Test method for the determination of the blend ratio of rubber blends of nitrile / butanerubber

Abstract

This invention provides a test method for the nitrile / chloroprene rubber blend ratio in a compound rubber, wherein the total weight of the compound rubber is 100 parts, including nitrile rubber and chloroprene rubber. The test method includes: using a differential scanning calorimeter to test the compound rubber to obtain a temperature-heat flow rate curve; and based on the temperature-heat flow rate curve, obtaining the glass transition temperature T of the nitrile rubber. NBR The glass transition temperature T of chloroprene rubber was obtained. CR Based on the temperature-heat flow rate curve, at T NBR The specific heat capacity change ΔCp of nitrile rubber was obtained at the site. NBR In T CR The change in specific heat capacity ΔCp of chloroprene rubber was obtained. CR According to ΔCp NBR With ΔCp CR The calculated nitrile / chloroprene rubber blend ratio of the rubber to be tested is obtained. This invention achieves the technical advantages of non-destructive testing of the nitrile / chloroprene rubber blend ratio, which is non-destructive to the sample, simple to test, time-saving, and highly accurate.

Description

Technical Field

[0001] This invention relates to the field of rubber testing technology, and more specifically, to a method for testing the blending ratio of nitrile butadiene rubber (NBR) and chloroprene rubber in a blended rubber compound. Background Technology

[0002] Nitrile butadiene rubber (NBR) and chloroprene rubber (CR) occupy important positions in the rubber products industry due to their unique chemical structures and physical properties. NBR, with its excellent oil resistance, abrasion resistance, and good airtightness, is widely used in automotive oil seals, fuel lines, and industrial sealing rings. Chloroprene rubber, on the other hand, plays an irreplaceable role in wire and cable sheathing, fire-retardant materials, and adhesives due to its superior weather resistance, ozone resistance, flame retardancy, and good adhesion. In practical engineering applications, to combine the advantages of both rubbers and compensate for the performance shortcomings of individual materials, it is often necessary to use NBR and CR in combination, thereby significantly improving the overall performance of the product. Therefore, accurately controlling the ratio of NBR to CR is crucial to ensuring the consistency of the final product quality and meeting the performance indicators of specific application scenarios.

[0003] In the field of rubber formulation analysis and quality control, accurately determining the proportions of each component in blended rubber is a core aspect of R&D verification, failure analysis, and production monitoring. Various qualitative and quantitative analysis methods for rubber components exist, among which pyrolysis gas chromatography-mass spectrometry (Py-GC / MS) is a common approach. This method decomposes high-molecular polymers into low-molecular-weight fragments through high-temperature pyrolysis, using chromatographic separation and mass spectrometry to identify the rubber type. However, Py-GC / MS has significant limitations when applied to NBR / CR blended systems. First, the characteristic fragment peaks generated during the pyrolysis process of NBR and CR may overlap or interfere, leading to complex quantitative analysis models, large calculation errors, and difficulty in achieving high-precision proportion determination. Second, Py-GC / MS is a destructive testing method; the sample is completely decomposed during the test, losing its original morphology. This limits its applicability to laboratory-level formulation reverse engineering and prevents its use for non-destructive testing of finished products or valuable samples. Furthermore, the pyrolysis process is sensitive to operating conditions, and repeatability is significantly affected by sample preparation and instrument status, restricting its application efficiency in rapid quality inspection on conventional production lines. Besides pyrolysis techniques, Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) are also commonly used analytical methods. While FT-IR is simple to operate, for materials like NBR and CR with similar structures and complex blending systems, their characteristic absorption peaks often mask each other, making accurate quantitative results difficult to obtain simply by comparing characteristic peak intensities. Furthermore, it is easily interfered with by signals from fillers, plasticizers, and other additives. Although NMR offers high quantitative accuracy, the equipment is expensive, the testing cycle is long, and the sample pretreatment requirements are stringent, making it unsuitable for large-scale routine detection. Differential scanning calorimetry (DSC), as a thermal analysis technique, is mostly focused on qualitative judgment or estimation of single-component content, lacking in-depth research and standardized calibration models for the linear relationship between the mass fractions of NBR / CR blending systems.

[0004] In summary, existing testing methods are either insufficiently accurate and prone to large errors, or destructive and time-consuming, failing to meet the demands of modern industry for efficient, non-destructive, and precise formulation analysis. Particularly in the quality traceability of automotive and high-end industrial products, there is an urgent need for an analytical method that can both protect sample integrity and provide reliable quantitative data. Therefore, providing a method with high accuracy for determining the NBR / CR ratio in blends of nitrile butadiene rubber and chloroprene rubber is one of the technical problems that needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a test method for the blend ratio of nitrile butadiene rubber (NBR) to chloroprene rubber in blended rubber, so as to solve the problem that the existing technology is difficult to accurately and quickly determine the NBR / CR blend ratio in blended rubber of nitrile butadiene rubber and chloroprene rubber.

[0006] To achieve the above objectives, this invention provides a method for testing the nitrile / chloroprene rubber blend ratio in a blended rubber compound, wherein the total weight of the blended rubber is 100 parts, including nitrile rubber and chloroprene rubber. The testing method includes: Step S1, using a differential scanning calorimeter to test the blended rubber compound to obtain a temperature-heat flow rate curve; based on the temperature-heat flow rate curve, obtaining the glass transition temperature of the nitrile rubber, denoted as T. NBR The glass transition temperature of chloroprene rubber is obtained and denoted as T. CR Step S2, based on the temperature-heat flow rate curve, at T NBR The change in specific heat capacity of nitrile rubber is obtained at the point, denoted as ΔCp. NBR In T CR The change in specific heat capacity of chloroprene rubber is obtained at the point, denoted as ΔCp. CR Step S3, based on ΔCp NBR With ΔCp CR The calculated value of the nitrile / chloroprene rubber blend ratio of the tested rubber was obtained.

[0007] Further, in step S2, based on the temperature-heat flow rate curve at T NBR The first derivative at point ΔCp is obtained. NBR According to the temperature-heat flow rate curve at T CR The first derivative at point ΔCp is obtained. CR .

[0008] Further, in step S3, the calculated value of the nitrile / chloroprene rubber blend ratio of the tested blend is based on ΔCp. NBR / ΔCp CR And thus obtained.

[0009] Furthermore, the test method also includes a process for correcting the calculated nitrile / chloroprene rubber blend ratio of the rubber to be tested: Step S4, provide n standard rubber blends and denot them as standard rubber n, and simultaneously record the actual nitrile / chloroprene rubber blend ratio P for each standard rubber n. 0n ; Record the actual value of CR (chromium ester rubber) as the number of chloroprene rubber parts by weight for each standard rubber n. 0n CR 0n =100 / (P 0n +1); n P's 0n All are different and independently range from 0.25 to 4; n is any integer from 2 to 5; in step S5, referring to steps S1, S2, and S3, the nitrile / chloroprene rubber blend ratio of each standard rubber n is calculated and denoted as P. 1n ; and then according to CR 1n =100 / (P 1n +1) Get n CRs 1nCR 1n Calculate the weight parts of chloroprene rubber for each standard rubber n; Step S6, based on n CRs 0n and n CR 1n Step S7: Based on the calculated value of the nitrile / chloroprene rubber blend ratio of the rubber to be tested and the calibration curve, obtain the calibration value of the nitrile / chloroprene rubber blend ratio of the rubber to be tested.

[0010] Furthermore, in step S4, n P 0n Each is independently 0.3 to 3.5; and / or, n is any integer from 2 to 3.

[0011] Furthermore, in step S6, the functional expression of the correction curve is CR r =a×CR1+b, where a is 1.0~1.2 and b is -4~-3.5.

[0012] Further, step S7 also includes: step S7-1, taking the calculated value of the nitrile / chloroprene rubber blend ratio of the blend to be tested as P1, and obtaining the calculated value of the chloroprene rubber weight parts CR1 of the blend to be tested according to CR1=100 / (P1+1); step S7-2, obtaining the corrected value CR1 of the chloroprene rubber weight parts of the blend to be tested according to the calibration curve. r Step S7-3, according to P r =(100-CR r ) / CR r The correction value of the nitrile / chloroprene rubber blend ratio of the tested rubber was obtained.

[0013] Furthermore, the functional expression for the correction curve is CR r =1.1064CR1-3.9274 or CR r =1.1066CR1-3.9940; and / or, the goodness of fit R of the calibration curve during the fitting process. 2 It is 1 ± 0.001.

[0014] Furthermore, the adhesive is a mixture of nitrile rubber and chloroprene rubber, wherein the weight ratio of nitrile rubber to chloroprene rubber is (20 / 80) to (80 / 20).

[0015] Furthermore, even further, prior to step S1, the test method also includes solvent extraction of the gel and the gel.

[0016] By applying the technical solution of this invention, a non-destructive thermal analysis test is performed on a nitrile rubber and chloroprene rubber blend based on a differential scanning calorimeter. The glass transition temperature of each nitrile rubber and chloroprene rubber is accurately identified by obtaining the temperature-heat flow rate curve. Then, the specific heat capacity change values ​​of each at the corresponding glass transition point are extracted. Finally, the blend ratio is calculated based on the relative ratio of the above specific heat capacity change values, which achieves the purpose of quantitatively characterizing the content of the two rubber components in the blend. Thus, the technical effect of non-destructive testing of the nitrile / chloroprene rubber blend ratio is achieved without destroying the sample, is simple to test, has a short time consumption, and has high accuracy. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 This is a temperature-heat flow rate curve of the sample to be tested and combined with adhesive in Example 1 of the present invention;

[0019] Figure 2 This is a calibration curve obtained by fitting three standard adhesive samples from Example 1 of the present invention;

[0020] Figure 3 This is a calibration curve obtained by fitting two standard adhesive samples in Example 6 of the present invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As described in the background section, existing technologies suffer from the difficulty of accurately and rapidly determining the NBR / CR ratio of nitrile rubber (NBR) in blends of nitrile rubber and chloroprene rubber. To address this technical problem, this invention provides a method for testing the NBR / CR ratio in blends of nitrile rubber and chloroprene rubber, where the total weight of the blends is 100 parts, including both nitrile rubber and chloroprene rubber. The testing method includes: Step S1, using a differential scanning calorimeter to test the blends and obtain a temperature-heat flow rate curve; based on the temperature-heat flow rate curve, obtaining the glass transition temperature of the nitrile rubber, denoted as T. NBR The glass transition temperature of chloroprene rubber is obtained and denoted as T. CR Step S2, based on the temperature-heat flow rate curve, at T NBR The change in specific heat capacity of nitrile rubber is obtained at the point, denoted as ΔCp. NBR In T CR The change in specific heat capacity of chloroprene rubber is obtained at the point, denoted as ΔCp.CR Step S3, based on ΔCp NBR With ΔCp CR The calculated value of the nitrile / chloroprene rubber blend ratio of the tested rubber was obtained.

[0023] The testing method provided by this invention utilizes the thermodynamic response characteristics of differential scanning calorimetry (DSC) to quantitatively characterize the blending ratio of nitrile rubber (NBR) and chloroprene rubber (CR) using a non-destructive method. Specifically:

[0024] Based on the glass transition, a second-order phase transition process in polymers, within the temperature range of the glass transition, polymer chains begin to acquire sufficient energy for microscopic motion. When the temperature rises to the glass transition temperature, the specific heat capacity of the polymer material undergoes a sudden change. This is because below the glass transition temperature, chain segment motion is frozen, and the material's ability to store thermal energy is low; while above the glass transition temperature, chain segment motion is activated, and the material needs to absorb more heat to drive changes in molecular conformation, resulting in a significant increase in specific heat capacity.

[0025] In the blend system of nitrile butadiene rubber (NBR) and chloroprene rubber (CR), the glass transition temperatures of NBR and CR differ significantly, resulting in two independent steps observed on the DSC curve. The aforementioned test method determines the glass transition temperature by locating the inflection point of the step, and thus determines ΔCp, thereby achieving the physical separation and quantification of different components in the NBR / CR blend system. Simultaneously, since NBR and CR are essentially two-phase separated or weakly compatible, the significant impact of compatibility-induced glass transition temperature shifts or peak broadening on the integral area can be ignored, allowing for the measurement of ΔCp. NBR Primarily derived from NBR components, ΔCp CR It mainly originates from CR components.

[0026] For pure polymers, the change in specific heat capacity at the glass transition is directly proportional to the polymer's mass (or mass fraction). Therefore, based on this, the above test method utilizes the abrupt change in specific heat capacity during the glass transition of polymer materials, combined with the difference in characteristic transition temperatures between the two types of rubber, to achieve non-destructive, rapid, and relatively accurate quantitative analysis.

[0027] Regarding the calculation of specific heat capacity, in step S2, it is preferable to use the temperature-heat flow rate curve at T NBR The first derivative at point ΔCp is obtained. NBR According to the temperature-heat flow rate curve at T CR The first derivative at point ΔCp is obtained. CRIn this preferred scheme, ΔCp is extracted using the first derivative, further reducing the impact of different calibration ranges on the determination of absolute heat flux values, resulting in more stable measurement results. In practical applications, the range of heat flux variation is determined based on the first derivative, thereby obtaining the heat flux at T g The change value at the specified location is then converted to obtain ΔCp. Generally, this unit conversion is automatically obtained by the DSC instrument, and can be directly determined by those skilled in the art during the testing process. Furthermore, in NBR / CR blends, T... NBR The actual temperature is generally -22±2℃, T CR The actual temperature is typically -37±2℃. In step S3, the calculated value of the nitrile / chloroprene rubber blend ratio of the tested rubber compound is based on ΔCp. NBR / ΔCp CR And thus obtained.

[0028] To further improve the accuracy and reliability of the above-mentioned nitrile / chloroprene rubber blend ratio test, and to address the quantitative deviation caused by differences in sample microstructure, differences in specific heat capacity changes in the pure phase states of the two rubbers, and errors in the testing system, the preferred test method also includes a process of correcting the calculated nitrile / chloroprene rubber blend ratio of the blend to be tested: Step S4, provide n standard blends and denot them as standard rubber n, and simultaneously record the actual nitrile / chloroprene rubber blend ratio P for each standard rubber n. 0n ; Record the actual value of CR (chromium ester rubber) as the number of chloroprene rubber parts by weight for each standard rubber n. 0n CR 0n =100 / (P 0n +1); n P's 0n All are different and independently range from 0.25 to 4; n is any integer from 2 to 5; in step S5, referring to steps S1, S2, and S3, the nitrile / chloroprene rubber blend ratio of each standard rubber n is calculated and denoted as P. 1n ; and then according to CR 1n =100 / (P 1n +1) Get n CRs 1n CR 1n Calculate the weight parts of chloroprene rubber for each standard rubber n; Step S6, based on n CRs 0n and n CR 1n Step S7 involves fitting a calibration curve to obtain the calibration curve. Based on the calculated nitrile / chloroprene rubber blend ratio of the tested rubber and the calibration curve, a calibration value for the nitrile / chloroprene rubber blend ratio of the tested rubber is obtained. In other words, by constructing the aforementioned empirical calibration function, the cumulative effects of instrument response nonlinearity, baseline drift, and the comparison of sample thermal history with measured heat capacity are eliminated, further improving the consistency and comparability of the test results.

[0029] In step S4, to balance data accuracy and test time, n P values ​​are preferred. 0n Each is independently 0.3 to 3.5; and / or, n is any integer from 2 to 3.

[0030] In several typical implementations, in step S6, the functional expression of the correction curve is CR. r =a×CR1+b, where a is 1.0~1.2 and b is -4~-3.5. The above linear fitting expression can reduce computational complexity while reducing the risk of noise amplification due to overfitting; the obtained function expression also has higher accuracy, reproducibility and stability. In order to further calculate the blending ratio correction value, preferred step S7 also includes: step S7-1, taking the calculated value of the nitrile / chloroprene rubber blending ratio of the blended rubber to be tested as P1, and obtaining the calculated value of the chloroprene rubber weight parts CR1 of the blended rubber to be tested according to CR1=100 / (P1+1); step S7-2, obtaining the chloroprene rubber weight parts correction value CR1 of the blended rubber to be tested according to the correction curve. r Step S7-3, according to P r =(100-CR r ) / CR r The correction value of the nitrile / chloroprene rubber blend ratio of the tested rubber was obtained.

[0031] In several more typical implementations, the functional expression for the correction curve is CR. r =1.1064CR1-3.9274 or CR r =1.1066CR1-3.9940; and / or, the goodness of fit R of the calibration curve during the fitting process. 2 The value is 1 ± 0.001. Based on the more accurate fitting results mentioned above, the accuracy of the final corrected ratio can be further improved, and the deviation from the actual value can be further reduced.

[0032] Furthermore, to more effectively eliminate thermal stress and thus provide a higher quality and more reproducible raw data basis for subsequent comparison calculations, in step S1, the preferred test procedure for the differential scanning calorimeter is as follows: in a protective atmosphere, starting at 25±2℃, then cooling to -140±5℃ at a rate of 10±1℃ / min, holding at that temperature for 1±0.2min, and then heating up to 30±2℃ at a rate of 20±1℃ / min. And, during the test, nitrogen is preferred as the protective atmosphere.

[0033] For the test object of the above test method, i.e., the mixed rubber, it is preferably a mixture of nitrile rubber and neoprene rubber, wherein the weight ratio of nitrile rubber to neoprene rubber is (20 / 80) to (80 / 20), preferably (25 / 75) to (75 / 25). This ratio range of the two rubbers ensures that the thermal signals of both NBR and CR are within the effective detection range of the instrument, thereby improving ΔCp. NBR and ΔCp CR The reliability of the calculation is improved, and a more accurate result is obtained compared with the test value.

[0034] Furthermore, to eliminate the influence of additives in the blended rubber sample on the results, the preferred test method before step S1 includes solvent extraction of the blended rubber to obtain more accurate test results. In several typical embodiments, to achieve a better balance between the thoroughness of extraction and the integrity of the rubber structure, the solvent extraction process preferably includes: using Soxhlet extraction to extract the blended rubber with a reflux frequency of ≥5 times / h and a total duration of 16±0.5h; and / or, the solvent used for solvent extraction is selected from one or more of ethanol, acetone, heptane, and n-hexane. Of course, any method commonly used in the art can be used for solvent extraction, and it is not limited to the above conditions.

[0035] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] Example 1

[0038] A test method for the nitrile / chloroprene rubber blend ratio in blended rubber:

[0039] (1) Determination of the change in specific heat capacity ΔCp of the sample: Weigh 15.91 mg of the sample to be tested (which is a blend of nitrile rubber (NBR) and chloroprene rubber (CR), with a total weight ratio of 100) and test it using a differential scanning calorimeter (DSC). Also, the sample mass has little impact on the test results; a range of 10 mg to 20 mg is acceptable.

[0040] Test procedure: Starting temperature 25℃, after the instrument stabilizes, under a nitrogen atmosphere, the temperature is lowered to -140℃ at a rate of 10℃ / min, held at that temperature for 1 min, and then raised to 30℃ at a rate of 20℃ / min. The resulting DSC curve, i.e., the temperature-heat flow rate curve, is shown below. Figure 1 .

[0041] Data analysis: The sample shows two glass transition steps in the DSC curve, indicating the glass transition temperature (Tb) of nitrile rubber (NBR). NBR At around -22℃, the CR transition temperature (T) of chloroprene rubber is... CR At around -37℃, NBR and CR can be distinguished based on their transition temperature.

[0042] (2) a. Plot the change in NBR specific heat capacity ΔCp based on the first derivative. NBR b. Plot the change in specific heat capacity ΔCp of CR based on the first derivative. CR The specific calculation methods for both are as follows: For the DSC curve (see...) Figure 1 The curve above is the function curve whose first derivative is drawn (see the curve above). Figure 1 (The curve below); then, based on the peak relationship of the first derivative curve, confirm the heat flow change steps of NBR and CR during the test process (taking NBR as an example, confirm the temperature at point A and point B based on the peak relationship of the first derivative curve, and the range of the vertical axis corresponding to these two horizontal axis temperature values ​​is the T value of NBR). g Steps, such as Figure 1 (as shown in the figure). Then, the heat flow change values ​​(in mW) of NBR and CR are calculated according to the heat flow change steps respectively. After unit conversion, the change value of specific heat capacity ΔCp of NBR and CR is obtained.

[0043] (3) According to CR1=ΔCp CR / (ΔCp CR +ΔCp NBR ) 100, the calculated CR1 of the chloroprene rubber weight parts of the tested rubber sample is 72 parts. Then, according to CR1=100 / (P1+1), the calculated nitrile / chloroprene rubber blend ratio P1 of the tested rubber sample is obtained (i.e., P1=(100-CR1) / CR1, and P1 can also be based on ΔCp). NBR / ΔCp CR (Calculation is performed), that is, NBR / CR=28 / 72.

[0044] (4) The ratio of self-made standard sample 1 is: NBR / CR=20 / 80, which is recorded as standard glue R1; the ratio of self-made standard sample 2 is: NBR / CR=50 / 50, which is recorded as standard glue R2; the ratio of self-made standard sample 3 is: NBR / CR=75 / 25, which is recorded as standard glue R3.

[0045] (5) Weigh 10mg to 20mg of the three self-made standard samples respectively, and perform DSC tests according to the test procedures in steps (1) to (3). The results are shown in Table 1.

[0046] Table 1 Test Results of Standard Samples

[0047]

[0048] (6) Establish a standard curve as a calibration curve based on the data in Table 1. The fitted linear calibration curve is shown in Table 1. Figure 2 Its function expression is CR r =1.1064CR1-3.9274, Goodness-of-Good R 2 The value is 1. Then, the weight part CR1 of the chloroprene rubber to be tested and blended with the adhesive obtained in step (3) is substituted into this function to calculate CR. r (Rounded to the nearest integer); then according to P r =(100-CR r ) / CR r P was obtained r This value was used as a correction value for the nitrile / chloroprene rubber blend ratio of the tested rubber compound, and the results are shown in Table 2.

[0049] Given that the actual NBR / CR ratio of the nitrile / chloroprene rubber in the tested compound is 25 / 75, the difference between the corrected NBR / chloroprene rubber ratio obtained in step (6) and the actual value is 1 part (based on the weight parts of chloroprene rubber). This result is also shown in Table 2.

[0050] Example 2

[0051] The only difference between this embodiment and Embodiment 1 is that the blending ratio of the tested rubber samples is changed, wherein the actual blending ratio of nitrile / chloroprene rubber is NBR / CR=30 / 70.

[0052] The sample was tested using the method described above, and the ΔCp of the sample was obtained. NBR =0.154 Jg -1 K -1 ,ΔCp CR =0.287 Jg -1 K -1 The remaining test and calculation results are shown in Table 2.

[0053] Example 3

[0054] The only difference between this embodiment and Example 1 is that the type of rubber sample to be tested is changed, wherein the actual value of the nitrile / chloroprene rubber blend ratio is NBR / CR=70 / 30.

[0055] The sample was tested using the method described above, and the ΔCp of the sample was obtained. NBR =0.432 Jg -1 K -1 ,ΔCp CR =0.191 Jg-1 K -1 The remaining test and calculation results are shown in Table 2.

[0056] Example 4

[0057] The only difference between this embodiment and Embodiment 1 is that no correction was performed, and the calculated value of the nitrile / chloroprene rubber blend ratio of the test rubber obtained in step (3) was directly used as the final result.

[0058] Example 5

[0059] The only difference between this embodiment and Embodiment 1 is that the type of the blended rubber sample to be tested is changed, wherein the actual value of the nitrile / chloroprene rubber blend ratio NBR / CR is 20 / 80. Simultaneously, in step (4), a standard sample with a blend ratio of NBR / CR = 80 / 20 is used as the standard rubber R1, i.e., its actual value of the nitrile / chloroprene rubber blend ratio P. 01 It is 80 / 20.

[0060] The calibration curve established in this embodiment is CR. r =1.1883CR1-7.6883, Goodness R 2 It is 0.9912.

[0061] Example 6

[0062] The only difference between this embodiment and Embodiment 1 is that in step (4), standard adhesive R2 is not used; instead, the calibration curve is obtained by fitting only standard adhesives R1 and R3. Figure 3 Its function expression is CR r =1.1066CR1-3.9940, Goodness-of-Good R 2 The value is 1.

[0063] Table 2 shows the calculated, corrected, and actual values ​​of the nitrile / chloroprene rubber blend ratio of the tested rubbers in the above embodiments and comparative examples.

[0064] Table 2

[0065]

[0066] As can be seen from the above description, the embodiments of the present invention are based on differential scanning calorimetry (DSC) to perform non-destructive thermal analysis tests on nitrile rubber and chloroprene rubber blends. By acquiring temperature-heat flow rate curves, the glass transition temperatures of nitrile rubber and chloroprene rubber are accurately identified. Then, the specific heat capacity change values ​​of the two rubbers at the corresponding glass transition points are extracted. Finally, the blend ratio is calculated based on the relative proportion of the above specific heat capacity change values, thereby achieving the purpose of quantitatively characterizing the content of the two rubber components in the blend. This achieves the technical effect of non-destructive testing of the nitrile / chloroprene rubber blend ratio without destroying the sample, with simple testing, short testing time, and high accuracy.

[0067] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the nitrile / chloroprene rubber blend ratio in a blended rubber compound, wherein the total weight parts of the blended rubber compound are 100, comprising nitrile rubber and chloroprene rubber, characterized in that, The testing method includes: Step S1: The test rubber is tested using a differential scanning calorimeter to obtain a temperature-heat flow rate curve; based on the temperature-heat flow rate curve, the glass transition temperature of the nitrile rubber is obtained, denoted as T. NBR The glass transition temperature of the chloroprene rubber is obtained and denoted as T. CR ; Step S2, based on the temperature-heat flow rate curve, at T NBR The change in specific heat capacity of the nitrile rubber was obtained at the specified location and denoted as ΔCp. NBR In the T CR The change in specific heat capacity of the chloroprene rubber was obtained at the site and denoted as ΔCp. CR ; Step S3, according to the ΔCp NBR With the ΔCp CR The calculated value of the nitrile / chloroprene rubber blend ratio of the tested rubber compound was obtained.

2. The method for testing the nitrile / chloroprene rubber blend ratio in a blended rubber compound according to claim 1, characterized in that, In step S2, based on the temperature-heat flow rate curve at T NBR The first derivative at point is used to obtain the ΔCp. NBR According to the temperature-heat flow rate curve at T CR The first derivative at point is used to obtain the ΔCp. CR .

3. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to claim 1 or 2, characterized in that, In step S3, the calculated value of the nitrile / chloroprene rubber blend ratio of the tested rubber compound is based on ΔCp. NBR / ΔCp CR And thus obtained.

4. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to any one of claims 1 to 3, characterized in that, The test method also includes a process for correcting the calculated nitrile / chloroprene rubber blend ratio of the tested blended rubber: Step S4: Provide n standard blended rubbers and denote them as standard rubber n, and simultaneously record the actual value of the nitrile / chloroprene rubber blending ratio of each standard rubber n as P. 0n ; Let the actual value of the chloroprene rubber weight parts of each of the aforementioned standard rubber n be CR. 0n CR 0n =100 / (P 0n +1); n P's 0n All are distinct and each independently ranges from 0.25 to 4; n is any integer from 2 to 5; Step S5: Referring to steps S1, S2, and S3, calculate the nitrile / chloroprene rubber blend ratio for each standard rubber n, and denote it as P. 1n ; and then according to CR 1n =100 / (P 1n +1) Get n CRs 1n The CR 1n These are the calculated weight parts of chloroprene rubber for each of the standard rubber n; Step S6, based on n of the CRs 0n and n CRs 1n The calibration curve is obtained by fitting the data. Step S7: Based on the calculated value of the nitrile / chloroprene rubber blend ratio of the rubber to be tested and the calibration curve, obtain the calibration value of the nitrile / chloroprene rubber blend ratio of the rubber to be tested.

5. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to claim 4, characterized in that, In step S4, n P 0n Each is independently 0.3 to 3.5; and / or, n is any integer from 2 to 3.

6. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to claim 4 or 5, characterized in that, In step S6, the functional expression of the correction curve is CR. r =a×CR1+b, where a is 1.0~1.2 and b is -4~-3.

5.

7. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to any one of claims 4 to 6, characterized in that, Step S7 further includes: Step S7-1: Take the calculated value of the nitrile / chloroprene rubber blend ratio of the rubber to be tested as P1, and obtain the calculated value of the chloroprene rubber weight parts CR1 of the rubber to be tested according to CR1=100 / (P1+1); Step S7-2: Based on the calibration curve, obtain the calibration value CR of the chloroprene rubber weight part of the tested compound. r ; Step S7-3, according to P r =(100-CR r ) / CR r The nitrile / chloroprene rubber blend ratio correction value of the tested blend is obtained.

8. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to claim 6, characterized in that, The functional expression of the correction curve is CR r =1.1064CR1-3.9274 or CR r =1.1066CR1-3.9940; and / or, the goodness of the calibration curve during the fitting process R 2 It is 1 ± 0.

001.

9. The test method for the nitrile / chloroprene rubber blend ratio in a blended rubber according to any one of claims 1 to 8, characterized in that, The blended adhesive is a mixture of nitrile rubber and chloroprene rubber, wherein the weight ratio of nitrile rubber to chloroprene rubber is (20 / 80) to (80 / 20).

10. The method for testing the nitrile / chloroprene rubber blend ratio in a blended rubber according to any one of claims 1 to 9, characterized in that, Prior to step S1, the test method further includes solvent extraction of the combined gel.

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