CN103293079A - Method for evaluating flame retardant efficiency of asphalt - Google Patents

Abstract

The invention relates to a method for evaluating the flame-retardant effect of asphalt, which belongs to the technical field of asphalt pavement, and solves the problem that it is difficult to accurately quantify the evaluation method of the flame-retardant performance of asphalt at present. The invention is based on the combination of thermogravimetric-differential heat synchronous test and thermal analysis kinetic theory formula calculation, and quantitatively evaluates the flame retardant effect of the flame retardant on asphalt. First, the asphalt and the prepared flame-retardant asphalt were tested separately by thermogravimetric-differential heat analyzer, and the test data such as TG, DTG, DTA and char formation rate were obtained; then, according to the theoretical formula of thermal analysis kinetics, ln[g (α)/T ² ] to the curve of 1/T, through the linear fitting of the least square method, determine the reaction mechanism function g(α) of the thermal decomposition process of asphalt material; secondly, make ln[g(α)/T ² ] For the straight line of 1/T, the kinetic parameters activation energy E and frequency factor A are obtained through the slope and intercept; finally, the magnitudes of E and A of the asphalt and the prepared flame-retardant asphalt are compared, so as to comprehensively and accurately evaluate different types of And the flame retardant effect of the amount of flame retardant on asphalt.

Description

A Method for Evaluating the Flame Retardant Effect of Asphalt

technical field

The invention relates to a method for accurately evaluating the flame retardant effect of a flame retardant on asphalt based on the combination of thermogravimetric-differential thermal synchronous test and thermal analysis kinetic theory calculation, and belongs to the technical field of road asphalt pavement.

Background technique

With the rapid development of highway construction, there are more and more highway tunnels. Asphalt pavement is widely used in long and large tunnels because of its advantages such as comfortable driving, good skid resistance, low noise, short construction period, and convenient maintenance. Because asphalt will pyrolyze and burn in the high-temperature environment of tunnel fire, and release a large amount of toxic smoke and heat, causing serious secondary disasters and bringing great difficulties to personnel escape and fire rescue. Therefore, the research on the flame retardancy of tunnel asphalt pavement has been paid more and more attention.

In order to suppress the burning of asphalt materials, adding flame retardant is one of the effective methods. The different types of flame retardants according to the components include inorganic salt flame retardants, organic flame retardants, and organic and inorganic mixed flame retardants. The main components of inorganic flame retardants are inorganic substances, such as aluminum hydroxide, magnesium hydroxide, monoammonium phosphate, ammonium chloride, boric acid, etc. The main components of organic flame retardants are organic substances, such as halogenated flame retardants, phosphate esters, halogenated phosphate esters, etc. Organic and inorganic mixed flame retardants are improved products of inorganic salt flame retardants, mainly using water-insoluble organic phosphate emulsions to partially replace inorganic salt flame retardants. Among the above flame retardant categories, inorganic flame retardants have the advantages of non-toxic, harmless, smoke-free, and halogen-free, and are widely used in various fields.

In order to exert the flame retardant performance of the flame retardant, it is necessary to add the flame retardant to the asphalt matrix first to prepare the flame retardant asphalt, that is, after the asphalt is heated to a certain temperature to melt and flow, a certain proportion of the above flame retardant is added, and fully high-speed Stir to fully mix the flame retardant with the asphalt matrix to prepare uniform and stable flame retardant asphalt. In order to evaluate the flame retardant effect of flame retardants on asphalt, it is necessary to carry out the flame resistance test on the flame retardant asphalt prepared above. At present, the test methods for evaluating the flame resistance of flame retardant materials mainly include flash point and fire point test, oxygen index test, and horizontal combustion test. , Cone calorimeter test, etc.

The above method has great limitations in evaluating the flame retardant effect of asphalt, and it is an extensive test, so it is difficult to accurately and quantitatively evaluate the flame resistance of flame retardant materials. Flash point and fire point tests can evaluate the safety of asphalt during storage and construction, but neither of them can evaluate the continuous burning ability of asphalt, and there are obvious shortcomings in evaluating the burning performance of asphalt; oxygen index test is mostly used in textile, chemical industry The evaluation of flame retardant materials in other industries, but the combustion of asphalt at room temperature is quite difficult, it needs to be heated to a certain temperature, and the combustion of asphalt is related to the gas flow rate, flow rate, etc. There are still great difficulties in the combustion effect; the horizontal combustion test is mainly used to evaluate the flame resistance of solid materials such as plastics and rubber under the direct combustion of a specified fire source, and to judge the fire resistance level of flame retardant materials. However, the asphalt material has become a flowing liquid before it is heated to the combustion temperature, so it is difficult to test, and this method can only qualitatively evaluate the fire resistance level, and cannot quantitatively evaluate the flame retardancy of the asphalt material; the cone calorimeter test is a kind of construction material. The test for determining the heat release rate of combustion of a sample under specific heat radiation conditions is mainly used to test solid materials, and has similar limitations to the horizontal combustion test.

Thermal analysis is a kind of technology that uses a thermal analyzer to measure the relationship between the physical properties of a substance and temperature under programmed temperature control. The present invention adopts a thermogravimetric-differential thermal synchronous thermal analysis test method. Thermogravimetry (TG for short) refers to the method of continuously measuring the function relationship between the mass change of the sample and the temperature or time under the condition of programmed temperature control. This method is a very simple and effective method for evaluating the thermal decomposition, combustion and flame retardancy of asphalt materials. The speed and intensity of thermal decomposition weight loss of asphalt before and after flame retardancy can be sensitively and intuitively reflected on the TG curve. The principle of thermogravimetric method is that the sample is raised from normal temperature to a specified temperature at a certain heating rate, and the computer automatically monitors the change of material quality with time or temperature during the reaction process, and directly measures the weight loss (TG) curve of mass and time or temperature. , differential weight loss (DTG) curve and char formation rate, where DTG curve is the first derivative of TG curve to time or temperature. Elemental carbon does not undergo thermal decomposition, and the char formation rate can reflect the flame retardancy of asphalt materials. The higher the char formation rate, the better the flame retardancy of asphalt materials. The method is easy to operate, high in sensitivity, fast, accurate and intuitive. Through qualitative and quantitative analysis of TG and DTG curves, important information about the decomposition process of the sample and the reaction kinetic parameters of the corresponding process can be obtained.

There are two types of thermogravimetric methods: non-isothermal thermogravimetric method and isothermal thermogravimetric method. Usually, non-isothermal thermogravimetric method is used for pyrolysis of organic matter. Compared with isothermal method, non-isothermal thermogravimetric method has the following advantages: ①The test volume is small, and the reaction constants of each temperature point within the reaction temperature range can be obtained with only one test. ②The test data is obtained on the same sample, which can eliminate the test error caused by the difference of the sample; ③It reflects the situation in the whole reaction temperature range, and eliminates the inaccurate test data caused by the improper selection of the temperature range. comparability.

Differential thermal analysis (DTA for short) is a technique for measuring the relationship between the temperature difference and temperature or time between a substance and a reference substance at a programmed temperature. The differential thermal analysis curve (DTA curve) describes the relationship between the temperature difference (ΔT) between the sample and the reference substance as a function of temperature or time. In DTA experiments, changes in sample temperature are caused by phase transitions or endothermic or exothermic effects of chemical reactions. According to the number, shape and position of various endothermic peaks or exothermic peaks on the DTA curve and the corresponding temperature, the substance under study can be qualitatively identified. The exothermic or endothermic process of a substance at different temperatures corresponds to the exothermic peak or endothermic peak on the DTA curve. Differential thermal analysis is one of the effective methods for the study of wood combustion and flame retardancy. Whether the exothermic peak or endothermic peak appears on the DTA curve and the size of the area change corresponds to the degree of exothermic or endothermic during the thermal decomposition of asphalt. Changes.

Thermal analysis kinetics is a branch of disciplines that uses the principles of chemical kinetics to study the relationship between the rate of change of physical quantities (such as mass, temperature, heat, etc.) obtained by thermal analysis methods and temperature. Kinetic analysis provides insight into various reaction processes and their mechanisms. The study of thermal analysis kinetics includes the reaction type, reaction process, reaction products, reaction speed and reaction kinetic parameters of asphalt materials during the thermal decomposition process. The kinetic parameters of thermal analysis include activation energy and frequency factor, which quantitatively describe the reaction ability of asphalt, and reflect the change law of the reaction ability of different asphalt with temperature. Therefore, the analysis of the change law of the kinetic parameters is helpful to evaluate the flame retardant effect of flame retardants on asphalt.

Activation energy is one of the main factors that determine the rate of a reaction. Activation energy is an inherent characteristic of substances. To participate in chemical reactions, the original molecular structure of the substance must be destroyed to activate the molecules, and then new molecules can be synthesized. The lower the activation energy of a pitch, the more reactive it is and the less likely its rate of reaction will vary with temperature. That is, the asphalt is not only easy to catch fire, but also flammable at a lower temperature; on the contrary, the greater the activation energy of a certain asphalt, the weaker its reaction ability, and the greater the possibility of the reaction speed changing with temperature. That is, only at a higher temperature can there be a greater reaction rate. This kind of asphalt is not only difficult to catch fire, but also requires a longer time to burn at a higher temperature.

The frequency factor reflects the collision frequency and orientation of particles in a chemical reaction. When the temperature increases, the effective collision frequency increases significantly, thereby increasing the reaction rate constant and ultimately the reaction rate. It also reflects the activity of the substance. If the frequency factor is large, it means that the asphalt has strong activity and needs more energy to activate the reaction and promote the reaction. Therefore, this kind of asphalt has good thermal stability and is not easy to thermally decompose and burn; on the contrary, if A small frequency factor indicates that the asphalt has weak activity and requires less energy to activate the reaction and promote the reaction. Therefore, this kind of asphalt has poor thermal stability and is easier to thermally decompose and burn.

In view of the many limitations of the current evaluation method of asphalt flame retardant effect, the present invention uses thermogravimetric-differential thermal simultaneous thermal analysis technology to provide a more accurate method for evaluating the flame retardant effect of flame retardant on asphalt, which is very necessary, so that it can be better , A more in-depth analysis of the flame retardant effects of different types of flame retardants and their dosage on the combustion process of asphalt.

Contents of the invention

(1) Technical problem: the purpose of this invention is to provide a new method for evaluating the flame retardant effect of flame retardants on asphalt. This method can solve the limitations of the current evaluation method in combination with laboratory tests and theoretical formula calculations, and more accurately Comprehensively evaluate the flame retardant effects of different types of flame retardants and their dosage on asphalt.

(2) Technical solution: In view of the limitations of the current evaluation methods for the flame retardant performance of asphalt materials, the present invention uses a method of combining laboratory tests and theoretical formula calculations to accurately evaluate the flame retardant performance of asphalt materials. Accurately obtain the TG, DTG, DTA data and char formation rate of asphalt material thermal decomposition process through thermogravimetric-differential thermal synchronous test, and understand the influence of different types of flame retardants and dosage on thermal decomposition of asphalt; then based on the acquired TG The experimental data uses the thermal analysis kinetic theory formula to calculate the thermal analysis kinetic parameters (activation energy and frequency factor) of asphalt material, so as to more accurately and quantitatively evaluate the flame retardant effect of different types of flame retardants and dosage on asphalt.

Thermogravimetric-differential thermal simultaneous thermal analysis test is to raise the sample from normal temperature to the specified temperature at a certain heating rate, and automatically monitor the change of material quality with time or temperature during the reaction process through the computer, and directly obtain the TG of the mass and time or temperature. , DTG, DTA curve and char formation rate. Through the qualitative and quantitative analysis of TG and DTG curves, important information about the decomposition process of the sample and the reaction kinetic parameters of the corresponding process can be obtained. According to the number, shape and position of various endothermic peaks or exothermic peaks on the DTA curve and the corresponding temperature, the substance under study can be identified. The exothermic or endothermic process of a substance at different temperatures corresponds to the exothermic peak or endothermic peak on the DTA curve. Differential thermal analysis is one of the effective methods for the study of wood combustion and flame retardancy. Whether the exothermic peak or endothermic peak appears on the DTA curve and the size of the area change corresponds to the degree of exothermic or endothermic during the thermal decomposition of asphalt. Changes.

During the thermogravimetric-differential thermal synchronous thermal analysis test process, when the asphalt is thermally decomposed, the volatile matter precipitates out and leaves the reaction system, and the thermobalance measures the mass loss of the asphalt. The present invention utilizes the reaction weight loss to study the thermal decomposition volatile matter kinetics, Accurately describe the complex thermal decomposition reactions in the pyrolysis of bitumen and understand the nature of the pyrolysis process. Its purpose is to quantitatively characterize the reaction (or phase transition) process, determine the thermal decomposition reaction mechanism function g(α) followed by it, obtain thermal analysis kinetic parameters, and evaluate the flame retardancy of asphalt materials.

The research methods of thermal analysis kinetics are divided into isothermal kinetics and non-isothermal kinetics. For the isothermal kinetic method, due to time-consuming and the restriction of factors such as the decomposition of the substance before reaching the specified temperature, it is rarely used in thermal analysis to study the reaction kinetics, so the present invention adopts the non-isothermal thermal analysis kinetic method. Non-isothermal thermal analysis is the most commonly used method to analyze pyrolysis kinetics. It is more accurate and reliable in analyzing the influence of various factors on the thermal decomposition process. Analyzing the change law of kinetic parameters is helpful for the study of asphalt thermal decomposition and combustion. Mechanism process. Non-isothermal thermal analysis kinetics can directly obtain the reaction kinetic parameters and analyze the reaction mechanism from the thermal analysis curve. A dynamic TG curve is equivalent to countless isothermal TG curves. In other words, a dynamic thermogravimetric test can replace countless isothermal thermogravimetric tests, and these large amounts of original data are obtained on the same sample, there is no difference between samples. The error is small, the sample consumption is small, the test time is saved, and the kinetic parameters can be continuously calculated in the whole range from the beginning of the reaction to the end of the reaction.

The thermal decomposition reaction process of asphalt is very complicated, and the reaction rate constant k is a function of temperature. The higher the temperature, the greater the reaction rate. The Arrhenius theory states that the rate constant is an exponential function of temperature.

k=Ae ^(-E/RT)

Substituting the obtained activation energy E and frequency factor A into the above-mentioned Arrhenius formula, further calculation can obtain the reaction rate constant k at a certain temperature in the corresponding stage. Under the same concentration conditions, the larger the rate constant, the faster the reaction.

The thermal decomposition reaction rate is a function of the heating rate, the final temperature and the quality of the thermal decomposition products. Assuming that the non-isothermal reaction in an infinitely short time is considered as an isothermal reaction, the essential kinetic equation of pyrolysis can be expressed as:

dα/dt=k·f(α)=Ae ^(-E/RT) f(α) (1)

In the formula: f(α) is a function related to the reaction rate and α, that is, the reaction rate function; α is the reaction rate, that is, the mass change rate, %, which can be expressed as Where m ₀ is the initial mass, m is the mass at any time T(t), m _∞ is the final mass, Δm is the mass loss at T(t), Δm _∞ is the maximum mass loss; A is the frequency factor, 1/s; E is the activation energy, KJ/mol; R is the molar gas constant, 8.314×10 ^-3 KJ/(mol·k); T is the reaction temperature, K.

代入(1)式，经变换可得For asphalt pyrolysis reaction, there are various possible reaction mechanisms, and the reaction rate function f(α) has different forms according to different reaction mechanisms. constant heating rate

Substituting into formula (1), after transformation, we can get

$\frac{\mathrm{<span\; class="notranslate">\; d\&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; RT</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; dT</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

At present, many kinetic analysis methods are given based on formula (2), the purpose of which is to derive reaction kinetic parameters, such as activation energy E and frequency factor A, from formula (2) based on the TG or DTG curve obtained from the experiment, and determine The form of the reaction rate function f(α). Integrate formula (2) and perform kinetic analysis in combination with TG curve.

Define the integral function g(α) as:

$\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; d\&alpha;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Combined with (2) to get

$\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; A</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; RT</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; dT</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Where: T ₀ is the initial temperature. The temperature integral on the right-hand side of the above equation cannot be quadratured analytically, and most integral kinetic analysis methods differ from each other in that they each use a different approximation for the temperature integral. The integral method proposed by Coats and Redfern directly uses the TG curve, the calculation process is relatively simple and the accuracy is good. The Coats-Redfern integral method was used to solve the reaction kinetic parameters. Coats-Redfern derived the following approximate integral equation through the approximate derivation of the temperature integral:

$\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; AR</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;E</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; RT</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; RT</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

When a kinetic model is used to describe the pyrolysis weight loss reaction of a specific substance, the model must be tested by various methods. Kinetic analysis itself is a test of the established model. The degree of linear correlation between ln[g(α)/T ² ] and 1/T reflects the quality of the established model.

近似等于一个常数ln[AR/(βT)]。式(5)求解的关键在于如何确定g(α)，对于正确的g(α)形式，作ln[g(α)/T²]对1/T的曲线应该是一条直线，该曲线是否呈现线性，就是判断选取的g(α)是否正确的标准。经最小二乘法拟和，并取相关系数R²最大所对应的g(α)作为该热解反应的反应机理函数。当确定了正确的g(α)后，就可以作ln[g(α)/T²]对1/T的直线，拟合直线的斜率为-E/R，而截距中包含频率因子A。因此，通过斜率和截距可以求得动力学参数E和A，如图1所示。It can be seen from formula (5) that since 2RT/E<<1, 2RT/E can be ignored,

It is approximately equal to a constant ln[AR/(βT)]. The key to solving formula (5) is how to determine g(α). For the correct g(α) form, the curve of ln[g(α)/T ² ] versus 1/T should be a straight line. Whether the curve presents Linearity is the criterion for judging whether the selected g(α) is correct. Fitted by the least square method, and take the g(α) corresponding to the maximum correlation coefficient R ² as the reaction mechanism function of the pyrolysis reaction. When the correct g(α) is determined, a straight line of ln[g(α)/T ² ] to 1/T can be made, the slope of the fitted line is -E/R, and the intercept includes the frequency factor A . Therefore, the kinetic parameters E and A can be obtained through the slope and intercept, as shown in Figure 1.

(3) Beneficial effect: the method that the thermogravimetric-differential thermal synchronous test that the present invention adopts combines with thermal analysis dynamics theoretical formula is a kind of very effective means of evaluating the flame retardancy of asphalt material, has test speed fast, reproducible Good performance, high sensitivity, reliable test data and so on. The thermal decomposition process of asphalt can be reflected by the TG, DTG, DTA curves and char formation rate, and the basic information related to the thermal decomposition process of asphalt can be obtained, and based on the thermal analysis kinetic theory formula, the thermal analysis kinetic parameters (activation energy and frequency) of asphalt materials can be calculated. factor), as a criterion for judging the flame retardant effect, so as to more deeply and accurately quantitatively evaluate the flame retardant effect of different types of flame retardants and their dosage on asphalt.

Therefore, this method shows unique advantages in the screening of asphalt flame retardant types and dosage, flame retardant performance evaluation, and flame retardant mechanism research. It can dynamically understand the thermal decomposition behavior of asphalt over time, so as to obtain asphalt The internal laws of thermal decomposition, while other research methods can only compare the final state of thermal decomposition with the changes in some parameters of raw asphalt, such as microstructure, elemental composition, and chemical composition, to predict the possible course of asphalt in the thermal decomposition process.

The application of the actual project proves that the method for evaluating the flame retardant effect of the flame retardant on asphalt provided by the present invention is accurate and reliable, and the method has successfully evaluated the flame retardant effect of the flame retardant used in the actual project on asphalt. Currently, the asphalt pavement uses The condition is good, which shows that the evaluation method of the present invention is reasonable, reliable and practical, and can be used to evaluate the flame retardancy of different types of flame retardants and dosages on asphalt.

Description of drawings

直线的斜率与截距示意图Figure 1ln[g(α)/T ² ] pair

Slope and intercept diagram of a straight line

  2-纵坐标轴ln[g(α)/T²]  3-斜率  4-截距1-Abscissa axis

2-axis of ordinate ln[g(α)/T ² ] 3-slope 4-intercept

Detailed ways

Adopt the method that the evaluation fire retardant that the present invention proposes to asphalt fire-retardant effect, concrete steps are as follows:

(1) Prepare the flame retardant asphalt sample, heat the asphalt to a certain temperature, and after melting and flowing, add different types and amounts of flame retardants respectively, and stir fully to make the flame retardant and asphalt matrix fully mixed, and prepare uniform, Stabilized flame retardant bitumen.

(2) The base asphalt and the prepared flame-retardant asphalt were tested separately by thermogravimetric-differential thermal analyzer. The atmosphere flow rate was 60ml/min, and the heating rate was 5°C/min. Test data such as DTG, DTA and char formation rate.

(3) According to the above formula (5), draw the curve of ln[g(α)/T ² ] against 1/T, linearly fit through the least square method, and take g(α) corresponding to the maximum correlation coefficient R ² as The reaction mechanism function of the thermal decomposition process.

(4) After determining g(α), make a straight line of ln[g(α)/T ² ] to 1/T, the slope of the fitted line is -E/R, and the intercept includes the frequency factor A, through Kinetic parameters E and A can be obtained from the slope and intercept.

(5) Comparing the activation energy E and frequency factor A of the base asphalt and the prepared flame-retardant asphalt, combined with the thermogravimetric-differential thermal analysis test results, comprehensively and accurately evaluate the effects of different types and dosages of flame retardants on asphalt Flame retardant effect.

Claims (1)

1. one kind is calculated based on thermogravimetric-differential thermal simultaneous test and Thermal Analysis Kinetics theoretical formula and to combine comprehensively, accurately to estimate fire retardant to the method for asphalt material flame retardant effect, it is characterized in that the concrete steps of this method are as follows:

(1) preparation flame-retardant pitch sample is heated to uniform temperature with pitch, after the melt-flow, adds dissimilar respectively and fire retardant volume, and fully stirs, and fire retardant is fully mixed with the pitch matrix, prepares even, stable flame-retardant pitch;

(2) adopt thermogravimetric-differential thermal synchronous analyzers that the flame-retardant pitch of matrix pitch and preparation is tested respectively, the atmosphere flow is 60ml/min, and heating rate is 5 ℃/min, is warming up to 750 ℃ from room temperature, obtains TG, DTG, DTA data and charring rate;

(3) according to above-mentioned formula (5), make ln[g (α)/T ²] to the curve of 1/T, fit through the least square method linearity, get coefficient R 2 maximum corresponding g (α) as the reaction mechanism function of this thermal decomposition process;

(4) determined g (α) after, make ln[g (α)/T ²] to the straight line of 1/T, the slope of fitting a straight line is-E/R, and comprise frequency factor A in the intercept, therefore can be in the hope of kinetic parameter E and A by slope and intercept;

(5) compare matrix pitch and the energy of activation E of preparation flame-retardant pitch and the size of frequency factor A, and in conjunction with the synchronous analytical test result of thermogravimetric-differential thermal, comprehensively, accurately estimate the fire retardant of dissimilar and volume to the flame retardant effect of pitch.

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