A method for determining the end point of the curing reaction of solid propellant
By combining strain scanning and frequency scanning tests during solid propellant curing process, the end point of the curing reaction is accurately judged, which solves the difficulty in judgment caused by the large modulus span in the prior art, and achieves efficient and accurate judgment of the end point of the reaction.
Patent Information
- Application Number
- CN202210504515.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-05-10
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2042-05-10
AI Technical Summary
The prior art is difficult to accurately and efficiently determine the end point of the solid propellant curing reaction, especially when the modulus span is large and the test conditions are not uniform, resulting in difficulty in judgment.
Using a combination of strain scanning test and frequency scanning test, the reaction end point is determined by periodically measuring the slope values of the energy storage modulus and log-loss modulus during the curing process on a rotary rheometer, and combining the intersection of the energy storage modulus platform area and the slope during the rising period.
The accurate judgment of the end point of the solid propellant curing reaction is achieved, and it has the advantages of being highly universal, easy to achieve and time and cost savings.
Smart Images
Figure CN114813475B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of polymer materials, and in particular, to a method for determining the end point of the curing reaction of solid propellants. Background Art
[0002] The preparation components of solid propellants usually include hydroxyl-containing polymer binders (such as hydroxyl-terminated polybutadiene, polyethylene glycol, or glycidyl azide polyether, etc.), as well as some components among plasticizers, isocyanate curing agents, curing catalysts, curing crosslinking agents, and many other functional components.
[0003] During the casting process of the propellant, the main reaction in the propellant is the reaction of hydroxyl groups with isocyanates to form polyurethanes, and this process often takes a long time. When studying its curing reaction kinetics by rheology, it is often necessary to accurately find the reaction end point and the modulus at the reaction end point.
[0004] Currently, the existing technology usually monitors the storage modulus in real time, and it is considered to reach the end point by judging that the storage modulus is within the range of 10 - 100 Pa.
[0005] For the propellant curing system, the reaction time is very long, and the sample changes from a fluid to a high-modulus elastomer, with a large span of modulus values, often changing from 10 -1 to 10 5 Pa. There are certain difficulties in unifying the test conditions and real-time monitoring.
[0006] In view of this, the present invention is specifically proposed. Summary of the Invention
[0007] The purpose of the present invention is to provide a method for determining the end point of the curing reaction of solid propellants, which is easy to implement, has strong universality, and high result accuracy.
[0008] The present application can be implemented as follows:
[0009] The present application provides a method for determining the end point of the curing reaction of solid propellants, including the following steps:
[0010] During the curing process of the solid propellant to be tested, perform strain sweep tests and frequency sweep tests to obtain the storage modulus data corresponding to the same reading frequency at different times, as well as the slope value of the curve of logarithmic loss modulus versus logarithmic frequency;
[0011] When the storage modulus data obtained at different times and the slope value of the curve of logarithmic loss modulus versus logarithmic frequency are basically unchanged, the corresponding plateau storage modulus is the storage modulus at the reaction end point, and the time corresponding to the intersection point of the slope of the storage modulus plateau region and the rising period of the storage modulus is the reaction end point time.
[0012] In an alternative embodiment, the strain sweep test and the frequency sweep test are carried out on a rotational rheometer.
[0013] In an alternative embodiment, when the solid propellant to be tested changes from a flowing state to a viscoelastic state during the curing process, a strain sweep test is carried out every 1 - 5 h.
[0014] In an alternative embodiment, the curing temperature of the solid propellant to be tested is 30 - 70 °C.
[0015] In an alternative embodiment, the solid propellant to be tested is subjected to a frequency sweep with the strain corresponding to the oscillating torque in the linear strain region.
[0016] In an alternative embodiment, the sweep frequency of the frequency sweep test is 0.628 - 62.8 rad / s.
[0017] In an alternative embodiment, the storage modulus at a reading frequency of 6.28 rad / s is read.
[0018] In an alternative embodiment, curing is carried out by uniformly laying the solid propellant to be tested in a container, and then carrying out a curing reaction in an oil bath oven.
[0019] In an alternative embodiment, the material of the container is polytetrafluoroethylene.
[0020] In an alternative embodiment, the laying thickness of the solid propellant to be tested is 2 - 3 mm.
[0021] In an alternative embodiment, the preparation raw materials of the solid propellant to be tested include nitrate - plasticized polyethylene glycol, isocyanate curing agent, and catalyst.
[0022] In an alternative embodiment, the isocyanate curing agent includes isophorone diisocyanate or N100.
[0023] In an alternative embodiment, the catalyst includes triphenylbismuth.
[0024] The beneficial effects of the present application include:
[0025] In the present application, during the curing process of the solid propellant to be tested, a strain sweep test and a frequency sweep test are carried out. When the storage modulus data obtained at different times and the slope values of the logarithmic loss modulus - logarithmic frequency curve are basically unchanged, the corresponding plateau storage modulus is the storage modulus at the reaction end point, and the time corresponding to the intersection point of the slope of the storage modulus plateau region and the rising period of the storage modulus is the reaction end point time to determine the reaction end point.
[0026] Judging the curing reaction end point of the solid propellant by comprehensively considering the above two characteristic conditions has the advantages of high accuracy, easy implementation, strong universality, and can also save time and cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.
[0028] Figure 1 is the strain scanning spectrum of the PEG-N100-TPB sample in Example 1;
[0029] Figure 2 This is the frequency scanning spectrum of the PEG-N100-TPB sample in Example 1;
[0030] Figure 3 Graph showing the change of storage modulus with reaction time in Example 1;
[0031] Figure 4 is the slope of the logarithmic loss modulus versus logarithmic frequency curve at different times in Example 1;
[0032] Figure 5 is the strain scanning spectrum of the PEG-IPDI-TPB sample in Example 2;
[0033] Figure 6 This is the frequency scan spectrum of the PEG-IPDI-TPB sample in Example 2;
[0034] Figure 7 Graph showing the change of storage modulus with reaction time in Example 2;
[0035] Figure 8 is the slope of the logarithmic loss modulus versus logarithmic frequency curve at different times in Example 2. DETAILED DESCRIPTION
[0036] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.
[0037] The method for determining the end point of the solid propellant curing reaction provided in this application is described in detail below.
[0038] This application proposes a method for determining the endpoint of a solid propellant curing reaction, comprising the following steps:
[0039] During the curing process of the solid propellant to be tested, strain sweep tests and frequency sweep tests are carried out to obtain the storage modulus data corresponding to the same reading frequency at different times and the slope values of the logarithmic loss modulus versus logarithmic frequency curves;
[0040] When the storage modulus data obtained at different times and the slope values of the logarithmic loss modulus versus logarithmic frequency curves are basically unchanged (the change in the results of the two tests is less than 5%), the corresponding plateau storage modulus is the storage modulus at the reaction end point, and the time corresponding to the intersection of the slope of the storage modulus plateau region and the rising period of the storage modulus is the reaction end point time.
[0041] In the casting process of the above-mentioned solid propellant to be tested, the main reaction is the reaction of hydroxyl groups with isocyanates to form polyurethanes.
[0042] In some alternative embodiments, the raw materials for preparing the solid propellant to be tested may include nitrate-plasticized polyethylene glycol (PEG), isocyanate curing agent, and catalyst.
[0043] Among them, the isocyanate curing agent may exemplarily but non-limitingly include isophorone diisocyanate (IPDI) or N100. The catalyst may exemplarily but non-limitingly include triphenylbismuth (TPB).
[0044] Curing is to evenly lay the solid propellant to be tested in a container, and then carry out the curing reaction in an oil bath oven.
[0045] It should be noted that in the curing process of this application, heating equipment such as an electric oven or a water bath oven is not used to improve the safety and accuracy of the entire testing process. Among them, the main reason for avoiding the use of a water bath is that water will react with the isocyanate curing agent, affecting the accuracy of the entire reaction system.
[0046] In some embodiments, the material of the above container is polytetrafluoroethylene, which can effectively avoid unnecessary reactions between the inner wall of the container and the solid propellant to be tested, and improve the accuracy of the measurement results. In addition, in other embodiments, the material of the above container can also be other inert materials that do not react with the solid propellant to be tested.
[0047] In this application, the laying thickness of the solid propellant to be tested is 2-3 mm, such as 2 mm, 2.5 mm or 3 mm.
[0048] It should be emphasized that for a reaction system with a large modulus span, when a certain degree of curing is reached, the difference in the sample thickness during the testing process will cause an error in the measured modulus, and the reaction end point cannot be accurately judged solely. By setting the laying thickness of the solid propellant to be tested to 2-3 mm in this application, the testing error can be effectively reduced and the accuracy of the testing results can be improved.
[0049] In this application, both the strain sweep test and the frequency sweep test are carried out on a rotational rheometer. The strain sweep test and the frequency sweep test are carried out step by step.
[0050] Referentially, when the solid propellant to be tested changes from a flowing state to a viscoelastic state during the curing process, a strain sweep test can be carried out every 1-5 hours. Specifically, the interval time can be, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, etc. In some preferred embodiments, the interval time can be 1-2 hours.
[0051] The curing temperature of the solid propellant to be tested can be 30-70 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C or 70 °C, etc., or any other value within the range of 30-70 °C. In some preferred embodiments, the curing temperature is 50 °C.
[0052] In an alternative embodiment, the frequency sweep of the solid propellant to be tested is carried out with the strain corresponding to the oscillating torque in the linear strain region.
[0053] In this application, the sweep frequency of the frequency sweep test can be 0.628-62.8 rad / s. The reading frequency can be 6.28 rad / s. This reading frequency is relatively easy to control, and more accurate test results can be obtained with fewer reading times. In addition, in some specific embodiments, the reading frequency can also be set to other values.
[0054] Continuing from the above, the method for determining the end point of the curing reaction of the solid propellant in this application can be carried out with reference to the following steps:
[0055] (1) Uniformly spread the polyurethane curing system to be tested over a polytetrafluoroethylene container;
[0056] (2) Place the above curing system in an oil bath oven at a certain temperature to carry out the curing reaction, and regularly take out the samples to carry out strain sweep and frequency sweep tests on a rotational rheometer;
[0057] (3) The frequency sweep is carried out in the linear strain region determined by the strain sweep, and the frequency range of the frequency sweep is 0.628-62.8 rad / s;
[0058] (4) Read the storage modulus at a reading frequency of 6.28 rad / s, and record the slope of the curve of the logarithmic loss modulus vs. logarithmic frequency;
[0059] (5) Plot the curves of the storage modulus and the slope of the curve of the logarithmic loss modulus vs. logarithmic frequency at different reaction times;
[0060] (6) When the storage modulus no longer changes and the slope value of the logarithmic loss modulus versus logarithmic frequency curve remains unchanged, the reaction reaches the end point; at this time, the plateau storage modulus is the storage modulus at the reaction end point, and the time corresponding to the intersection of the slope of the storage modulus plateau region and the rising period is the reaction end point time.
[0061] It should be noted that in the prior art, a certain time method is used to determine the end point during the curing process of propellants or their simple curing systems. In fact, there are differences in the curing times of different systems. In this application, the reaction end point time and modulus are determined by using a rotational rheometer to regularly measure the dynamic modulus of the curing reaction. The change trends of the storage modulus and loss modulus during the frequency scanning of the sample can truly reflect the cross-linking state of the sample, with high accuracy and universality.
[0062] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.
[0063] Example 1
[0064] This example provides a method for judging the end point of the curing reaction of solid propellants, which includes the following steps:
[0065] (1) Uniformly spread the mixture of nitrate plasticized polyethylene glycol (PEG), isocyanate curing agent N100, and catalyst TPB on a polytetrafluoroethylene container.
[0066] The polytetrafluoroethylene container is 9 cm long, 9 cm wide, and 2 mm deep, and the laying thickness of the solid propellant is 2 mm.
[0067] (2) Place the above PEG-N100-TPB curing system in an oil bath oven at 50 °C for curing reaction, and regularly take out the samples for testing.
[0068] (3) When the PEG-N100-TPB sample changes from a flowing state to a viscoelastic state, measure the strain sweep curve of the sample at intervals of 2 h. The plateau region of the storage modulus is the linear strain region. As Figure 1 shown in the strain sweep spectrum, the range of the oscillating torque from 1 to 1000 μN·m is the linear strain region.
[0069] (4) Select the strain at an oscillating torque of 1000 μN·m as the test condition to perform frequency scanning on the sample, and the frequency range is 0.628 - 62.8 rad / s.
[0070] As Figure 2 shown in the frequency sweep spectrum at 89 h of reaction, read the storage modulus corresponding to an oscillating frequency of 6.28 rad / , and the value is 1.332×10 5 Pa. At this time, the slope of the logarithmic loss modulus versus logarithmic frequency curve is 0.2402.
[0071] (5) Plot the measured storage modulus (G’) values and the slope of the logarithmic loss modulus versus logarithmic frequency curve (G”) against time, as shown in Figure 3 and Figure 4 .
[0072] It can be seen from Figure 3 that the storage modulus does not change after 61.4 h. At the same time, it can be seen from Figure 4 that the slope of the logarithmic loss modulus versus logarithmic frequency curve basically does not change after 6 h.
[0073] Therefore, through comprehensive judgment, it is determined that the reaction reaches the end point at 65 h, and the storage modulus at this time is 132600 Pa.
[0074] Example 2
[0075] This example provides a method for determining the end point of the curing reaction of solid propellants, which includes the following steps:
[0076] (1) Uniformly spread the mixture of nitrate-plasticized polyethylene glycol (PEG), isocyanate curing agent IPDI, and curing catalyst TPB in a polytetrafluoroethylene container.
[0077] The polytetrafluoroethylene container is 9 cm long, 9 cm wide, and 2 mm deep, and the laying thickness of the solid propellant is 2 mm.
[0078] (2) Place the above PEG-IPDI-TPB curing system in an oil bath oven at 50 °C for curing reaction, and regularly take out samples for testing.
[0079] (3) When the PEG-IPDI-TPB sample changes from a flow state to a viscoelastic state, measure the strain sweep curve of the sample every 1 h. The plateau region of the storage modulus is the linear strain region. As shown in Figure 5 , the strain sweep spectrum is shown, and the oscillation torque of 1 - 200 μN·m is the linear strain region.
[0080] (4) Select the strain at an oscillation torque of 100 μN·m as the test condition to perform a frequency sweep on the sample, and the frequency range is 0.628 - 62.8 rad / s.
[0081] As shown in Figure 6 , the frequency sweep spectrum at 199.3 h of the reaction is shown. Read the storage modulus corresponding to an oscillation frequency of 6.28 rad / s, and the value is 1312 Pa.
[0082] (5) Plot the measured storage modulus values and the slope of the logarithmic loss modulus versus logarithmic frequency curve (G”) against time, as shown in Figure 7 and Figure 8 .
[0083] It can be seen from Figure 7 that the storage modulus value basically remains unchanged after 216.5 h. At the same time, it can be seen from Figure 8 that the slope value of the logarithmic loss modulus versus logarithmic frequency curve remains unchanged after 240.5 h.
[0084] Therefore, through comprehensive judgment, it is considered that the reaction reaches the end point at 240.5 h, and the storage modulus at the end point is 3258 Pa.
[0085] In summary, in the present application, the end point time and modulus of the reaction are determined by regularly measuring the dynamic modulus of the curing reaction using a rotational rheometer. The change trends of the storage modulus and loss modulus during the frequency scanning of the sample can truly reflect the cross-linking state of the sample, with high accuracy and universality.
[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for determining the end point of the curing reaction of solid propellant, characterized in that, It includes the following steps: During the curing process of the solid propellant to be tested, perform strain sweep tests and frequency sweep tests to obtain the storage modulus data corresponding to the same reading frequency at different times and the slope values of the logarithmic loss modulus versus logarithmic frequency curve; When the storage modulus data and the slope values of the logarithmic loss modulus versus logarithmic frequency curve obtained at different times are basically unchanged, the corresponding plateau storage modulus is the reaction end-point storage modulus, and the time corresponding to the intersection point of the slope of the storage modulus plateau region and the storage modulus rising period is the reaction end-point time; When the solid propellant to be tested changes from a flowing state to a viscoelastic state during the curing process, perform a strain sweep test every 1 - 5 h; perform a frequency sweep on the solid propellant to be tested with the strain corresponding to the oscillating torque within the linear strain region; the scanning frequency of the frequency sweep test is 0.628 - 62.8 rad / s; Read the storage modulus value at a reading frequency of 6.28 rad / s; the strain sweep test and the frequency sweep test are carried out on a rotational rheometer; Curing is to evenly lay the solid propellant to be tested in a polytetrafluoroethylene container, and then carry out the curing reaction in an oil bath oven; the laying thickness of the solid propellant to be tested is 2 - 3 mm; the curing temperature of the solid propellant to be tested is 30 - 70 °C.
2. The method according to claim 1, wherein The preparation raw materials of the solid propellant to be tested include nitrate plasticized polyethylene glycol, isocyanate curing agent, and catalyst.
3. The method according to claim 2, characterized in that, The isocyanate curing agent includes isophorone diisocyanate or N100.
4. The method according to claim 2, wherein The catalyst includes triphenylbismuth.