Method for detecting the oil content of polyacrylonitrile-based filaments

Abstract

The present disclosure provides a method for detecting the oil content of polyacrylonitrile-based precursor, and relates to the technical field of carbon fiber precursor detection. The method comprises the following steps: preparing a polyacrylonitrile-based precursor sample; performing first drying treatment on the polyacrylonitrile-based precursor sample to obtain a first mass of dried polyacrylonitrile-based precursor sample; washing the dried polyacrylonitrile-based precursor sample with an alkaline detergent to obtain an oil-removed polyacrylonitrile-based precursor sample; performing second drying treatment on the oil-removed polyacrylonitrile-based precursor sample to obtain a second mass of dried oil-removed polyacrylonitrile-based precursor sample; and determining the oil content of the polyacrylonitrile-based precursor according to the first mass and the second mass. In this way, the oil content of the polyacrylonitrile-based precursor can be obtained quickly and accurately, and the use of hazardous chemicals is reduced during the detection process, thereby improving the safety of the operation.

Description

Technical Field

[0001] This disclosure relates to the field of carbon fiber precursor detection technology, and in particular to a method for detecting the oil content of polyacrylonitrile-based precursor fibers. Background Technology

[0002] Carbon fiber is a fibrous carbon material, with carbon accounting for over 90% of its total mass in its chemical composition. Based on its high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, electrical conductivity, thermal conductivity, and low coefficient of thermal expansion, carbon fiber is widely used in aerospace, aviation, transportation, sports equipment, and many other fields. In the production process of carbon fiber, oiling is a crucial step. The amount of oil applied must be appropriate; too much oil can cause silicon contamination, while too little oil can cause adhesion or tangling between monofilaments. Therefore, accurately detecting the oil content in polyacrylonitrile precursor fibers is of great significance to the production process.

[0003] Therefore, there is an urgent need to provide a method for detecting the oil content of polyacrylonitrile-based precursor fibers. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail in this disclosure. This overview is not intended to limit the scope of the claims.

[0005] This disclosure provides a method for detecting the oil content of polyacrylonitrile-based precursor fibers.

[0006] According to some embodiments, a first aspect of this disclosure provides a method for detecting the oil content of polyacrylonitrile-based precursor fibers, the method comprising:

[0007] Preparation of polyacrylonitrile-based precursor fiber samples;

[0008] The polyacrylonitrile-based precursor fiber sample is subjected to a first drying treatment to obtain a first mass of dried polyacrylonitrile-based precursor fiber sample.

[0009] The dried polyacrylonitrile precursor sample was washed with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample.

[0010] The degreased polyacrylonitrile precursor sample is subjected to a second drying treatment to obtain a second mass of the dried degreased polyacrylonitrile precursor sample.

[0011] The oil content of the polyacrylonitrile precursor fiber is determined based on the first mass and the second mass.

[0012] According to some embodiments of this disclosure, the step of washing the dried polyacrylonitrile precursor sample with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample includes:

[0013] The dried polyacrylonitrile precursor sample is placed in a first container, which contains a first preset volume of alkaline detergent, the alkaline detergent comprising a potassium hydroxide ethanol solution of a preset concentration.

[0014] Place the first container in a water bath at a first preset temperature and stir the liquid in the first container at a preset speed for a first preset time.

[0015] Take out the polyacrylonitrile-based precursor fiber sample from the first container and perform the first dehydration treatment;

[0016] The polyacrylonitrile precursor fiber sample after the above dehydration treatment was rinsed in a water bath at a second preset temperature.

[0017] The rinsed polyacrylonitrile precursor fiber sample was subjected to a second dehydration treatment to obtain the degreased polyacrylonitrile precursor fiber sample.

[0018] According to some embodiments of this disclosure, the detection method further includes: dissolving the potassium hydroxide in the ethanol to obtain a potassium hydroxide ethanol solution of a preset concentration, wherein the preset concentration ranges from 1.5% to 2.5%.

[0019] According to some embodiments of this disclosure, the first preset temperature is 50°C, the volume ratio of the water bath to the alkaline detergent is at least 20:1, the preset speed ranges from 200 r / min to 250 r / min, the first preset time ranges from 30 min to 40 min; and / or the second preset temperature ranges from 60°C to 70°C, and the water used in the water bath at the second preset temperature is grade III water.

[0020] According to some embodiments of this disclosure, at least one of the first dehydration treatment and the second dehydration treatment employs centrifugal dehydration. The centrifuge used in the centrifugal dehydration method includes centrifuge tubes and a water-permeable isolation structure disposed at the bottom of the centrifuge tubes, configured to reduce the risk of contact between the polyacrylonitrile-based precursor sample to be dehydrated and the liquid at the bottom of the centrifuge tubes.

[0021] According to some embodiments of this disclosure, a centrifuge body is provided with a centrifuge tube trough for accommodating the centrifuge tube, and the centrifuge body is configured to centrifuge the centrifuge tube; wherein, the water-permeable isolation structure is a support, and the support extends spirally in the length direction of the centrifuge tube.

[0022] According to some embodiments of this disclosure, the support is made of metal.

[0023] According to some embodiments of this disclosure, there are multiple dried polyacrylonitrile-based precursor fiber samples. Before the step of placing the dried polyacrylonitrile-based precursor fiber samples into the first container, the method further includes placing each of the dried polyacrylonitrile-based precursor fiber samples into a separate sample bag, the sample bag having multiple mesh openings.

[0024] According to some embodiments of this disclosure, the step of performing a first drying treatment on the polyacrylonitrile-based precursor fiber to obtain a first mass of dried polyacrylonitrile-based precursor fiber sample includes:

[0025] Place the polyacrylonitrile-based precursor fiber sample into a weighing dish;

[0026] Place the weighing dish in a drying oven at a third preset temperature and dry it for a second preset time;

[0027] Place the dried weighing dish containing the polyacrylonitrile-based precursor fiber sample into a desiccant and cool it to the fourth preset temperature.

[0028] Weigh the third mass of the weighing dish containing the dried polyacrylonitrile-based precursor fiber sample;

[0029] The dried polyacrylonitrile-based precursor fiber sample was removed from the weighing dish, and the fourth mass of the dried weighing dish was measured.

[0030] The first mass of the dried polyacrylonitrile-based precursor fiber sample is determined based on the third mass and the fourth mass.

[0031] According to some embodiments of this disclosure, the step of performing a second drying treatment on the degreased polyacrylonitrile precursor sample to obtain a second mass of the dried degreased polyacrylonitrile precursor sample includes:

[0032] Place the degreased polyacrylonitrile-based precursor fiber sample into the weighing dish;

[0033] Place the weighing dish in a drying oven at a fifth preset temperature and dry it for a third preset time;

[0034] Place the dried weighing dish containing the degreased polyacrylonitrile-based precursor fiber sample into a desiccant and cool it to the fourth preset temperature.

[0035] The fifth mass of the weighing dish containing the dried, degreased polyacrylonitrile-based precursor fiber sample is weighed.

[0036] The second mass of the dried, degreased polyacrylonitrile precursor sample is determined based on the fifth mass and the fourth mass.

[0037] The method for detecting the oil content of polyacrylonitrile precursor fibers disclosed herein uses an alkaline detergent to wash the oil in the dried polyacrylonitrile precursor fiber sample, and then obtains the oil content of the polyacrylonitrile precursor fiber based on the mass difference of the sample before and after washing. This method not only obtains the oil content of the polyacrylonitrile precursor fiber more quickly and accurately, but also reduces the use of hazardous chemicals during the detection process and improves operational safety.

[0038] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0039] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of these embodiments. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the present disclosure, but not all embodiments. Other drawings will be derived from these drawings by those skilled in the art without inventive effort.

[0040] Figure 1 This is a schematic flowchart illustrating a method for detecting the oil content of polyacrylonitrile-based precursor fibers according to an exemplary embodiment.

[0041] Figure 2 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent according to a first embodiment shown in an exemplary embodiment.

[0042] Figure 3 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent according to a first embodiment shown in an exemplary embodiment.

[0043] Figure 4 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent in a second embodiment as shown in an exemplary embodiment.

[0044] Figure 5 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent in a second embodiment as shown in an exemplary embodiment.

[0045] Figure 6 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent in a third embodiment shown in an exemplary practice.

[0046] Figure 7 This is a scanning electron microscope image of a polyacrylonitrile-based precursor fiber sample washed with an alkaline detergent in a third embodiment shown in an exemplary practice.

[0047] Figure 8 This is a scanning electron microscope image of a polyacrylonitrile precursor fiber sample washed with an alkaline detergent under the second condition shown in an exemplary embodiment.

[0048] Figure 9 This is a scanning electron microscope image of a polyacrylonitrile precursor fiber sample washed with an alkaline detergent under the second condition shown in an exemplary embodiment.

[0049] Figure 10 This is a scanning electron microscope image of an AC45-3K sample washed with an alkaline detergent, according to an exemplary embodiment.

[0050] Figure 11 This is a scanning electron microscope image of an AC45-12K sample washed with an alkaline detergent, according to an exemplary embodiment.

[0051] Figure 12 This is a scanning electron microscope image of an AC55-12K sample washed with an alkaline detergent, according to an exemplary embodiment.

[0052] Figure 13 This is a schematic diagram of the structure of a centrifuge according to an exemplary embodiment.

[0053] Figure 14 A schematic diagram of a centrifuge tube with a support shown according to an exemplary embodiment.

[0054] Explanation of reference numerals in the attached figures:

[0055] 10-Centrifuge; 11-Centrifuge body; 12-Centrifuge tube trough; 20-Centrifuge tube; 21-Support. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0057] In the carbon fiber production process, oiling is a crucial step in the preparation of polyacrylonitrile (PA) precursor fibers. Oiling involves uniformly coating the surface of the PA precursor fiber with a thin film of oil. While the oil can penetrate into the PA precursor fiber, most of it remains on the surface. This oil not only protects the PA precursor fiber from scratches but also improves its bundle bonding and antistatic properties, preventing filament bundling and breakage during further post-processing. Therefore, the oil content in the oiling process has a significant impact on improving the performance of PA precursor fibers and carbon fibers. Consequently, rapid and accurate detection of the oil content in PA precursor fibers is essential for guiding the production process.

[0058] Typically, the oil content in polyacrylonitrile (PA) precursor fibers is determined using an extraction method. Specifically, this method utilizes the fact that the oil is soluble in a specific organic solvent to extract the oil from the PA precursor fibers. The mass of the oil and the PA precursor fibers is then weighed to calculate the oil content. This method is cumbersome, time-consuming, and inefficient, and the extractant is highly toxic and harmful to human health. Therefore, there is an urgent need to develop a simple and relatively safe method for determining the oil content of PA precursor fibers.

[0059] Therefore, this disclosure provides a method for detecting the oil content of polyacrylonitrile (PAC) precursor fibers. The method includes preparing a PAC precursor fiber sample; subjecting the PAC precursor fiber sample to a first drying treatment to obtain a first mass of dried PAC precursor fiber sample; washing the dried PAC precursor fiber sample with an alkaline detergent to obtain a de-oiled PAC precursor fiber sample; subjecting the de-oiled PAC precursor fiber sample to a second drying treatment to obtain a second mass of dried de-oiled PAC precursor fiber sample; and determining the oil content of the PAC precursor fiber based on the first mass and the second mass. Thus, by using an alkaline detergent to remove the oil from the dried PAC precursor fiber sample, the oil content of the PAC precursor fiber can be obtained based on the mass difference of the PAC precursor fiber sample. This method not only provides a rapid and accurate determination of the oil content of the PAC precursor fiber but also reduces the probability of using hazardous chemicals and improves operational safety.

[0060] The following is in conjunction with the appendix Figure 1 The embodiments of this disclosure will be described, wherein, Figure 1 A flowchart illustrating a method for detecting the oil content of polyacrylonitrile-based precursor fibers is provided. This exemplary embodiment of the present disclosure provides a method for detecting the oil content of polyacrylonitrile-based precursor fibers, the method comprising the following steps:

[0061] Step S100: Prepare polyacrylonitrile-based precursor fiber samples.

[0062] As an example, a polyacrylonitrile precursor fiber with a mass range of 4g-6g is taken as a polyacrylonitrile-based precursor fiber sample, specifically, the weight is accurate to 0.1mg. Furthermore, for ease of the next step, the obtained polyacrylonitrile-based precursor fiber sample is placed in a weighing dish.

[0063] It should be understood that the above example is only an example of the preparation of polyacrylonitrile-based precursor fiber samples and does not limit them in any specific way. For example, the initial mass of the polyacrylonitrile-based precursor fiber sample is not limited to the above numerical range. For example, the initial mass of the polyacrylonitrile-based precursor fiber sample can be any of 6g-8g, 8g-10g, 10g-15g, or 15g-20g. The specific design can be made according to actual needs, which will not be elaborated here.

[0064] Step S200: Perform a first drying treatment on the polyacrylonitrile-based precursor sample to obtain a first mass of dried polyacrylonitrile-based precursor sample.

[0065] In at least one embodiment, the step of performing a first drying treatment on polyacrylonitrile-based precursor fibers to obtain a first mass of dried polyacrylonitrile-based precursor fiber sample includes: placing the polyacrylonitrile-based precursor fiber sample into a weighing dish; placing the weighing dish into a drying oven at a third preset temperature for a second preset time; placing the dried weighing dish containing the polyacrylonitrile-based precursor fiber sample into a drying dish and cooling it to a fourth preset temperature; weighing the third mass of the dried weighing dish containing the polyacrylonitrile-based precursor fiber sample; removing the dried polyacrylonitrile-based precursor fiber sample from the weighing dish and weighing the fourth mass of the dried weighing dish; and determining the first mass of the dried polyacrylonitrile-based precursor fiber sample based on the third mass and the fourth mass.

[0066] As an example, the process of performing a first drying treatment on polyacrylonitrile precursor fibers to obtain a first mass of dried polyacrylonitrile precursor fiber sample includes the following steps:

[0067] First, after placing the polyacrylonitrile-based precursor fiber sample obtained in step S100 into a weighing dish, the weighing dish is placed in a drying oven, and the drying temperature of the drying oven, i.e. the third preset temperature, is 120℃±3℃.

[0068] Then, after drying for a second preset time, such as 1 hour, the weighing dish is transferred to a drying dish and cooled to a fourth preset temperature, such as room temperature 23℃±3℃. That is, the dried polyacrylonitrile-based precursor sample and the dried weighing dish are cooled to the fourth preset temperature.

[0069] Next, the mass of the dried weighing dish containing the dried polyacrylonitrile precursor fiber sample, i.e., the third mass m3, and the mass of the dried weighing dish, i.e., the fourth mass m4, were weighed respectively.

[0070] Finally, the first mass m1 of the dried polyacrylonitrile-based precursor sample is determined based on the difference between the two, i.e., m1 = m3 - m4.

[0071] It should be understood that the above example only illustrates a design scheme for performing a first drying treatment on polyacrylonitrile precursor fibers to obtain a first mass of dried polyacrylonitrile precursor fiber sample, and does not specifically limit it. That is to say, the operating parameters involved in step S200, such as the third preset temperature, the fourth preset temperature, and the second preset time, can be adjusted according to actual needs. For example, the fourth preset temperature can be 25℃±5℃, and the second preset time can be 40min, 45min, 50min, 55min, 60min, or one and a half hours, etc. All of these can be designed according to the requirements of the polyacrylonitrile precursor fiber sample and experimental conditions, and will not be elaborated here.

[0072] Step S300: Wash the dried polyacrylonitrile precursor sample with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample.

[0073] In at least one embodiment, the step of washing the dried polyacrylonitrile precursor sample with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample includes: placing the dried polyacrylonitrile precursor sample into a first container, the first container containing a first preset volume of alkaline detergent, the alkaline detergent including a potassium hydroxide ethanol solution of a preset concentration; placing the first container into a water bath at a first preset temperature, and stirring the liquid in the first container at a preset speed for a first preset time; removing the polyacrylonitrile precursor sample from the first container and performing a first dehydration treatment; rinsing the polyacrylonitrile precursor sample after the above dehydration treatment in a water bath at a second preset temperature; and performing a second dehydration treatment on the rinsed polyacrylonitrile precursor sample to obtain a degreased polyacrylonitrile precursor sample.

[0074] Based on the above embodiments, in at least one embodiment, there are multiple dried polyacrylonitrile-based precursor fiber samples. Before placing the dried polyacrylonitrile-based precursor fiber samples into the first container, the method further includes: placing each dried polyacrylonitrile-based precursor fiber sample into a separate sample bag, the sample bag having multiple mesh openings. This reduces the problem of sample confusion during subsequent operations when there are multiple dried polyacrylonitrile-based precursor fiber samples.

[0075] As an example, the steps to obtain a degreased polyacrylonitrile precursor sample by washing a dried polyacrylonitrile precursor sample with an alkaline detergent include:

[0076] First, multiple dried polyacrylonitrile precursor fiber samples are placed into individual sample bags with multiple mesh openings, and each sample bag is labeled. This prevents sample confusion and tangling without affecting the subsequent washing effect of the dried polyacrylonitrile precursor fiber samples.

[0077] Then, place the numbered sample bags into beakers containing 50mL-100mL of alkaline detergent. Each sample bag contains a dried polyacrylonitrile precursor fiber sample and a potassium hydroxide ethanol solution of a preset concentration of alkaline detergent.

[0078] Next, after placing the polyacrylonitrile precursor sample in an alkaline detergent, the beaker is placed in a water bath at a first preset temperature, for example, 50°C, and the alkaline detergent in the beaker is stirred at a preset speed, for example, 200-250 rpm, for a first preset time, for example, 30-40 minutes, to ensure that the oil in the dried polyacrylonitrile precursor sample is thoroughly washed away by the alkaline detergent. Furthermore, in this step, the volume ratio of the water bath to the alkaline detergent is at least 20:1, for example, any one of 20:1, 25:1, or 30:1.

[0079] Then, the polyacrylonitrile precursor fiber samples treated with alkaline detergent were removed from the beaker and taken out of the sample bag, and the polyacrylonitrile precursor fiber samples were subjected to the first dehydration treatment.

[0080] Next, after the polyacrylonitrile-based precursor fiber sample undergoes a first dehydration treatment, it is then rinsed. Specifically, the dehydrated polyacrylonitrile-based precursor fiber sample is rinsed in a water bath at a second preset temperature, for example, 60°C-70°C, and the water used in the water bath is tertiary water to improve rinsing efficiency.

[0081] Finally, the rinsed polyacrylonitrile precursor fiber samples were subjected to a second dehydration treatment to obtain de-oiled polyacrylonitrile precursor fiber samples.

[0082] Step S400: Perform a second drying treatment on the degreased polyacrylonitrile precursor sample to obtain a second mass of dried degreased polyacrylonitrile precursor sample.

[0083] In at least one embodiment, the step of performing a second drying treatment on the degreased polyacrylonitrile precursor sample to obtain a second mass of dried degreased polyacrylonitrile precursor sample includes: placing the degreased polyacrylonitrile precursor sample into a weighing dish; placing the weighing dish into a drying oven at a fifth preset temperature and drying for a third preset time; placing the dried weighing dish containing the degreased polyacrylonitrile precursor sample into a desiccant and cooling it to a fourth preset temperature; weighing the fifth mass of the dried weighing dish containing the degreased polyacrylonitrile precursor sample; and determining the second mass of the dried degreased polyacrylonitrile precursor sample based on the fifth mass and the fourth mass.

[0084] As an example, the process of performing a second drying treatment on a degreased polyacrylonitrile precursor sample to obtain a second mass of dried degreased polyacrylonitrile precursor sample includes the following steps:

[0085] First, the degreased polyacrylonitrile-based precursor fiber sample is placed in a weighing dish. This weighing dish is the same one used in step S200 for the first drying treatment of the polyacrylonitrile-based precursor fiber sample. Therefore, the mass of this weighing dish is known to be the fourth mass, i.e., m4.

[0086] Then, the samples are dried. Specifically, the weighing dishes are placed in a drying oven at 120℃±3℃ for 1 hour. In this way, by controlling the temperature and time of the drying oven, the condition of the samples during drying is ensured, avoiding excessive reduction in the validity of the sample data.

[0087] Next, after drying, the sample is cooled. Specifically, the weighing dish containing the dried polyacrylonitrile-based precursor fiber sample is placed in a desiccator and cooled to room temperature, for example, 23℃±3℃.

[0088] Then, after cooling, weighing is performed. Specifically, the fifth mass m5 of the weighing dish containing the dried polyacrylonitrile-based precursor fiber sample is weighed.

[0089] Finally, based on the difference between the fifth and fourth masses, the second mass m2 of the dried and degreased polyacrylonitrile precursor sample is determined, i.e., m2 = m5 - m4.

[0090] Step S500: Determine the oil content of the polyacrylonitrile precursor fiber based on the first and second masses.

[0091] As an example, the oil content of polyacrylonitrile precursor fibers can be calculated using the formula: Q = [(m1-m2) / m1] × 100%.

[0092] Where Q is the oil content (%) of the polyacrylonitrile-based precursor fiber; m1 is the first mass in g; and m2 is the second mass in g.

[0093] It should be understood that the test results are based on the arithmetic mean of at least two samples. If the difference between two parallel tests exceeds 20%, the test must be repeated. Therefore, this test method is simple to learn, provides accurate data, and can quickly and accurately analyze the oil content of polyacrylonitrile-based carbon fiber precursor.

[0094] Based on the above embodiments, in at least one embodiment, the weighing dish used in steps S200 and S400 is an aluminum round box with a lid, which can effectively prevent polyacrylonitrile-based precursor fibers from absorbing water during the weighing process, thereby affecting the weighing results.

[0095] Based on the above embodiments, in at least one embodiment, the operations involving obtaining the mass of the polyacrylonitrile-based precursor fiber sample in the above steps all include repeated drying, cooling, and weighing operations until a constant weight is reached, i.e., the difference between two consecutive weighings does not exceed 0.05% of the latter weighing. This improves the accuracy of the data involved in the testing process.

[0096] Based on the above embodiments, in some embodiments, the detection method further includes: dissolving potassium hydroxide in ethanol to obtain a potassium hydroxide ethanol solution of a preset concentration, wherein the preset concentration ranges from 1.5% to 2.5%. That is, in step S300, a potassium hydroxide ethanol solution of 1.5%-2.5% concentration is used as an alkaline detergent. For example, the concentration of the potassium hydroxide ethanol solution is any one of 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, and 2.5%.

[0097] Based on the above embodiments, such as Figure 13 and Figure 14 As shown, in some embodiments, at least one of the first and second dehydration processes employs centrifugal dehydration. The centrifuge 10 used in the centrifugal dehydration process includes centrifuge tubes 20 and a water-permeable isolation structure disposed at the bottom of the centrifuge tubes 20, configured to reduce the risk of contact between the polyacrylonitrile-based precursor sample to be dehydrated and the liquid at the bottom of the centrifuge tubes 20.

[0098] As an example, in step S300, the first and second dehydration processes involved in washing the dried polyacrylonitrile precursor sample with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample are both performed using a centrifuge. Furthermore, the centrifuge 10 used in this dehydration process includes a centrifuge tube 20 and a water-permeable isolation structure located at the bottom of the centrifuge tube 20. This water-permeable isolation structure reduces the risk of one end of the sample (filamentous) falling to the bottom of the centrifuge tube 20 without affecting the outflow of centrifuged water.

[0099] It should be understood that the above example only illustrates a specific implementation of the first and second dehydration processes and does not limit them. For example, the first dehydration process can be achieved by wringing, or the second dehydration process can be achieved by wringing. The specific solution can be designed according to actual needs, and will not be elaborated here.

[0100] Based on the above embodiments, such as Figure 13 and Figure 14 As shown, in some embodiments, the centrifuge 10 further includes a centrifuge body 11, which has a centrifuge tube groove 12 for accommodating centrifuge tubes 20, and is configured to centrifuge the centrifuge tubes 20. The water-permeable isolation structure is a support 21, which extends spirally along the length of the centrifuge tubes 20. In at least one embodiment, the support 20 is made of metal.

[0101] As an example, the centrifuge tube is recessed, and the centrifuge body centrifuges the centrifuge tube. The centrifuge tube is placed in the centrifuge tube slot of the centrifuge body, and a support is provided at the bottom of the centrifuge tube. Specifically, the support is a wire ring that spirals upward along the length of the centrifuge tube (from the bottom of the centrifuge tube to the opening).

[0102] It should be understood that the water-permeable isolation structure is not limited to the aforementioned spiral-extended support; it can also adopt other design methods, such as using a structure formed of composite porous materials and setting it at the bottom of the centrifuge tube.

[0103] As an example, the following describes a method for detecting the oil content of polyacrylonitrile precursor fibers, based on the solutions described in the above embodiments.

[0104] First, two sets of AC45-3K, AC45-12K, and AC55-12K polyacrylonitrile-based precursor fibers, totaling 10g, were taken to prepare six sets of polyacrylonitrile-based precursor fiber samples. After accurate weighing, each sample was placed in a pre-weighed aluminum box (with a lid). The aluminum box (containing the sample) was then placed in a 120℃ drying oven for 1 hour. The dried sample was then placed in a desiccator to cool to room temperature and weighed (m1). Specific weighing procedures can be found in the above embodiments and will not be repeated here.

[0105] Then, the six labeled sample bags (containing six groups of polyacrylonitrile-based precursor fiber samples) were placed in 100 mL of a 1.5%-2.5% potassium hydroxide ethanol solution and washed at a stirring speed of 200-250 rpm for a preset time under a 50°C water bath. The six groups of polyacrylonitrile-based precursor fiber samples washed with the potassium hydroxide ethanol solution were then dehydrated, specifically by centrifugation at 4000 rpm for 2 minutes. Specific procedures can be found in the above embodiment and will not be repeated here.

[0106] Next, the six groups of polyacrylonitrile-based precursor fiber samples, after being washed with potassium hydroxide ethanol solution, were repeatedly rinsed three times in a 65°C three-stage water bath to remove residual detergent from the fiber surface. The rinsed polyacrylonitrile-based precursor fiber samples were then dehydrated by centrifugation at 4000 rpm for 2 minutes. Specific procedures can be found in the above-described embodiments and will not be repeated here.

[0107] After rinsing, the sample is weighed. Specifically, the aluminum box (containing the washed and rinsed polyacrylonitrile-based precursor fiber sample) is opened and placed in a 120℃ drying oven for 1 hour. The dried polyacrylonitrile-based precursor fiber sample is then placed in a desiccator and cooled to room temperature, for example, 23℃±3℃, and its weight (m2) is measured. For details on the weighing procedure, please refer to the above embodiment, which will not be repeated here.

[0108] Finally, the oil content of the polyacrylonitrile-based precursor fiber is calculated using the formula.

[0109] Based on the operations of the above embodiments, this embodiment first tests the effect of the concentration of alkaline washing solution in the detection scheme on the measurement results. The test results are shown in Table 1, which shows the oil content of polyacrylonitrile-based precursor fibers under different schemes. The specific contents are as follows:

[0110] The first method uses a 1.5% potassium hydroxide ethanol solution (1.5g potassium hydroxide dissolved in 100mL ethanol). The solution is stirred at low speed in a water bath for 40 minutes. Other steps are the same as in the previous example and will not be repeated here. The final oil content of the polyacrylonitrile precursor sample under these conditions, and the scanning electron microscope images of the polyacrylonitrile precursor sample after washing with the potassium hydroxide ethanol solution, are shown below. Figure 2 and Figure 3 .

[0111] The second method uses a 2% potassium hydroxide ethanol solution (1g potassium hydroxide dissolved in 50mL ethanol). The solution is stirred at low speed in a water bath for 40 minutes. Other steps are the same as in the previous example and will not be repeated here. The final oil content of the polyacrylonitrile precursor sample under these conditions, and the scanning electron microscope images of the polyacrylonitrile precursor sample after washing with the potassium hydroxide ethanol solution, are shown below. Figure 4 and Figure 5 .

[0112] The third method uses a 2.5% potassium hydroxide ethanol solution (1g potassium hydroxide dissolved in 40mL ethanol). The solution is stirred at low speed in a water bath for 40 minutes. Other steps are the same as in the previous example and will not be repeated here. The final oil content of the polyacrylonitrile precursor sample under these conditions, and the scanning electron microscope images of the polyacrylonitrile precursor sample after washing with the potassium hydroxide ethanol solution, can be found in [link to relevant documentation]. Figure 6 and Figure 7 .

[0113] It should be understood that the polyacrylonitrile precursor samples used in the above three test schemes are of the same specification.

[0114] Table 1. Oil content of polyacrylonitrile precursor fibers under different schemes

[0115]

[0116]

[0117] Theoretically, the higher the concentration of alkaline detergent, the more thoroughly the oil will be removed from the polyacrylonitrile precursor fiber sample, resulting in a higher oil content in the final sample. Referring to Table 1 and the scanning electron microscope images:

[0118] In the first scheme, the test results of the polyacrylonitrile precursor sample were significantly lower than the theoretical value. Furthermore, electron microscopy revealed that a large amount of oil stains remained on the surface of the polyacrylonitrile precursor sample, proving that the ratio of potassium hydroxide ethanol solution could not completely remove the oil from the surface of the polyacrylonitrile precursor.

[0119] In the second scheme, the test results of the polyacrylonitrile precursor sample were consistent with the theoretical values. Furthermore, electron microscopy showed that there were no oil stains on the surface of the polyacrylonitrile precursor sample, proving that the potassium hydroxide ethanol solution in this scheme could completely remove the oil from the surface of the polyacrylonitrile precursor.

[0120] In the third scheme, the test results of the polyacrylonitrile precursor sample were relatively lower than the theoretical value. Furthermore, electron microscopy showed that there were no oil stains on the surface of the polyacrylonitrile precursor sample, proving that the potassium hydroxide ethanol solution in this scheme could completely remove the oil from the surface of the polyacrylonitrile precursor. However, a large amount of debris was attached to the surface, which was considered to be due to the excessive concentration of alkaline detergent. During the subsequent drying process, the potassium hydroxide adhered to the surface of the precursor after drying, causing the test results to deviate from the theoretical value.

[0121] Therefore, it is not true that the higher the concentration of alkaline detergent, the more accurate the oil content test result of the polyacrylonitrile precursor fiber. The concentration of alkaline detergent, especially potassium hydroxide ethanol solution, can be selected between 1.5% and 2.5% to obtain an oil content test result of polyacrylonitrile precursor fiber that is less different from the theoretical value.

[0122] Furthermore, based on the above embodiments, this embodiment also tests the time required for low-speed stirring in a water bath when washing with a 2% potassium hydroxide ethanol solution. The test results are shown in Table 2 for the oil content of polyacrylonitrile-based precursor fibers under different conditions, and the specific details are as follows:

[0123] In the first condition, the polyacrylonitrile precursor fiber sample was washed with a 2% potassium hydroxide ethanol solution (1g potassium hydroxide dissolved in 50mL ethanol) and stirred at low speed in a water bath for 40min during the washing process. The detection results under this condition can be seen in the verification process above (the detection results of the second scheme). That is, the detection results of the polyacrylonitrile precursor fiber sample are consistent with the theoretical values, and scanning electron microscopy shows that the oil stains on the surface of the polyacrylonitrile precursor fiber sample are relatively smooth. This proves that, under the premise of a 2% potassium hydroxide ethanol solution, stirring at low speed in a water bath for 40min during the washing process yields highly accurate detection results. The scanning electron microscopy image of the polyacrylonitrile precursor fiber sample washed with potassium hydroxide ethanol solution is shown below. Figure 4 and Figure 5 .

[0124] Therefore, in order to improve detection efficiency and shorten detection time, a second set of conditions was designed by controlling the concentration of potassium hydroxide ethanol solution to 2% and changing the low-speed stirring time in the water bath.

[0125] In the second condition, the polyacrylonitrile precursor fiber sample was washed with a 2% potassium hydroxide ethanol solution (1 g potassium hydroxide dissolved in 50 mL ethanol), and the mixture was stirred at low speed in a water bath for 30 min during the washing process. Other steps were the same as in the above embodiment and will not be repeated here. The final oil content of the polyacrylonitrile precursor fiber sample under these conditions, and the scanning electron microscope image of the polyacrylonitrile precursor fiber sample after washing with the potassium hydroxide ethanol solution, can be found in [reference needed]. Figure 8 and Figure 9 .

[0126] Table 2 shows the oil content of polyacrylonitrile precursor fibers under different conditions.

[0127]

[0128] After shortening the low-speed stirring time in the water bath, data comparison showed that the test results of the samples under the stirring condition of 30 minutes were lower than the theoretical values. Furthermore, scanning electron microscopy revealed that a small amount of oil stains still adhered to the sample surface, proving that this stirring time was insufficient to completely remove the oil from the surface of the raw silk. Therefore, stirring at low speed in the water bath for 40 minutes yielded the best experimental results.

[0129] Therefore, the oil content of polyacrylonitrile-based precursor fibers of different specifications was detected using a 2% potassium hydroxide ethanol solution (1 g potassium hydroxide dissolved in 50 mL ethanol) and low-speed stirring in a water bath for 40 min. Specific results are shown in Table 3.

[0130] See the scanning electron microscope image of the AC45-3K washed polyacrylonitrile precursor fiber sample. Figure 10 Scanning electron microscope images of the AC45-12K washed polyacrylonitrile precursor fiber sample are shown below. Figure 11 Scanning electron microscope images of the AC55-12K washed polyacrylonitrile precursor fiber sample are shown below. Figure 12 For specific instructions, please refer to the above embodiments, which will not be repeated here.

[0131] Table 3. Oil content of polyacrylonitrile precursor fibers of different specifications

[0132]

[0133] In this disclosure, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase “comprising…” does not exclude the presence of additional identical elements in the article or device that includes that element.

[0134] Although preferred embodiments of the present disclosure have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this disclosure.

[0135] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from its spirit and scope. Thus, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, the intent of this disclosure also includes these modifications and variations.

Claims

1. A method for detecting the oil content of polyacrylonitrile-based precursor fibers, characterized in that, The detection method includes: Preparation of polyacrylonitrile-based precursor fiber samples; The polyacrylonitrile-based precursor fiber sample is subjected to a first drying treatment to obtain a first mass of dried polyacrylonitrile-based precursor fiber sample. The dried polyacrylonitrile precursor sample was washed with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample. The degreased polyacrylonitrile precursor sample is subjected to a second drying treatment to obtain a second mass of the dried degreased polyacrylonitrile precursor sample. The oil content of the polyacrylonitrile precursor fiber is determined based on the first mass and the second mass. The steps for washing the dried polyacrylonitrile precursor sample with an alkaline detergent to obtain a degreased polyacrylonitrile precursor sample include: The dried polyacrylonitrile precursor sample is placed in a first container, which contains a first preset volume of alkaline detergent, the alkaline detergent comprising a potassium hydroxide ethanol solution of a preset concentration. Place the first container in a water bath at a first preset temperature and stir the liquid in the first container at a preset speed for a first preset time. Take out the polyacrylonitrile-based precursor fiber sample from the first container and perform the first dehydration treatment; The polyacrylonitrile precursor fiber sample after the above dehydration treatment was rinsed in a water bath at a second preset temperature. The rinsed polyacrylonitrile precursor fiber sample was subjected to a second dehydration treatment to obtain the degreased polyacrylonitrile precursor fiber sample. The first preset temperature is 50°C, the volume ratio of the water bath to the alkaline detergent is at least 20:1, the preset speed ranges from 200r / min to 250r / min, and the first preset time ranges from 30min to 40min. The second preset temperature range is 60℃-70℃, and the water used in the water bath at the second preset temperature is grade III water.

2. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 1, characterized in that, The detection method further includes: The potassium hydroxide is dissolved in the ethanol to obtain a potassium hydroxide ethanol solution of a preset concentration, wherein the preset concentration ranges from 1.5% to 2.5%.

3. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 1, characterized in that, At least one of the first dehydration treatment and the second dehydration treatment is performed by centrifuge dehydration; The centrifuge used in the centrifuge dehydration method includes centrifuge tubes and a water-permeable isolation structure. The water-permeable isolation structure is located at the bottom of the centrifuge tubes and is configured to reduce the risk of the polyacrylonitrile-based precursor sample to be dehydrated coming into contact with the liquid at the bottom of the centrifuge tubes.

4. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 3, characterized in that, The centrifuge also includes: The centrifuge body is provided with a centrifuge tube trough for accommodating the centrifuge tubes, and the centrifuge body is configured to centrifuge the centrifuge tubes. The water-permeable isolation structure is a support, which extends spirally along the length of the centrifuge tube.

5. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 4, characterized in that, The bracket is made of metal.

6. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 1, characterized in that, There are multiple dried polyacrylonitrile precursor fiber samples, and the step of placing the dried polyacrylonitrile precursor fiber samples into the first container includes: Each of the dried polyacrylonitrile precursor fiber samples was placed in a separate sample bag, which had multiple mesh openings.

7. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to any one of claims 1-6, characterized in that, The steps of performing a first drying treatment on the polyacrylonitrile-based precursor fiber to obtain a first mass of dried polyacrylonitrile-based precursor fiber sample include: Place the polyacrylonitrile-based precursor fiber sample into a weighing dish; Place the weighing dish in a drying oven at a third preset temperature and dry it for a second preset time; Place the dried weighing dish containing the polyacrylonitrile-based precursor fiber sample into a desiccant and cool it to the fourth preset temperature. Weigh the third mass of the weighing dish containing the dried polyacrylonitrile-based precursor fiber sample; The dried polyacrylonitrile-based precursor fiber sample was removed from the weighing dish, and the fourth mass of the dried weighing dish was measured. The first mass of the dried polyacrylonitrile-based precursor fiber sample is determined based on the third mass and the fourth mass.

8. The method for detecting the oil content of polyacrylonitrile-based precursor fibers according to claim 7, characterized in that, The steps of performing a second drying treatment on the degreased polyacrylonitrile precursor sample to obtain a second mass of the dried degreased polyacrylonitrile precursor sample include: Place the degreased polyacrylonitrile-based precursor fiber sample into the weighing dish; Place the weighing dish in a drying oven at a fifth preset temperature and dry it for a third preset time; Place the dried weighing dish containing the degreased polyacrylonitrile-based precursor fiber sample into a desiccant and cool it to the fourth preset temperature. The fifth mass of the weighing dish containing the dried, degreased polyacrylonitrile-based precursor fiber sample is weighed. The second mass of the dried, degreased polyacrylonitrile precursor sample is determined based on the fifth mass and the fourth mass.

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