阅读说明：本技术 一种碳纤维生产过程中聚丙烯腈原丝中残余二甲亚砜含量的测试方法 (Method for testing content of residual dimethyl sulfoxide in polyacrylonitrile precursor in carbon fiber production process ) 是由 杨永岗 胡培贤 于 2020-03-27 设计创作，主要内容包括：本发明涉及一种检测方法,具体地说,是涉及一种碳纤维生产过程中聚丙烯腈原丝中残余二甲亚砜含量的测试方法,量取待测样品至圆底烧瓶,加定量去离子水混合,待溶液冷却后,配制1000mL水溶液,加入定量高锰酸钾溶液,加入稀硫酸,摇匀后,量取待测样品制成的水溶液,加入碘化钾溶液,摇匀,硫代硫酸钠溶液滴定至浅黄色,加入淀粉指示剂,继续滴至无色即为终点。本发明的测试方法,是一种可以简单、准确测试聚丙烯腈原丝中残余二甲亚砜含量的测试方法,解决了目前聚丙烯腈原丝中残余二甲亚砜含量无法准确测试,从而解决了准确控制原丝中残余二甲亚砜含量的问题。(The invention relates to a detection method, in particular to a method for testing the content of residual dimethyl sulfoxide in polyacrylonitrile precursor in the production process of carbon fiber. The testing method provided by the invention is a testing method capable of simply and accurately testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor, and solves the problem that the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor can not be accurately tested at present, so that the problem of accurately controlling the content of the residual dimethyl sulfoxide in the precursor is solved.)

1. A method for testing the content of residual dimethyl sulfoxide in polyacrylonitrile protofilament in the production process of carbon fiber is characterized by measuring a sample to be tested into a round bottom flask, adding a certain amount of deionized water for mixing, cooling the solution, preparing 1000mL of aqueous solution, adding a certain amount of potassium permanganate solution, adding dilute sulfuric acid, shaking uniformly, measuring an aqueous solution prepared from the sample to be tested, adding a potassium iodide solution, shaking uniformly, titrating a sodium thiosulfate solution to be light yellow, adding a starch indicator, and continuously dripping until the solution is colorless, namely the end point.

2. The method for testing the content of residual dimethyl sulfoxide in polyacrylonitrile precursor as claimed in claim 1, is characterized in that:

step 1: weighing 2-4 m polyacrylonitrile precursor fiber, putting the polyacrylonitrile precursor fiber into a round-bottom flask, and adding deionized water into the round-bottom flask;

step 2: adding a plurality of zeolites into a round-bottom flask, installing a condensing device at a bottle mouth, plugging absorbent cotton on the upper end of the condensing device, and heating;

and step 3: stopping heating after the aqueous solution is boiled for 3h, closing cooling water when the solution is cooled to room temperature, and leaching the condenser by using 100mL of deionized water;

and 4, step 4: transferring the solution in the round-bottom flask into a volumetric flask, and spraying the polyacrylonitrile precursor with deionized water to prepare 1000mL of aqueous solution;

and 5: putting the rinsed polyacrylonitrile protofilament into a blast drying oven to be dried for 3 hours, taking out and weighing, and recording the mass M of the protofilament₁；

Step 6: taking 25mL of potassium permanganate solution by a pipette, taking 5mL of sulfuric acid, shaking uniformly, taking 100mL of prepared polyacrylonitrile protofilament aqueous solution by the pipette, weighing on a balance, and recording the mass M of sulfoxide water₂Placing in a 250mL conical flask, adding 5mL potassium iodide solution, shaking, and standing in dark for 5 min;

and 7: titrating the mixture to light yellow by using sodium thiosulfate solution, adding 3mL of starch indicator, continuously dropping the mixture until the mixture is colorless to obtain a terminal point, and recording the volume V₁；

And 8: blank test, taking 25mL potassium permanganate solution by a pipette, taking 5mL sulfuric acid, adding 5mL potassium iodide solution, shaking up, standing in the dark for 5min, titrating to light yellow by sodium thiosulfate solution, adding 3mL starch indicator, continuously dropping until colorless to obtain the end point, and recording the volume V;

step 9 according to the formula

Aqueous solution of polyacrylonitrile precursor

(CH₃)₂SO％＝[(V-V₁)×C×0.039065/M₂]×100％

Precursor (CH)₃)₂SO% ═ aqueous solution (CH)₃)₂SO％×1000/M₁

Calculating the percentage (%) of the dimethyl sulfoxide in the polyacrylonitrile protofilament;

in the formula: m₁Raw silk mass g of dried after poaching

M₂Mass g of taking 100mL of sulfoxide aqueous solution out of 1000mL of sulfoxide aqueous solution

V: the blank test consumes the volume, mL, of the Na2S2O3 standard solution;

V₁: the volume of the Na2S2O3 standard solution consumed by the sample is mL;

c: na2S2O3 specifies the molar concentration of the solution, mol/L.

0.039065: equivalent to 1mL equivalent of sodium thiosulfate consumed the amount of dimethyl sulfoxide, g/moL

1000 weight of poached protofilament sulfoxide aqueous solution, g.

3. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: the capacity of the round-bottom flask in the step 1 is 1000mL, and the addition amount of the deionized water is 300 mL.

4. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: the zeolite in the step 2 is 8-12 zeolite, the condensing device is a spiral condenser, and the heating method is that the condensing device is placed on an electric heating sleeve for heating.

5. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: the volume of the volumetric flask in the step 4 is 1000mL, and the volume of the plasma water taken is 200 mL.

6. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: and 5, controlling the temperature in the air drying oven to be 100 +/-5 ℃.

7. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: the concentration of the potassium permanganate solution in the step 6 is 0.003mol/L, and the volume ratio of the sulfuric acid is 1: 11, the mass fraction of the potassium iodide solution is 10%.

8. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: and 7, the concentration of the sodium thiosulfate solution is 0.01-0.02 mol/L.

Technical Field

The invention relates to a test method, in particular to a test method for the content of residual dimethyl sulfoxide in polyacrylonitrile precursor in the carbon fiber production process.

Background

The polyacrylonitrile-based carbon fiber has a series of excellent service properties, such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, creep resistance, good electrical conductivity, thermal conductivity and the like, and has no replaceable application value in the field of advanced composite materials (including aerospace, aviation, advanced sports goods and the like). Dimethyl sulfoxide is generally adopted as a solvent in the production process of polyacrylonitrile, the content of the residual dimethyl sulfoxide in polyacrylonitrile protofilament is difficult to detect by the traditional method, and the content of the residual dimethyl sulfoxide in the polyacrylonitrile finished protofilament is an important factor influencing the performance of the base carbon fiber, because the plasticizing effect of the dimethyl sulfoxide enables the fiber monofilaments to be easily fused in the processing process.

The currently used method for detecting dimethyl sulfoxide in polyacrylonitrile protofilament usually adopts a spectral analysis method, i.e. a spectrophotometer or a gas chromatograph is used for performing spectral analysis on a sample to be detected. Although the method can accurately detect the content of the dimethyl sulfoxide in the polyacrylonitrile protofilament, the method has high requirements on test equipment, high cost and complex use.

Disclosure of Invention

The invention provides a test method capable of efficiently, conveniently, quickly and accurately detecting the residual dimethyl sulfoxide in polyacrylonitrile protofilament.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for testing the content of residual dimethyl sulfoxide in polyacrylonitrile protofilament in the process of carbon fiber vitamin production comprises the steps of measuring a sample to be tested into a round bottom flask, adding a certain amount of deionized water for mixing, cooling the solution, preparing 1000mL of aqueous solution, adding a certain amount of potassium permanganate solution, adding dilute sulfuric acid, shaking uniformly, measuring an aqueous solution prepared from the sample to be tested, adding a potassium iodide solution, shaking uniformly, titrating a sodium thiosulfate solution to be light yellow, adding a starch indicator, and continuously dripping until the solution is colorless, namely the end point. A blank test was run to calculate the residual acrylonitrile monomer content of the sample.

The method specifically comprises the following steps:

step 1: weighing 2-4 m polyacrylonitrile precursor fiber, putting the polyacrylonitrile precursor fiber into a round bottom flask, and adding deionized water into the round bottom flask;

step 2: adding a plurality of zeolites into a round-bottom flask, installing a condensing device at a bottle mouth, plugging absorbent cotton on the upper end of the condensing device, and heating;

and step 3: stopping heating after the aqueous solution is boiled for 3h, closing cooling water when the solution is cooled to room temperature, and leaching the condenser by using 100mL of deionized water;

and 4, step 4: transferring the solution in the round-bottom flask into a volumetric flask, and pouring the polypropylene nitrile protofilament with deionized water to prepare 1000mL of aqueous solution;

step (ii) of5: putting the rinsed polyacrylonitrile protofilament into a blast drying oven to be dried for 3 hours, taking out and weighing, and recording the mass M of the protofilament₁；

Step 6: taking 25mL of potassium permanganate solution by a pipette, taking 5mL of sulfuric acid, shaking uniformly, taking 100mL of prepared polyacrylonitrile protofilament aqueous solution by the pipette, weighing on a balance, and recording the mass M of sulfoxide water₂Placing in a 250mL conical flask, adding 5mL potassium iodide solution, shaking, and standing in dark for 5 min;

and 7: titrating the mixture to light yellow by using sodium thiosulfate solution, adding 3mL of starch indicator, continuously dropping the mixture until the mixture is colorless to obtain a terminal point, and recording the volume V₁；

And 8: blank test, taking 25mL potassium permanganate solution by a pipette, taking 5mL sulfuric acid, adding 5mL potassium iodide solution, shaking up, standing in the dark for 5min, titrating to light yellow by sodium thiosulfate solution, adding 3mL starch indicator, continuously dropping until colorless to obtain the end point, and recording the volume V;

step 9 according to the formula

Aqueous solution of polyacrylonitrile precursor

(CH₃)₂SO％＝[(V-V₁)×C×0.039065/M₂]×100％

Precursor (CH)₃)₂SO% ═ aqueous solution (CH)₃)₂SO％×1000/M₁

Calculating the percentage (%) of the dimethyl sulfoxide in the polyacrylonitrile protofilament;

in the formula: m₁Raw silk mass g of dried after poaching

M₂Mass g of taking 100mL of sulfoxide aqueous solution out of 1000mL of sulfoxide aqueous solution

V: the blank test consumes the volume, mL, of the Na2S2O3 standard solution;

V₁: the volume of the Na2S2O3 standard solution consumed by the sample is mL;

c: na2S2O3 specifies the molar concentration of the solution, mol/L.

0.039065: equivalent to 1mL equivalent of sodium thiosulfate consumed the amount of dimethyl sulfoxide, g/moL

1000 amount of poached protofilament sulfoxide aqueous solution, g

3. The method for testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile precursor in the carbon fiber production process, according to claim 2, is characterized in that: the capacity of the round-bottom flask in the step 1 is 1000mL, and the addition amount of the deionized water is 300 mL.

Further, the plurality of zeolites in the step 2 are 8-12 zeolites, the condensing device is a spiral condenser, and the heating method is that the spiral condenser is placed on an electric heating sleeve for heating.

Further, the volumetric flask described in step 4 had a volume of 1000mL and 200mL of plasma water was used.

Further, the temperature in the forced air drying oven in the step 5 is 100 +/-5 ℃.

Further, the concentration of the potassium permanganate solution in the step 6 is 0.003mol/L, and the volume ratio of the sulfuric acid is 1: 11, the mass fraction of the potassium iodide solution is 10%.

Further, the concentration of the sodium thiosulfate solution in the step 7 is 0.01-0.02mol/L, preferably 0.01033 mol/L.

Compared with the traditional method for detecting the content of the dimethyl sulfoxide residue in the polyacrylonitrile precursor, the technical scheme of the invention has the advantages that:

1) the testing method provided by the invention is a testing method capable of simply and accurately testing the content of the residual dimethyl sulfoxide in the polyacrylonitrile protofilament, and solves the problem that the content of the residual dimethyl sulfoxide in the polyacrylonitrile protofilament can not be accurately tested at present, so that the content of the residual dimethyl sulfoxide in the protofilament can be accurately controlled.

2) The testing method disclosed by the invention does not need other complex detecting instruments, can detect the content of the residual dimethyl sulfoxide by using simple experimental devices or medicines such as a flask, a balance, a condenser and a starch indicator, and has the advantages of low detection requirement and high detection efficiency.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.