Polymer crystallization dynamics,as reflected by differential scanning calorimetry. Part 1: On the calibration of the apparatus

In this paper a method for the calibration of the heat transfer coefficient between pan and furnace is given. This (second) calibration is necessary in addition to the usual calibration of the temperature scale. Indeed, with increasing cooling rates as required for kinetic measurements, the finite heat flow resistance between pan and furnace becomes evident anyway. We also propose to enlarge this resistance deliberately, in order to separate the time scales of the control system and of the exponential return of the heat flow curve to the base line, as occurring after completion of the phase transition. Only in this way can the heat transfer coefficient be determined with some accuracy. Another advantage of a lowered heat transfer coefficient will be treated in a third paper. It enables an approximate treatment of polymer crystallization kinetics.     

Effect of sample size on isothermal crystallization measurements performed in a differential scanning calorimeter: A method to determine avrami parameters without sample thickness effects

Isothermal crystallization studies of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) using differential scanning calorimetry (DSC) were performed using different sample thicknesses to determine the effect of non-ideal heat-transfer. Polyethylene was chosen because of its importance, its extensive coverage in the literature, and its fast crystallization kinetics. Thermal gradients were found to significantly affect the measured crystallization exotherm; slower crystallization rates were observed for thicker samples measured at lower temperatures (greater supercoolings). Differences between different sample thicknesses disappeared at higher temperatures, consistent with finite heat-transfer rates being responsible for the effect. A power-compensation and a heat-flux DSC were used; these experiments also enabled the determination that the performance of the latter was acceptable for this study. Finally, thickness-independent Avrami parameters have been calculated.     

H-bonding in entrapped water in poly(o-methoxyaniline): Results from a differential scanning calorimetry study

Differential scanning calorimetry (DSC) was used to investigate entrapped water in poly(o-methoxyaniline) (POMA) in powder form. Two endothermic peaks were attributed to removal of water molecules that were adsorbed with distinct energies. By obtaining thermograms at various heating rates, we succeeded in applying Kissinger's approaches to estimate activation energies for the water adsorbed. The values obtained were ca. 25 and 53 kJ/mol, which correspond to H-bonding interactions, probably at the amine and imine centers of POMA, respectively.     

A new simple,low-cost approach for generation of the PM10 fraction from soil and related materials: Application to human health risk assessment

A new simple, robust and low-cost wet laboratory method for the generation of the <10 μm (PM₁₀) particle size fraction is reported. A sedimentation method is directly compared with a centrifugation method for generation of the PM₁₀ fraction. Both approaches are based on an integrated form of Stokes’ law. Subsequently the sedimentation method was adopted. The results from the sedimentation method were corroborated using particle size distribution measurements. This approach for the generation of the PM₁₀ fraction was applied to soil and mine waste samples from Mitrovica, Kosovo as part of an investigation in to the human risk assessment from inhalation of the PM₁₀ fraction containing potentially harmful elements (PHEs). The average daily dose for Cd from the inhalation of suspended soil particles was calculated to be 0.021 and 0.010 μg kg⁻¹_BW d⁻¹ for a child and an adult, respectively. This corresponded to an inhalation dose of 0.50 and 0.70 μg Cd d⁻¹ for a child (20 kg) and an adult (70 kg), respectively.