CN102967620A - Method for evaluating service life of high-molecular material - Google Patents

Abstract

The invention discloses a method for evaluating the service life of a high-molecular material, which comprises the following steps: carrying out a thermal decomposition experiment by selecting lignins of the high-molecular material as experimental materials; carrying out thermogravimetric analysis on the lignins respectively through a dynamics method and an isothermic experimental method; establishing a life equation with the life upper limit of 10% weightlessness of the lignins, and carrying out a comparative experiment on a nitrogen atmosphere and an air atmosphere; and determining the life of the lignins through a thermogravimetric point-slope method. According to the invention, the life, which is determined by the thermogravimetric point-slope method, of the 10% weightless lignins at different atmospheres and different temperatures is very approximate to the life determined by the dynamics method and the life determined by the isothermic experimental method, therefore the thermogravimetric point-slope method can well evaluate the service life of the high-molecular material.

Description

A Method for Assessing the Service Life of Polymer Materials

technical field

The invention relates to a polymer material, in particular to a method for evaluating the service life of the polymer material.

Background technique

Polymer materials are widely used in industrial production and residential life, such as equipment components, power cords, etc. Since polymer materials will age during use or in the natural environment, which will seriously affect the safety of production, it is very important to simply and correctly assess the service life of polymer materials in order to deal with material aging in a timely manner.

The test method that has been used for a long time at home and abroad is the conventional aging method (CA), and its principle is that the logarithm of the insulation life is in a linear relationship with the reciprocal of the absolute temperature.

Artificial thermal aging test is an artificial accelerated aging test method to evaluate the thermal aging resistance of composite materials. The research on the thermal aging test method is relatively mature, but it is not ideal enough. In recent years, the work of thermal aging experimental research with oxygen absorption method, differential thermal analysis, and thermogravimetric analysis has been widely valued and developed.

When the material is used at high temperature for a long time, the performance gradually declines, which is the result of chemical reactions such as thermal degradation and cross-linking under the action of energy such as light and heat. Therefore, the essence of the thermal aging life is the aging speed, that is, the reaction kinetics learning problem. Generally, the life of materials at lower temperatures is often very long, but we can use the life at a certain temperature to quickly calculate the thermal aging life of the material in order to evaluate its service life.

Contents of the invention

The purpose of the present invention is to provide a method for evaluating the service life of polymer materials to quickly calculate the thermal aging life of the material so as to evaluate its service life.

The technical scheme of the present invention is: a method for evaluating the service life of polymer materials. Select lignin polymer materials as experimental materials, conduct thermal decomposition experiments, and conduct thermogravimetric analysis of lignin by kinetic methods and isothermal experimental methods respectively, and establish 10% weight loss of lignin is the life equation of the upper limit of life, and the comparative experiment of nitrogen atmosphere and air atmosphere is carried out.

The lignin, also known as Lignin, is a natural organic macromolecular substance synthesized by secondary metabolism of plants. The various functional groups contained in the lignin structure, such as aromatic nucleus, hydroxyl group, carboxyl group, methoxyl group, etc., have various abilities in the synthesis of polymer compounds, so the structure of lignin makes it a potential important resource for a series of organic chemicals .

Thermogravimetric analysis refers to a technique for measuring the relationship between the mass change of a substance and temperature at the program recharging temperature. It is usually called thermogravimetric method. is the quality of the sample, and the abscissa is the temperature or time of the sample.

The activation energy obtained by Ozawa for thermal decomposition of lignin is E=91.54kJ/mol (in nitrogen atmosphere) and E=108.67kJ/mol (in air atmosphere), a=4781.11 (in nitrogen atmosphere) and a=5675.57 (in air atmosphere), b=-7.61581 (in nitrogen atmosphere) and b=-8.75879 (in air atmosphere) were calculated by the isothermal experiment method, and finally the lignin life equation was obtained.

The lifetime equations of the lignin are respectively lgt=4781/T-7.6185 (in nitrogen atmosphere) and lgt=5675.57/T-8.7588 (in air atmosphere).

The present invention has the advantage that: the lifespan of lignin calculated by thermal point slope method under different temperatures in different atmospheres with a weight loss of 10% is very close to the lifespan obtained by kinetic method and the lifespan obtained by isothermal experiment method, so thermal The key slope method is a very good method to evaluate the service life of polymer materials.

Detailed ways

The life equation is derived by isothermal experiment method in nitrogen atmosphere:

Lignin was selected as the experimental material, N ₂ was used as the purge gas, and the flow rate was 150mL/min as the experimental conditions. The lignin was kept at 90°C, 100°C, 110°C, 120°C, 150°C, and 200°C for 120 minutes respectively. Record the experimental data in Table 1.

Table 1 Parameter changes of N ₂ purge lignin at different temperatures

T(°C) T(K) τ(min) 1/T(K ^-1 ) lgτ(min) 90 363.15 1895.8904 0.002754 3.2778 100 373.15 1249.5069 0.002680 3.0967 110 383.15 1204.1641 0.002610 3.0807 120 393.15 757.4903 0.002544 2.8794 150 423.15 233.6026 0.002363 2.3685 200 473.15 4.1324 0.002113 0.6160

According to the value, the final life equation is obtained: lgt=4050.315/T-7.6185

Isothermal comparison experiment of lignin in air atmosphere:

In order to make the experimental conditions closer to the natural environment, we again selected lignin as the experimental material, and used air as the purge gas at a flow rate of 150mL/min as the experimental conditions. The lignin was kept at 90°C, 100°C, 110°C, 120°C, 150°C, and 200°C for 120 minutes respectively. The recorded experimental data are listed in Table 2.

Table 2 Parameter changes of air purged lignin at different temperatures

T(°C) T(K) τ(min) 1/T(K ^-1 ) lgτ(min) 90 363.15 1887.3878 0.002754 3.2759 100 373.15 1239.3829 0.002680 3.0932 110 383.15 780.4809 0.002610 2.8924 120 393.15 481.0021 0.002544 2.6821 150 423.15 129.3281 0.002363 2.1116 200 473.15 2.3321 0.002113 0.3677

According to the value, the final life equation is obtained: lgt=4446.073/T-8.7588

Calculation of activation energy E by Ozawa method

Using lignin as the experimental material, carry out the thermal decomposition reaction experiment of 5K/mic, 10K/min, 15K/min, 20K/min, 30K/min respectively under nitrogen atmosphere, the temperature end point temperature when delignification loses 10% , data list 3.

In the following thermal decomposition reaction experiment, the temperature at the end of delignification when the weight loss is 10%, the data list 3.

Table 3 Changes of nitrogen atmosphere on thermal decomposition parameters of lignin at different temperatures

T(°C) T(K) 1000/T beta lgβ 202.16 475.31 2.1039 5 0.6990 212.78 485.93 2.0579 10 1.0000 222.61 495.76 2.0171 15 1.1761 227.97 501.12 1.9955 20 1.3010 239.67 514.82 1.9500 30 1.4771

According to the value, the final life equation is: lgt=4781.11/T-8.01426

Calculation of activation energy E of lignin decomposition in air atmosphere by Ozawa method

Using lignin as the experimental material, carry out 5K/mic, 10K/min, 15K/min, 20K/min, 30K/min, thermal decomposition reaction experiment in air atmosphere, focus on the temperature when delignification loses 10% Temperature, data list 4.

Table 4 Changes of air atmosphere on thermal decomposition parameters of lignin at different temperatures

T(°C) T(K) 1000/T beta lgβ 201.24 474.39 2.1080 5 0.6990 208.30 481.45 2.0771 10 1.0000 222.02 495.17 2.0195 15 1.1761 225.33 498.48 2.0061 20 1.3010 227.10 500.25 1.9990 30 1.4771

According to the value, the final life equation is: lgt=5675.57/T-9.5675

The present invention carries out the linear heating experiment of different rates and the isothermal experiment of different temperature in nitrogen atmosphere and air atmosphere to lignin respectively, then obtains the life equation of lignin by kinetic method and isothermal experiment method respectively, and according to the life The equation calculates the lifetime of lignin with 10% weight loss at different temperatures.

Experiments show that the Ozawa method and the isothermal experiment method are more suitable. The new method obtained by combining the two - the life of lignin obtained by the thermal point slope method at 10% weight loss in different atmospheres and at different temperatures and the life obtained by the kinetic method It is also very close to the lifetime obtained by the isothermal experiment method; therefore, the thermal point slope method is completely feasible, that is, the activation energy E is obtained by the Ozawa method in the kinetic method to further obtain a; the linear regression is performed by the isothermal experiment method, Find intercept, thereby find b; So the life-span equation of lignin can be summarized as following two equations in the hot point slope method that the present invention discusses:

(1) In a nitrogen atmosphere, the activation energy E=91.54kJ/mol is obtained by the Ozawa method, a=4781.1 is obtained, and b=-7.61581 is obtained by the isothermal experiment method, thereby obtaining the life equation: lgt=4781/T-7.6185;

(2) In the air atmosphere, the activation energy E=108.67kJ/mol is obtained by the Ozawa method, a=5675.57 is obtained, and b=-8.75879 is obtained by the isothermal experiment method, thereby obtaining the life equation: lgt=5675.57/T-8.758.

Combined with the actual situation, we can see that the Kissinger method is not suitable for calculating the activation energy E of the thermal decomposition of lignin in air or nitrogen atmosphere, while the Ozawa method is used to calculate The activation energy E of lignin is more reliable.

Claims (2)

1. evaluate the macromolecular material method in serviceable life for one kind, it is characterized in that:

(1) chooses lignin as experiment material, carry out the thermal decomposition experiment;

(2) utilize respectively dynamic method and isothermal experiment method in nitrogen atmosphere and air atmosphere, to compare experiment;

(3) asking for lignin with Ozawa is E=91.54kJ/mol at the energy of activation of nitrogen atmosphere thermal decomposition, activation energy=108.67kJ/mol in air atmosphere;

(4) ask for the b=-7.61581 of lignin thermal decomposition in nitrogen atmosphere with the isothermal test method, b=-8.75879 in air atmosphere;

(5) determine that the life-span equation of lignin in nitrogen atmosphere is that lgt=4781/T-7.6185 and the life-span equation in air atmosphere are lgt=5675.57/T-8.7588.

2. a kind of macromolecular material method in serviceable life of evaluating according to claim 1, it is characterized in that: described lignin, claim again lignin (Lignin), it is the synthetic a kind of natural organic high-molecular material of plant secondary metabolism, the multiple functional group of containing in the lignin structure such as aromatic proton, hydroxyl, carboxyl, methoxyl etc. have many-sided ability when synthetic macromolecular compound, so the structure of lignin makes it become the potential valuable source of a series of organic chemicalss.