Quantitative calculation method for coupling effect of heat response of a flame retardant compounding system

Abstract

The present invention discloses a quantitative calculation method for the coupling effect of the heat response of a flame-retardant composite system. Using the mass fractions of the raw materials for preparing the flame-retardant composite as weights, the derivative thermogravimetric curves of the raw materials are weighted and superimposed. The obtained superimposed derivative thermogravimetric curve serves as the comparison baseline for the derivative thermogravimetric experimental measurement curve of the flame-retardant composite sample prepared under the corresponding formulation. By subtracting the "superimposed curve of the derivative thermogravimetric curves of the raw materials with the mass fractions of the raw materials as weights" from the "derivative thermogravimetric experimental measurement curve of the flame-retardant composite sample", a "difference curve" characterizing the thermal decomposition coupling characteristics of the raw materials is obtained. An integral calculation model of the product of the absolute value of the "difference curve" and "temperature" is constructed, and a calculation model for the change rate of the thermal decomposition coupling degree of each raw material with the mass fraction of the flame retardant is developed, determining the sensitive interval of the flame retardant content where the change in the flame retardant content induces a rapid change in the thermal decomposition coupling degree for the optimization of the flame-retardant formulation of the composite material.

Description

Technical Field

[0001] The present invention relates to the field of flame retardant material design and flame retardant performance detection, and particularly relates to a method for quantitatively calculating the coupling effect of the heat response of a flame retardant compound system. Background Art

[0002] Polymer materials such as polyethylene, polypropylene, ethylene-vinyl acetate are widely used in production and life. However, most polymer materials are flammable. Once on fire, they spread rapidly and release a large amount of toxic smoke quickly. Therefore, in actual applications, appropriate flame retardants are often added to such polymer materials to reduce their flammability, so as to meet the fire prevention requirements of various application sites, especially public place decoration materials, and reduce the fire risk in production and living places. For the research and development of flame retardant polymer materials, the core link is the design of the flame retardant formula. Among them, the coupling response characteristics of the added flame retardant and the matrix material under typical heating environments are the key scientific basis for the design and adjustment of the flame retardant formula. For the flame retardant performance test of polymer materials after adding flame retardants under heating conditions, the existing technologies mainly judge based on their comprehensive response performance under heating conditions. For example, in the paper "Thermal Degradation and Combustion Behaviors of Polyethylene / Alumina Trihydrate / Graphene Nanoplatelets" published in "Polymers", Volume 11, Issue 5, Page 772 in 2019, thermogravimetric analysis and a cone calorimeter were used to measure the thermal stability and heat release characteristics of the flame retardant composite material, and a scanning electron microscope was used to observe the char morphology of the polymer material after combustion, so as to characterize the comprehensive flame retardant performance and flame retardant characteristics of the material. Another example is that Patent 202110371790.4 proposes to use thermogravimetric analysis at different heating rates, calculate the comprehensive apparent reaction activation energy of the flame retardant composite material, and use this reaction activation energy to characterize the difficulty of the reaction occurring during the heating process, so as to conduct an overall evaluation and analysis of the flame retardant performance of the material.

[0003] The existing flame retardant performance analysis and evaluation technologies for flame retardant composite materials can only overall characterize the comprehensive flame retardant performance of the flame retardant composite material under a certain flame retardant formula, and cannot conduct a detailed quantitative calculation on the mutual coupling mechanism of the heat response behaviors of the components corresponding to the flame retardant formula. They cannot give the coupling correlation model between the heat response characteristics of each single component material and the common heat response characteristics of multiple components in the flame retardant formula, and can only rely on the "random shooting" strategy for continuous attempts. As a result, the design of the flame retardant formula lacks a quantitative basis and an optimization direction, which greatly increases the R & D cost of the flame retardant formula design and is not conducive to the rapid optimization design of advanced flame retardant systems. Summary of the Invention

[0004] To solve the above problems, the present invention aims to propose a quantitative calculation method for the coupling effect of the heat response of a flame retardant composite system, which is used to quantitatively calculate the coupling degree between the flame retardant and the matrix polymer material during the pyrolysis process of the flame retardant composite material, and further give the influence strength of the flame retardant formulation parameters in the flame retardant composite material on the coupling degree of the heat decomposition of each component material.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions: A quantitative calculation method for the coupling effect of the heat response of a flame retardant composite system, comprising the following steps:

[0006] S1: Determine the matrix polymer material (P) and each flame retardant (R i , i = 1 to n, where n is the number of types of flame retardants), preliminarily determine the possible series of formulations (j, j = 1 to m, where m is the number of formulations) of the matrix polymer material and each flame retardant, and give the mass fractions of the matrix polymer material and each flame retardant under each formulation condition, that is, under the j-th formulation condition, the mass fraction of the matrix polymer material is p j %, and the mass fractions of each flame retardant are r j-i % (j = 1 to m, where m is the number of formulations, i = 1 to n, where n is the number of types of flame retardants);

[0007] S2: For the matrix polymer material (P) and each flame retardant (R i , i = 1 to n, where n is the number of types of flame retardants), conduct thermogravimetric experiments to obtain the derivative thermogravimetric curve f P (T) of the matrix polymer material and the derivative thermogravimetric curves , (i = 1 to n, where n is the number of types of flame retardants);

[0008] S3: For each possible formulation j (j = 1 to m, where m is the number of formulations), uniformly melt-blend p j % of the matrix polymer material (P) and r j-i % of each flame retardant (i = 1 to n, where n is the number of types of flame retardants) to prepare m types of flame retardant composite material samples;

[0009] S4: Conduct thermogravimetric experiments on each flame retardant composite material sample (j, j = 1 to m, where m is the number of formulations) under the same conditions as in S2 to obtain the derivative thermogravimetric experimental curve f e-j (T) of each flame retardant composite material sample (j);

[0010] S5: To analyze the coupling mechanism of the heat decomposition process after the matrix polymer material (P) and each flame retardant (R i , i = 1 to n, where n is the number of types of flame retardants) are blended, the derivative thermogravimetric curves of the matrix polymer material (P) and the flame retardant (R i ) measured in S2 (f P(T) and ), with the mass fractions (p i %) of the matrix polymer material (P) and the flame retardant (R j %) corresponding to those in formulation j and r j-i %) in formula j as weights, as shown in the following formula (1), perform weighted superposition of each curve to obtain the differential thermogravimetric calculation curve f c-j (T);

[0011]

[0012] S6: Subtract the differential thermogravimetric calculation curve f e-j (T) from the differential thermogravimetric experimental curve f c-j (T) of each flame-retardant composite material sample (j, j = 1 to m, where m is the number of formulations), as shown in the following formula (2), to obtain the differential thermogravimetric difference curve df j (T);

[0013] df j (T) = f e-j (T) - f c-j (T) j = 1 to m (2)

[0014] S7: Under the conditions of each flame-retardant composite material formulation, based on the differential thermogravimetric difference curve df j (T), take the union of the similar thermal decomposition temperature ranges or adjacent thermal decomposition temperature ranges of the matrix polymer material (P) and each flame retardant (R i , i = 1 to n, where n is the number of types of flame retardants) to obtain the coupling action temperature range of the matrix polymer material (P) and each flame retardant (R i );

[0015] S8: Under the conditions of each flame-retardant composite material formulation (j), for each coupling action temperature range k (T j-k-1 , T j-k-2 ), calculate the coupling degree of the thermal decomposition process after blending the matrix polymer material (P) and each flame retardant (R i ), as shown in the following formula (3), to obtain the thermal decomposition coupling degree S j-k ;

[0016]

[0017] S9: For each flame retardant (R i , i = 1 to n, where n is the number of types of flame retardants), based on the change in the mass fraction of the flame retardant in different series of flame-retardant composite material formulations, calculate the change in the unit mass fraction of each flame retardant within different mass fraction ranges on the thermal decomposition coupling degree (S j-k) The influence strength is as shown in the following formula (4) to obtain the pyrolysis coupling degree (S j-k ) and the change factor θ of the pyrolysis coupling degree with the mass fraction of each flame retardant i-k-j ;

[0018]

[0019] S10: Compare the change factor θ of the pyrolysis coupling degree of each flame retardant within different mass fraction ranges i-k-j , and determine the mass fraction range corresponding to the maximum change factor θ of the pyrolysis coupling degree of each flame retardant i-k-j . This is the content range where the influence of the flame retardant on the pyrolysis coupling degree of the flame-retardant composite material is the most intense.

[0020] The present invention has the following advantages compared with the prior art:

[0021] (1) Using the mass fraction of each raw material for preparing the flame-retardant composite material as the weight, the derivative thermogravimetric curves of each raw material are weighted and superimposed. The obtained superimposed derivative thermogravimetric curve is used as the comparison baseline for the derivative thermogravimetric experimental measurement curve of the flame-retardant composite material sample prepared under the corresponding formula. The proposal of this baseline provides a necessary premise for the analysis of the mutual coupling effect and its strength of the thermal decomposition process of each raw material in the flame-retardant composite material.

[0022] (2) By subtracting the "superimposed curve of the derivative thermogravimetric curves of raw materials with the mass fraction of each raw material as the weight" from the "derivative thermogravimetric experimental measurement curve of the flame-retardant composite material sample", the "difference curve" characterizing the thermal decomposition coupling characteristics of the raw materials is obtained. A product integral calculation model of the absolute value of this "difference curve" and "temperature" is constructed, as shown in formula (3), and a quantitative parameter for measuring the pyrolysis coupling degree (S j-k ) between each raw material under this formula condition is given, providing an important basis for the design and optimization of the flame-retardant compounding system.

[0023] (3) Developed a calculation model for the change rate of the pyrolysis coupling degree (S j-k ) of each raw material with the mass fraction of the flame retardant, as shown in formula (4). The detailed distribution of the change rate of the pyrolysis coupling degree with the content of the flame retardant under each flame-retardant formula can be determined, and the flame retardant content sensitive interval where the change in the flame retardant content induces a rapid change in the pyrolysis coupling degree is determined for the optimization of the flame-retardant formula of the composite material. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 This is the flow chart of the quantitative calculation method for the coupling effect of the heat response of the flame retardant composite system in the embodiments of the present invention;

[0026] Figure 2 This is the derivative thermogravimetric curve of the matrix polymer material and two flame retardants in an air atmosphere;

[0027] Figure 3 This is the derivative thermogravimetric experimental curve of the flame retardant composite corresponding to five flame retardant formulations in an air atmosphere;

[0028] Figure 4 This is the derivative thermogravimetric calculation curve of the flame retardant composite corresponding to five flame retardant formulations in an air atmosphere;

[0029] Figure 5 This is the derivative thermogravimetric difference curve of the flame retardant composite corresponding to five flame retardant formulations in an air atmosphere. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention.

[0032] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] The present invention proposes a quantitative calculation method for the coupling effect of the heat response of a flame retardant composite system, which is used to quantitatively calculate the coupling degree between the flame retardant and the matrix polymer material during the pyrolysis process of the flame retardant composite, and further gives the influence strength of the flame retardant formulation parameters on the heat decomposition coupling degree of each component material in the flame retardant composite. As Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 shown, a flame retardant composite using a matrix polymer material and two flame retardants is used as a preferred embodiment in this article.

[0034] As the preference of the above embodiment, the implementation flow chart is as Figure 1 shown, and the specific implementation process is described as follows.

[0035] First, determine the matrix polymer material (P) and two flame retardants (R1, R2), and preliminarily determine five formulations (j, j = 1 to 5) of the matrix polymer material and the two flame retardants, and give the mass fractions of the matrix polymer material and each flame retardant under each formulation condition, that is, under the j-th formulation condition, the mass fraction of the matrix polymer material is p j %, and the mass fractions of each flame retardant are r j-i % (j = 1 to 5, i = 1 to 2).

[0036] As an optimization of the above embodiments, the mass fractions of the matrix polymer material and the two flame retardants in each formulation are shown in Table 1.

[0037] Table 1 Mixing ratio table of flame retardant composites

[0038]

[0039] Secondly, for the matrix polymer material (P) and the two flame retardants (R1, R2), perform thermogravimetric experiments to obtain the derivative thermogravimetric curve f P (T) of the matrix polymer material and the derivative thermogravimetric curves of each flame retardant

[0040] As an optimization of the above embodiments, the measured derivative thermogravimetric curves are as Figure 2 shown.

[0041] When performing the thermogravimetric experiment, preferably, take 5 - 6 mg of the matrix polymer material (P), flame retardant 1 or flame retardant 2 samples for a single experiment. The experimental atmosphere is an air atmosphere, and the heating program is to hold at 30°C for 5 min, and then heat up to 800°C at a rate of 20°C / min. Normalize the obtained mass loss data and take the derivative to obtain the derivative thermogravimetric curve. Further explanation, because the heat response behaviors of each raw material are weaker at lower and higher temperatures, the derivative thermogravimetric curves in the range of 230°C - 540°C are calculated and analyzed.

[0042] Meanwhile, for each possible formulation j (j = 1 to 5), mix 5% of the matrix polymer material (P) and r j % of the two flame retardants (i = 1 to 2) uniformly by melting to prepare five types of flame retardant composite material samples. And perform thermogravimetric experiments on them to obtain the derivative thermogravimetric experimental curves f j-i (T) of each flame retardant composite material sample (j), as e-j (shown). It should be noted that the experimental conditions of the flame retardant composite materials should be the same as those of the raw material experiments. Figure 3 shown.

[0043] In order to analyze the coupling mechanism of the thermal decomposition process after blending the matrix polymer material (P) and the two flame retardants (R1, R2),Figure 2 The derivative thermogravimetric curves (f P (T)) of the matrix polymer material (P) and the flame retardants (R1, R2) ), with the mass fractions (p j %, and r j-i %) of the corresponding matrix polymer material (P) and the flame retardants (R1, R2) in the 5 formulations as weights, as shown in Equation (1), are weighted and superimposed for each curve to obtain the derivative thermogravimetric calculation curve f c-j (T) of each flame retardant composite material sample (j), as Figure 4 shown.

[0044] Furthermore, using Equation (2), the derivative thermogravimetric experimental curve f e-j (T) of each flame retardant composite material sample (j, j = 1 - 5) is subtracted from the corresponding derivative thermogravimetric calculation curve f c-j (T) to obtain the derivative thermogravimetric difference curve df j (T), as Figure 5 shown.

[0045] Under the conditions of each flame retardant composite material formulation, based on the derivative thermogravimetric difference curve df j (T), the approximate thermal decomposition temperature ranges or adjacent thermal decomposition temperature ranges of the matrix polymer material (P), flame retardant 1 (R1), and flame retardant 2 (R2) are unionized to obtain the coupling action temperature range of the matrix polymer material (P) and the two flame retardants (R1, R2): among them, 230°C - 350°C is the influence stage of flame retardant 1, with the peak first positive and then negative and the negative peak being larger, indicating that under the coupling action of flame retardant 1 and the matrix polymer material, the thermal decomposition in this stage is delayed, the peak temperature increases, and the peak value increases; 350°C - 430°C is the influence stage of flame retardant 2, with the peak first negative and then positive, and the positive peak being greater than or equal to the negative peak, indicating that under the coupling action of flame retardant 2 and the matrix polymer material, the thermal decomposition in this stage is advanced, the peak temperature decreases, and the peak value remains unchanged or slightly decreases; 430°C - 500°C is the stage where the pyrolysis products of the two flame retardants jointly act, and there are two peaks in this stage. When the content of flame retardant 1 is 45%, the two peaks are first positive and then negative and the positive peak is larger, indicating that under the coupling action of the flame retardant and the matrix polymer material, the thermal decomposition in this stage is delayed and the peak value decreases. However, when the content of flame retardant 1 is less than 45%, both peaks are positive values, indicating that under the coupling action of the matrix polymer material and the flame retardant, the thermal decomposition rate decreases in this stage. Compared with the calculation curve, it can be seen that the two peaks are caused by the shoulder peaks of the calculation curve in this stage; finally, due to the coupling action during the thermal decomposition of the matrix polymer material, an independent peak appears in the temperature range of 500 - 540°C, which is the carbon oxidation stage in this preferred example.

[0046] Next, under the conditions of each flame-retardant composite material formulation (j), for each coupling temperature range, the first stage (k = 1) (230°C - 350°C), the second stage (k = 2) (350°C - 430°C), and the third stage (k = 3) (430°C - 500°C), use Equation (3) to calculate the pyrolysis coupling degree of the matrix polymer material (P) and the two flame retardants (R1, R2) during the thermal decomposition process after blending, and obtain the pyrolysis coupling degree S j-k , as shown in Table 2

[0047] Table 2 Pyrolysis coupling degree of matrix polymer material and flame retardants at each stage under air atmosphere

[0048]

[0049] As shown by the pyrolysis coupling degree in Table 2, by comparing the pyrolysis coupling degrees of the flame retardants and the matrix polymer material at different stages in different flame-retardant composite material formulations (j), it can be seen that as the content of flame retardant 1 increases, the pyrolysis coupling degree in the first stage increases; as the content of flame retardant 2 increases, the pyrolysis coupling degree in the second stage fluctuates and increases; as flame retardant 1 decreases and flame retardant 2 increases, the pyrolysis coupling degrees in the third stage are similar for other formulations except for formulation 1 which is the largest

[0050] Finally, for the two flame retardants (R1, R2), based on the change in the mass fraction of the flame retardants in different flame-retardant composite material series formulations, use Equation (4) to calculate the influence strength of the change in the unit mass fraction of each flame retardant within different mass fraction ranges on the pyrolysis coupling degree (S j-k ), and obtain the change factor θ of the pyrolysis coupling degree (S j-k ) with the mass fraction of each flame retardant i-k-j , as shown in Table 3

[0051] Table 3 Change factors of pyrolysis coupling degree of matrix polymer material and two flame retardants during pyrolysis process under air atmosphere

[0052]

[0053] It should be noted that in this example, the first stage is the influence stage of flame retardant 1, so only the change factor of the change in the content of flame retardant 1 on the pyrolysis coupling degree is calculated; the second stage is the influence stage of flame retardant 2, so only the change factor of the change in the content of flame retardant 2 on the pyrolysis coupling degree is calculated

[0054] By analyzing Table 3, it can be seen that under air atmosphere, the change factor of the pyrolysis coupling degree is relatively high when the content of flame retardant 1 is in the range of 20.0% - 35%, and the change factor of the pyrolysis coupling degree is relatively high when the content of flame retardant 2 is in the range of 27.5% - 45.0%

[0055] In summary, in the formulations of Flame Retardant 1: Flame Retardant 2 = 27.5%: 27.5% and Flame Retardant 1: Flame Retardant 2 = 20.0%: 35.0%, the flame retardants have a greater impact on the pyrolysis coupling degree of the flame-retardant composite materials, and the formulation with the best flame retardant effect should be within this range.

[0056] The parts not elaborated in detail in the present invention belong to the well-known technologies of those skilled in the art. The above-described embodiments are only descriptions of the preferred embodiments of the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A quantitative calculation method for the coupling effect of the heat response of a flame retardant compounding system, characterized in that, Comprising the following steps: S1: Determine the matrix polymer material P and each flame retardant R i , where i = 1 to n, and n is the number of types of flame retardants. Initially determine the possible formulations j of the matrix polymer material and each flame retardant, where j = 1 to m, and m is the number of formulations. Give the mass fractions of the matrix polymer material and each flame retardant under each formulation condition, that is, under the j-th formulation condition, the mass fraction of the matrix polymer material is p j %, and the mass fractions of each flame retardant are r j-i %; S2: For the matrix polymer material P and each flame retardant R i , perform a thermogravimetric experiment to obtain the derivative thermogravimetric curve f P (T) of the matrix polymer material and the derivative thermogravimetric curves of each flame retardant ; S3: For each possible formulation j, take p j % of the matrix polymer material P and r j-i % of each flame retardant and perform uniform melt blending to obtain m types of flame retardant composite material samples; S4: Conduct thermogravimetric experiments on each flame-retardant composite material sample under the same conditions as in step S2 to obtain the derivative thermogravimetric experimental curve f e-j (T); S5: To analyze the coupling mechanism of the thermal decomposition process after blending the matrix polymer material P and each flame retardant R i The derivative thermogravimetric curve f P of the matrix polymer material P measured in step S2 and the derivative thermogravimetric curve i of the flame retardant R are weighted and superimposed according to the mass fraction p j % of the matrix polymer material P corresponding to the formulation j and the mass fraction r i % of the flame retardant R j-i % as weights, as shown in the following formula (1), to obtain the derivative thermogravimetric calculation curve f c-j (T); (1) S6: Subtract the derivative thermogravimetric experimental curve f e-j (T) of each flame-retardant composite material sample from the corresponding derivative thermogravimetric calculation curve f c-j (T), as shown in the following formula (2), to obtain the derivative thermogravimetric difference curve df j (T); (2) S7: Under the conditions of each flame-retardant composite material formula, based on the differential thermogravimetric difference curve df j (T), take the union of the similar thermal decomposition temperature ranges or adjacent thermal decomposition temperature ranges of the matrix polymer material P and each flame retardant R i to obtain the coupling action temperature range of the matrix polymer material P and each flame retardant R i ; S8: Under the conditions of each flame retardant composite material formula, for each coupling temperature range k (T j-k-1 , T j-k-2 ), the coupling degree calculation of the thermal decomposition process after blending the matrix polymer material P and each flame retardant R i is carried out respectively, as shown in the following formula (3), and the pyrolysis coupling degree S j-k is obtained; (3) S9: For each flame retardant R i , based on the change in the mass fraction of the flame retardant in different series of flame retardant composite material formulations, calculate the influence strength of each flame retardant on the pyrolysis coupling degree S j-k when the mass fraction changes by a unit mass fraction within different mass fraction ranges, as shown in the following formula (4), and obtain the change factor θ j-k of the pyrolysis coupling degree S i-k-j with respect to the mass fraction of each flame retardant; (4) S10: Compare the pyrolysis decoupling degree change factor θ of each flame retardant within different mass fraction ranges i-k-j , and determine the mass fraction range corresponding to the maximum pyrolysis decoupling degree change factor θ i-k-j of each flame retardant.

2. The method according to claim 1, characterized in that, The variation factor θ of the maximum pyrolysis decoupling degree corresponding to each flame retardant i-k-j The mass fraction range is the content range in which the flame retardant has the most significant impact on the pyrolysis decoupling degree of the flame-retardant composite material.

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