Application of Differential Scanning Calorimeter in the Coating Industry

　1. Preface　　

With the continuous development of advanced composite materials, their application fields are becoming more and more extensive, and people are paying more attention to their quality control technology. Monitoring the curing process of thermosetting resins and determining curing conditions using thermal analysis methods is very effective. The DSC method is widely used due to its small sample size and high measurement accuracy, making it suitable for various curing systems.

Powder coating refers to a dry powder coating that can flow freely. The main difference between powder coating and traditional liquid paint is that powder coating does not require the use of solvents to keep the binder and filler in a liquid suspension state. It mainly forms a film on the surface of the component through electrostatic adsorption, heating and solidification.

　　2、 Preparation before the experiment

1.DZ-DSC300Differential scanning calorimeter(Instrument brand: Nanjing Dazhan Instrument)

2. Ordinary nitrogen gas (purity 99.99%), gas flow rate: 20ml/min

3. The tested sample is epoxy resin powder, and the sample size is required to be no less than 15mg

4. Standard tweezers and crucibles

5. Weighing balance: electronic balance, with a division value of 0.0001mg

6. Heating rate: 10 ℃/min

7. Cut off temperature: 200 ° C

　　3、 Experimental operation section

1. The experimental parameter settings are shown in the following figure:

2. The principle of the experiment: Differential Scanning Calorimetry (DSC) is to measure the relationship between the heat flow rate difference or power difference input to the sample and reference material during the heating, cooling, or constant temperature process and temperature or time under programmed temperature control conditions. Provide information on heat absorption, release, and heat capacity changes related to physical and chemical processes.

Generally, in DSC spectra, the endothermic effect is characterized by a raised peak (increase in enthalpy), while the exothermic effect is characterized by a reverse peak (decrease in enthalpy). We mainly need to examine a curing exothermic peak of the sample at around 140 ° C.

3. The results of the experiment:

　　4、 Experimental data analysis　

The testing conditions are a dosage of 15mg and a heating rate of 10 ℃/min. From the following figure, it can be seen that there is an exothermic peak in the range of 130~150 ℃, and a melting phase transition occurs. The peak value is 144.02 ℃, and the starting point is 142.32 ℃. Determination of decomposition temperature of cured materials: Different formulations reflect different decomposition temperatures of cured materials. Differential Scanning Calorimetry (DSC) can conveniently test the decomposition temperature of cured materials and reflect their thermal stability.

Most manufacturers of latent curing agents do not provide clear information on their chemical composition and structure, so quality monitoring is more complicated. We can use differential scanning calorimetry (DSC) to observe the DSC spectrum under programmed temperature conditions, and monitor the quality of latent curing agents based on the phase change, natural reaction heat, and thermal decomposition temperature information obtained from the DSC spectrum.