SH/T 1826-2019Plastics-Determination of melting enthalpy and crystallinity and melting temperature of ultra-high molecular weight polyethylene (PE-UHMW) materials and products Differential scanning calorimetry (DSC) (English PDF)

5.1 Differential scanning calorimeter

See GB/T 19466.1-2004 5.1.

SH/T 1826-2019

5.2 Sample dishes

Aluminum DSC sample pan. Used to hold the sample and reference sample. Press the lid on the sample dish. And made of the same material of the same quality. Is measuring Condition. The sample cuvette does not physically or chemically change with the sample and atmosphere.

5.3 Analytical balance

Weighing accuracy. ±0.01mg.

Note. When using a balance with an accuracy of 0.01 mg. The repeatability standard deviation of polyethylene fusion enthalpy is 1.2% [1].

5.4 Standard sample

See Appendix A of GB/T 19466.1-2004.Use standard samples of indium and tin.

5.5 Air source

Nitrogen or other inert gases. The purity is at least 99.9%.

9.1 Instrument preparation

9.1.1 Before the test. Power on the instrument. Make it balanced for at least 30min.

9.1.2 Place two empty sample dishes with the same mass on the sample holder. Adjust to the actual measurement conditions. At the required temperature Within range. The DSC curve should be a straight line. When you can't get a straight line. Record the DSC curve after confirming the repeatability.

9.1.3 During the entire test. The DSC test chamber should be filled with dry nitrogen or other inert gases. Flow at 50mL/min±5mL/min Purge at speed. And all calibrations and tests should use the same gas and purge rate.

9.2 Placement of the sample

9.2.1 Select a sample vessel with an appropriate volume. And make sure it is clean.

9.2.2 Use two identical sample dishes. One is used as a sample cuvette. (Sample cuvette where the sample is placed). The other serves as a reference cuvette (without placing the sample Sample dish) ꎻ

9.2.3 Weigh the sample vessel and lid. Accurate to 0.01 mg.

9.2.4 Place the sample in the sample cuvette. Seal the sample dish with the lid. Check the bottom of the sample cuvette to make sure it is flat. If it's not level. Then re-standard Sample preparation

9.2.5 Weigh the sample cuvette after placing the sample. The mass of the sample should be between 5 mg and 10 mg. Accurate to 0.01 mg. The quality of the repeated test samples the amount deviation is not more than 2mg. For materials or products containing additives. The sample mass refers to the polymer matrix after subtracting the additive mass quality.

9.3 Placement of sample dishes

Use tweezers or other suitable tools to place the sample cuvette into the sample holder. Close the cover of the sample holder. Ensure that between the sample and the dish, the contact between the dish and the support is good.

9.4 Test

9.4.1 Stable the sample at room temperature for at least 3min.

9.4.2 Heat the sample from room temperature to.200°C at a heating rate of 10°C/min. Record the enthalpy curve of the first heating process

9.4.3 Keep at this temperature for 5 minutes, if necessary. Re-cooling-heating cycle operation can be performed.

9.4.4 Decrease to room temperature at a cooling rate of 10°C/min. Keep it for 5min.

9.4.5 Repeat 9.4.2.Record the enthalpy curve of the second heating process.

Note. The information obtained from the first heating scan can indicate the thermal history of the polymer (such as processing and sample preparation). If you want to get unaffected by thermal history the crystallinity of the sample can use the result of the second heating scan. Generally, the second temperature rise is used for the raw materials. For products to reflect their processing heat history Impact. Use the first heating up more often.

9.4.6 During the test, if any weight loss is found due to chemical reaction. The upper temperature limit should be lowered. And it should be noted in the report.

10.1 Result calculation

10.1.1 In a heating cycle, connect the points corresponding to 50°C and 160°C on the curve to establish a straight baseline. If the melting process is 160°C does not end. You can move the baseline to a higher temperature. But this change must be recorded.

10.1.2 Integrate the area under the melting endothermic curve from the beginning of the heating cycle to the heat transition enthalpy. Get the heat of the endothermic process Variety. Divide the heat by the mass of the sample. Obtain the enthalpy of fusion per unit mass of the sample. That is, the enthalpy of fusion of the sample deltaHm.

10.1.3 See formula (1) for calculation of crystallinity.