Polyamide 6, Melting Behavior

Sample

Ultramid B3G5HsQ15 as pellets and recycled material

Conditions

Measuring Cell: DSC20

Pan: Aluminum standard 40μl, pierced lid

Sample preparation: Disk cut from center part pellet (7.5 mg), 9 mg powder

DSC measurement: Heating from 30 to 300 °C at 20 K/min, cooling to 100 °C at 20 K/min

                               Second heating run from 30 to 300 °C at 20 K/min

Atmosphere: Nitrogen, 50 cm³/min 

Note: If recrystallization occurs, the integral must include this exothermic peak. The resulting of fusion corresponds to the original crystallinity without recrystallization because the energy released by the formation of crystallites is equal to the energy required to melt them. To determine the maximum possible degree of crystallinity, the sample should be cooled by approx. 50 K immediately after the exothermic premelt peak occurs. The subsequent complete heating curve can then be used to measure the crystallinity. 

Interpretation

The first melting curve often shows a double peak. Possible causes are

• irregular heat transfer (depending on the shape of the sample),
• polymorphism (hexagonal crystallites melt at 215 C, the monoclinic fraction at 220 C
• crystallite segregation (thermal history, see Application Example "PE, melting curve and thermal history"). 

Conclusion

The first DSC melting peak is influenced by the thermal history of the sample. To characterize the material, the sample should be cooled under defined conditions after the first measurement.

_{Polyamide 6, Melting Behavior | Thermal Analysis Handbook No.HB225 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics}