Analysis of Toner Powder by DMA and DSC - METTLER TOLEDO

Analysis of Toner Powder by DMA and DSC

Sample

Toner powder as used in laser printers. The powder consists of thermoplastic base material to which different additives such as flow agents (waxes), pigments, UV-stabilizers and others have been mixed. The purpose of the analysis was to measure the characteristic glass transition and the melting temperature.

 

Conditions 

Measuring cell: DMA/SDTA861e with shear clamp sample holder DSC822e

Sample preparation: The powder was pressed to cylinders, 1.5-mm thick with a diameter of 12 mm, and mounted in the shear sample holder of DMA.
In the DSC, 40-μl aluminum pans were used. 

DMA measurement: The measurement was performed at 1, 10, 100 and 800 Hz at 2 K/min
Maximum force amplitude 3 N; maximum displacement amplitude 1 μm; offset control zero.

DSC measurement: Toner powder pressed to cylinders was heated at rates of 100, 10 and 0.5 K/min respectively 

Atmosphere: Static air

 

Interpretation

The storage modulus DMA curves show frequency-dependent behavior. At 800 Hz, two steps are visible in the curve, whereas at 1 Hz only one main step can be seen. Since the first step at 800 Hz and the step at 1 Hz have about the same onset temperature, one must assume that a frequency-dependent and a frequency-independent effect overlap. Toners are complex mixtures, so no one can conclude that the sample contains a component that melts at about 60 °C (melting is not frequency dependent). In contrast, the glass transition temperature of the thermoplastic base material depends on the applied frequency and shifts to higher temperatures at higher frequencies. The two effects are therefore separated at high shear frequency. 

 

Conclusion

Overlapping melting and glass transition processes can be easily separated by both DSC and DMA. In DSC, the fact that glass transition is dependent on the heating rate is used to separate the two effects. With DMA, separation is achieved because the frequency dependence of the two effects is different. In principle, both methods yield equivalent results. However, the sensitivity of DSC with regard to glass transition is appreciably lower than the sensitivity towards melting process. In contrast, DMA is sensitive towards changes in molecular mobility to the same extent. 


Analysis of Toner Powder by DMA and DSC | Thermal Analysis Handbook No.HB258 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics