Atmosphere-assisted carbon fiber ash content testing method

Abstract

The invention relates to an atmosphere-assisted carbon fiber ash content testing method, and belongs to the technical field of carbon fiber testing. Determining the depth size of the mouth of the muffle furnace as L; the number of used crucibles is determined, carbon fibers are made into small sections with a certain length, the small sections are put into the crucibles, and then the small sections are placed in a muffle furnace; the use atmosphere proportion is determined, the horizontal distance between the position of the last crucible and the heating wire is recorded as M, when L is smaller than or equal to 20 cm, the ratio of inert gas to oxygen is 5: 1, when L is larger than 20 cm and smaller than or equal to 40 cm, M / L is smaller than or equal to 1 / 2, the ratio of inert gas to oxygen is 5: 1, M / L is larger than 1 / 2, the ratio of inert gas to oxygen is 10: 3, when L is larger than 40 cm, M / L is smaller than or equal to 1 / 3, the ratio of inert gas to oxygen is 5: 1, 1 / 3 is larger than M / L and smaller than or equal to 2 / 3, the ratio of inert gas to oxygen is 10: 3, M / L is larger than 2 / 3, and the ratio of inert gas to oxygen is 5: 2; the state of residues is determined, a switch of the muffle furnace is turned on, when the temperature rises to 300 DEG C, filling of mixed gas is started, when the temperature rises to 900 DEG C, filling is stopped, then filling is conducted once every two hours, filling is conducted for 10 min to 20 min every time, and finally the fired crucible is taken out.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber testing, in particular to an atmosphere-assisted carbon fiber ash content testing method. Background Art

[0002] As we all know, the ash content of carbon fiber refers to the weight percentage of impurities and ash remaining in the carbon fiber, which is an important indicator for evaluating the performance of carbon fiber. At present, the pyrolysis method is usually used to detect the ash content of carbon fiber. Generally, the carbon fiber is placed in a crucible of a certain size and then placed in a muffle furnace. It is burned as the furnace temperature rises to 900°C. After burning until there is no carbon black (about 16 hours), the crucible is taken out and cooled to room temperature, weighed and the ash content is calculated. Due to the heating structure of the muffle furnace, the temperature in the depth direction of the muffle furnace is not uniform, and the temperature near the furnace mouth is low. Therefore, the standard requires that the circular hole of the furnace door should be opened for ventilation and oxidation during burning. If the muffle furnace has no circular hole design, the furnace door can be slightly opened by 3mm to 5mm to allow the carbon fiber to burn fully.

[0003] In fact, general muffle furnaces do not have circular hole designs. If circular holes are required, they can be specially customized, but there is no reference for the size of the circular holes, making the design difficult. If the furnace door is opened during the test, the spacing of 3mm to 5mm is not easy to control. The movement of people and air convection often cause the furnace door to be wide open, causing a large amount of air to enter the furnace, causing the carbon fiber to burn violently or even catch fire. Therefore, the furnace door is often not opened during the test. Due to the unique heating structure of the muffle furnace, if the furnace door is not opened, the carbon fiber in the crucible near the furnace door will not be fully burned, and carbon black will still exist in the residue, so it needs to be burned again, which seriously affects the test efficiency. The second burning may also affect the accuracy of the test results. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides an atmosphere-assisted carbon fiber ash content testing method, which solves the problem of long carbon fiber ash content testing cycle and different burning conditions.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for testing the ash content of carbon fiber assisted by atmosphere, characterized in that it comprises the following steps:

[0006] S1. Determine the depth of the muffle furnace mouth.

[0007] The depth of the muffle furnace is L.

[0008] S2. Determine the number of crucibles to be used.

[0009] The carbon fiber is made into small pieces of a certain length and loaded into a crucible, which is then placed in a muffle furnace;

[0010] S3. Determine the usage atmosphere ratio.

[0011] The horizontal distance between the last crucible and the heating wire is recorded as M, and the filling ratio of inert gas to oxygen is determined according to the ratio of M to L:

[0012] When L≤20cm, inert gas: oxygen = 5:1,

[0013] When 20cm<L≤40cm, M / L≤1 / 2, inert gas: oxygen=5:1,

[0014] M / L>1 / 2, inert gas:oxygen=10:3,

[0015] When L>40cm, M / L≤1 / 3, inert gas:oxygen=5:1,

[0016] 1 / 3<M / L≤2 / 3, inert gas:oxygen=10:3,

[0017] M / L>2 / 3, inert gas:oxygen=5:2;

[0018] S4. Determine the state of the residue,

[0019] After determining the filling ratio of the mixed gas, turn on the muffle furnace switch. When the temperature rises to 300°C, start filling the mixed gas. When the temperature reaches 900°C, stop. Then fill it every 2 hours, each time for 10min to 20min. Finally, take out the crucible after burning, check whether there is carbon black in the residue, and proceed to the next step.

[0020] The inert gas is nitrogen, helium or argon.

[0021] The crucible is a ceramic crucible, a quartz crucible, an alumina crucible or a platinum crucible.

[0022] The beneficial effects of the present invention are that the test efficiency is high, and the ratio of inert gas to oxygen is controlled according to the size of the muffle furnace, which can not only ensure the burning state of the carbon fiber, reduce the number of repeated tests, but also ensure the safety of the test. The repeatability is high, the test parameters are fixed, and when the tester is proficient in the method, the repeated test results are basically consistent. DETAILED DESCRIPTION

[0023] Embodiment 1:

[0024] S1. Determine the size of the muffle furnace.

[0025] The length of the muffle furnace L = 20 cm;

[0026] S2. Determine the number of crucibles to be used.

[0027] Three T300 carbon fibers were cut into small pieces of a certain length and loaded into nine ceramic crucibles, which were then placed in a muffle furnace;

[0028] S3. Determine the usage atmosphere ratio.

[0029] According to the filling rule, the muffle furnace is filled with a mixed gas, i.e. nitrogen: oxygen = 5:1;

[0030] S4. Determine the state of the residue,

[0031] Turn on the muffle furnace switch and set the burning temperature to 900℃. When the temperature rises to 300℃, start filling with mixed gas. When the temperature rises to 900℃, stop filling once every 2 hours, and each time for 10 minutes. After burning for 16 hours, take out the burned ceramic crucibles one by one and cool them down. The residue is all carbon black, and finally weigh and calculate.

[0032] Comparative Example 1:

[0033] Three T300 carbon fibers were made into small segments of a certain length and loaded into nine ceramic crucibles, which were then placed in a muffle furnace with a length of 20 cm. The muffle furnace was turned on and the calcination temperature was set to 900 °C. The crucibles were calcined for 16 hours, and then the calcined ceramic crucibles were taken out one by one and cooled. The residues were all carbon black and were finally weighed and calculated.

[0034] Embodiment 2:

[0035] S1. Determine the size of the muffle furnace.

[0036] The length of the muffle furnace L = 30 cm;

[0037] S2. Determine the number of crucibles to be used.

[0038] Four T300 carbon fibers were cut into small pieces of a certain length and loaded into 12 ceramic crucibles, which were then placed in a muffle furnace;

[0039] S3. Determine the usage atmosphere ratio.

[0040] According to the filling rule, the muffle furnace is filled with a mixed gas, i.e. nitrogen: oxygen = 10:3;

[0041] S4. Determine the state of the residue,

[0042] Turn on the muffle furnace switch and set the burning temperature to 900℃. When the temperature rises to 300℃, start filling the mixed gas. When the temperature rises to 900℃, stop filling once every 2 hours, and each time for 15 minutes. After burning for 16 hours, take out the burned ceramic crucibles one by one and cool them down. There is no carbon black in the residue, and finally weigh and calculate.

[0043] Comparative Example 2:

[0044] Four T300 carbon fibers were made into small sections of a certain length and loaded into 12 ceramic crucibles, which were then placed in a muffle furnace with a length of 30 cm. The muffle furnace was turned on and the calcination temperature was set to 900°C. The crucibles were calcined for 16 hours, and then the calcined ceramic crucibles were taken out one by one and cooled. There was a little carbon black in the residues in the outermost three crucibles. These three crucibles needed to be put back into the muffle furnace and calcined at 900°C for 8 hours. The calcined ceramic crucibles were then taken out one by one and cooled. There was no carbon black in the residues, and finally weighed and calculated.

[0045] Embodiment 3:

[0046] S1. Determine the size of the muffle furnace.

[0047] The length of the muffle furnace L = 50 cm;

[0048] S2. Determine the number of crucibles to be used.

[0049] 10 T300 carbon fibers were cut into small pieces of a certain length and loaded into 30 ceramic crucibles, which were then placed in a muffle furnace;

[0050] S3. Determine the usage atmosphere ratio.

[0051] According to the filling rule, the muffle furnace is filled with a mixed gas, i.e. nitrogen: oxygen = 5:2;

[0052] S4. Determine the state of the residue,

[0053] Turn on the muffle furnace switch and set the burning temperature to 900℃. When the temperature rises to 300℃, start filling the mixed gas. When the temperature rises to 900℃, stop filling once every 2 hours, and each time for 20 minutes. After burning for 16 hours, take out the burned ceramic crucibles one by one and cool them down. There is no carbon black in the residue, and finally weigh and calculate.

[0054] Comparative Example 3:

[0055] 10 T300 carbon fibers were made into small sections of a certain length and loaded into 30 ceramic crucibles, which were then placed in a muffle furnace with a length of 50 cm. The muffle furnace was turned on and the calcination temperature was set to 900°C. The crucibles were calcined for 16 hours, and then the calcined ceramic crucibles were taken out one by one and cooled. There was a little carbon black in the residues in the outermost 9 crucibles. These 9 crucibles needed to be put back into the muffle furnace and calcined at 900°C for 8 hours. The calcined ceramic crucibles were then taken out one by one and cooled. There was no carbon black in the residues, and finally weighed and calculated.

[0056] The burning states of the carbon fibers of Examples 1-3 of the present invention and Comparative Examples 1-3 are compared, and the results are shown in the following table:

[0057] Table 1 Comparison of burning status and test time

[0058]

[0059]

[0060] By observing the test results of the embodiments and comparative examples, it is found that the existing method is prone to insufficient burning, resulting in the need for repeated burning, ineffective extension of the test cycle, low test efficiency, and poor repeatability. The present invention sets the ratio of mixed gas in the muffle furnace according to the size of the furnace, which can achieve sufficient burning of carbon fiber, reduce the operating requirements of the test personnel, and the repeated test results are basically consistent.

[0061] It can be seen from the above technical solutions that the method for atmosphere-assisted carbon fiber ash content testing provided by the present invention has the advantages of: providing a process-controllable and reliable testing method, determining the ratio of inert gas to oxygen mixed gas according to the depth of the muffle furnace cavity and the number of crucibles used, and introducing the mixed gas during the ash content test, thereby improving the burning efficiency of the carbon fiber, avoiding the problem that the carbon fiber is not burned sufficiently due to the low proportion of oxygen and the carbon fiber is burned violently or even ignited due to the large proportion of oxygen. This method can ensure that the carbon fiber can be burned fully every time, reduce the operating requirements for personnel, ensure the stability and consistency of the carbon fiber ash content test, and greatly improve the test efficiency. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive.

[0062] In addition, it should be understood that although the present specification is described according to embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that those skilled in the art can understand.

[0063] The present invention determines the ratio of the inert gas to the oxygen mixed gas according to the depth of the inner cavity of the muffle furnace and the number of crucibles used, and introduces the mixed gas during the ash test process, thereby improving the burning efficiency of the carbon fiber, avoiding the problem of incomplete combustion of the carbon fiber due to too low an oxygen proportion and violent combustion or even fire of the carbon fiber due to a large oxygen proportion, and solves the problem of long carbon fiber ash test cycle and uneven burning conditions.

Claims

1. A method for testing the ash content of carbon fiber assisted by atmosphere, characterized in that: The following steps are included: S1. Determine the depth of the muffle furnace mouth. The depth of the muffle furnace is L. S2. Determine the number of crucibles to be used. The carbon fiber is made into small pieces of a certain length and loaded into a crucible, which is then placed in a muffle furnace; S3. Determine the usage atmosphere ratio. The horizontal distance between the last crucible and the heating wire is recorded as M, and the filling ratio of inert gas to oxygen is determined according to the ratio of M to L: When L≤20cm, inert gas: oxygen = 5:1, When 20cm<L≤40cm, M / L≤1 / 2, inert gas: oxygen=5:1, M / L>1 / 2, inert gas:oxygen=10:3, When L>40cm, M / L≤1 / 3, inert gas:oxygen=5:1, 1 / 3<M / L≤2 / 3, inert gas:oxygen=10:3, M / L>2 / 3, inert gas:oxygen=5:2; S4. Determine the state of the residue, After determining the filling ratio of the mixed gas, turn on the muffle furnace switch. When the temperature rises to 300°C, start filling the mixed gas. When the temperature reaches 900°C, stop. Then fill it every 2 hours, each time for 10min to 20min. Finally, take out the crucible after burning, check whether there is carbon black in the residue, and proceed to the next step.

2. The method for testing the ash content of carbon fiber assisted by atmosphere according to claim 1, characterized in that The inert gas is nitrogen, helium or argon.

3. The method for testing the ash content of carbon fiber assisted by atmosphere according to claim 1, characterized in that The crucible is a ceramic crucible, a quartz crucible, an alumina crucible or a platinum crucible.

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