Differential photocalorimetry DPC

The effect of infrared light can also be investigated in a similar manner [20]. These authors also highlight the ability to measure a simultaneous non-contact TMA signal from a sample placed in the DSC cell. 

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Differential photocalorimetry (DPC) is included here since the instrument used is essentially an adaptation of DSC instrumentation. The photocalorimeter comprises a DSC instrument with a UV/visible source mounted on top, such that light of appropriate wavelength or wavelength region from the source is focused onto the measuring head (both reference and sample pans). The most frequent use of DPC is in the study of polymer cure reactions, but it may also be used to follow such as UV degradation. 

Differential Photocalorimetry (DPC) (19.201. The polymerization being an exothermal process, the reaction can be monitored in real time by differential scanning calorimetry (DSC). From the recorded thermogram which shows the variation of the heat flow with the irradiation time, the rate of polymerization can be directly calculated, provided the standard heat of polymerization (AHq) is known. For acrylic monomers, AHg values are usually in the range of 78 to 86 kJ mol depending on the monomer considered. 

Combined simultaneous techniques—many of these techniques can be combined to give simrilta-neous or sequential measurements on the same sample, eg, TG/MS, TG/IR, DSC/XDR, DSC/TG/MS, pyrolysis/GC, Differential photocalorimetry (DPC), etc. 

The principal techniques that have been used in resin cure studies are differential scanning calorimetry (DSC Chapter 7), photocalorimetry (Sections 11.3.1 and 11.3.2), dielectric thermal analysis (DETA Section 12.2.1) and dynamic mechanical thermal analysis (DMTA Section 8.3.2). Earlier differential photocalorimetry (DPC) instruments were based on a DSC instrument. However, these were only partially successful in the analysis of photocurable polymers. The failure to develop a completely adequate system has been the result of two factors. The first and most significant is the change in the intensity of the light with time of operation - as much as an 80% reduction in the first 100 hours of operation. The second reason for the limited success was the lack of data analysis software to convert raw data into easy-to-understand results that could be correlated with actual performance. 

Groves IF, Lever TJ, Hawkins NA. Use of differential photocalorimetry (DPC) for the study of photoinitiator systems Polym Paint Color J 1993 43 8-16. 

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