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

Abstract

The invention discloses a method for evaluating the flame retardant efficiency of asphalt, belonging to the technical field of an asphalt pavement and solving the problem that a method for evaluating the flame retardant efficiency of the asphalt is difficultly accurately quantified by using an existing flame retardant. According to the method, based on the combination of a thermogravimetry-differential thermal analysis synchronous test and a thermal analysis kinetics theoretical equation, the flame retardant efficiency of a flame retardant to the asphalt is quantificationally evaluated. The method comprises the steps of: respectively testing the asphalt and prepared flame-retardant asphalt by adopting a thermogravimetry-differential thermal analyzer to obtain test data such as TGs (Thermal Gravity), DTGs (differential thermogravimetry), DTAs (Differential Thermal Analysis) and char yields; secondly, drawing curves of 1n[g(alpha)/T2] to 1/T according to the thermal analysis kinetics theoretical equation, and determining reaction mechanism functions g(alpha) in the thermolysis process of the asphalt and the prepared flame-retardant asphalt through linear fitting of a least square method; thirdly, drawing a straight line of the 1n[g(alpha)/T2] to the 1/T, solving kinetics parameter activation energies E and frequency factors A through a slope and an intercept; finally, comparing the E and the A of the asphalt with the E and the A of the prepared flame-retardant asphalt so as to completely and accurately evaluate the flame-retardant efficiency of the flame retardants with different types and doping quantities to the asphalt.

Description

A kind of method of estimating the asphalt flame-retardant effect

Technical field

The present invention be a kind of based on thermogravimetric-differential thermal simultaneous test and Thermal Analysis Kinetics theoretical calculate to combine accurately estimate fire retardant to the method for asphalt flame-retardant effect, belong to the technical field of asphalt road surface.

Background technology

Along with highway construction develops rapidly, vcehicular tunnel is increasing.Advantages such as bituminous pavement is comfortable because of its driving, cling property good, noise is little, the construction period is short, easy to maintenance are used widely in the type tunnel of growing up day by day.Because pitch is meeting pyrolysis, burning under the tunnel fire hazard hot environment, and discharges a large amount of poison gas and heat, causes serious secondary disaster, brings very big difficulty to personnel escape and fire rescue.Therefore, the tunnel sheet pavement Study on flame retardance is day by day generally paid attention to.

In order to suppress the asphalt material burning, adding fire retardant is one of effective ways.Different flame retardant kind by component comprises inorganic salts fire retardant, organic fire-retardant, organic and inorganic three kinds of the fire retardants that mix.The inorganic combustion inhibitor key component is inorganics, as aluminium hydroxide, magnesium hydroxide, monoammonium phosphate, ammonium chloride, boric acid etc.The key component of organic fire-retardant is organism, as halogenated flame retardant, phosphate, halogenated phosphate etc.Organic and inorganicly mix the improved products that fire retardant is the inorganic salts fire retardant, mainly use the aqueous emulsion of non-water-soluble organophosphate, part replaces the inorganic salts fire retardant.In above-mentioned classes of flame retardants, that inorganic combustion inhibitor has is nontoxic, harmless, smokeless, the advantage of Halogen, is widely used in all kinds of fields.

In order to bring into play the fire resistance of fire retardant, fire retardant need be joined earlier in the pitch matrix, the preparation flame-retardant pitch, after soon pitch will be heated to the uniform temperature melt-flow, the above-mentioned fire retardant that adds a certain ratio, and abundant high-speed stirred, fire retardant is fully mixed with the pitch matrix, prepare uniform and stable flame-retardant pitch.In order to estimate fire retardant to the flame retardant effect of pitch, need carry out flame resistance test to the flame-retardant pitch of above-mentioned preparation, the test method of estimating the fire proofing flame resistance at present mainly contains flash-point and burning point test, oxygen index test, horizontal burning test, the test of taper calorimeter etc.

There is big limitation in said method when estimating the flame retardant effect of pitch, be the test of extensive property, the difficult accurately flame resistance of quantitative evaluation fire proofing.Flash-point and burning point test can be estimated the security of pitch in storage and work progress, but they all can not estimate the sustained combustion ability of pitch, are used for estimating the asphalt fuel combustion performance and then have distinct disadvantage; Industries such as oxygen index test is applied to weave more, chemical industry are to the evaluation of fire proofing, but pitch burning at normal temperatures is difficulty quite, need be heated to uniform temperature, and asphalt fuel combustion and gas flow, flow velocity etc. have relation, use present oxygen index test method evaluation asphalt material flame retardant effect and also have big difficulty; Horizontal burning test is mainly used in estimating the firing resistance of solid materials such as plastics, rubber under the regulation burning things which may cause a fire disaster directly burns, and judges the fire resistance rating of fire proofing.But asphalt material has become working fluid before being heated to temperature of combustion, be difficult to test, and this method can only the qualitative evaluation fire resistance rating, fire resistance that can not the quantitative evaluation asphalt material; The test of taper calorimeter is a kind of test to building materials mensuration sample heating power rate of release under specific heat radiation condition, is mainly used to test solid material, exists and the similar limitation of horizontal burning test.

It is under temperature programmed control that heat is analyzed, and utilizes a class technology of the relation of the physical property of thermal analyzer measurement of species and temperature, and the present invention adopts thermogravimetric-differential thermal simultaneous thermal analysis test method.Thermogravimetric test method(s) (Thermogravimetry is called for short TG) refers to that under the temperature programmed control condition continuous coverage goes out the mass change of sample and the method for the funtcional relationship of temperature or time.This method is to estimate the very simple and effective method of asphalt material thermal decomposition, burning and fire resistance, and the speed of fire-retardant front and back pitch thermal decomposition weightlessness and severe degree can be sensitive, be reflected on the TG curve intuitively.The thermogravimetry (TG) principle is that sample is raised to assigned temperature with certain heating rate from normal temperature, by the quality of material in the computer automatic monitoring course of reaction in time or variation of temperature, and directly measure weightlessness (TG) curve, differential weightlessness (DTG) curve and the charring rate of quality and time or temperature, wherein the DTG curve is that the TG curve is to the first order derivative of time or temperature.Thermal decomposition can not take place in the simple substance charcoal, and charring rate can reflect the asphalt material fire resistance, and charring rate is more high, and the asphalt material fire resistance is more good.This method is simple to operate, and is highly sensitive, has fast, characteristics accurately and intuitively, carries out qualitative and quantitative analysis by TG and DTG curve, can obtain important information in the relevant sample decomposable process and the reaction power mathematic(al) parameter of respective process.

Thermogravimetry (TG) has two kinds of non-isothermal thermogravimetry (TG) and isothermal thermogravimetry (TG)s.The non-isothermal thermogravimetry (TG) is adopted in common organic pyrolysis, compares with isothermal method, and the non-isothermal thermogravimetry (TG) has advantage to have: 1. tested number is little, only needs single test just can obtain the reaction constant information of each temperature spot in the range of reaction temperature; 2. test figure obtains at same sample, can eliminate the test error that the difference because of sample causes; 3. it has reflected the situation in the entire reaction temperature range, has eliminated the noncomparabilities of selecting the improper test figure that causes because of temperature range.

Differential thermal analysis (Differential thermal analysis, be called for short DTA) is a kind of technology of temperature difference and temperature or time relationship between measurement of species and the reference substance under program control temperature.Temperature difference (Δ T) between differential thermal analysis curve (DTA curve) description sample and the reference substance is with the variation relation of temperature or time.In DTA test, the variation of sample temperature is owing to change mutually or the neither endothermic nor exothermic effect of chemical reaction causes.Number, shape and position and corresponding temperature according to the various endothermic peaks on the DTA curve or exothermic peak can be identified the material of studying qualitatively.Heat release or the endothermic process of material under different temperatures is corresponding to the exothermic peak on the DTA curve or endothermic peak.Differential thermal analysis (DTA) is one of effective method of combustion of wood and fire-retardant research, and whether the size variation of area appears reaching in the exothermic peak on the DTA curve or endothermic peak, corresponding to the situation of change of heat release or heat absorption in the pitch thermal decomposition process.

Thermal Analysis Kinetics is the pace of change of the physical quantity (as quality, temperature, heat etc.) that obtains with principle of chemical kinetics research heat analysis method and a subject branch of the relation between the temperature.Can understand various courses of reaction and mechanism thereof in depth by dynamic analysis.The research of Thermal Analysis Kinetics comprises the reaction type of asphalt material in thermal decomposition process, the reaction mechanism mechanism of reaction, reaction product, reaction velocity, reaction power mathematic(al) parameter etc.The Thermal Analysis Kinetics parameter comprises energy of activation and frequency factor, and they have described the reaction capacity of pitch quantitatively, has reflected the temperature variant rule of reaction capacity of different pitches.Therefore, the analysis to the kinetic parameter Changing Pattern helps to estimate fire retardant to the fire retardation of pitch.

Energy of activation is one of principal element that determines reaction velocity.Energy of activation is the inherent characteristic of material, and material will be participated in chemical reaction, will destroy the original molecular structure of material, makes molecule activation, could synthesize the recruit then.The energy of activation of a certain pitch is more little, and its reaction capacity is just more strong, and the temperature variant possibility of its reaction velocity is more little.Namely this pitch not only catches fire easily, and also easily burns under lower temperature; Otherwise, the energy of activation of a certain pitch is more big, then its reaction capacity is more weak, the temperature variant possibility of reaction velocity is more big, namely under higher temperature, just bigger reaction velocity can be arranged, this pitch not only is difficult to catch fire, and requires under higher temperature, and expending, the time of length just can burn.

Frequency factor has reflected collision frequency and the orientation of material particle in chemical reaction, and when temperature raise, effective collision frequency significantly increased, thereby reaction rate constant is increased, and reaction rate is increased.It has also reflected the activity of material, if frequency factor is big, the active strong of this pitch is described, needs more energy ability activating reaction, promotes reaction to carry out, so this kind pitch is thermally-stabilised good, is difficult for thermal decomposition, burning; Otherwise, if frequency factor is little, illustrate a little less than the activity of this pitch, need just energy activating reaction of less energy, promote reaction to carry out, so this kind pitch is thermally-stabilised relatively poor, easily thermal decomposition, burning.

In view of there are many limitation in present asphalt flame-retardant effect evaluation method, the present invention adopts thermogravimetric-differential thermal simultaneous thermal analysis technology, provide a kind of more accurate evaluation fire retardant that the method for asphalt flame-retardant effect is seemed very necessary, thereby can better, more in depth analyze dissimilar fire retardants and volume to the fire retardation of pitch combustion process.

Summary of the invention

(1) technical matters: the object of the invention provides a kind of fire retardant of estimating to the new method of asphalt flame-retardant effect, this method is calculated in conjunction with shop experiment and theoretical formula, can solve the limitation that present evaluation method exists, the dissimilar fire retardants of thoroughly evaluating and volume are to the flame retardant effect of pitch more exactly.

(2) technical scheme: in view of there is limitation at present existing asphalt material fire resistance evaluation method, the present invention adopts shop experiment and theoretical formula to calculate the method that combines, and accurately estimates the fire resistance of asphalt material.Accurately obtain TG, DTG, DTA data and the charring rate of asphalt material thermal decomposition process earlier by thermogravimetric-differential thermal simultaneous test, understand dissimilar fire retardants and volume to the thermal decomposition influence of pitch; Adopt the Thermal Analysis Kinetics theoretical formula based on the TG test figure obtained again, calculate asphalt material Thermal Analysis Kinetics parameter (energy of activation and frequency factor), thereby the dissimilar fire retardants of quantitative evaluation and volume are to the flame retardant effect of pitch more exactly.

Thermogravimetric-differential thermal simultaneous thermal analysis test is that sample is raised to assigned temperature with certain heating rate from normal temperature, by the quality of material in the computer automatic monitoring course of reaction in time or variation of temperature, and directly obtain TG, DTG, DTA curve and the charring rate of quality and time or temperature.Carry out qualitative and quantitative analysis by TG and DTG curve, can obtain important information in the relevant sample decomposable process and the reaction power mathematic(al) parameter of respective process.Number, shape and position and corresponding temperature according to the various endothermic peaks on the DTA curve or exothermic peak can be identified the material of studying.Heat release or the endothermic process of material under different temperatures is corresponding to the exothermic peak on the DTA curve or endothermic peak.Differential thermal analysis (DTA) is one of effective method of combustion of wood and fire-retardant research, and whether the size variation of area appears reaching in the exothermic peak on the DTA curve or endothermic peak, corresponding to the situation of change of heat release or heat absorption in the pitch thermal decomposition process.

In thermogravimetric-differential thermal simultaneous thermal analysis process of the test, when the pitch decomposes, reactive system is separated out and left to volatile matter, thermobalance is measured the mass loss of pitch, the present invention utilizes reaction weightlessness to study thermal decomposition volatile matter dynamics exactly, describe pyrolysis complicated in the asphalt pyrolysis process exactly, understand the essence of pyrolytic process.Its purpose is quantitatively characterizing reaction (or phase transformation) process, determines the pyrolysis mechanism function g (α) that it is followed, and obtains the Thermal Analysis Kinetics parameter, estimates the asphalt material fire resistance.

The research method of Thermal Analysis Kinetics is divided into isothermal dynamics and non-isothermal Kinetics.For the isothermal KINETIC METHOD, because consuming time and material reaches the restriction of factors such as having decomposed before the assigned temperature, less employing in heat analysis and research reaction kinetics is so the present invention adopts non-isothermal Thermal Analysis Kinetics method.The non-isothermal thermal analysis system is to analyze the most frequently used method of pyrolysis kinetics, is analyzing various factors to the influencing aspect the rule more accurately and reliably of thermal decomposition process, and the Changing Pattern of analytic dynamics parameter helps to study pitch thermal decomposition, combustion mechanism course.The non-isothermal Thermal Analysis Kinetics then can directly be asked for reaction power mathematic(al) parameter and analytical reactions mechanism from thermal analysis curve.Article one, dynamic TG curve is equivalent to not have several isothermals TG curve, in other words, once dynamically the thermogravimetry (TG) test can replace isothermal thermogravimetric test many times, and these a large amount of raw data obtain at same sample, the error that does not have sample room, sample consumption is few, saves test period, can begin to reacting continuous computational dynamics parameter in the gamut that finishes in reaction.

Pitch pyrolysis process is very complicated, and reaction rate constant k is the function of temperature, and temperature is more high, and reaction rate is more big.The Arrhenius theory thinks that rate constant is the exponential function of temperature.

k＝Ae ^(-E/RT)

With energy of activation E and the above-mentioned Arrhenius formula of frequency factor A substitution of trying to achieve, further calculating can draw the reaction rate constant k under the respective stage uniform temperature.Under the same concentrations condition, instead more big with rate constant, react more fast.

Pyrolysis speed is the function of heating rate, whole temperature and thermal decomposition product quality.Suppose that pyrolysis essence kinetics equation can be expressed as thinking isothermal reaction at the non-isothermal reaction of infinitesimal time:

dα/dt＝k·f(α)＝Ae ^(-E/RT)f(α) (1)

In the formula: f (α) is the function relevant with reaction rate and α, i.e. reaction rate function; α is reaction rate, i.e. mass change, and % can be expressed as M wherein ₀Be initial mass, m is any T (t) quality constantly, m _∞Be final mass, Δ m is T (t) mass loss amount constantly, Δ m _∞Be biggest quality loss amount; A is frequency factor, 1/s; E is energy of activation, KJ/mol; R is mol gas constant, 8.314 * 10 ^-3KJ/ (molk), T are temperature of reaction, K.

For the asphalt pyrolysis reaction, possible reaction mechanism is diversified, and reaction rate function f (α) has different forms according to the difference of reaction mechanism.By constant heating rate

Substitution (1) formula can get through conversion

$\frac{\mathrm{d\α}}{f\left(\mathrm{\α}\right)}=\frac{A}{\mathrm{\β}}{e}^{(-E/\mathrm{RT})}\mathrm{dT}---\left(2\right)$

At present, provided many dynamic analysis methods based on formula (2), its purpose just is based on TG or the DTG curve that test obtains, and derives the reaction power mathematic(al) parameter by formula (2), as energy of activation E and frequency factor A, and the form of definite reaction velocity function f (α).Formula (2) is carried out integration, carry out dynamic analysis in conjunction with the TG curve.

Defining integration function g (α) is:

$g\left(\mathrm{\α}\right)={\∫}_0^{\mathrm{\α}}\frac{1}{f\left(\mathrm{\α}\right)}\mathrm{d\α}---\left(3\right)$

Get in conjunction with (2) formula

$g\left(\mathrm{\α}\right)=\frac{A}{\mathrm{\β}}{\∫}_{T_0}^T{e}^{(-E/\mathrm{RT})}\mathrm{dT}---\left(4\right)$

In the formula: T ₀It is initial temperature.The temperature point of following formula right-hand member can not be resolved quadrature, and the difference each other of most of integration dynamic analysis methods just is that they use different temperature point approximate expressions separately.The integral method that Coats and Redfern propose is directly utilized the TG curve, and computation process is fairly simple and accuracy good.Adopt the Coats-Redfern integration method to find the solution the reaction power mathematic(al) parameter.Coats-Redfern has derived following approximate integral form equation by the approximate derivation to temperature point:

$\ln =\left[\frac{g\left(\mathrm{\α}\right)}{T^2}\right]=\ln \left[\frac{\mathrm{AR}}{\mathrm{\βE}}(1-\frac{2\mathrm{RT}}{E})\right]-\frac{E}{\mathrm{RT}}---\left(5\right)$

When adopting a kind of kinetic model to describe the pyrolysis weight loss reaction of a certain predetermined substance, must test to this model by the whole bag of tricks.Dynamic analysis itself is exactly to a kind of check of the model set up.Ln[g (α)/T ²] size of 1/T linear dependence degree embodied the quality of the model of setting up.

As seen from formula (5), because 2RT/E＜＜1,2RT/E can ignore,

Be approximately equal to a constant ln[AR/ (β T)].The key that formula (5) is found the solution is how to determine g (α), for correct g (α) form, makes ln[g (α)/T ²] should be straight line to the curve of 1/T, whether this curve presents linearity, judges whether correct standard of the g (α) that chooses exactly.Fit through least square method, and get coefficient R ²Maximum corresponding g (α) is as the reaction mechanism function of this pyrolytic reaction.After having determined correct g (α), just can make ln[g (α)/T ²] to the straight line of 1/T, the slope of fitting a straight line is-E/R, and comprises frequency factor A in the intercept.Therefore, can be in the hope of kinetic parameter E and A, as shown in Figure 1 by slope and intercept.

(3) beneficial effect: the method that thermogravimetric-differential thermal simultaneous test that the present invention adopts combines with the Thermal Analysis Kinetics theoretical formula is a kind of means of effectively evaluation asphalt material fire resistance, has characteristics such as test speed is fast, favorable reproducibility, sensitivity is high, test figure is reliable.By TG, DTG, DTA curve and charring rate reflection pitch thermal decomposition process, can obtain the relevant essential information of pitch thermal decomposition process, and based on the Thermal Analysis Kinetics theoretical formula, calculate asphalt material Thermal Analysis Kinetics parameter (energy of activation and frequency factor), as the judgment criteria of flame retardant effect quality, thereby more in depth, the dissimilar fire retardants of quantitative evaluation more accurately and volume be to the flame retardant effect of pitch.

Therefore, this method demonstrates unique advantages at aspects such as asphalt flame-retardant agent type and volume screening, fire resistance evaluation, Flame Retardant Mechanism, can dynamically understand the thermal decomposition behavior of pitch over time, thereby obtain the inherent law of pitch thermal decomposition, and other research method can only contrast the variation of some parameters of thermal decomposition final state and material asphalt, as micromechanism, element composition, chemical constitution, predict the possible course of pitch in thermal decomposition process.

Use proof by entity project, fire retardant provided by the invention to asphalt flame-retardant Evaluation on effect method accurately and reliably, adopt this method successfully to estimate fire retardant that entity project adopts to the flame retardant effect of pitch, this bituminous pavement behaviour in service is good at present, illustrate that evaluation method of the present invention is rational, reliable, practical, can be used for estimating dissimilar fire retardants and volume to the fire resistance of pitch.

Description of drawings

Fig. 1 ln[g (α)/T ²] right

The slope of straight line and intercept synoptic diagram

The 1-abscissa axis

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

Embodiment

Adopt the evaluation fire retardant of the present invention's proposition to the method for asphalt flame-retardant effect, concrete steps 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 test figures such as TG, DTG, DTA 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 ²Maximum corresponding g (α) is 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, 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.

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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