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A suitable specimen was selected to compare the glass transition measurement by several thermal analysis techniques. The specimen, an epoxy composite, was analyzed by Thermal mechanical analysis (TMA) using three different methods, including flexure, expansion, and stress relief, as a function of temperature. A dynamic mechanical analyzer (DMA) was then performed at three frequencies. A portion of the specimen was then selected for differential scanning calorimeter (DSC) analysis. Special care was taken to ensure that the specimen pre-treatment was identical and that thermal lag errors were corrected for, so that a direct glass transition comparison could be made between analytical techniques. The best agreement in Tg values between the various measurement methods was obtained between: DSC heat flow midpoint; TMA onset of expansion, flexure or stress relief; and the onset of the storage modulus for DMA data taken at 0.1 Hz. These were all within one degree of 122°C. The best correlations with the DSC and TMA data to be obtained from a 1-Hz DMA run was that of the onset of the loss modulus peak (121.7°C). The methods employed are described, and the results discussed.

Four new commercial grades of rubber toughened ABS (acrylonitrile-butadienestyrene) terpolymers were characterized by differential scanning calorimetry (DSC), mechanical analysis and gel permeation chromatography (GPC). These rubber toughened ABS molding compounds were manufactured by a new "blended technology" to yield resins which offer a broad range of flow properties and levels of toughness. Based upon DSC estimates of the level of rubber ineluded, the four ABS compounds can be divided into two groups; the first has about 11 wt. % butadiene and the second near 18 wt. %. In addition, two styrene-aerylonitrile copolymers with different average molecular weights were found blended within each ABS group. By this blending process four resins are produced with impact strengths ranging from below three to near seven ft-lb in -l. These analytical results show that a resin's impact strength is enhanced not only by increasing the level of rubber particles in a given ABS compound but also by raising the molecular weight of the SAN which is blended into the terpolymer.

Dynamic mechanical analysis (DMA) was employed to characterize the modulus behavior of a silver filled glass material. The method employed a simulated die attach process to understand the behavior of the storage modulus and the complex viscosity. Of specific interest are the various physical states of the silver glass material during the temperature excursions. Thermogravimetric analysis (TGA) and differential scanning carolimetry (DSC) were also employed to describe the transition stages of the material. A marked decrease in probe position during heating, which indicated the decrease in thickness of the silver glass paste, described the initiation of glass wetting the Ag flake and coalescing to form a glass-Ag composite. The analysis showed that the material remained in a low viscosity throughout this process. Solidification of the composite material occurred during the cooling cycle as the temperature went through the glass transition temperature, unlike thermoset polymers, in which gelation and curing occur during the heating process. The storage modulus of the solidified material was also verified by the three-point bending technique.the organic system comprises of a fugitive vehicle system made up of a resin, surfactant and solvent. The paste is dispensed into the package cavity, the die is placed on the paste during the die attach process, and the whole system is fired in air at an elevated temperature. The key events that occur during processing are depicted in Figure 1. The processing involves volatilizing the solvent and burning out the organic components. The glass melts and densification of the structure occurs during the firing. The successful adhesion of the die to substrate is when the glass wets the Ag flake and the interfaces before solidified into a glass-Ag composite. The elastic modulus of the solidified silver/glass ranges at 10" Pascals.Volatilization burnout I Heating . )