Method for rapidly calculating self-accelerating decomposition temperature of substance and application thereof
阅读说明：本技术 一种快速计算物质自加速分解温度的方法及其用途 (Method for rapidly calculating self-accelerating decomposition temperature of substance and application thereof ) 是由 金满平 王婷 王亚琴 于 2020-05-28 设计创作，主要内容包括：本发明公开了一种快速计算物质自加速分解温度的方法及其用途,属于研究快速确定物质热危害特性的技术领域。其解决了自加速分解温度测试周期长、测试样品量大导致的危险性高等技术问题。方法包括：对物质在空气中的分解反应和放热特性进行测试,得到物质的热流速曲线；其次观察热流速曲线在室温～300℃内是否出现放热峰,若出现放热峰,则计算该物质的热稳定性参数,并计算物质的热动力学参数；根据热动力学参数作温度随反应放热速率变化关系,根据物质对应的包装参数作温度随冷却系统移去热量流率变化关系；最后当q-(e)与q-(r)相切时,q-(e)对应的环境温度即为物质的SADT。本发明方法可以快速有效得到物质的自加速分解温度,且安全性高。(The invention discloses a method for rapidly calculating the self-accelerating decomposition temperature of a substance and application thereof, belonging to the technical field of research on rapidly determining the thermal hazard characteristics of the substance. The method solves the technical problems of long testing period of the self-accelerating decomposition temperature, high risk caused by large amount of tested samples and the like. The method comprises the following steps: testing the decomposition reaction and heat release characteristics of the substance in the air to obtain a heat flow rate curve of the substance; secondly, observing whether a heat flow rate curve has an exothermic peak within the temperature range of room temperature to 300 ℃, if so, calculating a thermal stability parameter of the substance, and calculating a thermodynamic parameter of the substance; making a temperature-reaction heat release rate change relation according to thermodynamic parameters, and making a temperature-reaction heat release rate change relation according to packaging parameters corresponding to substances; finally when q is e And q is r When tangent, q e The corresponding ambient temperature is the SADT of the substance. The method can quickly and effectively obtain the self-accelerating decomposition temperature of the substance, and has high safety.)
1. A method for rapidly calculating the self-accelerating decomposition temperature of a substance is characterized by comprising the following steps: the method comprises the following steps:
firstly, obtaining a heat flow rate curve of a substance;
calculating the thermal stability parameter of the substance by observing the exothermic peak of the heat flow rate curve, and further calculating the thermodynamic parameter of the substance; then, according to the thermodynamic parameters, making a temperature-to-reaction heat release rate variation relation, and according to the packaging parameters corresponding to the substances, making a temperature-to-cooling system heat removal flow rate variation relation;
and finally, observing the relation between the temperature and the reaction heat release rate and the relation between the temperature and the heat removal flow rate of the cooling system to obtain the SADT of the substance.
2. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 1, wherein: the heat flow rate curve of the substance is obtained by testing the decomposition reaction and the heat release characteristic of the substance in the air.
3. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 2, wherein: observing whether the heat flow rate curve has exothermic peak in room temperature-300 deg.c, calculating the heat stability parameter of the matter if the exothermic peak is present, and calculating the thermodynamic parameter of the matter based on the heat stability parameter.
4. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 3, wherein: the temperature is related to the exothermic rate of the reactionrF (t), the temperature is related to the flow rate of heat removed by the cooling system by qe＝f(T)。
5. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 4, wherein: observation of qeAnd q isrRelation, q by shiftingeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
6. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 3, wherein: if no exothermic peak appears at room temperature to 300 ℃, the material will not decompose at room temperature to 300 ℃.
7. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 3, wherein: and calculating thermodynamic parameters of the substance by using the thermal stability parameters and the Arrhenius law, wherein the thermodynamic parameters mainly comprise reaction activation energy Ea and a pre-exponential factor A.
8. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 3, wherein: the thermodynamic parameters are calculated as follows:
according to the theory of chemical reaction and the Arrhenius law, the rate of chemical reaction can be represented by the following formula:
in formula (1):
e-activation energy, kJ. mol-1；
A-pre-exponential factor, s-1；
T-temperature, K;
n-number of reaction stages;
x-chemical reaction consumption rate, which can be expressed as:
in formula (2):
M0initial mass of reactant, g;
m-mass of reactant at any moment, g;
bringing formula (2) into formula (1) to obtain formula (3):
if the reaction exotherm per unit reactant is Δ H, the reaction exotherm rate of the system is:
at the initial stage of the reaction, the reaction rate is low, M0After a deductive simplification of equation (4), the relationship (5) is obtained to describe the rate of evolution of heat of the chemical reaction of the substance:
transforming the formula (5) to obtain the formula (6)
Logarithm is taken from two sides of the pair formula (6) to obtain the formula (7)
The heat flow rate data of the substance at the initial stage of the reaction is substituted into the formula (6) andandafter linear regression processing, the activation energy Ea of each test sample was obtained from the slope of the straight line, and the pre-exponential factor a was obtained from the intercept.
9. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 2, wherein: the decomposition reaction and exothermic characteristics of the substance in air were tested by using a calorimeter.
10. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 9, wherein: the calorimeter is a differential scanning calorimeter, a microcalorimeter or an adiabatic calorimeter.
11. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 1, wherein: in step S3, a packaging material and a packaging specification suitable for the material are selected, and then a temperature variation relationship q with the flow rate of the heat removed by the cooling system is made according to the packaging parameters corresponding to the materiale＝f(T)。
12. According to the rightThe method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 4, wherein the method comprises the following steps: temperature dependence q of cooling system removal heat flow ratee(f) is obtained by the calculation formula:
qe＝U·S(T-To) (8)
in the formula:
qe-the cooling system removes a heat flow rate, W;
u-coefficient of heat transfer, W/(m)2·K)；
S-heat transfer area, m2；
T-temperature of substance, K;
To-a cooling temperature;
selecting proper packaging material and packaging specification, and making a relation q between the temperature and the flow rate of the heat removed by the cooling system according to corresponding packaging parameters, the contact area S between the system and the environment, the surface heat exchange coefficient U and the change of the temperature along with the heat removed by the cooling systeme＝f(T)。
13. The method for rapidly calculating the self-accelerated decomposition temperature of a substance according to claim 1, wherein: the substance is peroxide.
14. Use of a method according to any one of claims 1 to 13 for rapidly calculating the self-accelerated decomposition temperature of a substance in the determination of the self-accelerated decomposition temperature of a peroxide.
Technical Field
The invention relates to the technical field of research on rapid determination of thermal hazard characteristics of substances, in particular to a method for rapidly calculating a self-accelerated decomposition temperature (SADT) of a substance and application thereof.
Background
Currently, the Self-accelerated Decomposition Temperature (SADT), which is defined as the lowest ambient Temperature at which the material in the actual package undergoes Self-accelerated Decomposition within 7 days, is commonly used internationally to evaluate the thermal stability of the material. The self-accelerating decomposition temperature is not only related to the structure of the substance, but also related to the concentration and packaging form of the actual packaged product, so that the substance needs to be subjected to risk evaluation before storage and transportation so as to establish corresponding safety control conditions.
The united nations committee for the transport of hazardous materials (UN CETDG) recommends 4 methods for measuring SADT to people, namely, an american SADT test, an adiabatic storage test, an isothermal storage test and a heat accumulation storage test, but the 4 methods all have the defects of large test dosage, long test period, high test cost and the like, and even if different test methods are adopted for the same substance, the self-accelerated decomposition temperature difference is large. Therefore, how to safely and rapidly and effectively obtain the self-accelerating decomposition temperature of the substance becomes a key point of attention.
Disclosure of Invention
In order to solve the problems of long test period of the self-accelerated decomposition temperature, high risk caused by large amount of test samples and low accuracy of test results, the invention provides a method for quickly calculating the self-accelerated decomposition temperature of a substance, which establishes a set of test standards for quickly calculating the SADT of the substance, can quickly and effectively obtain the self-accelerated decomposition temperature of the substance and has high safety.
The technical scheme adopted by the invention is as follows:
a method for rapidly calculating the self-accelerated decomposition temperature of a substance, the method comprising:
firstly, obtaining a heat flow rate curve of a substance;
calculating the thermal stability parameter of the substance by observing the exothermic peak of the heat flow rate curve, and further calculating the thermodynamic parameter of the substance;
then, according to the thermodynamic parameters, making a temperature-to-reaction heat release rate variation relation, and according to the packaging parameters corresponding to the substances, making a temperature-to-cooling system heat removal flow rate variation relation;
and finally, observing the relation between the temperature and the reaction heat release rate and the relation between the temperature and the heat removal flow rate of the cooling system to obtain the SADT of the substance.
The heat flow rate curve of the substance is obtained by testing the decomposition reaction and the heat release characteristic of the substance in the air.
In a preferred embodiment of the present invention, the thermal stability parameter of the material is calculated by observing whether an exothermic peak occurs in a heat flow rate curve at room temperature to 300 ℃, and calculating the thermodynamic parameter of the material based on the thermal stability parameter.
As another preferred embodiment of the present invention, the temperature dependence of the exothermic rate of reaction is qrF (t), the temperature is related to the flow rate of heat removed by the cooling system by qe＝f(T)。
Further, observe qeAnd q isrRelation, q by shiftingeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
Further, in step S2, if no exothermic peak appears at room temperature to 300 ℃, the substance is not decomposed at room temperature to 300 ℃.
Further, in step S2, thermodynamic parameters of the substance, mainly reaction activation energy Ea and pre-exponential factor a, are calculated by using the thermal stability parameters and Arrhenius' law.
Further, the thermodynamic parameters are calculated as follows:
according to the theory of chemical reaction and the Arrhenius law, the rate of chemical reaction can be represented by the following formula:
in formula (1):
e-activation energy, kJ. mol-1；
A-pre-exponential factor, s-1；
T-temperature, K;
n-number of reaction stages;
x-chemical reaction consumption rate, which can be expressed as:
in formula (2):
M0initial mass of reactant, g;
m-mass of reactant at any moment, g;
bringing formula (2) into formula (1) to obtain formula (3):
if the reaction exotherm per unit reactant is Δ H, the reaction exotherm rate of the system is:
at the initial stage of the reaction, the reaction rate is low, M0After a deductive simplification of equation (4), the relationship (5) is obtained to describe the rate of evolution of heat of the chemical reaction of the substance:
transforming the formula (5) to obtain the formula (6)
Logarithm is taken from two sides of the pair formula (6) to obtain the formula (7)
The heat flow rate data of the substance at the initial stage of the reaction is substituted into the formula (6) andandafter linear regression processing, the activation energy Ea of each test sample was obtained from the slope of the straight line, and the pre-exponential factor a was obtained from the intercept.
Further, the decomposition reaction and exothermic property of the substance in the air were tested by using a calorimeter.
Preferably, the calorimeter is a differential scanning calorimeter, a microcalorimeter or an adiabatic calorimeter.
Preferably, in step S3, the material of the packaging material and the packaging specification are selected, and then the temperature is varied according to the heat flow rate q of the cooling system according to the packaging parameters corresponding to the materiale＝f(T)。
Preferably, the temperature is related to the flow rate of heat removed by the cooling system qe(t) D, which is calculated as:
qe＝U·S(T-To) (8)
in the formula:
qe-the cooling system removes a heat flow rate, W;
u-coefficient of heat transfer, W/(m)2·K)；
S-heat transfer area, m2；
T-temperature of substance, K;
To-a cooling temperature;
selecting proper packaging material and packaging specification, and making a relation q between the temperature and the flow rate of the heat removed by the cooling system according to corresponding packaging parameters, the contact area S between the system and the environment, the surface heat exchange coefficient U and the change of the temperature along with the heat removed by the cooling systeme＝f(T)。
Preferably, the substance is a peroxide.
Another object of the present invention is to provide the use of the above method for rapidly calculating the self-accelerating decomposition temperature of a substance.
The method for rapidly calculating the self-accelerating decomposition temperature of the substance is applied to measuring the self-accelerating decomposition temperature of the peroxide.
The above peroxides include cumene hydroperoxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, ammonium persulfate and hydrogen peroxide.
Compared with the prior art, the invention has the following beneficial technical effects:
(1) the decomposition reaction and heat release characteristics of a substance in the air are tested by a heat device to obtain a heat flow rate curve, the thermal stability parameter of the substance is calculated, the thermodynamic parameter of the substance is calculated according to the Arrhenius law, and then the temperature change relation (q) along with the reaction heat release rate is made according to the thermodynamic parameterrF (t)) and temperature as a function of cooling system removal heat flow rate (q)eWhen q is ═ f (t) >eAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance. The method mainly solves the problems of long self-accelerating decomposition temperature test period, high risk caused by large test sample amount, high test cost, low test result accuracy and the like in the prior art.
(2) By adopting the method, the experimental test time can be shortened to be within 24 hours from several weeks (one week is needed for testing the self-accelerated decomposition temperature of the substance by the traditional method, and several weeks or even more than one month is needed for completing the test of all the temperature points), and the self-accelerated decomposition temperature of the substance can be quickly calculated. In addition, by adopting the method, the sample amount of the experimental test sample can be reduced to 0.5-1 g from 800-1000 g required by the traditional method, and the safety risk caused by large sample amount of the test sample is greatly reduced. The invention has important guiding significance for scientific research institutions engaged in chemical heat hazard research, enterprises engaged in chemical production, storage, use and transportation and various institutions for dangerous chemical management, and the institutions also have certain requirements for a method for rapidly calculating the self-accelerating decomposition temperature of the substance. With the increasing standardization of dangerous chemical management in China, the method has great application and popularization values.
(3) The rapid test result of the peroxide self-accelerating decomposition temperature shows that the method has good experimental effect, stable use condition and safe and rapid test.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a flow chart of the present invention for rapidly calculating the self-accelerated decomposition temperature of a substance.
Detailed Description
The invention provides a method for rapidly calculating the self-accelerating decomposition temperature of a substance and application thereof, and the invention is described in detail below with reference to specific embodiments in order to make the advantages and technical scheme of the invention clearer and clearer.
First, the main apparatus and measurement method required for the method of the present invention will be described below.
The calorimeter for testing the decomposition reaction and heat release characteristics of the substance in the air can be selected from a differential scanning calorimeter, a microcalorimeter, an adiabatic calorimeter and the like.
The calorimeters are all commercial instruments and equipment.
The calorimeter, wherein the differential scanning calorimeter refers to ASTM E537-12 Standard test method for evaluating thermal stability in Chemicals by differential scanning calorimeter; the microcalorimeter refers to microcalorimeter testing method developed by Setaram (Setaram) FranceA method; adiabatic calorimeter refers to VSP bleed size calorimeter test method developed by the american emergency bleed system design society (DIERS); arrhenius law, reaction exotherm rate qrAnd cooling system removal heat flow rate qeIs a well-established empirical formula.
Referring to fig. 1, the method for rapidly calculating the self-accelerated decomposition temperature of a substance according to the present invention comprises the following steps:
firstly, testing the decomposition reaction and heat release characteristics of a substance in air by using a calorimeter to obtain a heat flow rate curve of the substance; wherein the calorimeter is a differential scanning calorimeter, microcalorimeter or adiabatic calorimeter;
secondly, observing whether a heat flow rate curve has an exothermic peak within the temperature range of room temperature to 300 ℃, if so, calculating a thermal stability parameter of the substance, and calculating a thermodynamic parameter of the substance by utilizing an Arrhenius law according to the thermal stability parameter, wherein the thermodynamic parameter mainly comprises reaction activation energy Ea and a pre-exponential factor A; if no exothermic peak appears, the material is not decomposed within the range of room temperature to 300 ℃, which indicates that the SADT of the material is meaningless to be calculated within the range of room temperature to 300 ℃;
thirdly, making a temperature-reaction heat release rate change relation q according to thermodynamic parametersrF (T), selecting proper packaging material and packaging specification, and making temperature change relation (q) along with the heat flow rate of the cooling system according to corresponding packaging parameters (the contact area S of the system and the environment, and the surface heat exchange coefficient U)e＝f(T))；
Fourth step, observe qeAnd q isrRelation, q by shiftingeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
The following detailed description is given with reference to specific embodiments.
Example 1:
this example uses differential scanning calorimetry to perform thermal scanning testing on a material.
1.1, a test method:
the heat scanning test is carried out on the substance within the range of room temperature to 300 ℃ by using a calorimeter, and the relation of the heat flow of the substance changing along with the temperature is calculated by calorimeter test software.
Required instruments, equipment and materials:
calorimeters (differential scanning calorimeter, microcalorimeter, adiabatic calorimeter, etc.) are all commercial instruments.
The differential scanning calorimeter refers to ASTM E537-12 Standard test method for evaluating thermal stability in Chemicals by differential scanning calorimeter.
The microcalorimeter was tested by the C80 microcalorimeter test method developed by Setaram (Setaram), France.
Adiabatic calorimetry refers to the VSP bleed size calorimeter test method developed by the american emergency bleed system design association (DIERS).
The specific test method comprises the following steps: the differential scanning calorimetry comprises the following specific steps:
(1) preparation of the test: respectively weighing 0.0007g of alpha-alumina (used as a reference substance) and 0.00001g of measured substance by using an analytical balance, respectively pouring the weighed alpha-alumina and the measured substance into crucibles with cover plates, and numbering for later use;
(2) covering the crucibles with cover plates respectively, and curling edges on a tablet press; for a sample which has a melting process when the temperature is increased, if necessary, the sample is placed in an aluminum flanging crucible for trimming and sealing;
(3) switching on a power supply, preheating for 20min, putting the crucible on a sample rod in an instrument heating furnace, setting the heating rate to be 0.5 ℃/min, inputting a heating rate value and a test predicted temperature value into a computer, carrying out a test according to the operation rule of the instrument, stopping the test when the test temperature reaches 300 ℃, and then respectively drawing differential scanning calorimetry curves of the measured substances by the computer.
1.2 exothermic peak screening and thermal stability parameter calculation
Observing whether a heat flow rate curve of the substance has an exothermic peak within the range of room temperature to 300 ℃, if not, the substance is not decomposed within the range of room temperature to 300 ℃, which indicates that the calculation of the SADT of the substance within the range of room temperature to 300 ℃ is meaningless; if the exothermic peak appears, calculating by thermal equipment analysis software to obtain the thermal stability parameter of the substance;
1.3 thermodynamic parameter calculation
According to the theory of chemical reaction and the Arrhenius law, the rate of chemical reaction can be represented by the following formula:
in the formula:
e-activation energy, kJ. mol-1；
A-pre-exponential factor, s-1；
T-temperature, K;
n-number of reaction stages;
x-chemical reaction consumption rate, which can be expressed as:
in the formula:
M0initial mass of reactant, g;
m-mass of reactant at any moment, g.
Bringing formula (2) into formula (1) to obtain formula (3):
if the reaction exotherm per unit reactant is Δ H, the reaction exotherm rate of the system is:
in the initial stage of the reaction, the reaction rate is low, the material consumed by the reaction is less, and the sample quality can be approximately considered to be unchanged, namely M0After a deductive simplification of equation (4), the equation describing the rate of evolution of the chemical reaction of a substance can be obtained:
transforming the formula to obtain
Taking logarithm of two sides
The heat flow rate data of the substance at the initial stage of the reaction is substituted into the formula (6) andandafter linear regression processing, the activation energy of each test sample can be obtained from the slope of the straight line, and the pre-exponential factor can be obtained from the intercept.
1.4, SADT calculation
Temperature dependence of reaction exotherm rate
Formula (5) is a relation of the heat release rate of the chemical reaction of the substances, and the temperature is taken as the relation of the change of the heat release rate of the reactionr＝f(T)。
Temperature as a function of flow rate of heat removed by the cooling system
The mass cooling system removal heat flow rate is calculated by the formula:
qe＝U·S(T-To) (8)
in the formula:
qe-the cooling system removes a heat flow rate, W;
u-coefficient of heat transfer, W/(m)2·K)
S-heat transfer area, m2；
T-temperature of substance, K;
Tothe cooling temperature.
Selecting proper packaging material and specification, and making the temperature change relation q with the heat flow rate removed by the cooling system according to the corresponding packaging parameters (the contact area S of the system and the environment, and the surface heat exchange coefficient U)e＝f(T)。
Translation qeLet q beeAnd q isrTangent
Observation of qeAnd q isrRelation by shifting qeLet q beeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
Example 2:
this example uses microcalorimetry for thermal scan testing of materials.
2.1, a test method:
the heat scanning test is carried out on the substance within the range of room temperature to 300 ℃ by using a calorimeter, and the relation of the heat flow of the substance changing along with the temperature is calculated by calorimeter test software.
Required instruments, equipment and materials:
calorimeters (differential scanning calorimeter, microcalorimeter, adiabatic calorimeter, etc.) are all commercial instruments.
The differential scanning calorimeter refers to ASTM E537-12 Standard test method for evaluating thermal stability in Chemicals by differential scanning calorimeter.
The microcalorimeter was tested by the C80 microcalorimeter test method developed by Setaram (Setaram), France.
Adiabatic calorimetry refers to the VSP bleed size calorimeter test method developed by the american emergency bleed system design association (DIERS).
The specific test method comprises the following steps: the microcalorimetry specifically comprises the following steps:
(1) sample preparation: selecting corresponding reaction tanks according to the properties of the sample, weighing the mass of two empty reaction tanks by balance, weighing no more than 1g of sample in one reaction tank, and adding aluminum oxide (Al) into the other reaction tank in equal amount2O3) As a reference cell;
(2) tightening the reaction tanks by using a special tool to seal the reaction tanks, respectively loading the two reaction tanks into corresponding positions of a micro calorimeter, and adding a cover to tighten the reaction tanks;
(3) switching on a power supply, preheating for 30min, placing the reaction tank on a reaction tank placing position in an instrument heating furnace, setting the heating rate to be 0.5 ℃/min, inputting the heating rate value and the test predicted temperature value into a computer, carrying out the test according to the operation rule of the instrument, stopping the test when the test temperature reaches 300 ℃, and then respectively making a micro-calorimetric curve of the measured substance by the computer.
2.2 exothermic peak screening and thermal stability parameter calculation
Observing whether a heat flow rate curve of the substance has an exothermic peak within the range of room temperature to 300 ℃, if not, the substance is not decomposed within the range of room temperature to 300 ℃, which indicates that the calculation of the SADT of the substance within the range of room temperature to 300 ℃ is meaningless; if the exothermic peak appears, calculating by thermal equipment analysis software to obtain the thermal stability parameter of the substance;
2.3 thermodynamic parameter calculation
According to the theory of chemical reaction and the Arrhenius law, the rate of chemical reaction can be represented by the following formula:
in the formula:
e-activation energy, kJ. mol-1；
A-pre-exponential factor, s-1；
T-temperature, K;
n-number of reaction stages;
x-chemical reaction consumption rate, which can be expressed as:
in the formula:
M0initial mass of reactant, g;
m-mass of reactant at any moment, g.
Bringing formula (2) into formula (1) to obtain formula (3):
if the reaction exotherm per unit reactant is Δ H, the reaction exotherm rate of the system is:
in the initial stage of the reaction, the reaction rate is low, the material consumed by the reaction is less, and the sample quality can be approximately considered to be unchanged, namely M0After a deductive simplification of equation (4), the equation describing the rate of evolution of the chemical reaction of a substance can be obtained:
transforming the formula to obtain
Taking logarithm of two sides
The heat flow rate data of the substance at the initial stage of the reaction is substituted into the formula (6) andandis subjected to linear regressionAfter the treatment, the activation energy of each test sample can be obtained from the slope of the straight line, and the pre-exponential factor can be obtained from the intercept.
2.4, SADT calculation
Temperature dependence of reaction exotherm rate
Formula (5) is a relation of the heat release rate of the chemical reaction of the substances, and the temperature is taken as the relation of the change of the heat release rate of the reactionr＝f(T)。
Temperature as a function of flow rate of heat removed by the cooling system
The mass cooling system removal heat flow rate is calculated by the formula:
qe＝U·S(T-To) (8)
in the formula:
qe-the cooling system removes a heat flow rate, W;
u-coefficient of heat transfer, W/(m)2·K)
S-heat transfer area, m2；
T-temperature of substance, K;
Tothe cooling temperature.
Selecting proper packaging material and specification, and making the temperature change relation q with the heat flow rate removed by the cooling system according to the corresponding packaging parameters (the contact area S of the system and the environment, and the surface heat exchange coefficient U)e＝f(T)。
Translation qeLet q beeAnd q isrTangent
Observation of qeAnd q isrRelation by shifting qeLet q beeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
Example 3:
this example uses an adiabatic calorimetry test to perform a thermal scan test on a material.
3.1, a test method:
the heat scanning test is carried out on the substance within the range of room temperature to 300 ℃ by using a calorimeter, and the relation of the heat flow of the substance changing along with the temperature is calculated by calorimeter test software.
Required instruments, equipment and materials:
calorimeters (differential scanning calorimeter, microcalorimeter, adiabatic calorimeter, etc.) are all commercial instruments.
The differential scanning calorimeter refers to ASTM E537-12 Standard test method for evaluating thermal stability in Chemicals by differential scanning calorimeter.
The microcalorimeter was tested by the C80 microcalorimeter test method developed by Setaram (Setaram), France.
Adiabatic calorimetry refers to the VSP bleed size calorimeter test method developed by the american emergency bleed system design association (DIERS).
The specific test method comprises the following steps: the adiabatic calorimetry test comprises the following specific steps:
(1) adding a sample into a calorimeter cell of a VSP discharge size calorimeter, connecting a heater according to an operation specification, sequentially connecting three pipelines, filling high-temperature-resistant glass wool into a gap between the heaters in a high-pressure kettle, and connecting corresponding circuits of a main heater, an auxiliary heater and a thermocouple;
(2) calibrating temperature and pressure sensors;
(3) switching on a power supply, preheating for 30min, respectively setting parameters such as reaction starting temperature, reaction finishing temperature, heat release starting temperature, temperature rising step, heat release detection limit and the like, carrying out a test according to the operation rule of an instrument, stopping the test when the test temperature reaches 300 ℃, and then respectively drawing adiabatic calorimetry curves of the measured substances by a computer.
3.2 exothermic peak screening and thermal stability parameter calculation
Observing whether a heat flow rate curve of the substance has an exothermic peak within the range of room temperature to 300 ℃, if not, the substance is not decomposed within the range of room temperature to 300 ℃, which indicates that the calculation of the SADT of the substance within the range of room temperature to 300 ℃ is meaningless; if the exothermic peak appears, calculating by thermal equipment analysis software to obtain the thermal stability parameter of the substance;
3.3 thermodynamic parameter calculation
According to the theory of chemical reaction and the Arrhenius law, the rate of chemical reaction can be represented by the following formula:
in the formula:
e-activation energy, kJ. mol-1；
A-pre-exponential factor, s-1；
T-temperature, K;
n-number of reaction stages;
x-chemical reaction consumption rate, which can be expressed as:
in the formula:
M0initial mass of reactant, g;
m-mass of reactant at any moment, g.
Bringing formula (2) into formula (1) to obtain formula (3):
if the reaction exotherm per unit reactant is Δ H, the reaction exotherm rate of the system is:
in the initial stage of the reaction, the reaction rate is low, the material consumed by the reaction is less, and the sample quality can be approximately considered to be unchanged, namely M0After a deductive simplification of equation (4), the equation describing the rate of evolution of the chemical reaction of a substance can be obtained:
transforming the formula to obtain
Taking logarithm of two sides
The heat flow rate data of the substance at the initial stage of the reaction is substituted into the formula (6) andandafter linear regression processing, the activation energy of each test sample can be obtained from the slope of the straight line, and the pre-exponential factor can be obtained from the intercept.
3.4, SADT calculation
Temperature dependence of reaction exotherm rate
Formula (5) is a relation of the heat release rate of the chemical reaction of the substances, and the temperature is taken as the relation of the change of the heat release rate of the reactionr＝f(T)。
Temperature as a function of flow rate of heat removed by the cooling system
The mass cooling system removal heat flow rate is calculated by the formula:
qe＝U·S(T-To) (8)
in the formula:
qe-the cooling system removes a heat flow rate, W;
u-coefficient of heat transfer, W/(m)2·K)
S-heat transfer area, m2；
T-temperature of substance, K;
Tothe cooling temperature.
Selecting proper packaging material and packaging specificationAccording to the corresponding packaging parameters (the contact area S of the system and the environment and the surface heat exchange coefficient U), making the relation q of the temperature to the flow rate of the heat removed by the cooling systeme＝f(T)。
Translation qeLet q beeAnd q isrTangent
Observation of qeAnd q isrRelation by shifting qeLet q beeAnd q isrTangent when q iseAnd q isrWhen tangent, qeThe corresponding ambient temperature is the SADT of the substance.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto.
The parts which are not described in the invention can be realized by taking the prior art as reference.
It should be noted that: any equivalents or obvious modifications thereof which may occur to persons skilled in the art and which are given the benefit of this description are deemed to be within the scope of the invention.