PA66/PA6 Batches of Different Processability

Sample

Polyamide 66, 2 batches of Ultramid C3ZM6 (pellets)

Gold batch, 12.0 mg, batch with monomer, 5.9 mg

Conditions

Measuring cell: DSC20

Pan: Aluminum standard 40 μl, pierced lid

Sample preparation: Disk cut from center of pellet

DSC measurement: Heating from 30 to 300 °C at 10 K/min

Atmosphere: Nitrogen, 50 cm³/min

Evaluation

Integration of the small melting peak gave a value of 8.9 mJ. The size of the peak is directly proportional to the monomer content. If the heat of fusion of ε-caprolactam is assumed to be 150 J/g, a value of 1% is calculated for the monomer content [8.9 mJ (150 J/g ⋅ 5.9 mg)] ⋅ 100%

Interpretation

The small endothermic peak at about 100 C is due to the melting of monomers (ε-caprolactam). The batch containing monomers caused manufacturing problems (clogging of the gas orifices in the blowing process). The good batch does not exhibit a peak around 100 C. 

Conclusions

Monomer contents greater than 0.2% can be detected in the DSC melting peak. TGA would be even more sensitive and is also applicable to non-crystalline monomers. In general, monomers usually evaporate on heating. 

_{PA66/PA6 Batches of Different Processability | Thermal Analysis Handbook No.HB230 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics}