Here are 5 classic experiments to take you throughDifferential scanning calorimeter(DSC)， Covering fields such as materials science, food analysis, and drug research and development:
1. Analysis of polymer melting and crystallization behavior
Experimental objective: To determine the melting temperature, crystallinity, and crystallization kinetics parameters of polymers.
Operation steps:
Take 5-10mg of polymer samples (such as polyethylene, polypropylene) and place them in an aluminum crucible.
Heat above the melting temperature (such as 200 ℃) at a heating rate of 10 ℃/min under a nitrogen atmosphere.
Maintain a constant temperature for 5 minutes to eliminate thermal history, then cool down to room temperature at the same rate.
Heat up again to above the melting temperature and record the DSC curve.
Result analysis:
The melting peak temperature corresponds to the melting point of the polymer, while the crystallization peak temperature reflects the crystallization ability.
Calculate crystallinity based on peak area (e.g. polyethylene crystallinity can reach over 80%).
The changes in crystal peak shape at different cooling rates can be studied for crystallization kinetics (such as Avrami equation analysis).
2. Identification of drug polymorphs and evaluation of thermal stability
Experimental objective: To distinguish different crystal forms of drugs and evaluate their thermal stability.
Operation steps:
Take drug samples (such as sulfur and chloramphenicol) and place them in a sealed crucible.
Heat to 300 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere.
Record the DSC curve and observe the endothermic or exothermic peaks.
Result analysis:
Different crystal forms exhibit melting peaks at different positions on the DSC curve (such as the melting point of sulfur's alpha crystal form at 112 ℃ and beta crystal form at 119 ℃).
The exothermic peak may correspond to drug decomposition or crystal transformation (such as chloramphenicol may decompose around 150 ℃).
3. Determination of oxidation induction period of food oils and fats
Experimental objective: To evaluate the antioxidant properties and storage stability of oils and fats.
Operation steps:
Take 5-10mg of oil samples (such as soybean oil and olive oil) and place them in an aluminum crucible.
Heat up to 100 ℃ at a rate of 20 ℃/min in an oxygen atmosphere and maintain the temperature for 5 minutes.
Switch to an oxygen atmosphere, continue to maintain constant temperature and record the DSC curve until an oxidation exothermic peak appears.
Result analysis:
The oxidation induction period (OIT) is the time from the oxygen switching point to the starting point of the oxidation exothermic peak (such as the OIT of high-quality soybean oil can reach more than 50 minutes).
The longer the OIT, the stronger the antioxidant properties of the oil and the higher the storage stability.
4. Determination of protein denaturation temperature
Experimental objective: To investigate the thermal stability and denaturation conditions of proteins.
Operation steps:
Take protein samples (such as bovine serum albumin) and dissolve them in buffer solution. Take 10-20 μ L of the solution and place it in an aluminum crucible.
Heat to 120 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere.
Record the DSC curve and observe the denaturation endothermic peak.
Result analysis:
The denaturation peak temperature corresponds to the denaturation temperature of the protein (such as the denaturation temperature of bovine serum albumin, which is about 65 ℃).
The peak area reflects the enthalpy change of denaturation and can be used to evaluate the stability of protein structure.
5. Study on Thermal Decomposition Dynamics of Lithium Battery Materials
Experimental objective: To analyze the thermal stability and decomposition mechanism of lithium battery materials.
Operation steps:
Place lithium battery materials (such as LiCoO ₂, graphite) in a high-pressure crucible.
Heat to 1000 ℃ at a heating rate of 5 ℃/min in an argon atmosphere.
Record the DSC curve and observe the decomposition heat release peak.
Result analysis:
The peak temperature of decomposition heat corresponds to the thermal decomposition temperature of the material (such as LiCoO ₂ may release oxygen around 200 ℃).
Calculate the decomposition activation energy using Kissinger or Ozawa methods to evaluate the thermal safety of materials (such as graphite, whose decomposition activation energy can reach over 200kJ/mol).