CN117949285A - RPA-based rubber dynamic thermal stability evaluation method and application - Google Patents
RPA-based rubber dynamic thermal stability evaluation method and application Download PDFInfo
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Abstract
The invention relates to the technical field of rubber industries such as tires, products and the like, in particular to an RPA-based method for evaluating dynamic thermal stability of rubber and application thereof, wherein the method comprises the following steps: firstly, performing an RPA aging test on rubber to be evaluated by using a rubber processing analyzer, wherein the RPA aging test comprises a scanning program before aging, an aging program and a scanning program after aging; secondly, acquiring rheological data points before rubber aging according to a scanning procedure before aging, mapping to obtain a rheological curve before rubber aging, acquiring rheological data points after rubber aging according to a scanning procedure after aging, and mapping to obtain a rheological curve after rubber aging; thirdly, calculating an RPA aging value of the rubber according to the rheological curve after rubber aging and the rheological curve before rubber aging, and evaluating the dynamic heat stability of the rubber according to the RPA aging value. The evaluation method can quantitatively characterize the dynamic heat stability of the rubber, and is simple and convenient to operate, high in reproducibility and accurate in judgment.
Description
Technical Field
The invention relates to the technical field of rubber industries such as tires, products and the like, in particular to an RPA-based rubber dynamic heat stability performance evaluation method and application thereof.
Background
The development of rubber industry makes rubber materials widely used in various fields of construction, automobiles, electronics and electrics, aerospace and the like. And the service life of the material is limited due to the easy aging property of the material, so that the material brings inconvenience to practical application. The rubber aging is that the rubber composition and structure are damaged by the comprehensive action and influence of internal and external factors in the storage, transportation or processing and use processes of raw rubber and vulcanized rubber (including rubber products), so that the rubber gradually loses the original excellent performance and even loses the use value. "aging" is an irreversible chemical reaction, and is the property of all polymer materials, and the appearance of the aging is shown by deterioration and deterioration of performance. In recent years, the market demands on the ageing resistance of rubber are becoming stricter, more and more novel antioxidants are emerging, the use effects of the antioxidants in rubber are different from self-synergistic antioxidants, high-molecular-weight antioxidants, anti-extraction antioxidants to reactive antioxidants, a few evaluation methods are needed, the acceptance of the traditional evaluation methods is high, the test period is long, and a quick and quantifiable characterization method and related indexes of the ageing resistance of rubber raw materials are needed at present.
The rubber aging resistance testing method can be divided into three main categories, namely thermal analysis, structural characterization and mechanical analysis. Thermal analysis, in which a substance is oxidized in a heated state and the change in heat release, heat absorption or mass is measured by an instrument, typically includes: differential Scanning Calorimetry (DSC), thermogravimetric loss (TGA) and Differential Thermal Analysis (DTA). The sample environment of the TGA was hot air and the mass lost in the process of the sample was detected by temperature programming.
The method for structural characterization is used for researching structural change in the oxidation process of a substance, and the method for exploring the oxidation mechanism of the substance mainly comprises the following steps: nuclear Magnetic Resonance (NMR) and fourier transform infrared spectroscopy (FTIR). NMR is a powerful tool for studying rubber microstructure. The oxidative degradation mechanism of the rubber material aging process can be predicted, the chain segment movement and the change of chemical structure can be clarified, and the NMR and the data obtained by other detection methods are generally comprehensively analyzed. The mechanical characterization method mainly comprises the following steps: oven aging-mooney viscosity analysis, uv aging-mooney viscosity analysis, oven aging-tensile strength testing, dynamic thermo-mechanical analysis (DMA), haak rheology analysis (HAKKE).
The mechanical characterization method of the ageing resistance of the rubber is a common laboratory method, the mechanical property of the rubber changes along with structural change in the oxidation process according to the principle, and the mechanical characterization method is divided into a plurality of types according to different test thermodynamic conditions and mechanical states. Wherein the constant temperature hot box aging-Mooney viscosity analysis belongs to the static thermo-oxidative aging of the sample, and the rubber aging environment is oxygen-enriched; ultraviolet light aging-mooney viscosity analysis belongs to static photo aging; the constant temperature hot box aging-tensile strength test and dynamic thermal mechanical analysis (DMA) are respectively used for dynamic and static aging resistance analysis of vulcanized rubber, wherein the dynamic thermal mechanical analysis (DMA) is thermal stability analysis of rubber in a micro-oxygen environment; RPA and haak rheology analysis (HAKKE) are dynamic thermal stability analyses of raw rubber.
Currently, dynamic thermal stability performance evaluation methods of rubber include dynamic thermo-mechanical analysis (DMA), haak rheology analysis (HAKKE) and RPA aging analysis. Wherein dynamic thermo-mechanical analysis (DMA) is used for evaluating the dynamic ageing resistance of the vulcanized rubber; the Hark rheology analysis (HAKKE) is used for dynamic thermal stability analysis of raw rubber, but the analysis and evaluation process is too complicated, the sample demand is large, and the degree of automation is not high; the existing RPA aging analysis method mainly comprises the steps of comparing elastic modulus (G') -strain curves of different samples to obtain a conclusion, wherein the conclusion is based on the relative conclusion obtained by the comparison method, is greatly influenced by the molecular weight of base rubber, is difficult to judge the performance of an antioxidant in rubber products with different molecular weights, has little data quantification significance, and cannot fully exert the high-precision characteristic of the RPA.
The dynamic thermal stability of rubber is positively correlated with other ageing resistance, and the ageing resistance of a rubber product and an antioxidant after the process is matched is unified and has a convincing measuring and characterizing method. RPA (rubber processing analysis) is a convenient method for testing dynamic thermal stability of rubber, so that development of an RPA-based dynamic thermal stability performance evaluation method of rubber is necessary for deep digging of RPA functions.
The method is suitable for evaluating different antioxidants of the same rubber only due to the lack of pre-scanning data and belongs to a relative comparison method among samples, and the aging resistance of the rubber cannot be quantitatively reflected. The paper "research on the detection function of RPA 2000" (rubber and plastic resource utilization "2010. No4) mentions an RPA three-stage aging program model of the aging performance of vulcanized rubber, but the program is not elaborated and related research is not developed. The Chinese patent publication No. CN109709276B discloses a detection method for the silanization reaction degree of white carbon black and a silane coupling agent in white carbon black rubber, which relates to a formula for processing RPA data by using curve integration, but the data processing formula is only suitable for detecting white carbon black rubber, has a small application range and cannot meet the requirement for evaluating the thermal stability of rubber.
Disclosure of Invention
The invention provides an RPA-based dynamic thermal stability evaluation method for rubber, which overcomes the defects of the prior art and can effectively solve the problems of small application range, complicated analysis process and poor evaluation effect of the existing dynamic thermal stability evaluation method for rubber.
One of the technical schemes of the invention is realized by the following measures: the dynamic thermal stability evaluation method of the rubber based on the RPA comprises the following steps:
firstly, performing an RPA aging test on rubber to be evaluated by using a rubber processing analyzer, wherein the RPA aging test comprises a scanning program before aging, an aging program and a scanning program after aging;
Secondly, acquiring rheological data points before rubber aging according to a scanning procedure before aging, mapping to obtain a rheological curve before rubber aging, acquiring rheological data points after rubber aging according to a scanning procedure after aging, and mapping to obtain a rheological curve after rubber aging;
Thirdly, calculating an RPA aging value of the rubber according to the rheological curve after rubber aging and the rheological curve before rubber aging, and evaluating the dynamic heat stability of the rubber according to the RPA aging value.
The following are further optimizations and/or improvements to one of the above-described inventive solutions:
in the third step, the calculation formula of the RPA aging value is as follows:
in the method, in the process of the invention,
S deltay is the RPA aging value,
F (y Aa) is the rheology curve after ageing of the rubber,
F (y Ba) is the rheology curve before rubber ageing,
X 1、x2 is the upper and lower abscissa limits in the RPA aging test.
The above criteria for evaluating the dynamic heat stability of rubber based on RPA aging values are:
When the RPA aging value SDeltay is positive, the thermal processing crosslinking degree of the rubber is indicated, and the larger the SDeltay is, the more the thermal processing crosslinking of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is a negative value, the thermal processing degradation degree of the rubber is indicated, and the smaller the SDeltay is, the more the thermal processing degradation of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is close to 0, the change of rheological property before and after heat processing is smaller, which shows that the dynamic heat stability of the rubber is better.
The RPA aging test specific operation when the rubber to be evaluated is styrene-butadiene rubber is as follows: preheating for 2min at 75-100deg.C; the scan before aging was: the scanning form is elastic modulus-strain scanning, the scanning condition is that the temperature is 75 ℃ or 100 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190-200 ℃; the post-aging scan is the same as the pre-aging scan.
The RPA aging test specific operation when the rubber to be evaluated is butadiene rubber is as follows: preheating for 0 to 2min at 65 ℃; the scan before aging was: the scanning form is elastic modulus-strain scanning, and the scanning conditions are as follows: the temperature is 60 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 120-190 ℃; the post-aging scan is the same as the pre-aging scan.
The RPA aging test specific operation when the rubber to be evaluated is thermoplastic styrene-butadiene rubber is as follows: preheating for 5 to 10min at 90 ℃; the scan before aging was: the scanning mode is complex dynamic viscosity-temperature scanning, and the scanning conditions are that the temperature is 90 ℃ to 160 ℃, the frequency is 5Hz and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 1Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190 ℃; the post-aging scan is the same as the pre-aging scan.
The RPA aging test specific operation of the rubber to be evaluated as a low cis-polybutadiene rubber is as follows: preheating for 0 to 5min at the temperature of 60 to 100 ℃; the scan before aging was: the scanning form is elastic modulus-frequency, the scanning condition is that the temperature is 100 ℃, the frequency ranges from 1 to 25Hz, and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 10Hz, the reciprocating angle is 6.975%, and the time is 30min at 200 ℃; the post-aging scan is the same as the pre-aging scan.
The second technical scheme of the invention is realized by the following measures: the method for evaluating the dynamic heat stability of the rubber based on the RPA is applied to the evaluation of the dynamic heat stability of the rubber with the same type and the same grade of rubber with different antioxidants or/and the rubber with different grades of rubber with the same antioxidants or/and the rubber with different grades of rubber with different antioxidants.
The third technical scheme of the invention is realized by the following measures: the RPA-based rubber dynamic heat stability evaluation method is applied to the aspects of evaluating the influence of the same type of rubber or/and different heat processing technologies or production device post-treatment technologies on the dynamic heat stability of the rubber or/and the quantitative evaluation of the dynamic heat stability of the rubber under the stable production technology condition.
The method for evaluating the dynamic thermal stability of the rubber based on the RPA takes raw rubber as a specific research object, classifies, edits and screens the RPA program according to the raw rubber variety, uses a three-section type RPA aging program, integrates and calculates the difference value of the mechanical property curves of samples before and after aging, provides a dynamic thermal stability judgment formula of the rubber based on the RPA, removes the influence of the sample itself including molecular weight, molecular weight distribution, microstructure and the like on the oxidation resistance of the sample, quantitatively evaluates the dynamic thermal stability of the rubber, and is suitable for various raw rubber samples. The evaluation method can quantitatively represent the dynamic heat stability of the rubber, and is simple and convenient to operate, high in reproducibility and accurate in judgment.
Drawings
FIG. 1 is a graph of rheology before and after aging of rubber in terms of elastic modulus-strain in the present invention.
FIG. 2 is a graph of elastic modulus vs. strain for samples of example 10 before and after RPA aging.
FIG. 3 is a graph of elastic modulus vs. strain for samples of example 11 before and after RPA aging.
Detailed Description
The present invention is not limited by the following examples, and specific embodiments can be determined according to the technical scheme and practical situations of the present invention. The various chemical reagents and chemical supplies mentioned in the invention are all commonly known and used in the prior art unless specified otherwise; the percentages in the invention are mass percentages unless otherwise specified.
The invention is further described below with reference to examples:
Example 1: the method for evaluating the dynamic thermal stability of the rubber based on the RPA comprises the following steps:
firstly, performing an RPA aging test on rubber to be evaluated by using a rubber processing analyzer, wherein the RPA aging test comprises a scanning program before aging, an aging program and a scanning program after aging;
Secondly, acquiring rheological data points before rubber aging according to a scanning procedure before aging, mapping to obtain a rheological curve before rubber aging, acquiring rheological data points after rubber aging according to a scanning procedure after aging, and mapping to obtain a rheological curve after rubber aging;
Thirdly, calculating an RPA aging value of the rubber according to the rheological curve after rubber aging and the rheological curve before rubber aging, and evaluating the dynamic heat stability of the rubber according to the RPA aging value.
The rubber in the invention is Styrene Butadiene Rubber (SBR), butadiene rubber (BR, LCBR), thermoplastic elastomer (SBS, TPU and the like) and all high molecular polymers in rubber state at normal temperature; the dynamic thermal stability is the change of the mechanical property of the rubber material after being heated and sheared in a micro-oxygen environment; the rheology curves before and after aging of different rubbers according to the scanning form in the RPA aging test can be specifically in the forms of elastic modulus (G ') -strain curve, complex dynamic viscosity (η) -temperature (Tem) curve, elastic modulus (G') -frequency curve and the like.
Under the heated state, unsaturated double bonds in the rubber are attacked by oxygen to generate chain scission or crosslinking reaction, and both reactions can influence the mechanical properties of the rubber. In the hot air aging test, the excessively high temperature setting can generate combustion risk and environmental pollution, and static aging can lead the molecular chains of the rubber not to be fully contacted with oxygen, so that the period of the rubber aging test is prolonged. The aging test of the RPA (rubber processing analyzer) is a closed test, is a micro-oxygen environment, utilizes a time-temperature equivalent principle, can be aged at 150-190 ℃, sets strain and frequency momentum to accelerate the aging process, and the aging of the rubber in the micro-oxygen environment is crosslinking, and the rheology and mechanical index of the rubber after aging are generally increased, so that the dynamic heat stability of the rubber is measured by calculating the difference value of the change amount of the mechanical index of the rubber RPA before and after aging through curve integral. The method removes the rheological property of the rubber, and the integral difference value only represents the change amount of the rheological property of the rubber under the hot processing condition, so that the method can provide a raw material selection basis for manufacturers adopting hot shearing extrusion, thermal expansion, banburying, mold filling and other processing technologies.
Example 2: as an optimization of the above embodiment, in the third step, the RPA aging value is calculated as:
in the method, in the process of the invention,
S deltay is the RPA aging value,
F (y Aa) is the rheology curve after ageing of the rubber,
F (y Ba) is the rheology curve before rubber ageing,
X 1、x2 is the upper and lower abscissa limits in the RPA aging test.
Example 3: as an optimization of the above examples, the criteria for evaluating the dynamic heat stability performance of the rubber according to RPA aging values were:
When the RPA aging value SDeltay is positive, the thermal processing crosslinking degree of the rubber is indicated, and the larger the SDeltay is, the more the thermal processing crosslinking of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is a negative value, the thermal processing degradation degree of the rubber is indicated, and the smaller the SDeltay is, the more the thermal processing degradation of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is close to 0, the change of rheological property before and after heat processing is smaller, which shows that the dynamic heat stability of the rubber is better.
According to the Paen effect theory, the rheological properties of the rubber are mainly affected by the fluid effect, the filler network structure, the acting force between the filler and the rubber and the acting force between the filler, respectively, and for raw rubber, the rheological properties of the rubber are mainly affected by the fluid effect, so that the microstructure, the molecular weight, the antioxidant formula and the heated state of the rubber with the same brand are consistent under the condition of stable production state, and therefore, the heated state of the rubber with the same brand is consistentThe test can be repeated for a plurality of times, and the test again does not need to test calculation again. Samples were subjected to the same RPA test procedure and therefore the same brand rubber product/>The test can be repeated for a plurality of times, and the test again does not need to test calculation again. Therefore, the S delta y of the rubber products with the same brand is the same, and the S delta y can be used as a factory index of the heat stability of any rubber brand.
Example 4: as an optimization of the above examples, the RPA aging test specific operation when the rubber to be evaluated is Styrene Butadiene Rubber (SBR) was: preheating for 2min at 75-100deg.C; the scan before aging was: the scanning form is elastic modulus (G') -strain scanning (the abscissa of the obtained data points is strain, the ordinate is elastic modulus), the scanning condition is that the temperature is 75 ℃ or 100 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190-200 ℃; the post-aging scan is the same as the pre-aging scan.
In the present invention, when the sweep is performed in the elastic modulus (G ') -strain mode, the obtained rheological curve before and after aging of the rubber is represented by the elastic modulus as a variable, and the RPA aging value SΔy obtained by the formula 1 can be represented by SΔG'. As shown in fig. 1: 2550-Ba and 2550-Aa are respectively the rheology curves before and after aging of the rubber expressed in elastic modulus-strain before and after aging of the sample No. 2550. 1cp-Ba and 1cp-Aa are respectively rubber rheology curves expressed by elastic modulus-strain before and after aging of a sample with the number of 1cp. In fig. 1, sΔg' 2550、SΔG'1cp is a geometric representation of the integrated difference of the curves before and after aging of the corresponding sample. The S.DELTA.G' 1cp>SΔG'2550 is evident, which indicates that the heat stability of sample 2550 is better than that of sample 1cp, and further indicates that the ageing resistance of 2550 is better than that of sample 1cp.
Example 5: as an optimization of the above examples, the RPA aging test specific operation when the rubber to be evaluated is Butadiene Rubber (BR) was: preheating for 0 to 2min at 65 ℃; the scan before aging was: the scan is in the form of elastic modulus (G') -strain scan (data points obtained are strain on abscissa and elastic modulus on ordinate), the scan conditions are: the temperature is 60 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 120-190 ℃; the post-aging scan is the same as the pre-aging scan.
Example 6: as an optimization of the above examples, the RPA aging test specific operation when the rubber to be evaluated is thermoplastic styrene-butadiene rubber (SBS) was: preheating for 5 to 10min at 90 ℃; the scan before aging was: the scanning form is complex dynamic viscosity (eta) -temperature (Tem) scanning (the abscissa of the obtained data points is temperature, the ordinate is complex dynamic viscosity), and the scanning conditions are that the temperature is 90-160 ℃, the frequency is 5Hz and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 1Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190 ℃; the post-aging scan is the same as the pre-aging scan.
Example 7: as an optimization of the above examples, the RPA aging test specific operation for the rubber to be evaluated being low cis polybutadiene rubber (LCBR) was: preheating for 0 to 5min at the temperature of 60 to 100 ℃; the scan before aging was: the scanning form is elastic modulus (G') -frequency (the abscissa of the obtained data points is frequency, the ordinate is elastic modulus), the scanning condition is that the temperature is 100 ℃, the frequency ranges from 1 to 25Hz, and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 10Hz, the reciprocating angle is 6.975%, and the time is 30min at 200 ℃; the post-aging scan is the same as the pre-aging scan.
Example 8: the method for evaluating the dynamic heat stability of the rubber based on the RPA is applied to the evaluation of the dynamic heat stability of the rubber with the same type and the same grade (rubber type refers to SSBR, SBS, BR, LCBR) added with different antioxidants or/and the rubber with the same type and the different grade added with the same antioxidants or/and the rubber with the same type and different grades added with different antioxidants.
Example 9: the RPA-based rubber dynamic heat stability evaluation method is applied to the aspects of evaluating the influence of the same type of rubber or/and different heat processing technologies or production device post-treatment technologies on the dynamic heat stability of the rubber or/and the quantitative evaluation of the dynamic heat stability of the rubber under the stable production technology condition.
Example 10: the method is carried out by using an RPA2000 type rubber processing analyzer manufactured by Alpha company in the United states.
The cis-butadiene rubber BR9000 uses an antioxidant which is a solid antioxidant a (the dosage is 6.5kg/t of dry rubber, hereinafter expressed as an a antioxidant system), the preparation process is at risk, a workshop is planned to try out a certain liquid antioxidant b (the dosage is 2kg/t of dry rubber, hereinafter expressed as a b antioxidant system) instead of the solid antioxidant, BR9000 samples of two different antioxidant systems are planned to be prepared, and the evaluation is carried out by adopting the dynamic thermal stability evaluation method of rubber based on RPA, wherein the two groups of BR9000 samples are in antioxidant formula.
Butadiene Rubber (BR) RPA aging test was performed using RPA2000, the test procedure was:
The initial temperature is 60 ℃, no preheating exists, and scanning is carried out before aging: the scanning form is elastic modulus (G') -strain, and the scanning conditions are as follows: the temperature is 60 ℃, the frequency is 1Hz, and the strain scanning range is 0 to 101.5 percent. The aging procedure was: the scanning frequency is 10Hz, the reciprocating angle is 6.975 percent, the aging is carried out for 30 minutes, and the aging temperature is 190 ℃. The scanning procedure after aging is as follows: elastic modulus (G') -strain sweep at 60℃and frequency 1Hz, strain sweep range from 0% to 101.5%. The program run time was 50min, and the results obtained are shown in FIG. 2 (in the figure, aa corresponds to the post-aging rheology curve and Ba corresponds to the pre-aging rheology curve).
As can be seen in FIG. 2, the BR9000 samples increase in elastic modulus (G') after dynamic aging, indicating that the samples crosslink under aging conditions. Wherein the G' increase in sample # 2 (employing b antioxidant system) is less, indicating that the b antioxidant system is superior to the a antioxidant system. BR9000 is a tire rubber that produces high Wen Yifa green crosslinks during processing or high speed tire running, and the RPA dynamic aging procedure used in the test simulates the aging pattern of the product during use. From the above analysis, it is clear that the use of a smaller amount of antioxidant b in the BR9000 product is significantly better than a larger amount of antioxidant b.
Based on the observations made in fig. 2, RPA aging values for the samples are given in table 2. As shown in Table 2, S.DELTA.G' 1#>SΔG'2# shows that the application effect of the b antioxidant system in BR9000 rubber is better than that of the a antioxidant system. The experimental results are consistent with the experimental results of the conventional thermal oxidative ageing Mooney viscosity test.
Example 11: an RPA2000 type rubber process analyzer manufactured by Alpha corporation of America was used.
RC2557S styrene-butadiene rubber produced by the styrene-butadiene rubber device uses a main anti-c+auxiliary anti-d antioxidant system, and recently, the supply channel of an antioxidant needs to be expanded due to the requirements of energy conservation and consumption reduction. The performance of the secondary antioxidant e was evaluated in place of the secondary antioxidant d, and the antioxidant formulation of the experimental sample is shown in table 3.
Styrene Butadiene Rubber (SBR) RPA aging tests were performed using RPA2000, the test procedure being:
Preheating for 2min at 75 ℃; the scan before aging was: the scanning form is elastic modulus (G') -strain scanning, the scanning condition is that the temperature is 75 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is that the scanning frequency is 10Hz, the reciprocating angle is 6.975 percent, the time is 30 minutes, and the temperature is 190 ℃; the scanning procedure after aging is as follows. The elastic modulus (G') -strain curve of the obtained sample before and after aging is shown in FIG. 3 (in the figure, aa corresponds to the rheology curve after aging, and Ba corresponds to the rheology curve before aging).
As shown in fig. 3, Δg' before and after aging of the sample corresponding to the sample # 4 in the two samples is smaller, which indicates that the effect of the c-compound e-antioxidant system is better under the micro-oxygen dynamic aging condition. In the micro-oxygen state, the rubber is heated and decomposed to form free radicals, the free radicals react with a small amount of oxygen to generate small chain segments, the small chain segments have stronger crosslinking tendency than high polymers, and at the moment, if the peroxide can be timely decomposed, the aging crosslinking degree of the rubber can be reduced. As is clear from the discussion of thermal oxidative aging, the peroxide decomposing ability of the secondary antioxidant e was stronger than that of the secondary antioxidant d, and thus, the aging resistance of sample No. 4 was better in this test. The above is based on the observation that RPA aging values for the samples are listed in table 4 as a reference. As shown in Table 4, S.DELTA.G' 3#>SΔG'4# shows that the application effect of the auxiliary antioxidant anti-e in 2557S rubber is superior to that of the auxiliary antioxidant d. In addition, two samples respectively adopting the primary anti-c+secondary anti-d and the primary anti-c+secondary anti-e are respectively subjected to a thermal oxidative aging mooney viscosity test, an RPA aging test, a HAKKE thermal stability test and DSC thermal analysis, and the obtained conclusion is consistent with the evaluation result obtained by adopting the dynamic thermal stability performance evaluation method of the rubber based on the RPA.
The method for evaluating the dynamic thermal stability of the rubber based on the RPA takes raw rubber as a specific research object, classifies, edits and screens the RPA program according to the raw rubber variety, uses a three-section type RPA aging program, integrates and calculates the difference value of the mechanical property curves of samples before and after aging, provides a dynamic thermal stability judgment formula of the rubber based on the RPA, removes the influence of the sample itself including molecular weight, molecular weight distribution, microstructure and the like on the oxidation resistance of the sample, quantitatively evaluates the dynamic thermal stability of the rubber, and is suitable for various raw rubber samples. The evaluation method can quantitatively represent the dynamic heat stability of the rubber, and is simple and convenient to operate, high in reproducibility and accurate in judgment.
The technical characteristics form the embodiment of the invention, have stronger adaptability and implementation effect, and can increase or decrease unnecessary technical characteristics according to actual needs so as to meet the requirements of different situations.
TABLE 1
Table 2 RPA aging values for samples
Table 3 sample antioxidant formulation
TABLE 4 RPA aging values for samples
Claims (9)
1. The dynamic thermal stability evaluation method of the rubber based on the RPA is characterized by comprising the following steps of:
firstly, performing an RPA aging test on rubber to be evaluated by using a rubber processing analyzer, wherein the RPA aging test comprises a scanning program before aging, an aging program and a scanning program after aging;
Secondly, acquiring rheological data points before rubber aging according to a scanning procedure before aging, mapping to obtain a rheological curve before rubber aging, acquiring rheological data points after rubber aging according to a scanning procedure after aging, and mapping to obtain a rheological curve after rubber aging;
Thirdly, calculating an RPA aging value of the rubber according to the rheological curve after rubber aging and the rheological curve before rubber aging, and evaluating the dynamic heat stability of the rubber according to the RPA aging value.
2. The method for evaluating dynamic thermal stability of rubber based on RPA according to claim 1, wherein in the third step, the calculation formula of the aging value of RPA is:
in the method, in the process of the invention,
S deltay is the RPA aging value,
F (y Aa) is the rheology curve after ageing of the rubber,
F (y Ba) is the rheology curve before rubber ageing,
X 1、x2 is the upper and lower abscissa limits in the RPA aging test.
3. The RPA-based dynamic thermal stability evaluation method of rubber according to claim 1 or 2, wherein the criteria for evaluating dynamic thermal stability of rubber according to RPA aging value are:
When the RPA aging value SDeltay is positive, the thermal processing crosslinking degree of the rubber is indicated, and the larger the SDeltay is, the more the thermal processing crosslinking of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is a negative value, the thermal processing degradation degree of the rubber is indicated, and the smaller the SDeltay is, the more the thermal processing degradation of the rubber is, the worse the dynamic thermal stability of the rubber is;
When the RPA aging value SDeltay is close to 0, the change of rheological property before and after heat processing is smaller, which shows that the dynamic heat stability of the rubber is better.
4. The method for evaluating dynamic thermal stability of an RPA-based rubber according to claim 1,2 or 3, wherein the RPA aging test when the rubber to be evaluated is styrene-butadiene rubber is specifically operated as: preheating for 2min at 75-100deg.C; the scan before aging was: the scanning form is elastic modulus-strain scanning, the scanning condition is that the temperature is 75 ℃ or 100 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190-200 ℃; the post-aging scan is the same as the pre-aging scan.
5. The method for evaluating dynamic thermal stability of rubber based on RPA according to any one of claims 1 to 4, wherein the RPA aging test specific operation when the rubber to be evaluated is butadiene rubber is: preheating for 0 to 2min at 65 ℃; the scan before aging was: the scanning form is elastic modulus-strain scanning, and the scanning conditions are as follows: the temperature is 60 ℃, the frequency is 1Hz, and the strain scanning range is 0% to 101.5%; the aging procedure is a Delay type test, the scanning frequency is 10Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 120-190 ℃; the post-aging scan is the same as the pre-aging scan.
6. The method for evaluating dynamic thermal stability of an RPA-based rubber according to any one of claims 1 to 5, wherein the RPA aging test specific operation when the rubber to be evaluated is a thermoplastic styrene-butadiene rubber is: preheating for 5 to 10min at 90 ℃; the scan before aging was: the scanning mode is complex dynamic viscosity-temperature scanning, and the scanning conditions are that the temperature is 90 ℃ to 160 ℃, the frequency is 5Hz and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 1Hz, the reciprocating angle is 6.975%, the time is 30min, and the temperature is 190 ℃; the post-aging scan is the same as the pre-aging scan.
7. The method for evaluating dynamic thermal stability of rubber based on RPA according to any one of claims 1 to 6, wherein the RPA aging test specific operation of the rubber to be evaluated being low cis polybutadiene rubber is: preheating for 0 to 5min at the temperature of 60 to 100 ℃; the scan before aging was: the scanning form is elastic modulus-frequency, the scanning condition is that the temperature is 100 ℃, the frequency ranges from 1 to 25Hz, and the strain is 6.75%; the aging procedure is a Delay type test, the frequency is 10Hz, the reciprocating angle is 6.975%, and the time is 30min at 200 ℃; the post-aging scan is the same as the pre-aging scan.
8. Use of the RPA-based rubber dynamic heat stability performance evaluation method according to any one of claims 1 to 7 in dynamic heat stability performance evaluation of the same-grade rubber added with different antioxidants or/and the same-grade rubber added with the same antioxidants or/and the same-grade rubber added with different antioxidants.
9. Use of the RPA-based dynamic thermal stability performance evaluation method according to any one of claims 1 to 7 for evaluating the impact of the same type of rubber or/and different thermal processing processes or production device post-treatment processes on dynamic heat stability performance of rubber or/and quantitative evaluation of dynamic heat stability performance of rubber under stable production process conditions.
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