CN116052805A - Calculation method for analyzing thermal performance of PET flame-retardant master batch - Google Patents

Abstract

The invention relates to a calculation method for analyzing the thermal performance of PET flame-retardant master batch, which is characterized in that a large bright PET slice and a halogen-free flame retardant are processed to prepare the PET flame-retardant master batch, then a Scipy library of a Python tool is used for calling a cut_fit function, a fit function command of a Gnurlot tool and relevant experimental data for calculation are processed by a smooths csprines function, and then the thermal performance of the PET flame-retardant master batch is analyzed by a Flynn-Wall-Ozawa method and a Kissinger method. The data fitting degree obtained by calculation through the method is high, the calculation time of researchers is greatly shortened, and the working efficiency and the reliability are improved.

Description

A calculation method for analyzing the thermal properties of PET flame retardant masterbatch

Technical Field

The invention relates to the technical field of PET flame retardant masterbatch, and in particular to a calculation method for analyzing the thermal performance of PET flame retardant masterbatch.

Background Art

Polyethylene terephthalate (PET) is a type of synthetic polymer and is widely used in the textile, automobile, electrical appliance and other industries. However, the above application scenarios have strict requirements on the flame retardancy and safety performance of the material. However, PET is a flammable material with a limiting oxygen index of only 20.8%, which is far lower than the flame retardant standard required for flame retardant occasions. In addition, there is a molten drop phenomenon in the combustion process of PET, which increases the danger of fire. There are great safety hazards in practical applications, which increases the difficulty for people to escape and firefighters to rescue. Therefore, the development of PET with flame retardant function has far-reaching significance for protecting public property and life safety. PET is a type of organic polymer, and its combustion is an exothermic decomposition reaction process. The pyrolysis kinetics, thermal stability and thermal performance parameters reflected in pyrolysis are closely related to the functional effects of polymer materials. Therefore, studying the thermal performance parameters of polymer materials is very meaningful for designing flame retardant PET. In order to solve the flammability problem of polymer materials, adding flame retardant masterbatch rich in flame retardant is one of the effective methods, among which the selection of flame retardant plays a vital role in the flame retardant modification effect of flame retardant masterbatch. Since the melting point of PET is around 255°C, it has high requirements on the decomposition temperature of the added flame retardant. The matching degree between the flame retardant and the thermal properties of PET directly affects the flame retardant effect. Therefore, studying the thermal performance related parameters of flame retardant masterbatch is very helpful for understanding the flame retardant effect.

In order to reveal and deeply analyze the flame retardant effect of flame retardants on PET, it is an effective method to understand the changes in thermal behavior from the thermodynamic process. In practical applications, thermogravimetric analyzers and differential scanning calorimeters are often used to analyze the physical properties related to thermodynamics in materials, and mathematical analysis is performed based on relevant thermodynamic classical equations. However, traditional calculation methods are often manual calculations, which take a long time to calculate, are not efficient, and bring great inconvenience to research and development work. In view of the above problems, the present invention makes innovative improvements.

Summary of the invention

In order to overcome the above-mentioned defects of the prior art, the present invention proposes a method for calculating the thermal properties of PET flame retardant masterbatch with high calculation efficiency.

The specific embodiments of the present invention are as follows:

A method for calculating the thermal properties of PET flame retardant masterbatch, characterized in that it comprises the following steps:

S1: Take 10 mg of the raw materials, PET slices with high gloss, and 10 mg of the halogen-free flame retardant, and place them in a crucible for thermogravimetric analysis to obtain thermogravimetric TG-DTG curves at multiple heating rates;

S2: Take 50-80% of high gloss PET chips and 20-50% of halogen-free flame retardant, dry at 120°C for 4-6 hours, mix the dried raw materials evenly with a high-speed mixer, extrude the mixed raw materials through a twin-screw extruder to obtain PET flame retardant masterbatch, and take 10 mg of PET flame retardant masterbatch and put it in a crucible for thermogravimetric analysis to obtain thermogravimetric TG-DTG curves at multiple heating rates;

S3: Obtain the data of the initial decomposition temperature, the peak temperature corresponding to the maximum weight loss rate, and the final carbonization amount, qualitatively evaluate the thermal stability of the PET chips, halogen-free flame retardant, and PET flame retardant masterbatch, analyze the initial decomposition temperature and peak temperature of the PET flame retardant masterbatch and the temperature difference corresponding to the PET chips, and infer the stage at which the halogen-free flame retardant plays a flame retardant role based on the final carbonization amount. If the final carbonization amount of the PET flame retardant masterbatch is significantly greater than the carbonization amount of the PET chips, it can represent the flame retardancy of the PET flame retardant masterbatch;

S4: The Scipy library of Python tool is used to call the curve_fit function, the fit function command of Gnuplot and the Smooth csplines function to process the relevant experimental data for calculation. During the application process, the command line is used to eliminate the noise interference in the data;

S5: The activation energy and logarithmic pre-exponential factor were calculated using the Flynn-Wall-Ozawa method and the Kissinger method to quantitatively analyze and evaluate the performance of halogen-free flame retardants.

Preferably, when the Flynn-Wall-Ozawa method in S5 is applied, the thermogravimetric data of the light-emitting PET slices, halogen-free flame retardants, and PET flame retardant masterbatch at different heating rates in the local document are retrieved in sequence through the Python tool, and the temperature data at the selected weight loss rate is substituted into the compiled Flynn-Wall-Ozawa method formula and the selected data is fitted using curve_fit.

Preferably, when the Kissinger method in S5 is applied, the DTG data is smoothed using Smooth cspline of Gnuplot, and the peak temperature when the weight loss rate is the largest is searched and substituted into the Kissinger method formula for calculation.

Preferably, the weight loss rate selected by the Flynn-Wall-Ozawa method in S5 is 5-70%.

Preferably, the thermogravimetric analysis is performed under the following conditions: a temperature range of 25-800° C., a heating rate of 10-25° C./min, and a nitrogen atmosphere of 30 ml/min.

Preferably, the temperature of each zone of the twin-screw extruder is 250-280°C.

Preferably, the halogen-free flame retardant is one or more of alkyl aluminum phosphate, alkyl zinc phosphate and alkyl magnesium phosphate.

Compared with the prior art, the present invention has the following beneficial effects:

The thermal performance parameters were calculated by using the Flynn-Wall-Ozawa method and the Kissinger method with the help of Python tools and Gnuplot. The activation energy and logarithmic pre-exponential factor of the high-gloss PET chips, halogen-free flame retardants and PET flame retardant masterbatch were calculated, so as to analyze the flame retardant modification effect of the halogen-free flame retardant on the high-gloss PET chips. The results showed that the flame retardancy of the prepared PET flame retardant masterbatch was mainly improved by increasing the activation energy and decomposing the halogen-free flame retardant into carbon to protect the PET matrix.

Computational tools (Python and Gnuplot) are used to automatically obtain experimental data and substitute them into compiled formulas for calculation. This method greatly reduces the inconvenience and errors of manual calculations and improves work efficiency and accuracy.

In addition, the calculation model of the present invention can be generally used for application analysis of other modified substrates, flame retardants, and formulations, which helps researchers analyze the effects of different types and proportions on the flame retardant effect of materials and quickly screen out the best proportion.

The beneficial effects of the present invention will be described in detail in the examples to make the beneficial effects more obvious.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flowchart of the operation steps for analyzing the calculation of thermal performance parameters of PET flame retardant masterbatch in a specific embodiment of the present invention;

FIG2 is a schematic diagram showing a comparison of activation energies of a large PET slice at different weight loss rates calculated by the Flynn-Wall-Ozawa method according to a specific embodiment of the present invention;

3 is a schematic diagram showing a comparison of activation energies of halogen-free flame retardants at different weight loss rates calculated using the Flynn-Wall-Ozawa method in a specific embodiment of the present invention;

4 is a schematic diagram showing a comparison of activation energies of PET flame retardant masterbatch at different weight loss rates calculated by the Flynn-Wall-Ozawa method in a specific embodiment of the present invention;

FIG5 is a schematic diagram of the linear relationship of the Kissinger method for a large light PET slice in a specific embodiment of the present invention;

6 is a schematic diagram of the linear relationship of the Kissinger method of the halogen-free flame retardant in a specific embodiment of the present invention;

FIG. 7 is a schematic diagram of the linear relationship of the Kissinger method of the PET flame retardant masterbatch in a specific embodiment of the present invention.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and/or" in the specification and claims represents at least one of the connected objects, and the character "/" generally indicates that the objects associated with each other are in an "or" relationship.

Example 1

A method for calculating the thermal properties of PET flame retardant masterbatch, in a specific embodiment of the present invention, comprises the following steps:

S1: Take 10 mg of the raw materials, PET slices with high gloss, and 10 mg of the halogen-free flame retardant, and place them in a crucible for thermogravimetric analysis to obtain thermogravimetric TG-DTG curves at multiple heating rates;

S2: Take 50-80% of bright PET chips and 20-50% of halogen-free flame retardant, dry at 120°C for 4-6 hours, mix the dried raw materials evenly with a high-speed mixer, extrude the mixed raw materials through a twin-screw extruder to obtain PET flame retardant masterbatch, and take 10mg of PET flame retardant masterbatch and place it in a crucible for thermogravimetric analysis to obtain the thermogravimetric TG-DTG curve under multiple heating rates. The conditions of the thermogravimetric analysis are: temperature range of 25-800°C, heating rate of 10-25°C/min, and nitrogen atmosphere condition of 30ml/min. The halogen-free flame retardant is one or more of alkyl aluminum phosphate, alkyl zinc phosphate, and alkyl magnesium phosphate, all of which have excellent flame retardant effects. The twin-screw extruder has a total of ten zones, and the temperature of each zone is 250-280°C.

S3: Obtain the data of the initial decomposition temperature, the peak temperature corresponding to the maximum weight loss rate, and the final carbonization amount, qualitatively evaluate the thermal stability of the PET chips, halogen-free flame retardant, and PET flame retardant masterbatch, analyze the initial decomposition temperature and peak temperature of the PET flame retardant masterbatch and the temperature difference corresponding to the PET chips, and infer the stage at which the halogen-free flame retardant plays a flame retardant role based on the final carbonization amount. If the final carbonization amount of the PET flame retardant masterbatch is significantly greater than the carbonization amount of the PET chips, it can represent the flame retardancy of the PET flame retardant masterbatch;

S4: The Scipy library of Python tool is used to call the curve_fit function, the fit function command of Gnuplot and the Smooth csplines function to process the relevant experimental data for calculation. During the application process, the command line is used to eliminate the noise interference in the data;

S5: The activation energy and logarithmic pre-exponential factor were calculated using the Flynn-Wall-Ozawa method and the Kissinger method to quantitatively analyze and evaluate the performance of halogen-free flame retardants.

When applying the Flynn-Wall-Ozawa method, the Python tool is used to retrieve the thermogravimetric data of Dayouguang PET chips, halogen-free flame retardants and PET flame retardant masterbatch at different heating rates in the local document, and the temperature data at the selected weight loss rate is substituted into the compiled Flynn-Wall-Ozawa method formula and curvefit is used to fit the selected data.

The weight loss rate selected by the Flynn-Wall-Ozawa method is 5-70%. The standard for selecting the feasible range of weight loss rate by the Flynn-Wall-Ozawa method is that the difference between the maximum and minimum activation energy in this range is 10-20% of the average activation energy value, which proves that the selected method has a high calculation reliability.

Generally speaking, the thermal degradation rate equation of the thermal degradation process can be expressed as

In formula (1): f(α) is the reaction rate function, α is the weight loss rate, and T is the absolute temperature.

Substituting the Aron-Unis formula into formula (1) yields:

In formula (2), E is the activation energy (kJ/mol) and R is the gas constant (8.314 J/mol·K).

代入公式(2)，经变化可得：

Heating rate

Substituting into formula (2), we can get:

In formula (3): f(α) is a function related to the weight loss rate α.

Taking the integral we get:

代入公式(4)通过导数运算法则，可得：

make

Substituting into formula (4) and using the derivative operation rule, we can get:

Let 20≤y≤100, and we can get: lgρ(y)≈2.315-0.4567y (6)

In formula (7), F(α) is the integral function of the mechanism function f(α).

Thus, the Flynn-Wall-Ozawa method formula is obtained:

When α is a constant, it can be seen from Formula 9 that by establishing an equation relationship between lgβ and 1000/T, the slope can be obtained as d(lgβ)/d(1/T), thereby converting the activation energy corresponding to each weight loss rate of the material during the pyrolysis process, that is, E=-(R/0.4567)×d(lgβ)/d(1/T).

Specifically: as shown in Table 1-4 and Figure 2-4, with 1000/T as the horizontal axis and lgβ as the vertical axis, β is the heating rate (the value is 10, 15, 20 and 25℃/min), the activation energy E of the glossy PET chips, halogen-free flame retardant and PET flame retardant masterbatch is calculated at the weight loss rate of 5%, 20%, 40% and 70%, respectively.

Table 1: Activation energy of glossy PET chips, halogen-free flame retardants and PET flame retardant masterbatch calculated by Flynn-Wall-Ozawa method at 5% weight loss

Table 2: Activation energy of glossy PET chips, halogen-free flame retardants and PET flame retardant masterbatch calculated by Flynn-Wall-Ozawa method at a weight loss rate of 20%

Table 3: Activation energy of bright PET chips, halogen-free flame retardants and PET flame retardant masterbatch calculated by Flynn-Wall-Ozawa method at a weight loss rate of 40%

Table 4: Activation energy of glossy PET chips, halogen-free flame retardants and PET flame retardant masterbatch calculated by Flynn-Wall-Ozawa method at a weight loss rate of 70%

In order to further analyze the thermal properties, the activation energy at weight loss rates of 10%, 15%, 30%, 50% and 60% is given at the same time. Table 5 shows the activation energy and correlation coefficient of the bright PET chips, halogen-free flame retardants and PET flame retardant masterbatch at different weight loss rates according to the fitting curves of Figures 2 to 4. It can be seen that lgβ and 1000/T have a good linear correlation, and the correlation coefficient r is greater than 0.98, which proves that the calculation method has high credibility and accuracy.

At the same time, by comparing the thermal degradation activation energy in Table 5, it is found that the activation energy of halogen-free flame retardant and PET flame retardant masterbatch is higher than that of PET chips. This shows that the addition of halogen-free flame retardant has alleviated the degradation of PET flame retardant masterbatch to a certain extent. This is mainly because PET flame retardant masterbatch will produce residual carbon when heated, and the carbon layer plays the role of isolating air and protecting the matrix.

Table 5: Activation energy of bright PET chips, halogen-free flame retardants and PET flame retardant masterbatch at different weight loss rates calculated by Flynn-Wall-Ozawa method

Combined with the final charring amount, the stage at which the halogen-free flame retardant plays a flame retardant role can be inferred. If the final charring amount of the PET flame retardant masterbatch is significantly greater than the charring amount of the glossy PET slice, it can represent the flame retardancy of the PET flame retardant masterbatch, as shown in Table 6.

Table 6: T _5% , T _max and final charring data of Dayouguang PET chips, halogen-free flame retardant and PET flame retardant masterbatch at a heating rate of 10℃/min

As can be seen from Table 6, at a heating rate of 10°C/min, the initial decomposition temperature of the halogen-free flame retardant (the temperature at 5% weight loss, T _5% ) and the peak temperature (T _max ) corresponding to the maximum weight loss rate are both 30°C higher than the corresponding temperature of the glossy PET slice, indicating that it can be used for the preparation of PET flame retardant masterbatch, which is conducive to the processing. The determination of T _max is searched after smoothing the DTG data by Gnuplot using Smooth csplines. Combined with the results of the final carbonization, after the addition of the halogen-free flame retardant, the carbonization of the PET flame retardant masterbatch increased by 41% compared with the pure glossy PET slice. This shows that the halogen-free flame retardant forms a carbon layer during the decomposition process, which plays a barrier role, slows down the decomposition of PET, and has a flame retardant effect, thereby increasing the carbonization.

和截距

从而求得活化能E和对数指前因子lnA。该方法求得的活化能为失重速率最大时的活化能和对数指前因子。When the Kissinger method is applied, the DTG data is smoothed using the Smooth cspline of Gnuplot, and the peak temperature at the maximum weight loss rate is searched and substituted into the Kissinger method formula for calculation. The slope is obtained by linear solution

and the intercept

Thus, the activation energy E and the logarithmic pre-exponential factor lnA are obtained. The activation energy obtained by this method is the activation energy and the logarithmic pre-exponential factor when the weight loss rate is the maximum.

The Kissinger method formula is:

Specifically, during the pyrolysis process, find out the temperature T _max corresponding to the maximum weight loss rate of the PET chips, halogen-free flame retardants and PET flame retardant masterbatch during the pyrolysis process at a heating rate of 10-25°C/min (as shown in Table 6, T _max under the condition of a heating rate of 10°C/min), and then substitute it into the Kissinger formula to calculate and fit the Kissinger linear relationship diagram of the PET chips, halogen-free flame retardants and PET flame retardant masterbatch, as shown in Figures 5-7, and the specific activation energy and logarithmic pre-exponential factor and other data are shown in Table 7. The absolute values of the correlation coefficients r of the linear relationship diagram of the Kissinger method are all greater than 0.99, indicating that the diagram drawn by Gnuplot using the Kissinger method has a high degree of fit, proving that the Kissinger method has a high credibility in calculating the activation energy at the maximum weight loss rate.

Table 7: Activation energy and logarithmic pre-exponential factor of bright PET chips, halogen-free flame retardants and PET flame retardant masterbatch at T _max calculated by Kissinger method

It can be seen from Table 7 that after adding halogen-free flame retardant to PET, the activation energy and logarithmic pre-exponential factor of PET flame retardant masterbatch at the maximum weight loss rate are higher than those of bright PET chips, which is consistent with the analysis results of Flynn-Wall-Ozawa method.

The linear relationship diagrams of the Kissinger method for the bright PET chips, halogen-free flame retardants and PET flame retardant masterbatch are shown in Figures 5 to 7, and the absolute values of the correlation coefficients are all greater than 0.99. It can be seen that the graph drawn by Gnuplot using the Kissinger method has a high degree of fit, proving that the Kissinger method has a high credibility in calculating the activation energy at the maximum weight loss rate.

From the experimental results, it can be seen that the present invention can effectively and accurately help researchers analyze the thermal properties of PET flame retardant masterbatch, the flame retardant effect of flame retardants and potential influencing factors. Combining the two methods, by analyzing the thermal performance parameters of Dayouguang PET slices, halogen-free flame retardants and PET flame retardant masterbatch, the thermal stability of PET flame retardant masterbatch was qualitatively and quantitatively analyzed. The time and manpower used for analyzing the test data of the present invention are greatly reduced compared with traditional manual calculations, which significantly helps to improve the efficiency of developing PET flame retardant masterbatch and other flame retardant materials.

It should be noted that, in this article, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and may also add, omit, or combine different steps. In addition, the features described with reference to certain examples may be combined in other examples.

The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present application and the claims, all of which are within the protection of the present application.

Claims (7)

1. A calculation method for analyzing thermal performance of PET flame-retardant master batch is characterized by comprising the following steps: the method comprises the following steps:

s1: respectively taking 10mg of big bright PET slices and 10mg of halogen-free flame retardant as raw materials, placing the raw materials in a crucible, and performing thermogravimetric analysis to obtain a thermogravimetric TG-DTG curve at multiple heating rates;

s2: taking 50-80% of large bright PET slices and 20-50% of halogen-free flame retardant, drying at 120 ℃ for 4-6 hours, uniformly mixing the dried raw materials by a high-speed mixer, extruding the mixed raw materials by a double-screw extruder to prepare PET flame-retardant master batches, placing 10mgPET flame-retardant master batches into a crucible, and performing thermogravimetric analysis to obtain a thermogravimetric TG-DTG curve at multiple heating rates;

s3: acquiring peak temperature and final char formation data corresponding to the maximum initial decomposition temperature and the maximum weight loss rate, qualitatively evaluating the thermal stability of the large bright PET slices, the halogen-free flame retardant and the PET flame retardant master batch, analyzing the temperature difference between the initial decomposition temperature and the peak temperature of the PET flame retardant master batch and the temperature corresponding to the large bright PET slices, deducing the stage that the halogen-free flame retardant plays a flame retardant role by combining the final char formation, and if the numerical value of the final char formation of the PET flame retardant master batch is obviously larger than the numerical value of the char formation of the large bright PET slices, representing the flame retardance of the PET flame retardant master batch;

s4: the related experimental data for calculation is processed by adopting a Scipy library of a Python tool to call a cut_fit function and a fit function command of Gnupplot and a Smooth csprines function, and noise interference existing in the data is eliminated by utilizing a command line in the application process;

s5: the activation energy and the logarithmic pre-finger factor were calculated by using the Flynn-Wall-Ozawa method and the Kissinger method to quantitatively evaluate the performance of the halogen-free flame retardant.

2. The method for calculating the thermal performance of the PET flame-retardant master batch according to claim 1, which is characterized in that: and when the Flynn-Wall-Ozawa method in the S5 is applied, sequentially calling thermal weight data of large bright PET slices, halogen-free flame retardant and PET flame retardant master batches in a local document at different heating rates through a Python tool, substituting the temperature data at the selected weight loss rate into a compiled Flynn-Wall-Ozawa method formula, and fitting the selected data by using a curve_fit.

3. The method for calculating the thermal performance of the PET flame-retardant master batch according to claim 1, which is characterized in that: and (3) smoothing the DTG data by utilizing the Gnupplot' S Smooth cspline when the Kissinger method is applied in the S5, searching out the peak temperature when the weightlessness rate is maximum, and substituting the peak temperature into a Kissinger method formula for operation.

4. The method for calculating the thermal performance of the PET flame-retardant master batch according to claim 2, which is characterized in that: the loss rate of the Flynn-Wall-Ozawa method in the S5 is 5-70%.

5. A method of calculating thermal performance of a profiled PET flame retardant masterbatch according to any one of claims 1-4, characterized by: the thermogravimetric analysis in S1 and S2 was performed under the following conditions: the temperature range is 25-800 ℃, the temperature rising rate is 10-25 ℃/min, and the nitrogen atmosphere condition is 30ml/min.

6. The method for calculating the thermal performance of the PET flame-retardant master batch according to claim 5, which is characterized in that: the temperature of each zone of the twin-screw extruder in the step S2 is 250-280 ℃.

7. The method for calculating the thermal performance of the PET flame-retardant master batch according to claim 6, which is characterized in that: the halogen-free flame retardant is one or more of aluminum alkyl phosphate, zinc alkyl phosphate and magnesium alkyl phosphate.

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