illustration, various
modifications and enhancements may be made without departing from
the spirit and scope of the present invention. Accordingly, the
present invention is not to be limited except as by the appended
claims.
* * * * *