A chemiluminescence-based monitoring method for the thermal degradation pathway of tunable polymers

Abstract

A method for monitoring the thermal degradation pathway of controllable polymers based on chemiluminescence belongs to the technical field of thermal aging control and real-time detection of polymer materials. The chemiluminescence kinetic curves and luminescence spectra of polymers and polymer composites with added inorganic fillers are recorded, and the thermal degradation reaction products and pathways are inferred through the luminescent species. The kinetic rate constants and reaction activation energies are calculated to explore the influence mechanism of different types and contents of additives on the polymer degradation process. The principle of inorganic additives inhibiting polymer aging by regulating the thermal degradation pathway of polymers is explained. This method provides a method for real-time monitoring and quantitative research on the thermal degradation process of polymers, and can be used to study the factors affecting the thermal degradation process of polymers with high sensitivity, real-time performance and accuracy, providing new ideas and research methods for the design and preparation of anti-aging polymer composites.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal aging regulation and real-time detection of polymer materials, and specifically relates to a method for studying the thermal aging reaction path of polymer materials under the regulation of inorganic fillers and their aging species through real-time chemiluminescence monitoring and quantitative analysis. Background Art

[0002] Polymer materials inevitably age and degrade in the external environment, generating different products through various reaction pathways. Polymer degradation not only contributes to the accumulation of hazardous substances but is also a crucial component of the plastics recycling economy. Therefore, effectively regulating the polymer degradation process is crucial.

[0003] During polymer aging, hydroperoxide (ROOH) is a key substance initiating degradation reactions. It continuously accumulates under heat and oxygen conditions. ROOH further decomposes to produce various free radicals, such as alkyl radicals, alkoxy radicals, and hydroxyl radicals. These free radicals then undergo various reactions, altering the polymer degradation pathway and final product. Therefore, the detection and identification of hydroperoxides and related free radicals are of great significance.

[0004] The commonly used methods for detecting and monitoring free radicals mainly use electron spin resonance spectroscopy, which requires the use of free radical scavengers. However, in the study of polymer aging and degradation processes, it is necessary to add free radical scavengers to the polymer in advance, or to dissolve the polymer in a certain solvent with certain polarity. However, these treatment methods will affect the degradation process of the polymer itself and cannot provide an accurate and non-destructive detection of the polymer's own degradation reaction. Therefore, it is urgent to develop a real-time, non-destructive detection method for the free radicals and derivatives generated during the aging and degradation process of polymers to provide a basis for the study of the aging and degradation process of polymer materials.

[0005] The method of the present invention is based on the free radicals and derived luminescent species generated during the thermal degradation of polymers under the control of inorganic additives. They are monitored in real time by chemiluminescence, and the products and reaction paths of the thermal degradation of polymers under the influence of inorganic additives are explored in combination with chemiluminescence spectroscopy. The mechanism of the influence of inorganic additives on the thermal degradation reaction path of polymers and the ability to regulate reaction kinetics are explored through kinetic rate equations and reaction activation energy calculations. The regulatory mechanism of inorganic additives is also verified by the anti-aging ability of polymer composites. This method is rapid, effective, and real-time, and successfully realizes the monitoring and kinetic study of the degradation mechanism of polymers under the action of inorganic additives, providing a new method for deepening the understanding of polymer degradation mechanisms and selecting suitable inorganic additives. Summary of the Invention

[0006] Polymer materials undergo oxidative degradation in thermal environments, undergoing different thermal degradation reactions, generating a variety of free radicals and derived luminescent species. Real-time monitoring and control of the thermal degradation process is an important step in understanding the polymer degradation mechanism.

[0007] The technical solution of the present invention is to construct a polymer and a polymer composite film with different amounts of inorganic fillers added, cut it into a specific shape, fix it on a chemiluminescence instrument, control the parameters of the chemiluminescence instrument, and record the chemiluminescence kinetic spectrum; through quantitative analysis of specific parameters and kinetic equation fitting of the luminescence signal intensity, the chemiluminescence behavior of the polymer film with added inorganic fillers is obtained; the chemiluminescence spectrometer is combined with a fluorescence spectrometer to record the chemiluminescence spectrum, and the changes in the polymer thermal degradation path and its reaction products in the presence and absence of inorganic additives are explored using a high-sensitivity real-time chemiluminescence method. The kinetic rate constants and reaction activation energies of different reactions are explored through kinetics, and the regulatory mechanism of inorganic additives is verified through the anti-aging ability of the polymer composite material. This method is simple to operate, produces accurate results, and is sensitive and reliable. It is suitable for monitoring the thermal degradation process of various polymers and studying the influence mechanism of additives.

[0008] A method for monitoring the thermal degradation pathway of a controllable polymer based on chemiluminescence, characterized by comprising the following steps:

[0009] (1) Selecting inorganic fillers, mixing them with polymer materials in different proportions and hot pressing them to construct polymer@inorganic additive composite film materials;

[0010] (2) Conducting X-ray powder diffraction tests on the constructed composite material to confirm the successful preparation of the inorganic filler, polymer, and polymer composite film material;

[0011] (3) The polymer (i.e., without adding inorganic fillers) and polymer composite film materials were cut into the size specified by the instrument, fixed on a chemiluminescent ceramic heating rod, and detected by an ultra-weak chemiluminescence spectrometer to obtain a chemiluminescence kinetic spectrum. The test conditions were: the heating temperature was set to 70-140°C, the carrier gas flow rate was set to 200-800 mL / min, the operating voltage was set to -600-1000 V, and the integration time was set to 0.1-1.0 s;

[0012] (4) Quantitatively analyzing the chemiluminescence kinetic spectra of the polymer and the polymer composite film materials with different additive amounts to determine the effects of different additive contents on the polymer chemiluminescence signal; the quantitative analysis includes: recording quantitative data such as the number of peaks n, the intensity of each kinetic luminescence peak I n , peak growth rate tanα n(tangent slope value at 1 / 2 peak intensity), etc., to explore the difference in chemiluminescence signals of composite film materials under varying addition amounts;

[0013] The quantitative analysis of polymers and polymer composite film materials can be performed according to certain rules, such as testing and quantitative analysis using a method in which the amount of addition is gradually increased.

[0014] (5) Determine the luminescent species by measuring the chemiluminescence spectra of polymers and polymer composite film materials: Combine an ultra-weak chemiluminescence spectrometer with a fluorescence spectrometer, turn off the excitation light source of the fluorescence spectrometer, and record the chemiluminescence spectra of the polymer film at different times during the heating process to confirm the free radicals or / and derivative luminescent species generated by the first peak, the second peak, and so on during the heating process of the polymer and polymer composite film materials (e.g., each kinetic luminescence peak corresponds to a free radical or / and derivative luminescent species, which can be obtained by combining the chemiluminescence spectrum with the chemiluminescence kinetic spectrum for analysis). The thermal degradation products and pathways can be further inferred by generating different free radicals or / and derivative luminescent species over time;

[0015] The above methods can be used to investigate the effects of different inorganic additives on the luminescent species produced during polymer degradation;

[0016] The conditions for ultra-weak chemiluminescence spectrometer detection in this step are the same as those for the test of polymer composite film materials with specific inorganic additives added;

[0017] (6) The chemiluminescence kinetics of polymers and polymer composite film materials at different temperatures are measured to determine the kinetic equations corresponding to different peaks and verify the chemiluminescent species in step (5); by applying the existing quantitative formula for acyl groups to the relationship between the chemiluminescence intensity I and the reaction time t, (μ is a constant, X=[ROOH] ∞ ) and the quantitative formula for carbonyl (in ) were fitted for multiple peak intensities; the fitting correlation coefficient R was obtained according to the fitting kinetic equation 2 The largest fitting equation is the kinetic equation of the chemiluminescence peak, which verifies the type of luminescent species confirmed in step (5);

[0018] (7) Calculating the kinetic equations of the polymer and polymer composite film materials at different temperatures to obtain the thermal degradation reaction kinetic rate constants and activation energies of different luminescence kinetic peaks; specifically, calculating the reaction kinetic rate constants according to the kinetic equations of the chemiluminescence peaks at different temperatures obtained in step (6); calculating the activation energies of different chemiluminescence kinetic peaks (i.e., different reaction paths) according to the Arrhenius equation, determining the changes in the aging paths of the polymer materials under the influence of different additives, and indicating the inhibitory effect of the additives on the thermal aging path of the polymer;

[0019] (8) The anti-aging ability of polymers and polymer composite film materials was studied to verify the aging path transformation mechanism; polymers and polymer composite film materials were treated at 80-150℃ for different time periods, and the infrared spectra of the corresponding films were tested. According to the existing carbonyl value calculation formula CI=I 1715 / I 2915 , calculate the carbonyl value of each corresponding film material after heat treatment for different times.

[0020] The method of the present invention can also be used to explore the anti-aging effects of different inorganic additives on polymer materials under heat treatment.

[0021] The inorganic additives mentioned above can be layered double hydroxides of different metal compositions and morphologies (such as LDHs such as MgAl-, CaAl-, ZnAl-), layered double metal oxides of different metal compositions and morphologies (such as LDOs such as MgAl-, CaAl-, ZnAl-), hydroxides of different metal compositions (such as Mg(OH)2, Al(OH)3, etc.) and metal salts (such as Mg(NO3)2, Al(NO3)3, etc.).

[0022] The polymer material may be polyolefins, such as polyethylene, polypropylene, etc., and blended polymers.

[0023] The present invention proposes to use chemiluminescence kinetic spectra and luminescence spectra to track the luminescence signals of polymers and composite materials with added inorganic fillers in real time, and to explore the thermal degradation reaction process of polymers and the influence mechanism of inorganic fillers on their thermal degradation process through chemiluminescent species. The specific process is: recording the chemiluminescence kinetic curves and luminescence spectra of polymers and polymer composite materials with added inorganic fillers, inferring the thermal degradation reaction products and paths through luminescent species, calculating the kinetic rate constants and reaction activation energies, exploring the research mechanism of the effects of additives of different types and contents on the degradation process of polymers, and explaining the principle of the anti-aging effect of inorganic additives on polymers. This method provides a method for real-time monitoring and quantitative research on the thermal degradation process of polymers, and can be used to study the factors affecting the thermal degradation process of polymers by inorganic additives. It has high sensitivity, real-time performance and accuracy, and provides new ideas and research methods for the design and preparation of anti-aging polymer composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 (A) MgAl-LDH, (B) pure PE film and (C) MgAl-LDH with 2 wt% addition

[0025] X-ray diffraction pattern of PE@2%MgAl-LDH composite.

[0026] Figure 2 PE@x%MgAl-LDH composites and pure PE@x%MgAl-LDH composites when the addition amount of MgAl-LDH is 0.5%, 1.0%, 2.0% and 3.0%

[0027] Chemiluminescence kinetics obtained when PE film was heated at 110°C.

[0028] Figure 3 The kinetic curve analysis diagram of PE@x%MgAl-LDH composite materials with different MgAl-LDH addition amounts: (A)

[0029] Physical schematic diagrams, (B) shows the change of the first chemiluminescence peak intensity and growth rate with the addition amount of MgAl-LDH, and (C) shows the change of the second chemiluminescence peak intensity and growth rate with the addition amount of MgAl-LDH.

[0030] Figure 4 PE and PE@2%MgAl-LDH composite films were heated at 110°C for (A) 10 min and (B) 40 min

[0031] The chemiluminescence spectrum of the film is shown in Figure 5, where the gray represents the PE film and the black represents the PE@2%MgAl-LDH composite film.

[0032] Figure 5(A) is the chemiluminescence kinetic curve of PE@2%MgAl-LDH composite film at different temperatures, (B) and (C)

[0033] They are the rate change and activation energy calculation of the first luminescence peak and the second luminescence peak respectively.

[0034] Figure 6 The infrared spectra of PE and PE@2%MgAl-LDH composite films were analyzed after heating at 110℃ for different times.

[0035] Measure the carbonyl value (I 1715 / I 2915 ) changes. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.

[0037] Example 1:

[0038] (1) Preparation of PE and PE@MgAl-LDH composite film materials

[0039] Layered double hydroxides (LDHs) were selected as inorganic fillers, and PE was selected as the polymer matrix. PE@MgAl-LDH composite film materials with a thickness of 0.25 mm were constructed by hot pressing at 120°C.

[0040] (2) Preparation of PE and PE@MgAl-LDH composite film materials

[0041] like Figure 1 Figure A shows the XRD diffraction pattern of MgAl-LDHs, which shows the typical layered structure of LDHs. Polyethylene (PE) was selected as the polymer matrix, and a 0.25 mm thick PE film material was constructed by hot pressing at 120°C. Figure 1 Figure B shows a crystallization peak. MgAl-LDHs were weighed at 0.5, 1.0, 2.0, and 3.0 wt% of the weight of PE, and a PE@MgAl-LDH composite film with a thickness of 0.25 mm was constructed by hot pressing at 120°C. Figure 1 Figure C shows the XRD pattern of the PE@2%MgAl-LDH composite film, which has diffraction peaks of MgAl-LDH and PE, indicating the successful preparation of the composite material.

[0042] (3) Chemiluminescence kinetic spectrum test of PE and PE@MgAl-LDH composite film materials

[0043] Cutting size is 4×1cm 2The film material was fixed on a chemiluminescent ceramic heating rod, the heating temperature was set to 110℃, the integration time was 0.1s, the carrier gas flow rate was 250mL / min, and the working voltage was 1000V. The chemiluminescence kinetic spectra of PE and PE@MgAl-LDH composite films were recorded.

[0044] (4) Quantitative study of chemiluminescence kinetics of PE and PE@MgAl-LDH composite film materials

[0045] Depend on Figure 2 As can be seen, the PE film itself exhibits a weak chemiluminescence signal, showing only one kinetic chemiluminescence peak during the 40-minute heating process. In contrast, the PE@MgAl-LDH composite film exhibits two kinetic chemiluminescence peaks during heating: the first peak at approximately 5 minutes, and the second peak between 15 and 25 minutes. The intensities of both kinetic chemiluminescence peaks gradually increase with increasing MgAl-LDH addition.

[0046] The chemiluminescence signals of PE and PE@MgAl-LDH composite films with different amounts of MgAl-LDH added were quantitatively analyzed, such as Figure 3 As shown in Figure A, record the peak intensities I1 and I2 of the first and second peaks, as well as the growth rates tanα1 and tanα2 of the first and second peaks. Figure 3 As shown in Figure B, with the increase of MgAl-LDH addition, the peak intensity I1 and growth rate tanα1 of the first peak show a linear growth, indicating that MgAl-LDH directly affects the change of the first emission peak of PE. Figure 3 As shown in Figure C, as the addition amount of MgAl-LDH increases from 0.0% to 2.0%, the peak intensity I2 and growth rate tanα2 of the second peak continue to increase. After reaching 2%, the continued addition of MgAl-LDH has little effect on the second peak. These results prove that MgAl-LDH converts the single chemiluminescence peak of the original PE into two chemiluminescence peaks. The intensity and shape of each peak change with the addition amount of MgAl-LDH, indicating that MgAl-LDH effectively regulates the luminescence behavior of PE during the heating process. (5) Luminescence spectrum measurement and luminescent species determination of PE and PE@2%MgAl-LDH composite films

[0047] In order to study the chemiluminescent species of PE and PE@MgAl-LDH composite films with different amounts of MgAl-LDH added, we tested their chemiluminescence spectra. Figure 4 As shown in A, the maximum emission peak of PE is at 500 nm at 10 minutes; as the heating process reaches 40 minutes, its emission peak red-shifts to 525 nm, indicating that the luminescent species is carbonyl (such as Figure 4(B) This change is attributed to a shift in the luminescent species during heating. For the PE@2%MgAl-LDH composite film, the emission peak starts at 350nm at 10 minutes and reaches a peak at 525nm, indicating that the chemiluminescence signal originates from acyl groups. At 40 minutes, the emission peak starts at 420nm, indicating that the chemiluminescence signal originates from triplet carbonyl groups. These results demonstrate that the addition of MgAl-LDH effectively alters the free radicals and luminescent species generated during the heating of PE, causing acyl groups to form in the first stage (first chemiluminescence peak) and carbonyl groups to form in the second stage (second chemiluminescence peak), effectively modulating the thermal aging pathway of PE.

[0048] (6) Determination of the kinetic equation for the thermal degradation process of PE@2%MgAl-LDH composite film

[0049] The PE@2%MgAl-LDH composite film was further heat-treated at different temperatures of 120, 110, 95, and 80°C, and the chemiluminescence kinetic spectra were recorded. It can be observed that at different temperatures, the film showed two chemiluminescence kinetic peaks, and as the temperature increased, the chemiluminescence signal continued to increase ( Figure 5 In order to calculate the kinetic rate constants of the growth process of the first peak and the second peak, the relationship between their chemiluminescence intensity and time was calculated respectively, and then it was introduced into different reaction kinetic formulas to obtain R 2 The largest is its fitting formula. For the first peak, follow the formula (μ is a constant, X=[ROOH] ∞ ) was fitted to confirm that the acyl group was a luminescent species. (in ) were fitted to confirm that the carbonyl group was the luminescent species. The above results are consistent with the luminescent species obtained in step (5). The results show that the addition of MgAl-LDHs adjusted the luminescent species of PE to acyl and carbonyl groups.

[0050] (7) Kinetic study on thermal degradation process of PE@2%MgAl-LDH composite film

[0051] According to the kinetic equation in step (5), the rate constant of the first chemiluminescence peak of the PE@2%MgAl-LDH composite film was obtained from 1.1×10 -2 s -1 Increased to 4.8×10 at 120℃ -2 s -1 ( Figure 5 B); the rate constant of the second chemiluminescence peak increased from 5.1×10 -4 s-1 Increased to 5.8×10 at 120℃ -3 s -1 ( Figure 5 C). Further calculation of the activation energy for the acyl-forming reaction in the first peak using the Arrhenius equation yielded a value of 40.2 kJ / mol, while the activation energy for the carbonyl-forming reaction in the second peak was 76.3 kJ / mol. This indicates that the addition of 2.0% MgAl-LDHs transforms the carbonyl-forming process of PE thermal degradation into a two-step reaction of acyl and carbonyl, altering the reaction pathway of the original PE.

[0052] (8) Study on the anti-aging ability of PE and PE@2%MgAl-LDH composite films

[0053] The infrared spectra of PE and PE@2%MgAl-LDH composite films heat-treated at 110℃ for different times were calculated and the infrared spectra at 1715 and 2915 cm -1 According to the carbonyl value calculation formula, the carbonyl values ​​(I 1715 / I 2915 ).like Figure 6 As shown in the figure, the carbonyl value of PE increased from 0.0082 in the untreated state to 0.0388, while the carbonyl value of the PE@2%MgAl-LDH composite film only increased from 0.0060 to 0.0201. These results demonstrate that MgAl-LDH exerts its anti-aging properties, effectively inhibiting the carbonyl formation in the PE film during thermal aging. The resulting PE@MgAl-LDH composite film exhibits excellent anti-aging properties and durability.

Claims

1. A method for monitoring the thermal degradation pathway of a controllable polymer based on chemiluminescence, characterized in that: The specific steps include: (1) Select inorganic fillers, blend them with polymer materials in different proportions and hot press them to construct polymer@inorganic additive composite film materials; (2) Conduct X-ray powder diffraction tests on the constructed composite materials to confirm the successful preparation of inorganic fillers, polymers, and polymer composite film materials; (3) Cut the polymer and polymer composite film materials into the size specified by the instrument, fix them on the chemiluminescent ceramic heating rod, and use the ultra-weak chemiluminescence spectrometer to detect and obtain the chemiluminescence kinetic spectrum. The test conditions are as follows: set the heating temperature to 70-140 °C, the carrier gas flow rate to 200-800 mL / min, the working voltage to -600-1000 V, and the integration time to 0.1-1.0 s; (4) Quantitatively analyzing the chemiluminescence kinetic spectra of polymers and polymer composite film materials with different additive amounts to determine the effects of different additive contents on the chemiluminescence signals of polymers; the quantitative analysis includes: recording quantitative data such as the number of peaks n , corresponding to each kinetic luminescence peak intensity I n , peak growth rate tan α n , explore the differences in chemiluminescence signals of composite thin film materials under changes in addition amount; (5) Determine the chemiluminescence spectra of polymers and polymer composite film materials to determine the luminescent species: Combine an ultra-weak chemiluminescence spectrometer with a fluorescence spectrometer, turn off the excitation light source of the fluorescence spectrometer, and record the chemiluminescence spectra of the polymer film at different times during the heating process to confirm the free radicals and / or derivative luminescent species generated by the first peak, the second peak, and so on during the heating process of the polymer and polymer composite film materials. Infer the thermal degradation products and paths by generating different free radicals and / or derivative luminescent species over time; The conditions for ultra-weak chemiluminescence spectrometer detection in this step are the same as those for the test of polymer composite film materials with specific inorganic additives added; (6) Measure the chemiluminescence kinetics of polymers and polymer composite film materials at different temperatures, determine the kinetic equations corresponding to different peaks, and verify the chemiluminescent species in step (5); I and reaction time t The relationship between the two groups was established, and the existing quantitative formulas for acyl and carbonyl groups were applied to fit multiple peak intensities respectively; the fitting correlation coefficient R was obtained according to the fitting kinetic equation. 2 The largest fitting equation is the kinetic equation of the chemiluminescence peak, which verifies the type of luminescent species confirmed in step (5); (7) Calculating the kinetic equations of polymers and polymer composite film materials at different temperatures to obtain the thermal degradation reaction kinetic rate constants and activation energies of different luminescence kinetic peaks; specifically, calculating the reaction kinetic rate constants according to the kinetic equations of the chemiluminescence peaks at different temperatures obtained in step (6); calculating the activation energies of different chemiluminescence kinetic peaks according to the Arrhenius equation, determining the changes in the aging paths of polymer materials under the influence of different additives, and indicating the inhibitory effect of the additives on the thermal aging path of the polymer; (8) The anti-aging ability of polymers and polymer composite film materials was studied to verify the aging path transformation mechanism; polymers and polymer composite film materials were treated at 80-150℃ for different time periods, and the infrared spectra of the corresponding films were tested. According to the existing carbonyl value calculation formula CI = I 1715 / I 2915 , calculate the carbonyl value of each corresponding film material after heat treatment for different times.

2. The method according to claim 1, characterized in that The inorganic additive is one or more of layered double metal hydroxides with different metal compositions and morphologies, layered double metal oxides with different metal compositions and morphologies, hydroxides with different metal compositions, and metal salts.

3. The method according to claim 1, characterized in that Polyolefins are selected as polymer materials.

4. The method according to claim 3, characterized in that The polyolefins are selected from polyethylene, polypropylene, and polymer blends.

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