PE, Characterization by Peak Temperature

Sample

PE-LD and PE-LLD as pellets, PE-HD as a film.

                                                                                         (-CH2 -CH₂-)_n

Conditions

Measuring cell: DSC821^e with air cooling

Pan: Aluminum standard 40 ul, lid hermetically sealed

Sample preparation: PE-LD: Disk of 9.796 mg cut from pellet

                                     PE-LLD: Disk of 8.128 mg cut from pellet

                                     PE-HD: Disk of 10.314 mg punched from film

DSC measurement: Heating from 30 to 108°C at 10 K/min

Atmosphere: Static air

Evaluation

Note: Two values can be used to characterize the peak temperature: the extrapolated intersection point of the inflection tangents, and the maximum of the DSC curve. The extrapolated peak temperature is not influenced so much by the arbitrary shape of the peak where random noise may cause the actual maximum to differ slightly from run to run, leading to an irreproducible <<peak temperature>>. For this reason the reproducibility of the extrapolated value is usually better.

Interpretation

The melting peaks are typical for the different PE qualities with their distinctive peak temperatures.

Conclusions

The peak temperature of the DSC melting curve is the most frequently determined property of semicrystalline polymers. It is the key parameter for processing and serves generally for identification. 

^{PE, Characterization by Peak Temperature | Thermal Analysis Application No. HB200 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics}