Method for measuring content of sizing agent in fiber

Abstract

The invention provides a method for measuring the content of a sizing agent in fibers, and relates to the technical field of fibers, and the method comprises the following steps: obtaining a TG curve of a sizing agent stock solution; calculating the ash content W in the sizing agent stock solution according to the TG curve of the sizing agent stock solution; obtaining a TG curve of the fiber; calculating the weightlessness weight G3 of the fiber according to the TG curve of the fiber; wherein the fibers are the fibers subjected to sizing; and calculating the content of the sizing agent in the fiber according to the ash content W in the sizing agent stock solution and the weightlessness weight G3 of the fiber. According to the method, the ash content W and the weightlessness weight G3 of the fiber can be obtained through the TG curve, so that the sizing agent content in the fiber is calculated; therefore, errors caused by balance fluctuation, temperature control accuracy and the like can be avoided, and the accuracy of a sizing agent content measurement result is ensured.

Description

Technical Field

[0001] The invention belongs to the field of fiber technology, and in particular relates to a method for measuring the content of sizing agent in fibers. Background Art

[0002] In the production process of carbon fiber and graphite fiber, sizing treatment is an indispensable process, especially the sizing agent content (adhesion mass) of carbon fiber and graphite fiber is an important indicator to test the sizing effect. The sizing agent content of carbon fiber and graphite fiber is usually controlled between 0.4% and 1.4% (mass fraction). Too high sizing agent content will lead to stiffness of the tow, which is not conducive to fiber opening, width expansion and deep processing.

[0003] At present, the measurement methods of sizing agent content of carbon fiber and graphite fiber mainly include solvent extraction method and high temperature thermal decomposition method. Among them, the extractant of solvent extraction method generally uses dangerous chemicals such as acetone, which are harmful to human body, environment, equipment and facilities; in addition, during the reflux process, due to the temperature control fluctuation of the heating jacket and the difficulty in controlling the number of refluxes during 2 hours, the fiber knots may not be washed clean during the detection process, thus affecting the accuracy of the measurement results. The high temperature decomposition method is prone to errors due to manual operation in weighing, measurement, equipment temperature control, etc., which may lead to the accuracy of the measurement results. Summary of the invention

[0004] Therefore, the present invention provides a method for determining the content of sizing agent in fiber to solve the problem that the prior art is harmful to human body, environment, equipment and facilities, etc.

[0005] In order to solve the above problems, the present invention provides a method for determining the content of sizing agent in fiber, comprising the following steps:

[0006] Step 1) obtaining a TG curve of a sizing agent stock solution; calculating the ash content W in the sizing agent stock solution according to the TG curve of the sizing agent stock solution;

[0007] Obtaining a TG curve of the fiber; calculating the weight loss G3 of the fiber according to the TG curve of the fiber; wherein the fiber is a sizing fiber;

[0008] Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber.

[0009] Further, in step 1): the step of calculating the ash content W in the sizing agent stock solution comprises:

[0010] In the TG curve of the sizing agent stock solution, the initial weight M1 of the sizing agent stock solution and the weight M2 of the sizing agent stock solution at the first set temperature are obtained; then the ash content W in the sizing agent stock solution is calculated;

[0011] in, The first set temperature is greater than the end weight loss temperature of the sizing agent stock solution;

[0012] Preferably, the first set temperature is 800-900°C.

[0013] Further, in step 1): the step of calculating the weight loss G3 of the fiber includes:

[0014] The initial weight G1 of the fiber and the weight G2 of the fiber at the second set temperature are obtained on the TG curve of the fiber; and then the weight loss G3 of the fiber is calculated;

[0015] Wherein, G3=G1-G2; the second set temperature is greater than the end weight loss temperature of the fiber;

[0016] Preferably, the second set temperature is 800-900°C.

[0017] Further, in the step 2):

[0018] Furthermore, in the step 1), the method for obtaining the TG curve of the sizing agent stock solution includes:

[0019] Placing the sizing agent stock solution in a crucible of a thermal analyzer, setting test conditions, and obtaining a TG curve of the sizing agent stock solution;

[0020] Preferably, the test conditions are: the atmosphere is nitrogen; the temperature is raised to the preheating temperature, and then the temperature is raised to the first set temperature after being kept warm;

[0021] Preferably, the heating rate is 5 to 10°C / min;

[0022] Preferably, the preheating temperature is 100-110° C.; and the insulation time is 10-15 minutes.

[0023] Furthermore, in step 1): the fiber is carbon fiber or graphite fiber; and / or

[0024] The method for obtaining the TG curve of the fiber includes:

[0025] The fiber is placed in a crucible of a thermal analyzer, and test conditions are set to obtain a TG curve of the fiber;

[0026] Preferably, the test conditions are: the atmosphere is nitrogen; the temperature is raised to the preheating temperature, and then the temperature is raised to the second set temperature after being kept warm;

[0027] Preferably, the heating rate is 5 to 10°C / min;

[0028] Preferably, the preheating temperature is 100-110° C.; and the insulation time is 10-15 minutes.

[0029] Furthermore, the initial weight G1 is the weight of the fiber at the preheating temperature.

[0030] Furthermore, before placing the fiber in a thermal analyzer, the method further includes: performing a baseline test on the crucible of the thermal analyzer.

[0031] Furthermore, the baseline detection step includes: setting detection conditions and operating a thermal analyzer; wherein the detection conditions are: nitrogen atmosphere; heating to a preheating temperature, keeping the temperature, and then heating to a detection temperature;

[0032] Preferably, the heating rate is 5 to 10°C / min;

[0033] Preferably, the preheating temperature is 100-110°C; the insulation time is 10-15 minutes;

[0034] Preferably, the detection temperature is 800-900°C.

[0035] Furthermore, before placing the fiber in a thermal analyzer, the method further includes: evacuating a crucible of the thermal analyzer;

[0036] Preferably, the vacuuming cycle is performed three times.

[0037] The method for determining the content of sizing agent in fiber provided by the present invention has the following beneficial effects:

[0038] 1. The present invention obtains the TG curve of the sizing agent stock solution and the TG curve of the fiber respectively; then calculates the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber; and then calculates the sizing agent content in the fiber according to the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber; based on the above method, the present invention can obtain the ash content W and the weight loss G3 of the fiber through the TG curve, thereby calculating the sizing agent content in the fiber; therefore, the present invention does not need to use chemicals such as extractants, thereby avoiding harm to human body, environment, equipment and facilities, etc.; at the same time, the present invention can avoid errors caused by fluctuations in balances, temperature control accuracy, etc., and ensure the accuracy of the sizing agent content measurement results.

[0039] 2. Furthermore, the present invention can reduce the system error of the instrument by performing a baseline test on the empty crucible of the thermal analyzer; can reduce the influence of moisture on the measurement result by taking the weight at the preheating temperature as the initial weight; and can further avoid the influence of ash on the measurement result by calculating the ash content, thereby ensuring the accuracy of the measurement result of the sizing agent content. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0041] Figure 1 is a TG curve diagram of the carbon fiber in the present invention;

[0042] Figure 2 is a TG curve diagram of the graphite fiber in the present invention;

[0043] Figure 3 is a TG curve diagram of the sizing agent stock solution in the present invention;

[0044] Figure 4 It is a TG curve diagram of the fiber after high temperature carbonization in the present invention. DETAILED DESCRIPTION

[0045] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0046] The present invention provides a method for determining the content of sizing agent in fiber, comprising the following steps:

[0047] Step 1) placing a sizing agent stock solution in a crucible of a thermal analyzer, setting test conditions, and obtaining a TG curve of the sizing agent stock solution; calculating an initial weight M1 of the sizing agent stock solution and a weight M2 of the sizing agent stock solution at a first set temperature on the TG curve of the sizing agent stock solution;

[0048] Then calculate the ash content W in the sizing agent stock solution; where,

[0049] The first set temperature is greater than the end weight loss temperature of the sizing agent stock solution; the initial weight M1 is the weight of the sizing agent stock solution at the preheating temperature; the preheating temperature is 100-110°C, preferably 105°C; the first set temperature is 800-900°C, preferably 800°C; the test conditions are: the atmosphere is nitrogen; the temperature is raised to 100-110°C, preferably 105°C, and the temperature is raised to 800-900°C, preferably 800°C after keeping warm for 10-15 minutes;

[0050] The fiber is placed in a crucible of a thermal analyzer, and the test conditions are set to obtain a TG curve of the fiber; the initial weight G1 of the fiber and the weight G2 of the fiber at a second set temperature are calculated on the TG curve of the fiber; wherein the second set temperature is greater than the end weight loss temperature of the fiber;

[0051] Then the weight loss G3 of the fiber is calculated; wherein G3 = G1-G2;

[0052] Wherein, the fiber is a carbon fiber or graphite fiber after sizing; the initial weight G1 is the weight of the fiber at the preheating temperature; the preheating temperature is 100-110°C, preferably 105°C; the second set temperature is 800-900°C, preferably 800°C; the test conditions are: the atmosphere is nitrogen; the temperature is raised to 100-110°C, preferably 105°C, and the temperature is raised to 800-900°C, preferably 800°C after keeping warm for 10-15 minutes; wherein, the weight at 105°C is selected as the initial weight G1 because heating at 105°C can eliminate the influence of moisture in the fiber on the determination of the sizing agent content; the sizing agent (stock solution) starts to have a constant weight at 650°C, that is, it no longer loses weight, and 800°C is to ensure that the sizing agent in the fiber is completely burned, and at the same time, the carbon fiber or graphite fiber does not lose weight at 800°C, and the temperature of the high-temperature carbonization section on the production line (i.e., the high-temperature carbonization temperature) is about 800°C;

[0053] Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber; wherein the sizing agent content in the fiber

[0054] In some embodiments, in order to eliminate systematic errors, before the step of placing the carbon fiber in the thermal analyzer, the step also includes: a baseline detection step: setting the detection conditions, running the thermal analyzer, and performing a baseline detection on the empty crucible of the thermal analyzer; wherein the detection conditions are nitrogen atmosphere; heating to 105°C, keeping the temperature for 15 minutes, and then heating to 800°C.

[0055] Furthermore, in order to completely replace the air and ensure that the atmosphere is a nitrogen atmosphere; before placing the carbon fiber in the thermal analyzer, the step also includes: evacuating the crucible of the thermal analyzer; preferably, the vacuuming cycle is performed three times.

[0056] The present invention is further described below in conjunction with specific examples and comparative examples. The temperature control program of the thermal analyzer in the example is shown in Table 1.

[0057] Table 1

[0058] step atmosphere flow Temperature range Heating rate time ① Vacuuming cycle*3 - - - Waiting for completion ② Nitrogen 80ml / min 25℃-105℃ 5℃ / min 16min ③ Nitrogen 80ml / min 105℃-105℃ 0 15min ④ Nitrogen 80ml / min 105℃-800℃ 5℃ / min 139min ⑤ Nitrogen 20ml / min 800℃-25℃ - Waiting for completion

[0059] Among them, in Example 1: the sizing agent is F1043 sizing agent (recorded as sizing agent 1), the carbon fiber is TG800 carbon fiber (recorded as carbon fiber 1), and the graphite fiber is TG46MJ graphite fiber (recorded as graphite fiber 1); in Example 2: the sizing agent is F1043 sizing agent (recorded as sizing agent 2), the carbon fiber is TG700 carbon fiber (recorded as carbon fiber 2), and TG46MJ graphite fiber (recorded as graphite fiber 2); in Example 3: the sizing agent is F1043 sizing agent (recorded as sizing agent 3), the carbon fiber is TG300 carbon fiber (recorded as carbon fiber 3), and the graphite fiber is TG46MJ graphite fiber (recorded as graphite fiber 3).

[0060] Example 1

[0061] This embodiment provides a method for determining the content of sizing agent in carbon fiber, comprising the following steps:

[0062] Step 1) Baseline detection step: setting the detection conditions, running the thermal analyzer, and performing a baseline detection on an empty crucible of the thermal analyzer to obtain baseline data; wherein the detection conditions are that the atmosphere is nitrogen; the temperature is raised to 105° C., kept at this temperature for 15 minutes, and then raised to 800° C.;

[0063] Load the baseline data into the thermal analyzer, then set the test conditions, place the sizing agent in the crucible of the thermal analyzer, and obtain the TG curve of the sizing agent, see Figure 3 ; Test conditions: nitrogen atmosphere; heating to 105°C, keeping warm for 15 minutes and then heating to 800°C;

[0064] Under the above test conditions, carbon fiber, graphite fiber, and high-temperature carbonized segment tow were placed in the crucible of the thermal analyzer in turn to obtain the corresponding TG curves, see Figure 1 ;

[0065] On the TG curve of the sizing agent stock solution, the initial weight M1 of the sizing agent stock solution and the weight M2 of the sizing agent stock solution at the set temperature are obtained; the ash content W in the sizing agent stock solution is calculated; wherein,

[0066]

[0067] On the TG curve of the fiber or tow, find the initial weight G1 of the fiber or tow and the weight loss G2 of the fiber or tow; calculate the weight loss G3 of the fiber; wherein G3 = G1-G2;

[0068] Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber; wherein the sizing agent content in the fiber

[0069] Example 2

[0070] This embodiment provides a method for determining the content of sizing agent in carbon fiber, comprising the following steps:

[0071] Step 1) Baseline detection step: setting the detection conditions, running the thermal analyzer, and performing a baseline detection on an empty crucible of the thermal analyzer to obtain baseline data; wherein the detection conditions are that the atmosphere is nitrogen; the temperature is raised to 105° C., kept at this temperature for 15 minutes, and then raised to 800° C.;

[0072] Load the baseline data into the thermal analyzer, then set the test conditions, place the sizing agent in the crucible of the thermal analyzer, and obtain the TG curve of the sizing agent, see Figure 3 ; Test conditions: nitrogen atmosphere; heating to 105°C, keeping warm for 15 minutes and then heating to 800°C;

[0073] Under the above test conditions, carbon fiber, graphite fiber, and high-temperature carbonized segment tow were placed in the crucible of the thermal analyzer in turn to obtain the corresponding TG curves, see Figure 1 ;

[0074] On the TG curve of the sizing agent stock solution, the initial weight M1 of the sizing agent stock solution and the weight M2 of the sizing agent stock solution at the set temperature are obtained; the ash content W in the sizing agent stock solution is calculated; wherein,

[0075]

[0076] On the TG curve of the fiber or tow, find the initial weight G1 of the fiber or tow and the weight loss G2 of the fiber or tow; calculate the weight loss G3 of the fiber; wherein G3 = G1-G2;

[0077] Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber; wherein the sizing agent content in the fiber

[0078] Example 3

[0079] This embodiment provides a method for determining the content of sizing agent in carbon fiber, comprising the following steps:

[0080] Step 1) Baseline detection step: setting the detection conditions, running the thermal analyzer, and performing a baseline detection on an empty crucible of the thermal analyzer to obtain baseline data; wherein the detection conditions are that the atmosphere is nitrogen; the temperature is raised to 105° C., kept at this temperature for 15 minutes, and then raised to 800° C.;

[0081] Load the baseline data into the thermal analyzer, then set the test conditions, place the sizing agent in the crucible of the thermal analyzer, and obtain the TG curve of the sizing agent, see Figure 3 ; Test conditions: nitrogen atmosphere; heating to 105°C, keeping warm for 15 minutes and then heating to 800°C;

[0082] Under the above test conditions, carbon fiber, graphite fiber, and high-temperature carbonized segment tow were placed in the crucible of the thermal analyzer in turn to obtain the corresponding TG curves, see Figure 1 ;

[0083] On the TG curve of the sizing agent stock solution, the initial weight M1 of the sizing agent stock solution and the weight M2 of the sizing agent stock solution at the set temperature are obtained; the ash content W in the sizing agent stock solution is calculated; wherein W=M2M-1M1;

[0084] On the TG curve of the fiber or tow, find the initial weight G1 of the fiber or tow and the weight loss G2 of the fiber or tow; calculate the weight loss G3 of the fiber; wherein G3 = G1-G2;

[0085] Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent and the weight loss G3 of the fiber; wherein the sizing agent content in the fiber

[0086] The weight measurement results of the sizing agent (sizing agent stock solution), fiber, and high-temperature carbonized section tow in Examples 1 to 3 are shown in Table 2. Wherein, for the sizing agent stock solution, G1 is the initial weight M1 of the sizing agent stock solution, and G2 is the weight M2 of the sizing agent stock solution at a set temperature.

[0087] Table 2

[0088]

[0089] The production environment of the high-temperature carbonized tow is an 800°C nitrogen atmosphere. After cooling, it enters the sizing tank. The sizing agent is a liquid that will adhere to the surface of the tow. After the drying stage, it finally becomes a finished carbon fiber. Therefore, in the above embodiment, by measuring the sizing agent content of the high-end tow, the influence of the tow itself can be eliminated, ensuring that the carbon fiber is burned in an 800°C nitrogen atmosphere, and the lost mass is the sizing agent part.

[0090] The existing acetone extraction method was used to measure the sizing agent content in the carbon fibers and graphite fibers in the above-mentioned Examples 1 to 3, and the results are shown in Table 3. It can be seen that the measurement results in the embodiments of the present application are close to the detection results of the existing methods. Therefore, compared with the acetone extraction method, the method for measuring the sizing agent content in the fiber of the present invention is safer and more reliable, and is not easy to cause harm to the human body, the environment, equipment and facilities, etc.

[0091] Table 3

[0092] Sample name Sampling volume (g) Tow mass after extraction (g) Sizing agent content (%) Carbon fiber 1 3.2531 3.2139 1.21 Carbon Fiber 2 3.2377 3.200 1.16 Carbon Fiber 3 3.1929 3.1540 1.22 Graphite fiber 1 3.1154 3.0727 1.37 Graphite Fiber 2 3.1447 3.1013 1.38 Graphite Fiber 3 3.0797 3.0389 1.32

[0093] The sizing agent samples in the above Examples 1 to 3 were taken, and the sampling amount was first measured by a balance, and then the sizing agent was placed in a muffle furnace, heated to 800° C., and after cooling, the mass of the ash after drying was measured, and the ash content in the corresponding sizing agent stock solution was calculated, and the results are shown in Table 4. It can be seen that the ash content in the sizing agent measured in the embodiment of the present invention is more accurate.

[0094] Table 4

[0095] Sample name Sizing agent sampling amount (g) Mass after evaporation (g) Ash content (%) Sizing agent 1 10.0426 0.9034 8.99 Sizing agent 2 10.0617 0.9068 9.01 Sizing agent 3 9.9905 0.9027 9.04

[0096] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A method for determining the sizing agent content in a fiber, characterized in that: The following steps are involved: Step 1) obtaining a TG curve of a sizing agent stock solution; calculating the ash content W in the sizing agent stock solution according to the TG curve of the sizing agent stock solution; Obtaining a TG curve of the fiber; calculating the weight loss G3 of the fiber according to the TG curve of the fiber; wherein the fiber is a sizing fiber; Step 2) Calculate the sizing agent content in the fiber based on the ash content W in the sizing agent stock solution and the weight loss G3 of the fiber.

2. The method for determining the sizing agent content in a fiber according to claim 1, characterized in that: In the step 1): the step of calculating the ash content W in the sizing agent stock solution comprises: In the TG curve of the sizing agent stock solution, the initial weight M1 of the sizing agent stock solution and the weight M2 of the sizing agent stock solution at the first set temperature are obtained; then the ash content W in the sizing agent stock solution is calculated; in, The first set temperature is greater than the end weight loss temperature of the sizing agent stock solution; Preferably, the first set temperature is 800-900°C.

3. The method for measuring the sizing agent content in a fiber according to claim 1, characterized in that: In the step 1), the step of calculating the weight loss G3 of the fiber comprises: The initial weight G1 of the fiber and the weight G2 of the fiber at the second set temperature are obtained on the TG curve of the fiber; and then the weight loss G3 of the fiber is calculated; Wherein, G3=G1-G2; the second set temperature is greater than the end weight loss temperature of the fiber; Preferably, the second set temperature is 800-900°C.

4. The method for determining the sizing agent content in a fiber according to any one of claims 1 to 3, characterized in that: In the step 2):

5. The method for determining the sizing agent content in a fiber according to claim 1, characterized in that: In the step 1), the method for obtaining the TG curve of the sizing agent stock solution includes: Placing the sizing agent stock solution in a crucible of a thermal analyzer, setting test conditions, and obtaining a TG curve of the sizing agent stock solution; Preferably, the test conditions are: the atmosphere is nitrogen; the temperature is raised to the preheating temperature, and then the temperature is raised to the first set temperature after being kept warm; Preferably, the heating rate is 5 to 10°C / min; Preferably, the preheating temperature is 100-110° C.; and the insulation time is 10-15 minutes.

6. The method for determining the sizing agent content in a fiber according to claim 1, characterized in that: In the step 1): the fiber is carbon fiber or graphite fiber; and / or The method for obtaining the TG curve of the fiber includes: The fiber is placed in a crucible of a thermal analyzer, and test conditions are set to obtain a TG curve of the fiber; Preferably, the test conditions are: the atmosphere is nitrogen; the temperature is raised to the preheating temperature, and then the temperature is raised to the second set temperature after keeping the temperature; Preferably, the heating rate is 5 to 10°C / min; Preferably, the preheating temperature is 100-110° C.; and the insulation time is 10-15 minutes.

7. The method for determining the sizing agent content in a fiber according to claim 6, characterized in that: The initial weight G1 is the weight of the fiber at the preheating temperature.

8. The method for determining the sizing agent content in a fiber according to claim 6, characterized in that: Before placing the fiber in the thermal analyzer, the method further includes: performing a baseline test on the crucible of the thermal analyzer.

9. The method for determining the sizing agent content in a fiber according to claim 6, characterized in that: The baseline detection step includes: setting detection conditions and running a thermal analyzer; wherein the detection conditions are: nitrogen atmosphere; heating to a preheating temperature, keeping the temperature, and then heating to a detection temperature; Preferably, the heating rate is 5 to 10°C / min; Preferably, the preheating temperature is 100-110°C; the insulation time is 10-15 minutes; Preferably, the detection temperature is 800-900°C.

10. The method for determining the sizing agent content in fiber according to claim 6, characterized in that: Before placing the fiber in the thermal analyzer, the step further includes: evacuating the crucible of the thermal analyzer; Preferably, the vacuuming cycle is performed three times.

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