A method for quantitatively detecting the hydroxyl value of hydroxy-terminated polybutadiene compounds

Abstract

The present invention proposes a method for quantitatively detecting the hydroxyl value of terminal hydroxyl polybutadiene compounds, and belongs to the technical field of detection of high molecular polymers. The method comprises the following steps: using a mixed monolayer loading method or a three-layer loading method, HTPB sample solution, DCTB matrix solution and silver trifluoroacetate solution are applied to a sample target, dried naturally, and co-crystallized between the sample solution and the matrix solution to form a thin layer, and the thin layer is subjected to MALDI-TOF MS analysis to obtain a sample ion peak, and the sample ion peak is calibrated, and the amount of the substance of the terminal hydroxyl polybutadiene is calculated according to the number average molecular weight of the terminal hydroxyl polybutadiene, and the content of the terminal hydroxyl group is calculated according to the ratio of different hydroxyl end structures. The method for quantitatively detecting the terminal hydroxyl value of a polymer of the present invention has simple sample preparation, high accuracy, no strict requirements on the purity of the sample, rapid data acquisition, simple processing, and is more suitable for rapid quantitative detection.

Description

Technical Field

[0001] The invention belongs to the technical field of high molecular polymer detection, and in particular relates to a method for quantitatively detecting the hydroxyl value of a hydroxy-terminated polybutadiene compound. Background Art

[0002] Hydroxyl-terminated polybutadiene (HTPB) is commonly known as hydroxy-butyl rubber. It can react with chain extenders and crosslinkers at room temperature or high temperature to generate a curing agent with a three-dimensional network structure. It has properties such as acid and alkali resistance, wear resistance, and low temperature resistance. It can be used as an adhesive, damping material, cast elastomer, and seal, etc. It is widely used in the electronics industry, aerospace technology, and building materials. Different applications require hydroxy-butyl rubber to have different physical and chemical properties, so it is necessary to comprehensively, accurately, and quickly characterize various physical and chemical properties during production and use. Among them, hydroxyl is the active group of HTPB and plays a decisive role in forming a cross-linked network. The hydroxyl value is a quantitative description of the number of hydroxyl groups in a unit mass sample. The amount of hydroxyl value and the size of the functionality are important indicators that determine the performance of hydroxyl-terminated polymers. It varies with the molecular weight of the polymer and is crucial to polymer modification.

[0003] There are many methods reported to determine the hydroxyl value, including chemical analysis, spectroscopy, nuclear magnetic resonance, etc. The chemical analysis method is mainly carried out by titration. For example, when determining the hydroxyl value of HTPB, the national standard adopts the acetic anhydride-toluenesulfonic acid method; when determining the phenolic hydroxyl group in polyphenylene ether, the phenolic hydroxyl group is reacted with 4-methoxybenzoyl chloride to generate HCl, and then a standard potassium hydroxide aqueous solution is used to titrate the HCl generated by the reaction to calculate the phenolic hydroxyl value. However, this type of method is relatively cumbersome to operate, and the titration endpoint is difficult to control. In addition, near-infrared spectroscopy and gel permeation chromatography can be used to determine the number average molecular weight. The hydroxyl value can be calculated based on the molecular weight, but this method has certain requirements on the sample quantity and purity, which increases the difficulty of sample preparation. The nuclear magnetic resonance method can use the internal standard method to quantitatively test the hydroxyl value, such as the peak of the polyester terminal hydroxyl group and other 1 The spectral peaks of H do not overlap. Styrene is used as the internal standard, and the amount of α-H on the same carbon as the hydroxyl group is measured by the internal standard method. The hydroxyl content in the polyester is then calculated from the ratio with the hydroxyl group, and then the polyester hydroxyl value is calculated. This method requires that the sample must be soluble, and that the target signal cannot overlap with other signals. Hydroxyl groups are not easy to detect directly.

[0004] Matrix-assisted laser desorption ionization flight mass spectrometry (MALDI-TOF MS) can accurately analyze the relative molecular mass, repeating units, terminal groups, and block length of high molecular weight polymers. It has the characteristics of low sample usage, fast analysis speed, high resolution, and wide detection mass range. Separation and identification can be performed simultaneously, and it can provide multi-faceted information about polymers. At present, MALDI-TOF MS uses the internal standard quantitative method to achieve quantitative detection of perfluorooctane sulfonic acid (PFOS) in environmental water samples; the mass spectrometry double internal standard method can be used to detect nucleic acids, proteins, small molecule peptides, etc., introducing standard samples and using oligonucleotides of known concentrations for double internal standard calibration; curve fitting is currently a commonly used quantitative test method. However, there is currently no method for directly quantitatively detecting the terminal hydroxyl value of polymers using MALDI-TOF MS. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for quantitatively detecting the hydroxyl value of terminal hydroxyl polybutadiene compounds. The method has simple sample preparation, high accuracy, no strict requirements on the purity of the sample, rapid data collection, simple processing process, and is more suitable for rapid quantitative detection.

[0006] To achieve the above object, the present invention provides a method for quantitatively detecting the hydroxyl value of a hydroxy-terminated polybutadiene compound, comprising the following steps:

[0007] (1) dissolving hydroxyl-terminated polybutadiene (HTPB) in tetrahydrofuran (THF) to obtain a sample solution, dissolving a matrix in tetrahydrofuran (THF) to obtain a matrix solution, and dissolving silver trifluoroacetate (CF3COOAg) in tetrahydrofuran (THF) to obtain a silver trifluoroacetate solution;

[0008] (2) using a mixed monolayer loading method, the sample solution, the matrix solution and the silver trifluoroacetate solution are mixed, and the mixture is shaken and stirred to obtain a mixed solution. 1 μL of the mixed solution is measured with a pipette and applied to the sample target, and the mixture is dried naturally. The sample solution and the matrix solution are co-crystallized to form a thin layer;

[0009] Alternatively, using the three-layer loading method, first use a pipette to measure 1 μL of silver trifluoroacetate solution and spot it on the target plate, then take 1 μL of matrix solution and spot it on the target plate after drying, and finally take 1 μL of sample solution and spot it on the target plate, dry it naturally, and the sample solution and matrix solution will co-crystallize to form a thin layer;

[0010] (3) performing MALDI-TOF MS analysis on the thin layer to obtain sample ion peaks;

[0011] (4) calibrating the sample ion peaks and calculating the terminal group structure of each ion peak and the number average molecular weight of the hydroxyl-terminated polybutadiene;

[0012] (5) Integrate the peak intensity of the sample ions, calculate the average peak intensity of different end group structures, and obtain the ratio of different hydroxyl end-capping structures;

[0013] (6) The amount of the hydroxyl-terminated polybutadiene is calculated based on the number average molecular weight of the hydroxyl-terminated polybutadiene, and the content of the terminal hydroxyl group is calculated based on the ratio of different hydroxyl-terminated structures.

[0014] Furthermore, before step (1), the method further includes a step of calibrating the mass of the instrument using a polystyrene standard.

[0015] Furthermore, in step (1), the substrate is trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB).

[0016] Furthermore, in step (1), the concentration of the sample solution is 10 mg / mL, the concentration of the matrix solution is 10-20 mg / mL, and the concentration of the silver trifluoroacetate solution is 10 mg / mL.

[0017] Furthermore, in step (2), the volume ratio of the sample solution, the matrix solution and the silver trifluoroacetate solution is 10:(25-30):5.

[0018] Furthermore, in step (3), the MALDI-TOF MS analysis adopts positive ion linear mode, the scanning range is 1000-9000 m / z, the acceleration voltage / ion source voltage is 19.5 V, the laser type is LTBMNL100 (106PD) V002.61, the laser frequency is 60 Hz, the temperature is 39°C, the sampling rate is 1.00 GS / s, the grating point shooting range is 50, the detector overflow voltage linear base oscillation is 2400 V, the laser irradiation energy range is 40%-50%, the cumulative shooting is 100 times, and the molecular weight range is 1000-10000 Da.

[0019] Further, in step (4), according to the sample ion peak, according to the formula M n =[M n (repeating unit)*n+M n (Ag + ion)+M n (end group)], and calculate the end group structure of each ion peak.

[0020] Furthermore, in step (4), the mass spectrum data is imported into FlexAnalysis software, the ion peaks in the mass spectrum are calibrated, and mass lists are generated. Then, PolyTools is opened for data analysis, the original spectra are matched, and the parameters are adjusted, including the mass spectrum starting molecular weight, repeating unit, end group, ion salt, etc., to calculate the number average molecular weight of the hydroxy-terminated polybutadiene.

[0021] Furthermore, in step (5), the sample ion peak intensity is integrated using FlexAnalysis software.

[0022] Furthermore, in step (6), the amount of the hydroxyl-terminated polybutadiene is calculated based on the number average molecular weight of the hydroxyl-terminated polybutadiene:

[0023] The content of terminal hydroxyl groups (mmol / g)=(n+n*R) / g is calculated according to the ratio of different hydroxyl-terminated structures, where R is the ratio of dihydroxy-terminated polybutadiene in different hydroxyl-terminated structures.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The method for quantitatively detecting the hydroxyl value of terminal hydroxyl polybutadiene compounds of the present invention has simple sample preparation, high test result accuracy, strong tolerance for polymer samples, no strict requirements on sample purity, rapid data collection (data can be obtained in 5 to 10 seconds), simple processing process, and is more suitable for rapid quantitative detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 This is the instrument calibration chart for determination using polypropylene oxide of different molecular weights;

[0028] Figure 2 These are the MALDI-TOF crystallization images of HTPB tested by the target, where a is the crystallization image of Example 1 using the three-layer loading method, and b is the crystallization image of Example 2 using the mixed single-layer loading method.

[0029] Figure 3 This is a MALDI-TOF image of HTPB tested by the three-layer loading method in Example 1;

[0030] Figure 4 This is a partial enlarged view of the MALDI-TOF image collected in Example 1;

[0031] Figure 5 This is a MALDI-TOF image of HTPB tested by the mixed monolayer loading method in Example 2;

[0032] Figure 6 This is a partial enlarged view of the MALDI-TOF image collected in Example 2;

[0033] Figure 7 This is a MALDI-TOF image of HTPB tested by the mixed monolayer loading method in Example 3;

[0034] Figure 8 This is a partial enlarged view of the MALDI-TOF image collected in Example 3;

[0035] Fig. 9 This is a MALDI-TOF image of HTPB in Example 4 after preparing a sample using a DCTB matrix with a concentration of 20 mg / L and then mixed with a single layer loading method for spot target testing;

[0036] Fig.10 This is a partial enlarged view of the MALDI-TOF image collected in Example 4. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] Prior to the present invention, the instrument was calibrated using polystyrene standards, specifically:

[0043] (1) Using polystyrene standards (PS, M n =13000) mass calibration of the instrument: weighing 10 mg of polystyrene, dissolving it in 1 mL of THF solution to prepare a polystyrene solution with a concentration of 10 mg / mL; dissolving silver trifluoroacetate in THF to prepare a silver trifluoroacetate solution with a final concentration of 10 mg / mL, weighing 1 mg of DCTB and dissolving it in 100 μL of THF to obtain a matrix solution, mixing the polystyrene solution, the matrix solution and the silver trifluoroacetate solution in a volume ratio of 5:25:1, taking 1 μL of the mixed solution and spotting it on the target plate, using linear positive ion mode to collect data, collecting the MALDI-TOF mass spectrum of the polystyrene standard, and calibrating the polystyrene ion peak using the standard ion peak within the preset mass range;

[0044] (2) In order to verify the accuracy of the calibration, the MALDI-TOF mass spectra of poly(propylene oxide) (PO) with different molecular weights were tested. The molecular weights of poly(propylene oxide) are as follows: 500, 1000, 2000, 3000, 4000, 5000, 8000 and 12000. THF was used as the solvent to prepare 10 mg / mL PO solution, 20 mg / mL DCTB solution and 5 mg / mL sodium trifluoroacetate solution. The three were mixed in a volume ratio of 5:25:4 for testing. The linear positive ion mode was used to collect data to obtain a series of mass spectra. The average molecular weight and number of repeating units of each poly(propylene oxide) sample were calculated and plotted using origin. The instrument calibration chart for the determination of poly(propylene oxide) with different molecular weights is shown in Figure 2. Figure 1 , R 2 >0.99.

[0045] The instrument used in the embodiment of the present invention is a Microflex LRF series MALDI-TOF MS produced by Bruker.

[0046] The HTPB used in the examples of the present invention was purchased from Junxiang Technology, with a model of HB-50 and a hydroxyl value of 0.53 mmol / g.

[0047] The technical solution of the present invention is further illustrated by the following embodiments.

[0048] Example 1

[0049] (1) dissolving HTPB in THF to obtain a sample solution with a concentration of 10 mg / mL, dissolving DCTB in THF to obtain a matrix solution with a concentration of 10 mg / mL, and dissolving silver trifluoroacetate in THF to obtain a silver trifluoroacetate solution with a concentration of 10 mg / mL;

[0050] (2) Select a 96-well stainless steel target plate for spotting. Use the three-layer loading method to firstly take 1 μL of silver trifluoroacetate solution with a pipette and spot it on the target plate. After drying, take 1 μL of matrix solution and spot it on the target plate. Finally, take 1 μL of sample solution and spot it on the target plate. Dry it naturally. The sample solution and the matrix solution co-crystallize to form a thin layer.

[0051] (3) The thin layer was subjected to MALDI-TOF MS analysis, using positive ion linear mode LP-12KDa, a scan range of 1000-9000 m / z, an acceleration voltage / ion source voltage of 19.5V, a laser type of LTBMNL100(106PD)V002.61, a laser frequency of 60Hz, a temperature of 39°C, a sampling rate of 1.00GS / s, a grating point shooting range of 50, a detector overflow voltage linear base oscillation of 2400V, an energy range of laser irradiation of 40%, a cumulative shooting of 100 times, a time consumption of 5s, a molecular weight range of 1000-10000Da, and a sample ion peak was obtained (MALDI-TOF figure, Figure 3 ), Figure 4 This is a partial enlarged view of the MALDI-TOF image collected in Example 1, showing three groups of ion peaks;

[0052] (4) Import the obtained mass spectrum data into FlexAnalysis software and calibrate the sample ion peak. n =[M n (repeating unit)*n+M n (Ag + ion)+M n (end group)], calculate the end group structure of each ion peak, and the results show that there are two types of terminal hydroxyl groups, one is dihydroxyl end-capping and the other is monohydroxyl end-capping; import the obtained mass spectrum data into FlexAnalysis software, calibrate the ion peaks in the mass spectrum, generate mass lists, and then open PolyTools for data analysis, match the original spectrum, adjust the parameters, including mass spectrum starting molecular weight, repeating unit, end group, ion salt, etc., and calculate the number average molecular weight of terminal hydroxyl polybutadiene

[0053] (5) The FlexAnalysis software was used to integrate the peak intensity of the sample ions, and the average peak intensity of the two different terminal structures was calculated to obtain the ratio of different hydroxyl-terminated structures. The dihydroxy-terminated polybutadiene accounted for 82.2%, and the monohydroxy-terminated polybutadiene accounted for 17.8%;

[0054] (6) Calculate the amount of hydroxyl-terminated polybutadiene based on the number average molecular weight of the hydroxyl-terminated polybutadiene: (calculated based on a unit mass of 1 mg), and based on the ratio of different hydroxyl-terminated structures, the content of terminal hydroxyl groups (mmol / g) = (n+n*82.2%) / g = 0.574 mmol / g was calculated.

[0055] Example 2

[0056] (1) dissolving HTPB in THF to obtain a sample solution with a concentration of 10 mg / mL, dissolving DCTB in THF to obtain a matrix solution with a concentration of 10 mg / mL, and dissolving silver trifluoroacetate in THF to obtain a silver trifluoroacetate solution with a concentration of 10 mg / mL;

[0057] (2) Select a 96-well stainless steel target plate for spotting, and adopt a mixed monolayer loading method to mix the sample solution, matrix solution and silver trifluoroacetate solution in a volume ratio of 10:25:5, shake and stir to obtain a mixed solution, use a pipette to measure 1 μL of the mixed solution and spot it on the sample target, dry it naturally, and the sample solution and matrix solution co-crystallize to form a thin layer;

[0058] (3) The thin layer was subjected to MALDI-TOF MS analysis, using positive ion linear mode LP-12KDa, a scan range of 1000-9000 m / z, an acceleration voltage / ion source voltage of 19.5V, a laser type of LTBMNL100(106PD)V002.61, a laser frequency of 60Hz, a temperature of 39°C, a sampling rate of 1.00GS / s, a grating point shooting range of 50, a detector overflow voltage linear base oscillation of 2400V, an energy range of laser irradiation of 45%, a cumulative shooting of 100 times, a time consumption of 5s, a molecular weight range of 1000-10000Da, and a sample ion peak (MALDI-TOF figure, Figure 5 ), Figure 6 Then Figure 5 A partial magnification of the acquired MALDI-TOF image, showing three groups of ion peaks;

[0059] (4) Import the obtained mass spectrum data into FlexAnalysis software and calibrate the sample ion peak. n =[M n (repeating unit)*n+M n (Ag+ ion)+M n (end group)], calculate the end group structure of each ion peak, and the results show that there are two types of terminal hydroxyl groups, one is dihydroxyl end-capping and the other is monohydroxyl end-capping; import the obtained mass spectrum data into FlexAnalysis software, calibrate the ion peaks in the mass spectrum, generate mass lists, and then open PolyTools for data analysis, match the original spectrum, adjust the parameters, including mass spectrum starting molecular weight, repeating unit, end group, ion salt, etc., and calculate the number average molecular weight of terminal hydroxyl polybutadiene

[0060] (5) The FlexAnalysis software was used to integrate the peak intensity of the sample ions, and the average peak intensity of the two different terminal structures was calculated to obtain the ratio of different hydroxyl-terminated structures. The dihydroxy-terminated polybutadiene accounted for 82.3%, and the monohydroxy-terminated polybutadiene accounted for 17.7%;

[0061] (6) Calculate the amount of hydroxyl-terminated polybutadiene based on the number average molecular weight of the hydroxyl-terminated polybutadiene: (calculated based on a unit mass of 1 mg), and according to the ratio of different hydroxyl-terminated structures, the content of terminal hydroxyl groups (mmol / g) = (n+n*82.3%) / g = 0.576 mmol / g was calculated.

[0062] Figure 2 These are the MALDI-TOF crystallization images of HTPB tested by the target, where a is the crystallization image of Example 1 using the three-layer loading method, and b is the crystallization image of Example 2 using the mixed single-layer loading method.

[0063] Example 3

[0064] (1) dissolving HTPB in THF to obtain a sample solution with a concentration of 10 mg / mL, dissolving DCTB in THF to obtain a matrix solution with a concentration of 10 mg / mL, and dissolving silver trifluoroacetate in THF to obtain a silver trifluoroacetate solution with a concentration of 10 mg / mL;

[0065] (2) Select a 96-well stainless steel target plate for spotting, and adopt a mixed monolayer loading method to mix the sample solution, matrix solution and silver trifluoroacetate solution in a volume ratio of 10:30:5, shake and stir to obtain a mixed solution, use a pipette to measure 1 μL of the mixed solution and spot it on the sample target, dry it naturally, and the sample solution and matrix solution co-crystallize to form a thin layer;

[0066] (3) The thin layer was subjected to MALDI-TOF MS analysis, using positive ion linear mode LP-12KDa, a scan range of 1000-9000 m / z, an acceleration voltage / ion source voltage of 19.5V, a laser type of LTBMNL100(106PD)V002.61, a laser frequency of 60Hz, a temperature of 39°C, a sampling rate of 1.00GS / s, a grating point shooting range of 50, a detector overflow voltage linear base oscillation of 2400V, an energy range of laser irradiation of 50%, a cumulative shooting of 100 times, a time consumption of 5s, a molecular weight range of 1000-10000Da, and a sample ion peak (MALDI-TOF figure, Figure 7 ), Figure 8 Then Figure 7 A partial magnification of the acquired MALDI-TOF image, showing three groups of ion peaks;

[0067] (4) Import the obtained mass spectrum data into FlexAnalysis software and calibrate the sample ion peak. n =[M n (repeating unit)*n+M n (Ag + ion)+M n (end group)], calculate the end group structure of each ion peak, and the results show that there are two types of terminal hydroxyl groups, one is dihydroxyl end-capping and the other is monohydroxyl end-capping; import the obtained mass spectrum data into FlexAnalysis software, calibrate the ion peaks in the mass spectrum, generate mass lists, and then open PolyTools for data analysis, match the original spectrum, adjust the parameters, including mass spectrum starting molecular weight, repeating unit, end group, ion salt, etc., and calculate the number average molecular weight of terminal hydroxyl polybutadiene

[0068] (5) The FlexAnalysis software was used to integrate the peak intensity of the sample ions, and the average peak intensity of the two different terminal structures was calculated to obtain the ratio of different hydroxyl-terminated structures. The dihydroxy-terminated polybutadiene accounted for 82.4%, and the monohydroxy-terminated polybutadiene accounted for 17.6%;

[0069] (6) Calculate the amount of hydroxyl-terminated polybutadiene based on the number average molecular weight of the hydroxyl-terminated polybutadiene: (calculated based on a unit mass of 1 mg), and according to the ratio of different hydroxyl-terminated structures, the content of terminal hydroxyl groups (mmol / g) = (n+n*82.4%) / g = 0.565 mmol / g was calculated.

[0070] Example 4

[0071] Same as Example 2, except that HTPB was dissolved in THF to obtain a sample solution with a concentration of 10 mg / mL, DCTB was dissolved in THF to obtain a matrix solution with a concentration of 20 mg / mL, and silver trifluoroacetate was dissolved in THF to obtain a silver trifluoroacetate solution with a concentration of 10 mg / mL. Calculation of the number average molecular weight of hydroxy-terminated polybutadiene The dihydroxyl-terminated polybutadiene accounts for 82.1%, the monohydroxyl-terminated polybutadiene accounts for 17.9%, and the terminal hydroxyl content is 0.570 mmol / g.

[0072] Example 4: MALDI-TOF image of HTPB prepared by using 20 mg / L DCTB matrix and then mixed with monolayer loading method for spot target testing. Fig. 9 , Fig.10 This is a partial enlarged view of the MALDI-TOF image collected in Example 4.

[0073] Comparative Example 1

[0074] (1) HTPB was dissolved in THF to obtain a sample solution with a concentration of 10 mg / mL, DIT was dissolved in THF to obtain a matrix solution with a concentration of 10 mg / mL, and sodium trifluoroacetate was dissolved in THF to obtain a sodium trifluoroacetate solution with a concentration of 5 mg / mL;

[0075] (2) Select a 96-well stainless steel target plate for spotting, and adopt a mixed monolayer loading method to mix the sample solution, matrix solution and sodium trifluoroacetate solution in a volume ratio of 10:25:5, shake and stir to obtain a mixed solution, use a pipette to measure 1 μL of the mixed solution and spot it on the sample target, dry it naturally, and the sample solution and matrix solution co-crystallize to form a thin layer;

[0076] (3) The thin layer was subjected to MALDI-TOF MS analysis, and the analysis process was the same as in Example 1. It was found that the MALDI-TOF mass spectrum obtained by this method was very poor and no ion peak of the sample could be obtained.

[0077] Comparative Example 2

[0078] (1) HTPB was dissolved in THF to obtain a sample solution with a concentration of 10 mg / mL, DCTB was dissolved in THF to obtain a matrix solution with a concentration of 10 mg / mL, and sodium trifluoroacetate was dissolved in THF to obtain a sodium trifluoroacetate solution with a concentration of 5 mg / mL;

[0079] (2) Select a 96-well stainless steel target plate for spotting, and adopt a mixed monolayer loading method to mix the sample solution, matrix solution and sodium trifluoroacetate solution in a volume ratio of 10:25:5, shake and stir to obtain a mixed solution, use a pipette to measure 1 μL of the mixed solution and spot it on the sample target, dry it naturally, and the sample solution and matrix solution co-crystallize to form a thin layer;

[0080] (3) The thin layer was subjected to MALDI-TOF MS analysis, and the analysis process was the same as in Example 1. It was found that the MALDI-TOF mass spectrum obtained by this method was very poor and no ion peak of the sample could be obtained.

[0081] It can be seen from the measurement results of Examples 1-4 that the hydroxyl value calculated using the method of the present invention for quantitatively detecting the terminal hydroxyl value of the polymer is 0.57 mmol / g, which is close to the hydroxyl value provided by the manufacturer of the purchased HTPB, indicating that the method of the present invention has high accuracy.

[0082] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for quantitatively detecting the hydroxyl value of a hydroxy-terminated polybutadiene compound, characterized in that: The following steps are involved: (1) dissolving terminal hydroxyl polybutadiene in tetrahydrofuran to obtain a sample solution, dissolving a matrix in tetrahydrofuran to obtain a matrix solution, and dissolving silver trifluoroacetate in tetrahydrofuran to obtain a silver trifluoroacetate solution, wherein the matrix is ​​trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile; (2) using a mixed monolayer loading method, the sample solution, the matrix solution and the silver trifluoroacetate solution are mixed to obtain a mixed solution, 1 μL of the mixed solution is applied to the sample target, and dried naturally to form a thin layer; Alternatively, using a three-layer loading method, first take 1 μL of silver trifluoroacetate solution and spot it on the target plate, then take 1 μL of matrix solution and spot it on the target plate after drying, and finally take 1 μL of sample solution and spot it on the target plate, and dry it naturally to form a thin layer; the volume ratio of the sample solution, matrix solution and silver trifluoroacetate solution is 10:(25-30):5; (3) performing MALDI-TOF MS analysis on the thin layer to obtain sample ion peaks; (4) Calibrate the sample ion peak, and use the sample ion peak according to the formula M n =[M n (repeating unit)*n1+M n (Ag + ion)+M n (end group)], calculate the end group structure of each ion peak, and use PolyTools software to calculate the number average molecular weight of hydroxyl-terminated polybutadiene; (5) Integrate the peak intensity of the sample ions, calculate the average peak intensity of different terminal group structures, and obtain the ratio of different hydroxyl-terminated structures. There are two types of terminal hydroxyl groups, one is dihydroxyl-terminated and the other is monohydroxyl-terminated; (6) The amount of the hydroxy-terminated polybutadiene is calculated based on the number average molecular weight of the hydroxy-terminated polybutadiene. Calculated based on a unit mass of 1 mg, is the number average molecular weight of the hydroxyl-terminated polybutadiene, the unit is Da, the unit of the amount of substance n of the hydroxyl-terminated polybutadiene is mmol, the unit of m is mg, and the content of the terminal hydroxyl group is calculated according to the ratio of different hydroxyl-terminated structures, the content of the terminal hydroxyl group = (n + n * R) / 10 -3 , R is the proportion of dihydroxy-terminated polybutadiene in different hydroxy-terminated structures, and the unit of the terminal hydroxyl content is mmol / g.

2. The method for quantitatively detecting the hydroxyl value of hydroxy-terminated polybutadiene compounds according to claim 1, characterized in that: In step (1), the concentration of the sample solution is 10 mg / mL, the concentration of the matrix solution is 10-20 mg / mL, and the concentration of the silver trifluoroacetate solution is 10 mg / mL.

3. The method for quantitatively detecting the hydroxyl value of hydroxy-terminated polybutadiene compounds according to claim 1, characterized in that: In step (3), MALDI-TOF MS analysis adopts positive ion linear mode, the energy range of laser irradiation is 40%-50%, and the molecular weight range is 1000-10000Da.

4. The method for quantitatively detecting the hydroxyl value of hydroxy-terminated polybutadiene compounds according to claim 1, characterized in that: In step (5), the sample ion peak intensity is integrated using FlexAnalysis software.

Images