Thermoplastics dielectric analysis

Dielectric analysis (DEA) measures changes in the properties of a polymer as it is subjected to a periodic (or alternating) electric field. In DEA a sample is placed between two electrodes. The traditional electrode geometry used for thermoplastics is a parallel-plate capacitor. The parallel-plate electrode measures the bulk dielectric response of the material subjected to a sinusoidal voltage applied to the electrodes. The electrodes typically are formed by vapor deposition or sputtering of a metal onto the polymer surfaces. A more contemporary dielectric electrode geometry is the interdigitated comb type of electrode which is particularly well... 

Dielectric analysis is used most frequently with thermoplastics to provide information on and an understanding of the molecular basis for relaxations. This is a more traditional context for DEA and ample information with munerous interesting examples is available in the literature, particularly in the text by McCrum (71) and the review by Chartoff (77). The reader is referred to these references for further insights. More recently, DEA has had extensive appUcations in the characterization and in situ process monitoring of the ciu-e of thermosets, particularly in the manufacturing of composites. Since this topic is not as well known, we summarize in a subsequent section some of the more salient aspects of the use of DEA for the cure characterization of thermosets. 

The use of differential scanning calorimetry to identify secondary transitions in thermoplastics is studied. The temperature and breadth of the secondary transition are related to the those of the alpha transition in a variety of methacrylate, acrylate and styrene polymers, as well as polycarbonate. The effect of thermal history and the position and sharpness of these endothermic transitions is discussed. Some comparisons are made between this technique and results obtained via dielectric analysis and dynamic mechanical analysis obtained in the laboratory. 7 refs. 

Sudarsan AP, Wang J, Ugaz VM (2005) Thermoplastic elastomer gels an advanced substrate for microfiuidic chemical analysis systems. Anal Chem 77 5167-5173 Szabo JP, Hiltz JA, Cameron CG et al (2003) Elastomeric composites with high dielectric constant for use in Maxwell stress actuators. Proc SPIE 5051 180-190 Tallury SS, Spontak RJ, Pasquinelli MA (2014) Dissipative particle dynamics of triblock copolymer melts a midblock conformational study at moderate segregation. J Chem Phys 141 047448... 

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