SynopsisThe curing reaction of a thermoset polyester was investigated by using the isothermal and dynamic techniques of ditferential scanning calorimetry (DSC). The heats of reaction (at different curing temperatures) and a kinetic expression of the crosslinking reaction are presented and compared to the results of the previous studies. The proposed kinetic model can be utilized to obtain the rates of heat generation and the extent of cure at different cure temperatures and time. The overall activation energy of the curing reaction was calculated on the basis of experimental data as 17.0 kcal/ mole and the overall reaction rate constant as 2.60 X lo9 exp (-17,000/RT) min-'.

This paper describes the high-pressure volumetric properties of three commonly used poly(α-olefin) base oilsPAO 2, PAO 4, and PAO 8with nominal 100 °C kinematic viscosities of 2, 4, and 8 cSt. Using a special variable-volume view cell that permits continuous pressure scan and volume measurements, densities were determined at 298, 323, 348, 373, and 398 K at pressures up to 40 MPa. Isothermal compressibilities, isobaric thermal expansivities, thermal pressure coefficients, and internal pressures were then evaluated. At each temperature, density–pressure correlations were developed for the range from 10 to 40 MPa. Density–temperature correlations were developed at 10, 20, 30, and 40 MPa. It is shown that the densities of PAO 2 (which were in the range from 0.7364 to 0.8214 g/cm3) are lower than those of PAO 4 (in the range from 0.7663 to 0.8470 g/cm3) or PAO 8 (in the range from 0.7664 to 0.8498 g/cm3). The densities of PAO 4 and 8 were essentially the same. Isothermal compressibilities of each base oil were of the same order of magnitude at each temperature (with the range being from 6.8 to 10.2 × 10–4 MPa–1), with PAO 2 showing slightly higher values. Isobaric thermal expansivities were in the range (7.2–9.5) × 10–4 K–1. PAO 2 showed higher expansivity values at all pressures. Thermal pressure coefficients were in the range 0.8–1.2 MPa K–1. The values were higher for PAO 2 at 323 K and higher temperatures. PAO 8, while showing the highest thermal pressure coefficient at 298 K, became lower than that of PAO 2 at 323 K and lower than that of PAO 4 at 348 K and higher temperatures. At 398 K, PAO 4 shows the highest thermal pressure coefficients. The trends observed with the thermal pressure coefficients were also reflected in the internal pressures for the respective oils. The internal pressure values were in the range from 260 to 370 MPa. The internal pressure value in each system was observed to decrease with pressure. These observations were interpreted in terms of the differences in the carbon chain lengths, ease of packing, and relative significance of attractive versus repulsive forces that develop as a function of the pressure or temperature.

No abstract

SynopsisMolecular weight and thermal stability measurements on the presumed polymers of aminoborane, H2BNH2, and aminodifluoroborane, F2BNH2, were explored using a laser light scattering technique for the molecular weight measurements and both differential thermal analyses and thermogravimetric analyses for the thermal stability studies. Weight-average molecular weight of polymeric aminodifluoroborane in water was determined as 23,000 g/mole, whereas the molecular weight of polymeric aminoborane could not be determined since a suitable solvent was not found. Both DTA and TGA observations showed partial decomposition of polymeric aminoborane between 135' and 200°C, and the vaporization of polymeric aminodifluoroborane between 250' and 360°C.

No abstract