Detection Method for the Distribution of Active -NCO during the HTPB -IPDI Curing Reaction Process

Abstract

The present invention discloses a method for detecting the active - NCO distribution during the curing reaction process of HTPB - IPDI block polyurethane propellant. First, prepare an IPDI standard sample solution, an isocyanate - terminated HTPB standard sample solution, and an isocyanate - terminated cross - linker standard sample solution. Then, calculate the relative correction factor of the internal standard to the IPDI standard sample and the relative correction factor of the internal standard to the isocyanate - terminated HTPB standard sample according to the gel permeation chromatograms of the above solutions. 、 The relative correction factor of the internal standard to the isocyanate - terminated cross - linker sample; Finally, obtain the mass fractions of free IPDI, isocyanate - terminated HTPB, and - NCO in the isocyanate - terminated cross - linker in the HTPB - IPDI sample according to the above relative correction factors. The present invention fills the blank in the testing of the sequence structure in the network structure of HTPB - IPDI block polyurethane propellant and can obtain the active - NCO distribution during the curing reaction process of each component of the block polyurethane.

Description

Technical Field

[0001] The present invention belongs to the technical field of real-time detection in the manufacturing process of composite solid propellants, and particularly relates to a dynamic monitoring method for the sequence structure in the curing reaction process of HTPB-IPDI block polyurethane propellants. Background Art

[0002] Composite solid propellants (grains), as an important part of solid rocket motors, are both the power source of missile engines and the structural materials that bear the load of the engine system. Therefore, it is required that the propellants have excellent mechanical properties to ensure the integrity of the engine charge structure and meet the needs of long-term storage and reliable operation of missile engines.

[0003] Composite solid propellants are energetic composites based on polyurethane, which are crosslinked and cured by isocyanate curing agents and binders, crosslinking agents, bonding agents, etc. Usually, the reactivity of these components is an important parameter for the study of the curing performance, process performance, and mechanical property analysis of propellants. In the process of propellant formulation calculation, not only the total hydroxyl value should be considered, but also the influence of the activity of hydroxyl groups in each component on the structure of the cured product should be considered. Therefore, it is very important to accurately determine the sequence structure of each component in the network structure of the propellant.

[0004] Isophorone diisocyanate (abbreviated as IPDI), with the chemical name 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, as a common curing agent for HTPB-IPDI propellants, is an aliphatic isocyanate developed by Hess Company in Germany. Corresponding to the possible orientation of the substituents on the cyclohexane, IPDI can be divided into cis (Z) and trans (E) isomers, and the structure is as Figure 2 shown. Industrial-grade IPDI is a mixture of isomers, and the ratio of isomers is approximately 77:23, mainly cis (Z).

[0005] From these 4 types of -NCO groups, the reaction of IPDI with hydroxyl groups will form 4 types of urethane groups, and there are 4 different kinetic constants (see Figure 3 ); when IPDI is in excess, it will react with the secondary amine on the urethane to produce urea groups; when water is present, IPDI will react with water to produce the corresponding urea. Therefore, the reaction kinetics may be very complex. To obtain a true kinetic equation, various side reactions must be prevented, and most importantly, the reaction must be ensured to be complete.

[0006] Due to the relatively large electron cloud density on the oxygen and nitrogen atoms in the -NCO group of the IPDI compound, its electronegativity is relatively large. The oxygen atom in the -NCO group has the largest electronegativity and is the nucleophilic center, which can attract the hydrogen atom on the molecule of the active hydrogen-containing compound to form a hydroxyl group. However, the hydroxyl group on the unsaturated carbon atom is unstable and rearranges to form a carbamate (if the reactant is an alcohol) or a urea (if the reactant is an amine). The carbon atom has the lowest electron cloud density, shows a strong positive charge, and is the electrophilic center, which is easily attacked by nucleophiles. The reaction of isocyanate with the active hydrogen compound is caused by the nucleophilic center in the active hydrogen compound molecule attacking the carbon atom of the -NCO group.

[0007] In the HTPB-IPDI propellant system, the curing process is mainly the curing reaction process of each active hydrogen component with the curing agent. Therefore, the research on the reaction mechanism of each active hydrogen component is a key point in the research of the entire HTPB-IPDI propellant curing system. The components containing active hydrogen in the HTPB-IPDI propellant mainly include components such as HTPB rubber, cross-linking agent, and functional additives. Conducting research on the monitoring and detection technology of the HTPB-IPDI propellant curing reaction process, analyzing and obtaining the reaction rates and activation energies of each reaction, and then obtaining the reaction competition relationship and reaction sequence of the active hydrogen groups in HTPB rubber, cross-linking agent, etc. Studying the influence of each active hydrogen component on the mechanical properties and cross-linking network helps to understand the microstructure of the HTPB-IPDI propellant system and the action of microscopic particles, which will provide a basis for further understanding the curing mechanism of the HTPB-IPDI propellant and has important significance.

[0008] The existing monitoring and detection methods for the IPDI-HTPB curing reaction process are limited to the testing of the content of free curing agent or the total isocyanate content in the polyurethane reaction product with simple composition. Due to the large amount of aluminum powder in the propellant, chemical titration analysis methods with hydrochloric acid as the standard titration solution cannot accurately detect; in high-performance liquid chromatography, the ultraviolet absorption of IPDI is weak, and its reaction activity is low, making it difficult to derivatize and unable to achieve quantitative detection; infrared spectroscopy can detect the reaction process of HTPB-IPDI bulk and simple systems. For systems such as propellants containing a high content of aluminum powder, due to the lack of a calibration method for the starting point, quantitative detection cannot be carried out, and only the change rate of the relative content can be obtained. At present, there is no reported quantitative method for the real-time and accurate -NCO distribution in propellants, and there is no relevant literature on the dynamic sequence structure of the propellant reaction process. Summary of the Invention

[0009] The object of the present invention is to overcome the above defects, and to provide a method for detecting the distribution of active - NCO during the curing reaction of HTPB - IPDI, which solves the technical problem that it is difficult to quantitatively detect the distribution of active - NCO during the curing reaction of existing HTPB - IPDI. The present invention fills the blank in the test of the sequence structure in the network structure of HTPB - IPDI block polyurethane propellant, and can obtain the distribution of active - NCO during the curing reaction of each component of the block polyurethane.

[0010] To achieve the above - mentioned invention object, the present invention provides the following technical solutions:

[0011] The present invention relates to a method for monitoring the distribution of active - NCO during the curing reaction of HTPB - IPDI block polyurethane propellant, which can obtain the reaction sequence of components during the curing process of cast polyurethane propellant in real - time. The GPC curve can clearly reflect the change trend of each component in the reaction system under the action of catalysts, plasticizers, moisture, and the acidity and alkalinity of the system. The method uses self - made isocyanate - terminated HTPB and isocyanate - terminated cross - linker standard samples, and uses 2,4,6 - trimethylaniline reagent with high active hydrogen as the solvent and derivatization reagent during the propellant reaction process. By separating through the GPC802 and GPC801 gel permeation chromatography combination columns and detecting the characteristic signals of the reaction terminator by an ultraviolet detector, the fine structural characteristics of the isocyanate (--NCO) connected to the binder, cross - linker, and free curing agent molecules during the propellant reaction process can be obtained, and the reaction degree and reaction status of the propellant can be detected in real - time. The method adopted by the present invention has high test sensitivity and high test accuracy for the sequence structure of block polyurethane propellant. Through the present invention, a method for monitoring the distribution of active - NCO for the curing reaction mechanism of HTPB - IPDI block polyurethane propellant cured with isophorone diisocyanate and the real - time state of the propellant can be provided, so as to achieve the purpose of freely adjusting the propellant formula.

[0012] A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction process includes:

[0013] S1 Mix 2,4,6 - trimethylaniline and toluene evenly to obtain a derivatization reaction reagent solution;

[0014] S2 Dissolve benzil as the internal standard in tetrahydrofuran to obtain an internal standard solution;

[0015] S3 After carrying out a derivatization reaction on the derivatization reaction reagent solution and the IPDI standard sample, add the internal standard solution to the obtained IPDI standard sample derivatization product to obtain an IPDI standard sample solution;

[0016] S4 cures HTPB with IPDI until the reaction is terminated when there is no free IPDI, obtaining an isocyanate-capped HTPB standard sample;

[0017] After the derivatization reaction reagent solution reacts with the isocyanate-capped HTPB standard sample, an internal standard solution is added to the obtained HTPB standard sample derivatization product to obtain an isocyanate-capped HTPB standard sample solution;

[0018] S6 cures the crosslinking agent with IPDI until the reaction is terminated when there is no free IPDI, obtaining an isocyanate-capped crosslinking agent standard sample;

[0019] After the derivatization reaction reagent solution reacts with the isocyanate-capped crosslinking agent standard sample, an internal standard solution is added to the obtained product to obtain an isocyanate-capped crosslinking agent standard sample solution;

[0020] S6 obtains the content of -NCO in the isocyanate-capped HTPB standard sample by titration; obtains the content of -NCO in the isocyanate-capped crosslinking agent standard sample by titration;

[0021] S7 obtains the gel permeation chromatograms of the IPDI standard sample solution, the isocyanate-capped HTPB standard sample solution, and the isocyanate-capped crosslinking agent standard sample solution;

[0022] S8 calculates the relative correction factor f'1 of the internal standard to the IPDI standard sample according to the gel permeation chromatogram of the IPDI standard sample solution;

[0023] Calculates the relative correction factor f'2 of the internal standard to the isocyanate-capped HTPB standard sample according to the gel permeation chromatogram of the isocyanate-capped HTPB standard sample solution and the content of -NCO in the isocyanate-capped HTPB standard sample;

[0024] Obtains the relative correction factor f'3 of the internal standard to the isocyanate-capped crosslinking agent sample according to the gel permeation chromatogram of the isocyanate-capped crosslinking agent standard sample solution and the content of -NCO in the isocyanate-capped crosslinking agent standard sample;

[0025] S9 obtains the gel permeation chromatogram of the HTPB-IPDI sample;

[0026] According to the gel permeation chromatogram of the HTPB-IPDI sample, and the relative correction factor f'1 of the internal standard to the IPDI standard sample, the relative correction factor f'2 of the internal standard to the isocyanate-capped HTPB standard sample, and the relative correction factor f'3 of the internal standard to the isocyanate-capped crosslinking agent sample, obtain the mass fractions of free IPDI, isocyanate-capped HTPB, and -NCO in the isocyanate-capped crosslinking agent in the HTPB-IPDI sample.

[0027] Further, in step S1, the concentration of benzil in the internal standard solution is 20 - 30 g / l;

[0028] In step S2, 2,4,6 - trimethylaniline and toluene are mixed evenly according to a volume ratio of 1:1 to obtain a derivatization reaction reagent solution.

[0029] Further, in step S3, the purity of the IPDI standard sample is not less than 99.9%;

[0030] In step S4, HTPB and IPDI are subjected to a curing reaction according to the ratio of curing parameter 2.0;

[0031] In step S5, the cross - linker and IPDI are subjected to a curing reaction according to the ratio of curing parameter 2.0;

[0032] In steps S3, S4, and S5, after adding the internal standard solution, dilution is also carried out using N,N - dimethylformamide.

[0033] Further, in step S6, the method for obtaining the content of - NCO in the isocyanate - terminated HTPB standard sample by titration is as follows:

[0034] S6.1.1 Take an isocyanate - terminated HTPB standard sample with a mass of m, add an excessive amount of hexahydropyridine toluene solution, and after the reaction is complete, add bromophenol blue indicator solution to obtain a blue solution;

[0035] S6.1.2 Titrate the blue solution with a hydrochloric acid standard titration solution until the blue solution turns green, and record the volume V1 of the hydrochloric acid standard titration solution consumed;

[0036] S6.1.3 Record the volume V′ of the excessive hexahydropyridine toluene solution added in step S6.1.1;

[0037] Add bromophenol blue indicator solution to the hexahydropyridine toluene solution with a volume of V′ to obtain a blue solution, titrate the blue solution with a hydrochloric acid standard titration solution until the blue solution turns green, and record the volume V2 of the hydrochloric acid standard titration solution consumed;

[0038] S6.1.4 Calculate the content X of - NCO in the isocyanate - terminated HTPB standard sample according to the following formula:

[0039]

[0040] In step S6, the method for obtaining the content of - NCO in the isocyanate - terminated cross - linker standard sample by titration is as follows:

[0041] S6.2.1 Take an isocyanate - terminated cross - linker standard sample with a mass of m1, add an excessive amount of hexahydropyridine toluene solution, and after the reaction is complete, add bromophenol blue indicator solution to obtain a blue solution;

[0042] S6.2.2 Titrate the blue solution with hydrochloric acid standard titrant until the blue solution turns green. Record the volume V1′ of hydrochloric acid standard titrant consumed.

[0043] S6.2.3: The volume of the excess hexahydropyridine toluene solution added in step S6.2.1 is V″;

[0044] Add bromophenol blue indicator to a volume V″ of hexahydropyridine toluene solution to obtain a blue solution. Titrate the blue solution with a standard hydrochloric acid solution until the blue solution turns green. Record the volume V2′ of the standard hydrochloric acid solution consumed.

[0045] S6.2.4 Calculate the -NCO content, Y, in the isocyanate-terminated crosslinker standard sample according to the following formula:

[0046]

[0047] Where c is the concentration of the standard hydrochloric acid solution and M1 is the molar mass of the isocyanate.

[0048] Furthermore, in step S7, a liquid chromatograph is used to obtain gel permeation chromatograms of the IPDI standard solution, the isocyanate-terminated HTPB standard solution, and the isocyanate-terminated crosslinker standard solution. The parameters of the liquid chromatograph include:

[0049] GPC802 and GPC801 gel permeation chromatography columns are connected in series;

[0050] The detector used was an ultraviolet-visible light detector with a detection wavelength of 235 nm;

[0051] The mobile phase was tetrahydrofuran, and the flow rate was 0.8-1.2 mL / min.

[0052] Furthermore, in step S8:

[0053]

[0054] Where m2 is the mass of -NCO in the IPDI standard solution, s n1 is the peak area of the internal standard in the gel permeation chromatogram of the IPDI standard solution, m n1 is the mass of the internal standard in the IPDI standard solution, s2 is the peak area of the IPDI standard derivatization product in the IPDI standard solution;

[0055]

[0056] Among them, m3 is the mass of -NCO in the isocyanate-capped HTPB standard sample solution, m3 = m0 × X, m0 is the mass of the isocyanate-capped HTPB standard sample added to the isocyanate-capped HTPB standard sample solution for obtaining the gel permeation chromatogram, and X is the content of -NCO in the isocyanate-capped HTPB standard sample, s n2 is the peak area of the internal standard in the isocyanate-capped HTPB standard sample solution, m n2 is the mass of the internal standard in the isocyanate-capped HTPB standard sample solution, and s3 is the peak area of the derivatization product of the isocyanate-capped HTPB standard sample in the isocyanate-capped HTPB standard sample solution;

[0057]

[0058] Among them, m4 is the mass of -NCO in the isocyanate-capped crosslinker standard sample solution, m4 = m0' × Y, m0' is the mass of the isocyanate-capped crosslinker added to the isocyanate-capped crosslinker standard sample solution for obtaining the gel permeation chromatogram, and Y is the content of -NCO in the isocyanate-capped crosslinker standard sample, s n3 is the peak area of the internal standard in the isocyanate-capped crosslinker standard sample solution, m n3 is the mass of the internal standard in the isocyanate-capped crosslinker standard sample solution, and s4 is the peak area of the derivatization product of the isocyanate-capped crosslinker in the isocyanate-capped crosslinker standard sample solution.

[0059] Further, in step S3, take n1 portions of IPDI standard samples with different masses, and after making n1 portions of the same volume of derivatization reaction reagent solution react with the n1 portions of IPDI standard samples respectively, add n1 portions of the same volume of internal standard solution to the obtained n1 portions of reaction products respectively, and after dilution with N,N-dimethylformamide, obtain n1 portions of IPDI standard sample solutions;

[0060] In step S4, take n2 portions of isocyanate-capped HTPB standard samples with different masses, and after making n2 portions of the same volume of derivatization reaction reagent solution react with the n2 portions of isocyanate-capped HTPB standard samples respectively, add n2 portions of the same volume of internal standard solution to the obtained n2 portions of reaction products respectively, and after dilution with N,N-dimethylformamide, obtain n2 portions of isocyanate-capped HTPB standard sample solutions;

[0061] In step S5, take n3 portions of isocyanate-capped crosslinker standard samples with different masses, and after making n3 portions of the same volume of derivatization reaction reagent solution react with the n3 portions of isocyanate-capped crosslinker standard samples respectively, add n3 portions of the same volume of internal standard solution to the obtained n3 portions of reaction products respectively, and after dilution with N,N-dimethylformamide, obtain n3 portions of isocyanate-capped crosslinker standard sample solutions;

[0062] In steps S3, S4, and S5, the volume of each portion of the derivatization reaction reagent solution and the internal standard solution added is equal; n1, n2, and n3 are integers greater than or equal to 1;

[0063] In step S8, n1 relative correction factors f'1 of the internal standard to the IPDI standard sample, n2 relative correction factors f'2 of the internal standard to the isocyanate-capped HTPB standard sample, and n3 relative correction factors f'3 of the internal standard to the isocyanate-capped crosslinker standard sample are obtained respectively using n1 portions of the IPDI standard sample solution, n2 portions of the isocyanate-capped HTPB standard sample solution, and n3 portions of the isocyanate-capped crosslinker standard sample solution;

[0064] In step S9, according to the gel permeation chromatogram of the HTPB-IPDI sample, and the average value f'4 of the n1 relative correction factors f'1 of the internal standard to the IPDI standard sample, the average value f'5 of the n2 relative correction factors f'2 of the internal standard to the isocyanate-capped HTPB standard sample, and the average value f'6 of the n3 relative correction factors f'3 of the internal standard to the isocyanate-capped crosslinker sample, the mass fractions of free IPDI, isocyanate-capped HTPB, and -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample are calculated.

[0065] Furthermore, in step S9, the method for obtaining the mass fractions of free IPDI, isocyanate-capped HTPB, and -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample is as follows:

[0066] S9.1 Weigh an HTPB-IPDI sample with a mass of m5. After the derivatization reaction reagent solution reacts completely with the HTPB-IPDI sample, add the internal standard solution to the resulting product to obtain an HTPB-IPDI sample solution;

[0067] S9.2 Obtain the gel permeation chromatogram of the HTPB-IPDI sample solution;

[0068] S9.3 Calculate the mass fraction w1 of free IPDI, the mass fraction w2 of isocyanate-capped HTPB, and the mass fraction w3 of -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample according to the following formula:

[0069]

[0070]

[0071]

[0072] where s A1 、s A2 、s A3are the peak areas of free IPDI, isocyanate-capped HTPB, and isocyanate-capped crosslinker in the gel permeation chromatogram of the HTPB-IPDI sample solution, m n1 is the mass of the internal standard in the IPDI standard sample solution, s n2 is the peak area of the internal standard in the gel permeation chromatogram of the HTPB-IPDI sample solution.

[0073] In steps S9.1, S3, S4, and S5, the volume of each portion of the derivatization reaction reagent solution and the internal standard solution added is equal.

[0074] Further, n1 = n2 = n3 = 5;

[0075] In step S3, 5 portions of IPDI standard samples with different masses are taken in the range of 0 - 0.6 g;

[0076] In step S4, 5 portions of isocyanate-capped HTPB standard samples with different masses are taken in the range of 0 - 9 g;

[0077] In step S5, 5 portions of isocyanate-capped crosslinker standard samples with different masses are taken in the range of 0 - 1.0 g.

[0078] Further, in step S7, it also includes:

[0079] Obtain the ratio of the peak area of the IPDI standard sample derivatization product to the peak area of the internal standard, the ratio of the peak area of the isocyanate-capped HTPB standard sample derivatization product to the peak area of the internal standard, and the ratio of the peak area of the isocyanate-capped crosslinker derivatization product to the peak area of the internal standard according to the gel permeation chromatograms of the IPDI standard sample solution, the isocyanate-capped HTPB standard sample solution, and the isocyanate-capped crosslinker standard sample solution;

[0080] Taking the concentration of n1 portions of the IPDI standard sample solution as the abscissa and the ratio of the peak area of the IPDI standard sample derivatization product to the peak area of the internal standard as the ordinate to obtain the IPDI standard sample calibration curve; taking the concentration of n2 portions of the isocyanate-capped HTPB standard sample solution as the abscissa and the ratio of the peak area of the isocyanate-capped HTPB standard sample derivatization product to the peak area of the internal standard as the ordinate to obtain the isocyanate-capped HTPB standard sample calibration curve; taking the concentration of n3 portions of the isocyanate-capped crosslinker standard sample solution as the abscissa and the ratio of the peak area of the isocyanate-capped crosslinker derivatization product to the peak area of the internal standard as the ordinate to obtain the isocyanate-capped crosslinker standard sample calibration curve;

[0081] Judge whether the IPDI standard sample calibration curve, the isocyanate-capped HTPB standard sample calibration curve, and the isocyanate-capped crosslinker standard sample calibration curve meet the linear requirement, and the linear requirement is that the correlation coefficient > 0.999;

[0082] When the linearity requirement is met, step S8 is continued; when the linearity requirement is not met, relevant steps in steps S1 to S7 are repeated to eliminate errors until the linearity requirement is met.

[0083] In other words, five IPDI standard samples with different masses are selected in the range of 0 to 0.6 g. The curve plotted with the ratio of the peak area of the IPDI derivative to the peak area of the internal standard as the ordinate and the concentration as the abscissa must meet the linearity requirement (correlation coefficient above 0.999), and be capable of accurately quantifying the -NCO mass fraction at any point within the specified range. 0.6 g is the actual maximum addition amount of IPDI in the propellant.

[0084] Five isocyanate-capped HTPB standard samples with different masses are selected in the range of 0 to 9 g. The curve plotted with the ratio of the peak area of the isocyanate-capped HTPB derivative to the peak area of the internal standard as the ordinate and the concentration as the abscissa must meet the linearity requirement (above 0.999), and be capable of accurately quantifying the -NCO mass fraction at any point within the specified range. 9 g is the actual maximum addition amount of HTPB in the propellant.

[0085] Five isocyanate-capped crosslinker standard samples with different masses are selected in the range of 0 to 1.0 g. The curve plotted with the ratio of the peak area of the isocyanate-capped crosslinker derivative to the peak area of the internal standard as the ordinate and the concentration as the abscissa must meet the linearity requirement (above 0.999), and be capable of accurately quantifying the -NCO mass fraction at any point within the specified range. 1.0 g is the actual maximum addition amount of the crosslinker in the propellant.

[0086] If the linearity requirement cannot be met, it indicates that the error in the previous steps is relatively large, making it difficult to accurately reflect the true situation of the propellant sample.

[0087] Furthermore, a method for detecting the active -NCO distribution during the HTPB-IPDI curing reaction further includes:

[0088] S10 Obtain the competitive reaction of HTPB and the crosslinker to the curing agent based on the mass fractions of -NCO in free IPDI, isocyanate-capped HTPB, and isocyanate-capped crosslinker in the HTPB-IPDI sample, and then quantitatively characterize the real-time sequence structure of the HTPB-IPDI sample.

[0089] The present invention has at least one of the following beneficial effects compared with the prior art:

[0090] (1) The present invention proposes a brand-new testing technology, filling the blank in the testing of the sequence structure in the network structure of HTPB-IPDI block polyurethane propellants, and obtaining the active -NCO distribution and its regularity during the curing reaction of each component of the block polyurethane.

[0091] (2) The present invention realizes the quantitative characterization of isocyanate (--NCO) linked to the molecules of the propellant binder, crosslinking agent, and free curing agent by using self-made isocyanate-capped HTPB, isocyanate-capped crosslinking agent standard sample, and IPDI standard sample, and can detect the reaction degree and reaction status of the propellant in real time;

[0092] (3) The present invention uses benzil as an internal standard substance, can accurately obtain the relative correction factor of —NCO in each standard sample, and can effectively improve the accuracy of the quantitative characterization of --NCO;

[0093] (4) The present invention uses the GPC curve to clearly reflect the detection method of the sequence relationship of changes in each component in the system under the action of external micro-perturbation for polymer macromolecules, and can obtain the component reaction sequence and curing process of the cast polyurethane propellant in real time;

[0094] (5) The detection method of the present invention is fast. By one injection, the differences in the reaction activities of the binder and crosslinking agent molecules in the HTPB-IPDI propellant can be obtained respectively and quantitative characterization can be realized;

[0095] (6) The present invention can obtain a monitoring and detection method for the "dynamic" sequence structure during the curing reaction of a block polyurethane propellant;

[0096] (7) The method of the present invention is simple and easy to implement, the instrument conditions are relatively easy to achieve, it has good separation efficiency and selectivity, high test accuracy, and strong reliability. Description of the Drawings

[0097] Figure 1 It is a diagram of the detection method for the distribution of active -NCO during the HTPB-IPDI curing reaction process of the present invention;

[0098] Figure 2 It is a structural diagram of IPDI isomers;

[0099] Figure 3 It is a schematic diagram of the reaction process of IPDI-HTPB;

[0100] Figure 4 It is a gel permeation chromatography (GPC) diagram of the HTPB-IPDI propellant sample of the present invention after only adding the internal standard solution;

[0101] Figure 5 It is a gel permeation chromatography (GPC) diagram of the HTPB-IPDI propellant sample of the present invention after adding the internal standard solution and the derivatization reaction reagent solution;

[0102] Figure 6 It is a gel permeation chromatography (GPC) diagram of the IPDI standard sample solution of the present invention;

[0103] Figure 7This is the gel permeation chromatography (GPC) diagram of the isocyanate-terminated HTPB standard sample solution of the present invention;

[0104] Figure 8 This is the gel permeation chromatography (GPC) diagram of the isocyanate-terminated crosslinker standard sample solution of the present invention. Detailed implementation manners

[0105] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite along with these descriptions.

[0106] The special term "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here does not have to be interpreted as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0107] The traditional detection method can only detect the content of residual curing agent, and it is impossible to obtain the distribution of the remaining -NCO in a complex system.

[0108] The purpose of the present invention is to provide a testing method, which can be used for testing the -NCO distribution during the curing reaction process of HTPB-IPDI block polyurethane propellant, and can also obtain the dynamic sequence structure during the propellant reaction process, that is, to achieve the purpose of freely adjusting the propellant formula. By studying the reaction characteristics of small molecule components and the hydroxyl groups of the binder, it is beneficial to optimize the block polyurethane propellant formula to achieve the purpose of freely adjusting the propellant formula. It has important guiding value for optimizing the network structure of HTPB-IPDI block polyurethane propellant.

[0109] The present invention provides a derivatization testing method that can identify both high-molecular-weight (HTPB) and detect medium (crosslinker) and low-molecular-weight substances (free IPDI). After separation by a gel permeation chromatography column, the peak area of the reaction terminator is obtained through a UV detector, and the content of isocyanate (-NCO) connected to the binder, crosslinker, and residual curing agent molecules during the propellant reaction process is obtained by calculation, so as to obtain the real-time -NCO distribution state.

[0110] In the above-mentioned monitoring and detection method for the curing reaction process of HTPB-IPDI block polyurethane propellant, the termination reaction uses 2,4,6-trimethylaniline to quickly terminate, dissolve and react with -NCO connected to the high-molecular-weight binder, medium-molecular-weight crosslinker, and part of the residual curing agent at one end.

[0111] The above-mentioned method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant, wherein the isocyanate - terminated cross - linker standard sample used for making the calibration curve is prepared by the synthesis method of isocyanate - terminated cross - linker.

[0112] Use the self - made isocyanate - terminated HTPB standard sample and isocyanate - terminated cross - linker standard sample to make a calibration curve for quantitative detection of the target.

[0113] The above - mentioned method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant, wherein the separation column is a gel permeation chromatography column combined with GPC802 and GPC802.

[0114] The above - mentioned method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant, wherein the gel permeation chromatography test uses an ultraviolet - visible light detector, the mobile phase is tetrahydrofuran, the flow rate is 1.0 mL / min, and the detection wavelength is 235 nm.

[0115] Compared with the prior art, the present invention not only establishes a new testing technology, fills the blank in the testing of the sequence structure in the network structure of HTPB - IPDI block polyurethane propellant, and obtains the distribution and regularity of active - NCO in the curing reaction process of each component of the block polyurethane. Moreover, this method is simple and easy to operate, the instrument conditions are relatively easy to achieve, it has good separation efficiency and selectivity, high testing accuracy and strong reliability.

[0116] The following further illustrates the testing process of the method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant of the present invention through examples.

[0117] Example:

[0118] A method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant can obtain the competitive reaction of components such as adhesives and cross - linkers to the curing agent in real - time during the propellant reaction process, fully identify and quantitatively detect the reaction characteristics of high, medium, and low - molecular - weight substances in the propellant that occur in real - time, and achieve the purpose of freely adjusting the propellant formula. At the same time, it also solves the problem of no detection signal for each component of HTPB - IPDI propellant. The detection method of the present invention quantitatively characterizes the sequence structure of the block polyurethane propellant by determining the reaction activity order of each linking unit in the curing process of the energetic polyurethane.

[0119] Specifically, as Figure 1 , the method for monitoring the distribution of active - NCO in the curing reaction process of HTPB - IPDI block polyurethane propellant includes the following steps:

[0120] Preparation of Standard Solutions

[0121] 1.1 Preparation of Internal Standard Solution

[0122] Weigh about 2 - 3 g of benzil, accurate to 0.0001 g, place it in a 100 mL volumetric flask, dilute it to the mark with tetrahydrofuran, and shake well. Benzil is used as the internal standard because it does not react with the components of HTPB - IPDI propellant, has a strong ultraviolet absorption signal, the relative correction factor with the standard sample is close to 1, and the detection error is smaller. At the same time, the concentration of the internal standard solution in this step is appropriate, and the generated signal intensity is high and does not exceed the detection range of the instrument.

[0123] 1.2 Preparation of Derivatization Reaction Reagent Solution

[0124] Mix 2,4,6 - trimethylaniline and toluene in a ratio of 1:1 and set aside. 2,4,6 - trimethylaniline is used as the derivatization reaction reagent to undergo an addition reaction with -NCO on HTPB containing isocyanate, cross - linker containing isocyanate, and free IPDI, introducing a benzene ring quantitatively on these target substances, which can solve the problem that there is no detection signal for the components of HTPB - IPDI propellant. Moreover, the benzene ring of 2,4,6 - trimethylaniline contains an electron - donating group -CH3, and the electron - donating group on the benzene ring can increase the electronegativity of -N- on the amino group through the electron - induction effect, thus facilitating the progress of the carbamate addition reaction and reacting quickly with -NCO in the propellant. It is the aniline - type compound with the highest reactivity with -NCO among the amine - based compounds with benzene rings discovered so far. Through it, the detection sensitivity of gel permeation chromatography can be greatly improved, and the detection limit can be increased. At the same time, the concentration of the 1:1 mixed solution in this step is appropriate, the reaction rate is moderate, and no side reactions occur.

[0125] 1.3 Preparation of IPDI Standard Sample Solution

[0126] Weigh 5 IPDI standard samples of 0 - 0.6 g, accurate to 0.0001 g, place them in 5 100 mL volumetric flasks respectively, add 20 mL of derivatization reaction reagent solution, dissolve and let stand for 30 min - 60 min to make IPDI react completely with 2,4,6 - trimethylaniline. Use a pipette to transfer 5.00 mL of the internal standard solution prepared in step 1.1 into each of the five volumetric flasks, add N,N - dimethylformamide to dilute to the mark, and mix well. The auxiliary solvent for the termination product is N,N - dimethylformamide. The reaction product of IPDI and 2,4,6 - trimethylaniline is a solid powder and is likely to precipitate from the reaction reagent. It is necessary to select a specific reagent (N,N - dimethylformamide) to dissolve the final product after the propellant is completely dissolved to terminate the reaction in order to accurately quantify.

[0127] 1.4 Preparation and Preparation of HTPB and Cross - linker Standard Solutions

[0128] 1.4.1 Isocyanate-Terminated HTPB Standard Sample

[0129] 1.4.1.1 Preparation of Isocyanate-Terminated HTPB Standard Sample

[0130] Weigh 45 g to 55 g of HTPB binder with a hydroxyl value in the range of 0.47 mmol / g to 0.53 mmol / g into a glass beaker, and weigh in the curing agent IPDI according to the ratio of curing parameter 2.0, accurate to 0.0001 g. Stir for 10 min, and place it in an electrothermal constant temperature oven at 60 ± 1 °C for reaction for 12 hours (or terminate the reaction when no free IPDI is detected by chromatography) to obtain the isocyanate-terminated HTPB standard sample.

[0131] 1.4.1.2 Calibration of Isocyanate-Terminated HTPB Standard Sample

[0132] Take out 3 g to 4 g of the above isocyanate-terminated HTPB standard sample and put it into an iodine flask, add 10 mL of toluene and 20.00 mL of hexahydropyridine toluene solution, shake to completely dissolve the sample. Let it stand for 15 min. Add 100 mL of anhydrous ethanol and 5 drops of bromophenol blue indicator solution, and titrate with a hydrochloric acid standard titration solution until the solution changes from blue to green as the end point. Then perform a blank titration.

[0133] The -NCO content linked to the prepared isocyanate-terminated HTPB standard sample is calculated according to formula (1):

[0134]

[0135] In the formula:

[0136] X——-NCO content in the isocyanate-terminated HTPB standard sample, %(m / m);

[0137] V2——Volume of hydrochloric acid standard titration solution consumed in blank titration, mL;

[0138] V1——Volume of hydrochloric acid standard titration solution consumed in titrating the sample, mL;[[ID=�3]]

[0139] c——Actual concentration of hydrochloric acid standard titration solution, mol / L;

[0140] m——Mass of each isocyanate-terminated HTPB standard sample actually weighed during calibration, g;

[0141] 42.02—Molar mass of isocyanate, g / mol.

[0142] 1.4.2 Isocyanate-Terminated Crosslinker Standard Sample

[0143] 1.4.2.1 Preparation of Isocyanate-Terminated Crosslinker Standard Sample

[0144] Weigh 10 g of a crosslinking agent with a hydroxyl value in the range of 2.8 mmol / g to 3.0 mmol / g into a glass beaker, and weigh in the curing agent IPDI according to the ratio of curing parameter 2.0, accurate to 0.0001 g. Stir for 10 min, and place it in an electrothermal constant temperature oven at 60 ± 1 °C for reaction for 12 hours (or terminate the reaction when no free IPDI is detected by chromatography) to obtain an isocyanate-terminated crosslinking agent standard sample.

[0145] 1.4.1.2 Calibration of the isocyanate-terminated crosslinking agent standard sample

[0146] Take out 0.65 g to 0.70 g of the above isocyanate-terminated crosslinking agent standard sample and put it into an iodine flask, add 10 mL of toluene and 20.00 mL of hexahydropyridine toluene solution, and shake to completely dissolve the sample. Let it stand for 15 min. Add 100 mL of anhydrous ethanol and 5 drops of bromophenol blue indicator solution, and titrate with a hydrochloric acid standard titration solution until the solution changes from blue to green as the end point. Then perform a blank titration.

[0147] The -NCO content linked to the prepared isocyanate-terminated crosslinking agent standard sample is calculated according to Equation (2):

[0148]

[0149] In the formula:

[0150] Y—the -NCO content in the isocyanate-terminated crosslinking agent standard sample, %(m / m);

[0151] V2′—the volume of the hydrochloric acid standard titration solution consumed in the blank titration, mL;

[0152] V1′—the volume of the hydrochloric acid standard titration solution consumed in the titration of the sample, mL;

[0153] c—the actual concentration of the hydrochloric acid standard titration solution, mol / L;

[0154] m1—the mass of each isocyanate-terminated crosslinking agent standard sample actually weighed during calibration, g;

[0155] 42.02—the molar mass of isocyanate, g / mol.

[0156] 1.5 Preparation of the isocyanate-terminated HTPB standard sample solution

[0157] Weigh 5 standard samples of isocyanate-terminated HTPB with a series of different masses ranging from 0 to 9 g, accurate to 0.0001 g. Respectively place them in five 100 mL volumetric flasks. Add 20 mL of the derivatization reaction reagent solution prepared in Step 1.2, dissolve and react for 30 min to 60 min to complete the derivatization reaction. Use a pipette to transfer 5.00 mL of the internal standard solution prepared in Step 1.1 into each of the five volumetric flasks, add N,N-dimethylformamide to dilute to the mark, and mix well.

[0158] 1.6 Preparation of the standard solution of isocyanate-terminated crosslinking agent

[0159] Weigh 5 standard samples of isocyanate-terminated crosslinking agent with a series of different masses ranging from 0 to 1.0 g, accurate to 0.0001 g. Respectively place them in five 100 mL volumetric flasks. Add 20 mL of the reaction reagent solution prepared in Step 1.2, dissolve and react for 30 min to 60 min to complete the reaction. Use a pipette to transfer 5.00 mL of the internal standard solution prepared in Step 1.1 into each of the five volumetric flasks, add N,N-dimethylformamide to dilute to the mark, and mix well.

[0160] 1.7 Determination of relative correction factor

[0161] 1.7.1 Start the high-performance liquid chromatograph and debug the instrument according to the following analysis conditions.

[0162] a) Connect the GPC802 and GPC801 gel permeation chromatography columns in series;

[0163] b) Ultraviolet-visible light detector;

[0164] c) The mobile phase is tetrahydrofuran;

[0165] d) The flow rate is 1.0 mL / min;

[0166] e) The detection wavelength is 235 nm;

[0167] 1.7.2 After the instrument is stable, use a microsyringe to respectively take 10 μL of the solutions prepared in Steps 1.3, 1.5, and 1.6, inject the samples and analyze them. The gel permeation chromatography (GPC) diagrams of the IPDI standard sample solution, the isocyanate-terminated HTPB standard sample solution, and the isocyanate-terminated crosslinking agent standard sample solution obtained are respectively as Figure 6 、 Figure 7 and Figure 8 ;

[0168] 1.7.3 The relative correction factors of the internal standard to the IPDI, isocyanate-terminated HTPB, and isocyanate-terminated crosslinking agent standard samples are calculated according to formulas (3), (4), and (5) respectively:

[0169]

[0170]

[0171]

[0172] In the formula:

[0173] f'1 —— The relative correction factor of the internal standard to the IPDI standard sample;

[0174] m2 —— The value of the -NCO mass in the IPDI standard sample, g;

[0175] s n1 —— The value of the peak area of the internal standard in the IPDI standard sample solution;

[0176] m n1 —— The value of the mass of the internal standard in the IPDI standard solution, g;

[0177] s2 —— The value of the peak area of IPDI in the IPDI standard solution.

[0178] f'2 —— The relative correction factor of the internal standard to the isocyanate - terminated HTPB standard sample;

[0179] m3 —— The -NCO mass in the isocyanate - terminated HTPB standard sample (mass of the isocyanate - terminated HTPB standard sample taken × X), g;

[0180] s n2 —— The value of the peak area of the internal standard in the isocyanate - terminated HTPB standard sample solution;

[0181] m n2 —— The value of the mass of the internal standard in the isocyanate - terminated HTPB standard sample solution, g;

[0182] s3 —— The value of the peak area of isocyanate - terminated HTPB in the isocyanate - terminated HTPB standard sample solution.

[0183] f'3 —— The relative correction factor of the internal standard to the isocyanate - terminated cross - linker standard sample;

[0184] m4 —— The -NCO mass in the isocyanate - terminated cross - linker standard sample (mass of the isocyanate - terminated cross - linker standard sample taken × Y), g;

[0185] s n3 —— The value of the peak area of the internal standard in the isocyanate - terminated cross - linker standard sample solution;

[0186] m n3 —— The value of the mass of the internal standard in the isocyanate - terminated cross - linker standard sample solution, g;

[0187] s4—the numerical value of the peak area of the isocyanate - terminated cross - linker in the isocyanate - terminated cross - linker standard sample solution.

[0188] Taking the ratios of the peak areas of IPDI, isocyanate - terminated HTPB, and isocyanate - terminated cross - linker to the peak area of the internal standard in the standard solutions (IPDI standard solution, isocyanate - terminated HTPB standard solution, isocyanate - terminated cross - linker standard solution) as the ordinate and the standard solution concentration as the abscissa to plot the internal standard standard working curve (calibration curve), when the correlation coefficient is not less than 0.999, it meets the detection requirements for accurately quantifying the - NCO mass fraction at any point within the specified range.

[0189] Calculate the relative correction factors of each standard sample to obtain the quantitative results during the multi - component reaction process of the propellant.

[0190] The average relative correction factor f'4 of free IPDI is obtained by taking the average of the relative correction factors (f'1) of five internal standards for the IPDI standard sample detected from the IPDI standard solution in 1.3.

[0191] The average relative correction factor f'5 of isocyanate - terminated HTPB is obtained by taking the average of the relative correction factors (f'2) of five internal standards for the isocyanate - terminated HTPB standard sample detected from the isocyanate - terminated HTPB standard solution in 1.5.

[0192] The average relative correction factor f'6 of isocyanate - terminated cross - linker is obtained by taking the average of the relative correction factors (f'3) of five internal standards for the isocyanate - terminated cross - linker standard sample detected from the isocyanate - terminated cross - linker standard solution in 1.6.

[0193] The obtained average relative correction factor results are all retained to four significant figures.

[0194] 1.8 Determination of Samples

[0195] 1.8.1 Preparation of sample solutions: Weigh two portions of the sample, approximately 5 g each, accurate to 0.0001 g, and place them in two 100 - mL volumetric flasks respectively. Add 20 mL of the reaction reagent 1.2 solution, dissolve and react for 30 min - 60 min. Pipette 5.00 mL of the internal standard solution specified in 1.1 into each of the two sample solutions, add N,N - dimethylformamide to dilute to the mark, and mix well. The GPC diagrams before and after derivatization are respectively as Figure 4 and Figure 5 , from which it can be seen that the derivatization of the present invention can produce obvious ultraviolet absorption peaks.

[0196] 1.8.2 After the instrument is stabilized, use a micro-syringe to take 10 μL of the sample solution prepared in Step 1.8.1, inject the sample, stop collecting data after 30 min, and record the chromatogram.

[0197] 1.8.3 The typical GPC chromatogram of the sample solution is shown in Figure 5 .

[0198] 1.9 Result calculation

[0199] The mass fractions of free IPDI, isocyanate-capped HTPB, and isocyanate-capped crosslinking agent in the sample are calculated according to formulas (6), (7), and (8) respectively:

[0200]

[0201]

[0202]

[0203] In the formula:

[0204] w1—the numerical value of the mass fraction of -NCO in free IPDI in the sample, %;

[0205] s A1 —the numerical value of the peak area of free IPDI in the sample;

[0206] f'4—the average relative correction factor of the internal standard to the free IPDI standard sample.

[0207] w2—the numerical value of the mass fraction of -NCO in isocyanate-capped HTPB in the sample, %;

[0208] s A2 —the numerical value of the peak area of isocyanate-capped HTPB in the sample;

[0209] f'5—the average relative correction factor of the internal standard to the isocyanate-capped HTPB standard sample;

[0210] m5—the numerical value of the sample mass, g;

[0211] s n2 —the numerical value of the internal standard peak area in the sample;

[0212] w3—the numerical value of the mass fraction of -NCO in isocyanate-capped crosslinking agent in the sample, %;

[0213] s A3 —the numerical value of the peak area of isocyanate-capped crosslinking agent in the sample;

[0214] f'6—the average relative correction factor of the internal standard to the isocyanate-capped crosslinking agent standard sample.

[0215] The difference between the two parallel determination values of the -NCO mass fraction in isocyanate-terminated HTPB is not more than 0.01%, the difference between the two parallel determination values of the -NCO mass fraction in isocyanate-terminated crosslinker is not more than 0.001%, and the difference between the two parallel determination values of the -NCO mass fraction in free IPDI is not more than 0.01%. The measurement results are expressed as the arithmetic mean, retaining four significant figures after the decimal point.

[0216] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0217] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction process, characterized in that, Including: S1 Mix 2,4,6-trimethylaniline and toluene evenly to obtain a derivatization reaction reagent solution; S2 Dissolve benzil as the internal standard in tetrahydrofuran to obtain an internal standard solution; S3 After carrying out a derivatization reaction on the derivatization reaction reagent solution and the IPDI standard sample, add the internal standard solution to the obtained IPDI standard sample derivatization product to obtain an IPDI standard sample solution; S4 Carry out a curing reaction on HTPB and IPDI until there is no free IPDI, then terminate the reaction to obtain an isocyanate-terminated HTPB standard sample; After carrying out a derivatization reaction on the derivatization reaction reagent solution and the isocyanate-terminated HTPB standard sample, add the internal standard solution to the obtained HTPB standard sample derivatization product to obtain an isocyanate-terminated HTPB standard sample solution; S6 Carry out a curing reaction on the crosslinking agent and IPDI until there is no free IPDI, then terminate the reaction to obtain an isocyanate-terminated crosslinking agent standard sample; After carrying out a derivatization reaction on the derivatization reaction reagent solution and the isocyanate-terminated crosslinking agent standard sample, add the internal standard solution to the obtained product to obtain an isocyanate-terminated crosslinking agent standard sample solution; S8 Obtain the content of -NCO in the isocyanate-terminated HTPB standard sample by titration method; obtain the content of -NCO in the isocyanate-terminated crosslinking agent standard sample by titration method; S9 Obtain the gel permeation chromatogram of the HTPB-IPDI sample; S10 Calculate the relative correction factor f'1 of the internal standard to the IPDI standard sample according to the gel permeation chromatogram of the IPDI standard sample solution; Calculate the relative correction factor f'2 of the internal standard to the isocyanate-terminated HTPB standard sample according to the gel permeation chromatogram of the isocyanate-terminated HTPB standard sample solution and the content of -NCO in the isocyanate-terminated HTPB standard sample; Obtain the relative correction factor f'3 of the internal standard to the isocyanate-terminated crosslinking agent sample according to the gel permeation chromatogram of the isocyanate-terminated crosslinking agent standard sample solution and the content of -NCO in the isocyanate-terminated crosslinking agent standard sample; S13 Obtain the gel permeation chromatogram of the HTPB-IPDI sample; According to the gel permeation chromatogram of the HTPB-IPDI sample, as well as the relative correction factor f'1 of the internal standard to the IPDI standard sample, the relative correction factor f'2 of the internal standard to the isocyanate-terminated HTPB standard sample, and the relative correction factor f'3 of the internal standard to the isocyanate-terminated crosslinking agent sample, obtain the mass fractions of free IPDI, isocyanate-terminated HTPB, and -NCO in the isocyanate-terminated crosslinking agent in the HTPB-IPDI sample; In step S6, the method for obtaining the content of -NCO in the isocyanate-terminated HTPB standard sample by titration method is: S6.1.1 Take an isocyanate-terminated HTPB standard sample with a mass of m, add an excessive amount of hexahydropyridine toluene solution and react completely, then add bromophenol blue indicator solution to obtain a blue solution; S6.1.2 Titrate the blue solution with a hydrochloric acid standard titration solution until the blue solution turns green, and record the volume V1 of the hydrochloric acid standard titration solution consumed; In step S6.1.3, record the volume of the excessive piperidine toluene solution added in step S6.1.1 as V'; Add bromophenol blue indicator solution to the piperidine toluene solution with a volume of V' to obtain a blue solution, and titrate the blue solution with a standard hydrochloric acid titrant until the blue solution turns green, and record the volume V2 of the consumed standard hydrochloric acid titrant; In step S6.1.4, calculate the content X of -NCO in the isocyanate-capped HTPB standard sample according to the following formula: In step S6, the method for obtaining the content of -NCO in the isocyanate-capped crosslinker standard sample by titration method is as follows: In step S6.2.1, take an isocyanate-capped crosslinker standard sample with a mass of m1, add an excessive piperidine toluene solution and react completely, then add bromophenol blue indicator solution to obtain a blue solution; In step S6.2.2, titrate the blue solution with a standard hydrochloric acid titrant until the blue solution turns green, and record the volume V1' of the consumed standard hydrochloric acid titrant; In step S6.2.3, record the volume of the excessive piperidine toluene solution added in step S6.2.1 as V''; Add bromophenol blue indicator solution to the piperidine toluene solution with a volume of V'' to obtain a blue solution, and titrate the blue solution with a standard hydrochloric acid titrant until the blue solution turns green, and record the volume V2' of the consumed standard hydrochloric acid titrant; In step S6.2.4, calculate the content Y of -NCO in the isocyanate-capped crosslinker standard sample according to the following formula: Wherein, c is the concentration of the standard hydrochloric acid titrant, and M1 is the molar mass of the isocyanate; In step S7, use a liquid chromatograph to obtain the gel permeation chromatograms of the IPDI standard sample solution, the isocyanate-capped HTPB standard sample solution and the isocyanate-capped crosslinker standard sample solution. The parameters of the liquid chromatograph include: GPC802 and GPC801 gel permeation chromatographic columns are connected in series; The detector uses an ultraviolet-visible light detector, and the detection wavelength is 235 nm; The mobile phase is tetrahydrofuran, and the flow rate is 0.8 - 1.2 mL / min.

2. The method for detecting the active - NCO distribution in the HTPB - IPDI curing reaction process according to claim 1, wherein, In step S1, the concentration of benzil in the internal standard solution is 20 - 30 g / l; In step S2, mix 2,4,6-trimethylaniline and toluene evenly according to a volume ratio of 1:1 to obtain a derivatization reaction reagent solution.

3. A method for detecting the distribution of active - NCO in the HTPB - IPDI curing reaction process according to claim 1, characterized in that, The purity of the IPDI standard sample in step S3 is not less than 99.9%; In step S4, carry out a curing reaction with HTPB and IPDI according to the ratio of curing parameter 2.0; In step S5, carry out a curing reaction with the crosslinker and IPDI according to the ratio of curing parameter 2.0; In steps S3, S4, and S5, it also includes diluting with N,N-dimethylformamide after adding the internal standard solution.

4. The method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction process according to claim 1, wherein In step S8: where m2 is the mass of -NCO in the IPDI standard solution, s n1 is the peak area of the internal standard in the gel permeation chromatogram of the IPDI standard solution, m n1 is the mass of the internal standard in the IPDI standard solution, and s2 is the peak area of the IPDI standard derivative in the IPDI standard solution; Among them, m3 is the mass of -NCO in the isocyanate-capped HTPB standard solution, m3 = m0×X, m0 is the mass of the isocyanate-capped HTPB standard added to the isocyanate-capped HTPB standard solution for obtaining the gel permeation chromatogram, X is the content of -NCO in the isocyanate-capped HTPB standard, s n2 is the peak area of the internal standard in the isocyanate-capped HTPB standard solution, m n2 is the mass of the internal standard in the isocyanate-capped HTPB standard solution, and s3 is the peak area of the derivatization product of the isocyanate-capped HTPB standard in the isocyanate-capped HTPB standard solution; Among them, m4 is the mass of -NCO in the isocyanate - terminated cross - linker standard solution, m4 = m0′×Y, m0′ is the mass of the isocyanate - terminated cross - linker added to the isocyanate - terminated cross - linker standard solution for obtaining the gel permeation chromatography diagram, Y is the content of -NCO in the isocyanate - terminated cross - linker standard, s n3 is the peak area of the internal standard in the isocyanate - terminated cross - linker standard solution, m n3 is the mass of the internal standard in the isocyanate - terminated cross - linker standard solution, and s4 is the peak area of the derivative product of the isocyanate - terminated cross - linker in the isocyanate - terminated cross - linker standard solution.

5. A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction according to claim 1, characterized in that, In step S3, take n1 portions of different masses of the IPDI standard sample, make n1 portions of the same volume of the derivatization reaction reagent solution react with n1 portions of the IPDI standard sample respectively, then add n1 portions of the same volume of the internal standard solution to the obtained n1 portions of reaction products, and after diluting with N,N-dimethylformamide, obtain n1 portions of IPDI standard sample solutions; In step S4, take n2 portions of isocyanate-capped HTPB standards with different masses. After allowing n2 portions of the same volume of derivatization reaction reagent solution to react with the n2 portions of isocyanate-capped HTPB standards respectively, add n2 portions of the same volume of internal standard solution to the resulting n2 reaction products, and after dilution with N,N-dimethylformamide, obtain n2 portions of isocyanate-capped HTPB standard solutions; In step S5, take n3 portions of isocyanate-capped crosslinker standards with different masses. After allowing n3 portions of the same volume of derivatization reaction reagent solution to react with the n3 portions of isocyanate-capped crosslinker standards respectively, add n3 portions of the same volume of internal standard solution to the resulting n3 reaction products, and after dilution with N,N-dimethylformamide, obtain n3 portions of isocyanate-capped crosslinker standard solutions; In steps S3, S4, and S5, the volume of each portion of the derivatization reaction reagent solution and the internal standard solution added is equal; n1, n2, and n3 are integers ≥ 1; In step S8, use n1 portions of IPDI standard solutions, n2 portions of isocyanate-capped HTPB standard solutions, and n3 portions of isocyanate-capped crosslinker standard solutions to obtain n1 relative correction factors f'1 of the internal standard to the IPDI standard, n2 relative correction factors f'2 of the internal standard to the isocyanate-capped HTPB standard, and n3 relative correction factors f'3 of the internal standard to the isocyanate-capped crosslinker standard; In step S9, based on the gel permeation chromatogram of the HTPB-IPDI sample, and the average value f'4 of the n1 relative correction factors f'1 of the internal standard to the IPDI standard, the average value f'5 of the n2 relative correction factors f'2 of the internal standard to the isocyanate-capped HTPB standard, and the average value f'6 of the n3 relative correction factors f'3 of the internal standard to the isocyanate-capped crosslinker standard, calculate the mass fractions of free IPDI, isocyanate-capped HTPB, and -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample.

6. A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction according to claim 5, characterized in that, In step S9, the method for obtaining the mass fractions of free IPDI, isocyanate-capped HTPB, and -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample is as follows: S9.1 Weigh an HTPB-IPDI sample with a mass of m5. After allowing the derivatization reaction reagent solution to react completely with the HTPB-IPDI sample, add the internal standard solution to the resulting product to obtain an HTPB-IPDI sample solution; m5 = 5 - 10 g; S9.2 Obtain the gel permeation chromatogram of the HTPB-IPDI sample solution; S9.3 Calculate the mass fraction w1 of free IPDI, the mass fraction w2 of isocyanate-capped HTPB, and the mass fraction w3 of -NCO in the isocyanate-capped crosslinker in the HTPB-IPDI sample according to the following formula: Among them, s A1 , s A2 , s A3 are the peak areas of free IPDI, isocyanate-capped HTPB, and isocyanate-capped crosslinker in the gel permeation chromatogram of the HTPB-IPDI sample solution, respectively. m n1 is the mass of the internal standard in the IPDI standard sample solution, and s n2 is the peak area of the internal standard in the gel permeation chromatogram of the HTPB-IPDI sample solution.

7. A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction according to claim 5, characterized in that, n1 = n2 = n3 = 5; In step S3, take 5 portions of IPDI standards with different masses in the range of 0 - 0.6 g; In step S4, take 5 portions of isocyanate-capped HTPB standards with different masses in the range of 0 - 9 g; In step S5, five different-mass isocyanate-capped crosslinker standard samples are taken within the range of 0 to 1.0 g.

8. A method for detecting the distribution of active - NCO during the HTPB - IPDI curing reaction process according to claim 7, characterized in that, In step S7, it further includes: Obtaining the ratio of the peak area of the IPDI standard sample derivatization product to the peak area of the internal standard, the ratio of the peak area of the isocyanate-capped HTPB standard sample derivatization product to the peak area of the internal standard, and the ratio of the peak area of the isocyanate-capped crosslinker derivatization product to the peak area of the internal standard according to the gel permeation chromatograms of the IPDI standard sample solution, the isocyanate-capped HTPB standard sample solution, and the isocyanate-capped crosslinker standard sample solution; Taking the concentration of n1 portions of the IPDI standard sample solution as the abscissa and the ratio of the peak area of the IPDI standard sample derivatization product to the peak area of the internal standard as the ordinate to obtain the IPDI standard calibration curve; taking the concentration of n2 portions of the isocyanate-capped HTPB standard sample solution as the abscissa and the ratio of the peak area of the isocyanate-capped HTPB standard sample derivatization product to the peak area of the internal standard as the ordinate to obtain the isocyanate-capped HTPB standard calibration curve; taking the concentration of n3 portions of the isocyanate-capped crosslinker standard sample solution as the abscissa and the ratio of the peak area of the isocyanate-capped crosslinker derivatization product to the peak area of the internal standard as the ordinate to obtain the isocyanate-capped crosslinker standard calibration curve; Judging whether the IPDI standard calibration curve, the isocyanate-capped HTPB standard calibration curve, and the isocyanate-capped crosslinker standard calibration curve meet the linearity requirement, where the linearity requirement is that the correlation coefficient > 0.999; When the linearity requirement is met, continue to execute step S8. When the linearity requirement is not met, repeat the relevant steps in steps S1 to S7 to eliminate errors until the linearity requirement is met.

9. A method for detecting the active -NCO distribution during the HTPB - IPDI curing reaction according to claim 1, further including: S10 Obtaining the competitive reaction of HTPB and the crosslinker to the curing agent based on the mass fractions of -NCO in the free IPDI, isocyanate-capped HTPB, and isocyanate-capped crosslinker in the HTPB - IPDI sample, and then quantitatively characterizing the real-time sequence structure of the HTPB - IPDI sample.

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