JP2022074231A - Thermogravimetric measurement method under isothermal condition using fast scanning calorimetry - Google Patents

Abstract

To investigate changes in relative weight of nanogram-sized polymer materials under isothermal condition using an FSC.SOLUTION: The present invention relates to a calorific value measurement method under an isothermal condition using fast scanning calorimetry. By repeating a cycle measurement in an order of isothermal heat treatment, quenching, and reheating, it becomes possible to track the decrease in weight due to the progress of thermal oxidation reaction at the isothermal condition as a change in heat capacity in real time. It is assumed that the relation of m=Cp,ti/Cp,t0 holds between a relative weight (m) and heat capacity (Cp,t). Here, Cp,ti represents heat capacity after ti seconds from the start of the isothermal condition, and Cp,t0 is heat capacity in an unreacted state immediately before the start of the isothermal condition.SELECTED DRAWING: Figure 5

Description

Patent Law Article 30, Paragraph 2 Application Applicable Website Publication Date October 20, 2nd Reiwa Website Address https: // doi. org / 10.1016 / j. tca. 2020.178804 Magazine name Thermochimica Acta 694 (2020) 178804, Publisher ELSEVIER

The present invention relates to a method for measuring thermogravimetric analysis under isothermal conditions using high-speed calorimetry (hereinafter, may be referred to as FSC).

The thermogravimetric analysis method (hereinafter, may be referred to as TG) is a method of measuring the mass of a substance as a temperature function while changing the temperature of the substance according to a regulated program (Non-Patent Document 1). .. In the conventional TG measurement, a sample of several mg to several hundred mg is required for each measurement, so that the measurement of a trace amount of nanogram size cannot be applied. Furthermore, when performing TG measurement under isothermal temperature, the rate of temperature rise to the target temperature is limited to several tens of degrees Celsius / min at most due to the configuration of the device in the conventional TG measurement, so before reaching the target temperature. In many cases, thermal decomposition and thermal oxidation reaction of the sample proceed. Therefore, there is also a problem that accurate TG measurement at an isothermal temperature is limited to a low temperature range.

High-speed calorimetry is a type of differential scanning calorimeter (hereinafter sometimes referred to as DSC), but it can raise and cool at a higher speed (tens of thousands of ° C / s) than conventional DSCs. This is a method for investigating the inflow and outflow of heat from a sample during high-speed scanning of temperature (Non-Patent Document 2-4). The weight of the sample used for high-speed calorimetry is several ng to several hundred ng, and it is also characterized in that it is a small amount as compared with the several mg to several hundred mg used in the conventional thermal analysis. Conventionally, high-speed calorimetry is often used for the purpose of simulating a high-speed heat treatment process in an industry in an analyzer and investigating the thermal behavior at that time. For polymer materials, mainly thermoplastic resins and heat are used. It has been used as an effective method for investigating the amount of heat, temperature, velocity theory, and specific heat in glass transition, crystallization, and melting of curable resins.

Yasutoshi Saito, Basics of Thermal Analysis for Material Science, Kyoritsu Shuppan Co., Ltd. (1990) 175-266. C. Schick, V. Mathot, Eds., Fast Scanning Calorimetry, Springer, Switzerland (2016). Keitomo Furushima, Basics of High-Speed Calorimetry-Analysis of Polymer Crystallization / Melting Behavior-, Journal of the Textile Society 76 (5), (2020) 191-196. E. Zhuravlev, C. Schick, Fast scanning power compensated differential scanning nano-calorimeter: 2. Heat capacity analysis, Thermochimica Acta 505 (2010) 14-21.

In the present invention, high-speed calorimetry can be used to capture weight changes using nanogram-sized samples that cannot be obtained with conventional TGs. Furthermore, since the temperature can be raised to the target temperature at high speed, it is possible to suppress the progress of thermal decomposition and thermal oxidation reaction until the target temperature is reached, and it is possible to measure the thermal weight under strict isothermal conditions. ..

In order to solve the above problems, the present invention has the following configurations. That is, it is a method for measuring thermogravimetric analysis under isothermal conditions using high-speed calorimetry.

By applying the measurement profile in the present invention to high molecular weight materials (thermosetting resin and thermoplastic resin) and low molecular weight materials, it becomes possible to control thermal decomposition and thermal oxidation reaction, and the same sample piece can be used. It is possible to track changes in weight as the reaction progresses.

In the present invention, polypropylene (hereinafter, sometimes referred to as PP), which is a typical thermoplastic resin, is subjected to high speed between room temperature and thermal oxidation reaction temperature (implemented at 270 ° C to 300 ° C for the resin) under air flow. It can be confirmed that the shape of the FSC curve during the heating or cooling process does not change (corresponding to the fact that the specific heat of the sample does not change) when the temperature is repeatedly raised and lowered at (3000 ° C / s). This means that the progress of the thermal oxidation reaction is suppressed by performing heating and cooling faster than the rate of the thermal oxidation reaction, and the weight change of the sample due to the thermal oxidation reaction does not occur.

By applying this phenomenon, the reaction progress can be stopped by rapidly cooling to room temperature while the resin is being heat-treated at an isothermal temperature in FSC. Further, if the temperature is raised again at high speed from this state, the reaction can proceed again. The midpoint of each vertical axis (heat flow) of the FSC curves obtained at this time is the baseline of the FSC curve, and according to Non-Patent Document 4, the width from the baseline of the FSC curve to the actually measured heat flow. Corresponds to the heat capacity. This heat capacity reflects the weight of the sample that has undergone the history of isothermal heat treatment before that, and if the thermal oxidation reaction is in progress, the weight decreases and the heat capacity also decreases, and finally the weight of the sample. Is zero and coincides with the baseline of the FSC curve. In this way, by repeating the cycle measurement in the order of heat treatment at isothermal heat treatment, quenching, and reheating, it is possible to track the decrease in weight due to the progress of the thermal oxidation reaction at isothermal temperature as a change in heat capacity in real time. .. In the present invention, it is assumed that the relationship of m = Cp, ti / Cp, t0 holds between the relative weight (m) and the heat capacity (Cp, t). Here, Cp and ti are heat capacities ti seconds after the start of isothermal temperature, and Cp and t0 are heat capacities in the unreacted state immediately before the start of isothermal temperature.

This is an example of an FSC measurement profile for confirming that the heat capacity does not change when the temperature is raised and cooled at high speed between room temperature and isothermal holding temperature (Tiso) in an air flow. This is the result of performing FSC measurement on PP using the measurement profile shown in Fig. 1. This is an example of an FSC measurement profile for investigating changes in heat capacity in an isothermal air flow. It is a superposition of FSC curves of PPs having different cumulative holding times (Δt _total ) at 300 ° C. performed in the measurement profile of FIG. It is the relationship between the relative weight and the holding time at 270 to 300 ° C.

First, as high-speed calorimetry, those capable of raising and cooling the temperature between 10 and 10000 ° C./s are preferable. The isothermal set temperature is preferably between room temperature and 400 ° C., and the holding time is preferably between 1 second and 6 hours. The measurement atmosphere is preferably an atmospheric flow, a nitrogen gas flow, and a helium gas flow, and the flow velocity is exemplified between 0 mL / min and 200 mL / min.

Polymer materials (thermocurable resins and thermoplastic resins) are desirable for analysis, and specifically, polyester resins, polyolefin resins, polyamide resins, polyimide resins, polyphenylene sulfide resins, polystyrene resins, and aromatic polyether ketones. , Polyvinyl resin, epoxy resin, phenol resin, urethane resin, acrylic resin, melamine resin, unsaturated polyester resin, urea resin, and alkyd resin are preferably exemplified.

With respect to the sample preparation part in the present invention, the set temperature and the set time can be freely set according to the type of resin. For example, in PP, the set temperature is preferably between room temperature and 300 ° C. The thickness of the sample to be used for FSC measurement is preferably 50 μm or less, and 2 μm to 20 μm is exemplified for PP.

As the heat capacity measuring part in the present invention, a scanning speed of 3000 ° C./s is preferably exemplified. When the experimental values of the FSC curves (vertical axis is heat flow, horizontal axis is temperature) acquired in the cooling process from Tiso to room temperature and the heating process from room temperature to Tiso are superimposed and displayed, the heat flow in the cooling process (heat flow (vertical axis is heat flow, horizontal axis is temperature)). When the heat flow (Qb = (Qc + Qh) / 2) at the center of the heat flow (Qh) in the Qc) and heating process is taken as the baseline point, each temperature in the temperature range where there is no crystallization, melting, glass transition, etc. The curve connecting the baseline points in is the baseline of the FSC curve, and the difference between the experimental values of the baseline and the FSC curve is the heat capacity (Cp). That is, the relationship of Cp = | Qc-Qb | = | Qh-Qb | holds between Qb, Qc, and Qh at each temperature. The temperature of the heat capacity to be adopted is preferably 200 ° C., which is equal to or higher than the melting temperature in PP. Further, it is preferable to use the heat flow (Qc) in the cooling process for calculating the heat capacity.

Hereinafter, the present invention will be described with reference to examples. The Flash DSC 1, a high-speed calorimetry device manufactured by METTLER TOLEDO, was used for the measurement. The measurement atmosphere was 50 mL / min air flow.

In order to confirm that the thermal oxidation reaction does not proceed during high-speed temperature rise and cooling in the air flow (flow velocity is 50 mL / min), the results of FSC measurement with the measurement profile shown in Fig. 1 for PP are shown. It is shown in FIG. The sample thickness used for the measurement is 2 μm. In this example, the temperature of Tiso was 270 ° C to 300 ° C. Figure 2 shows the heat capacity of the FSC curve during the cooling process minus the baseline of the FSC curve. The two heat capacity curves are superimposed and displayed). From this result, it can be confirmed that even if the measurement is performed using the measurement profile shown in FIG. 1, the thermal oxidation reaction does not proceed to such an extent that the heat capacity of the sample changes. Since the heat capacity has not changed, it is shown that the sample weight has not changed either. The sample weight used for a series of measurements is preferably 1 μg or less, and the sample weight is calculated according to the method described in 1.3.5 (from page 39) of Non-Patent Document 2. This example is the result of the sample weight of 20 ng to 80 ng. If the sample weight fluctuates, the reproducibility of the measurement results may decrease due to the effect of thermal delay. It is preferable to refer to Non-Patent Document 2 and Non-Patent Document 4 for the method of measuring the sample weight and the heat capacity.

FIG. 3 shows the measurement profile of FSC that has been isothermally heated for any time (ti; i is the number of cycles) in Tiso, and FIG. 4 shows the heat capacity obtained by subtracting the baseline of the FSC curve from the FSC curve during the cooling process. It can be confirmed that the longer the cumulative holding time (Δt _total = Σti) in Tiso, the smaller the heat capacity at each temperature. This means that the thermal oxidation reaction proceeded and the sample weight was reduced by keeping the sample at 300 ° C. The relationship of m = Cp, ti / Cp, t0 is recognized between the relative weight (m) and the heat capacity (Cp, t), and the heat capacity is converted to the relative mass. Here, Cp and ti are heat capacities ti seconds after the start of isothermal temperature, and Cp and t0 are heat capacities in the unreacted state immediately before the start of isothermal temperature. Moreover, in this example, the value of the heat capacity at 200 ° C. is adopted to estimate the relative weight. FIG. 5 shows the relationship between the relative weight and Δt _total obtained from the FSC measurement performed by changing the Tiso in the range of 270 to 300 ° C. It can be confirmed that the higher the temperature, the shorter the relative weight decreases, which means that the higher the temperature, the faster the thermal oxidation reaction proceeds, and the faster the sample weight decreases.

Claims (6)

A method for measuring thermogravimetric analysis under isothermal conditions using high-speed calorimetry. The method for measuring thermal weight under isothermal temperature using high-speed calorimetry according to claim 1, wherein a change in heat capacity due to thermal decomposition of a polymer material or weight loss due to a thermal oxidation reaction is investigated. The method for measuring the thermal weight of a polymer material under isothermal temperature using the high-speed calorimetry according to claim 1 or 2, wherein the measurement profile alternates between a sample preparation part and a heat capacity measurement part. The method for measuring the thermal weight of a polymer material under isothermal temperature using the high-speed calorimetry according to claim 3, wherein the sample preparation part arbitrarily determines a set temperature, a set time, and a scanning speed. The high speed according to claim 3, wherein the heat capacity measuring part has a cooling process and a reheating process having a scanning speed of 100 ° C./s or more and is carried out up to the temperature range of the desired isothermal measurement. A method for measuring heat weight under isothermal temperature using calorimetry. The method for measuring heat weight under isothermal temperature using the high-speed calorimetry according to claim 1, wherein the heat capacity before the start of isothermal temperature is used as the denominator, and the heat capacity after maintaining the isotherm is used as the numerator to obtain the time change of the relative weight.

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