DSC of Highly Oriented PE-HD Fiber

Sample

Dyneema fiber, produced by the DSM gel spinning process

Conditions

Measuring Cell: DSC821^e with sample changer and air cooling

Pan: Aluminum standard 40 ul, hermetically sealed, lid indented prior to sealing in order to ensure good thermal contact between pan and sample

Sample preparation: A length of approx. 25 cm (1.235 mg) of the PE fiber was rolled into a small ball and placed in the pan

DSC measurement: All heating runs were from 30 to 180°C at 10 K/min. Before the second run, the sample was quench-cooled. Before the third run, it was quench-cooled. Before the third run, it was quench cooled and then stored at 30°C at 10 h. After the third run, it was cooled to 100°C at 0.5 K/min. Quench-cooling was performed in the sample changer.

Atmosphere: Static air

Evaluation

Integrating the peaks over a straight baseline gives

Interpretation

All the heating curves show endothermic effects caused by the fusion of the crystalline regions of the polymer. The first fusion peak is completely different to the curves that follow. The Dyneema fiber is made of especially high molecular mass PE that is stretched on cooling to obtain maximum orientation. This high degree of order shifts the melting range to much higher temperatures. It is irreversibly destroyed on melting.

Conclusions

DSC is used to detect and compare the degree of order in semicrystalline polymers. It is easy to destroy a high degree of order. Reconstruction of the order is virtually impossible.

Quench-cooling a sample is done automatically in the sample changer: at the end of a measurement the hot pan is placed on the cold turntable where it cools to ambient temperature within a few seconds. The next measurement can then be performed with a quench-cooled sample. 

^{DSC of Highly Oriented PE-HD fiber | Thermal Analysis Application No. HB 212 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics}