Gelation of a PVC Plasticizer Mixture
Sample
PVC powder plasticizer mixture (Fimo® modeling material, Faber GmbH)
Plasticized PVC is made by thermal gelation of a PVC powder plasticizer mixture. The purpose of the experiment was to determine the temperature range of gelation as well as the glass transition range of the final product.
Conditions
Measuring cell: DMA/SDTA861e with the shear clamp holder
Sample preparation: Two balls of approx. 130 mg are formed and squeezed to 1-mm disks of approx. 10-mm diameter using the fixation screws of the shear clamps.
DMA measurement: First heating run from 25 °C to 140 °C at 3 K/min followed by a second heating measurement of the same specimen (the resulting plasticized PVC) after reclamping and starting at -25 °C.
The multi-frequency mode is used in which the sample is simultaneously measured at frequencies of 1,2,5 and 10 Hz. Maximum force amplitude 1 N; maximum displacement amplitude 10 μm; offset control zero
Atmosphere: Static Air
Interpretation
The initially viscous mixture with a shear modulus of approx. 20 MPa undergoes gelation between 80 °C and 105 °C. During this process the modulus increases by more than a decade. The curves measured at different frequencies show that the process is not frequency dependent and that it is different to a glass transition. On cooling to the glass state, the modulus of the resulting plasticized reaches 500 MPa.
Conclusions
The DMA with the shear clamp holder is ideal for measurements in which the sample changes from the viscous to the glass state. The use of different frequencies helps to interpret the effects measured by DMA.
Gelation of a PVC Plasticizer Mixture | Thermal Analysis Handbook No.HB224 | Application published in METTLER TOLEDO TA Application Handbook Thermoplastics