Differential scanning photocalorimetry

Polymerization Behavior. Both Fourier-transform infrared spectroscopy (FTIR) and differential scanning photocalorimetry (DPC) were used to characterize the polymerization behavior, curing time, and maximum double bond conversion in these systems. 

All the acylated polyimides retained solubility in organic solvents. This gave us reason to believe that photopolymerisation via the double bonds of polyimides could be conducted by the method of differential scanning photocalorimetry. This method, which is widely covered in the literature [73-76], is based on on the principle that heat released during any reaction can be measured. 

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. 

Thermal analysis is well suited for characterizing and identifying plastics, as their properties are temperature dependent. It involves methods in which the substance is subjected to a controlled temperature program and the changes in the physical and chemical properties are measured as a function of temperature or time. The ambient atmosphere also influences the properties of plastic. Thermal analysis comprises traditional techniques differential scanning calorimetry (DSC), differential thermal analysis, thermogravimetric analysis, thermomechanical analysis, and more recent methods pressure differential scanning calorimetry, dynamic mechanical analysis, and differential photocalorimetry. 

The experimental procedure involves initiation of the polymerization by irradiation followed by cutting off the light after a certain time at a degree of conversion chosen, and monitoring the reaction in the dark. As experimental methods, both isothermal differential scanning calorimetry (photocalorimetry, photo-DSC) [2,6, 7, 18-32] and real-time infrared... 

Two techniques, dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA), have been used for the study of resin cure. Differential scanning calorimetry (DSC) has also been employed (for a discussion of the theory and instrumentation of DSC, see Chapter 9). The application of differential photocalorimetry to the measurement of cure rates of photocurable resins is discussed in Chapter 12. 

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. 

The methods discussed in this book are differential photocalorimetry, differential scanning calorimetry, dielectric thermal analysis, differential thermal analysis, dynamic mechanical analysis, evcrived gas analysis, gas chromatography, gas chromatography (oml)ined with mass spectrometry, mass spectrometry, microthermal analysis, thermal volalilisalion, Ihermogravimetric analysis and thermomechanical analysis. 

A review is presented of the techniques involved in the thermal analysis of polymers. Techniques discussed include differential scanning calorimetry, differential photocalorimetry, thermogravimetric analysis, thermomechanical analysis, dynamic mechanical analysis, dielectric, thermally stimulated current/relaxation map analysis analysis, and thermal conductivity analysis. 381 refs. 

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