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It has been reported by Dow Chemical Co. that oxidation catalysts cause increased particulate emissions from automotive exhausts. We find that this particulate consists of aqueous H2SO4 droplets. Current work undertaken between Ford and Battelle Columbus Laboratories, using an engine dynamometer, shows that the fuel sulfur emerges from the engine as SO2. At 60 mph road load, a monolithic oxidation catalyst converts almost half of the SO2 into SO3, the bulk of which is emitted from the tailpipe as H2SO4. The mass median diameter is smaller than 0.25 μm. Some ammonium sulfate is present, but the predominant sulfate species is H2SO4, totalling some 40% of the gross particulate mass depending on humidity. The rest is primarily water, associated with the hygroscopic H2SO4. Without a catalyst, the H2SO4 is <1/50 as much as with catalyst, the bulk of the fuel sulfur being emitted as SO2.

Several resin-bonded friction materials were used to establish the interrelationship between the resin-cure state and the functional properties. Pyrolytic gas chromatography (PGC) was used to measure the cure state of the resin and the Friction Assessment Screening Test (FAST) was used to characterize the friction and wear behavior of the materials. A phenolic resin, an oil-modified phenolic resin, and two different cashew resins were used as binders for simple resin-asbestos composites as used in brake linings. Both the PGC and functional properties of these materials showed systematic variations with changes in cure conditions of the resin. For all resins studied, a linear or bilinear relationship was found to exist between the PGC measured cure state of the resin and wear as measured by the FAST machine. A chemical kinetic model was successfully applied to relate both sample wear and a characteristic PGC peak of the resin to a unique function of cure time and temperature.

A study was made of the responses of pyrolytic gas chromatography (PGC) and the friction assessment screening test (FAST) to variations in curing conditions for a liquid, oil-modified, phenolic resin system. Both PGC, which characterizes the organic resin, and FAST, which characterizes the friction and wear properties, show systematic variations with changes in cure time and temperature. A linear relationship exists between the area of one PGC peak (phenol) and the wear as determined by the FAST procedure. A chemical kinetic model is postulated which relates the concentration of phenol produced on pyrolysis to a function of cure time and temperature. An index of cure is introduced which defines the curing conditions in terms of a single parameter. The PGC phenol peak area, FAST friction, and FAST wear correlate well with this index of cure.