Differential Scanning Calorimetry (DSC), as a core tool for materials thermal analysis, directly impacts the reliability of experimental data due to its standardized operation. Many users fall into common pitfalls due to neglecting details or lack of experience, leading to biased results or even instrument damage. The following systematically outlines common usage misconceptions and avoidance strategies to help improve testing accuracy.

I. Typical Misconceptions in Sample Preparation

1. Blindly Pursuing "The More the Better" Sample Amount

Some operators believe that increasing the sample amount enhances signal strength, but this violates the design principles of DSC. Excessive sample can lead to:

- Thermal hysteresis: Heat cannot be transferred evenly, resulting in peak broadening and decreased resolution;

- Self-cooling effect: Endothermic and exothermic reactions cause localized temperature fluctuations, masking the true phase transition;

- Risk of crucible overflow: Especially with samples containing volatile components, this may contaminate the sensor.

*Recommendation*: Control the sample mass according to the crucible capacity, typically ≤10mg. For high thermal conductivity materials, the sample mass can be increased appropriately.

2. Inappropriate Sample Morphology and Processing

- Uneven Particle Size: Large particles have slow internal heat transfer, while small particles are easily oxidized, leading to poor reproducibility;

- Insufficient Drying Treatment: Moisture evaporates in the low-temperature region, forming a broad endothermic peak, interfering with key information such as the glass transition;

- Over-compaction: Disrupts the natural packing state of the sample, affecting heat flow distribution.

*Recommendation*: Powder samples should be ground to below 100 mesh, solid slices should be <1mm thick, and moist samples must be pre-dried.

II. Blind Spots in Experimental Parameter Settings

3. One-Size-Fits-All Heating Rate

Blindly adopting the standard recommended rate (e.g., 10°C/min) while ignoring sample characteristics:

- Polymer Materials: Rapid heating (>20°C/min) results in higher Tg measurements and a tailing of the melting peak;

- Inorganic Decomposition: Slow heating (<5°C/min) is necessary to resolve multi-step reactions;

- Kinetic Studies: Different rates need to be combined to fit the activation energy. *Recommendation*: Initially screen 3-5 rates, then optimize based on literature and observations.

4. Hidden Oversights in Atmosphere Control

- Insufficient inert gas purity: Oxygen content >10ppm in nitrogen will trigger high-temperature oxidation and exothermic reactions;

- Imbalanced gas flow rate: Too low a flow rate cannot remove volatiles in time, while too high a flow rate will disturb the heat flux signal;

- Incorrect switching timing: Switching between air and oxygen midway through the oxidation experiment causes abrupt changes in the baseline.

*Recommendation*: Use high-purity gas (≥99.999%), control the flow rate at 20-50mL/min, and stabilize for 30 minutes before switching. III. Fatal Errors in Instrument Operation

5. Improper Crucible Selection and Use

- Material Mismatch: Aluminum crucibles will melt when used for testing >600°C; platinum crucibles are prone to brittleness when in contact with sulfur-containing samples.

- Mixing of New and Old Crucibles: Repeated use of crucibles leads to deformation, resulting in poor sealing, and residues catalyze side reactions.

- Misunderstanding of Capping: Sealing caps hinder gas release, causing the decomposition peak temperature to rise.

*Recommendation*: Use aluminum crucibles for low temperatures, and alumina/platinum crucibles for high temperatures. Use only for single-use; puncture holes when venting is required.

6. Incorrect Calibration Cycle and Method

- Reliance on Factory Calibration: Horizontal shift after instrument relocation and changes in thermal resistance due to furnace aging.

- Arbitrary Standard Sample Selection: Using indium metal to calibrate the glass transition of organic materials results in mismatched measurement ranges.

- Limitations of Single-Point Calibration: Correcting only the melting point while ignoring enthalpy can lead to errors of ±10%. *Recommendation*: Perform monthly calibration using standard materials (e.g., In, Sn, Ga) at multiple points, covering the range of -50 to 700°C.

IV. Common Pitfalls in the Data Analysis Phase

7. Subjectivity in Baseline Processing

- Manual Baseline Bias: Misinterpreting the stepped Tg of amorphous materials as a plateau and forcibly connecting them with straight lines;

- Ignoring the Influence of Thermal History: Failure to subtract the baseline during secondary heating leads to incorrect calculation of the cold crystallization peak;

- Software Automatic Fitting Failure: Complex multi-peak systems are not manually corrected, resulting in the loss of weak signals.

*Recommendation*: Use the instrument's built-in algorithm combined with manual fine-tuning, comparing the primary/secondary heating curves.

8. Confusion Regarding Characteristic Temperature Definitions

- Misuse of Onset Points: The onset point of the copolymer melt peak does not represent the main chain melt; the peak value should be taken;

- Single Criterion for Tg Determination: Relying solely on the midpoint temperature, ignoring the ratio of the height of the preceding and following steps;

- Misinterpretation of Decomposition Temperature: Missing TGA-DTG crosslinking analysis, mistakenly treating the DTA inflection point as Td.

*Recommendation*: Refer to standards such as ASTM E1545 to clarify the physical meaning of each characteristic temperature.

V. Long-Term Hidden Dangers in Maintenance

9. Inadequate Cleaning and Maintenance

- Sample Residue Accumulation: Carbide adheres to the sensor, reducing sensitivity;

- Dust Deposition in the Furnace Chamber: Affects thermal insulation performance and reduces the linearity of temperature rise;

- Aging and Unreplaced Sealing Rings: Leaks lead to oxidation experiment failure.

*Recommendation*: Wipe the furnace chamber daily with a soft cloth dampened with ethanol, and ultrasonically clean the crucible support weekly.

10. Uncontrolled Environmental Conditions

- Temperature and Humidity Fluctuations: Direct airflow from the air conditioner causes a furnace temperature difference >2°C, and water vapor condensation corrodes the circuitry;

- Proximity to Electromagnetic Interference Sources: Centrifuge start-stop cycles cause data acquisition jumps;

- Unstable and Unregulated Voltage: Frequent compressor start-stop cycles introduce noise.

*Recommendation*: Equip with a precision air conditioner to maintain 20±2°C/50%RH, keep away from high-power equipment, and install a UPS power supply.