SYNOPSISThere are few quantitative comparisons in the literature between glass transitions ( Tg) measured by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMA). Also, in the case of DMA, two different operational definitions have been used to obtain the glass transition, namely, the loss modulus (F) and damping (tan 6) peak temperatures. We propose a new DMA definition of Tg and demonstrate that it agrees with DSC Tg measurements within k2OC for both thermoplastic polystyrene and thermoset cross-linked acrylic polyurethane films with measurable tan 6 peaks. The glass transitions for a single polystyrene standard and several cross-linked acrylic polyurethane films were measured by DSC. Additionally, E" and tan 6 peak temperatures were measured by DMA as a function of frequency and temperature. Empirically, it was determined that the average of the E" and tan 6 peak temperatures measured at 1 rad/s oscillation frequency corresponds to the glass transition measured by the ASTM El356 DSC test method. I NTRO D U CTlO NThe glass transition (T,) of a polymer can be determined by observing the temperature range over which a significant change takes place in some specific electrical, mechanical, thermal, or other physical property. This temperature range can vary significantly depending on the property chosen for observation and on details of the experimental technique (e.g., heating rate, test frequency). In this study, glass transitions measured by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are compared.In the literature, there are few quantitative comparisons between glass transitions measured by DSC and DMA. In part, quantitative comparisons are difficult because reported results vary with instrument

ABSTRACT:The differential scanning calorimetry glass transition (DSC T g ), measured by ASTM test method E-1356, and the dynamic mechanical analysis glass transition (DMA T g ), measured using a new definition of the DMA T g , generally agree within {4ЊC for a wide variety of commercially available polymers. The DMA T g is defined as the average of EЉ and tan d peak temperatures measured at a 1 rad/s oscillation frequency.

Figure 3. Sessile drop of a PbCI2-KCI-NaCI mixture (4/3/3 molar ratio) on graphite at 793 K under (1) argon atmosphere, (2 and 3) dry air.interfacial tensions of salt mixtures on BN substrate. Conclusions and 81°, and the contact angle formed on BN varied between 73 and 130°.2. Graphite and amorphous carbon substrates were the least wetted and under an argon atmosphere the contact angles varied between 90 and 150°.3. The contact angles formed on graphite substrates did not change when the argon atmosphere was replaced with chlorine gas. However, when air or dry air was introduced, the contact angle decreased rapidly and complete wetting was observed after about 5 min. This effect was not observed when the graphite substrate was replaced with BN.