This paper focuses on defining the reaction mechanism involved in the environmental etch of acrylic melamine-based automotive clearcoats via an identification of reaction products. This has been accomplished through a comparative study of products formed on acid treatment of neat crosslinkers, and those formed following laboratory acid treatment and field exposure of acrylic melamine clearcoat systems. Bulk elemental, X-ray photoelectron spectroscopy (XPS), and infrared (IR) analyses of sulfuric acid-treated melamine crosslinkers show that acid hydrolysis results primarily in the formation of melamine sulfate. Melamine sulfate formation was also observed following laboratory and field exposure of acrylic melamine clearcoat systems. These results confirm that the primary mode of melamine crosslink decomposition is through hydrolysis of acetal linkages and subsequent formation of melamine sulfates. However, data show that hydrolysis of pendent amino groups on the triazine ring also occurs.

This paper reports on the development of a laboratory test procedure for the evaluation of the environmental etch resistance of clearcoats. The test evaluates the bulk acid hydrolysis resistance of clearcoats by gravimetrically following material weight loss as a function of exposure time to a sulfuric acid solution, under conditions that simulate outdoor exposure. The bulk hydrolysis resistance of five production clearcoat technologies including acrylic melamine, acrylic melamine-silane, carbamate, acrylic urethane, and epoxy acid were evaluated. Results from the weight loss measurements were consistent with those anticipated based on the coating systems bulk chemistry and inherent hydrolysis resistance, for clearcoat systems processed under nominal processing conditions. The relative rankings from the laboratory test were found to correlate with field etch ratings. The test method is inexpensive, quantitative, and generates repeatable results that are not subject to environmental variations associated with current field etch testing.

A laboratory test procedure was developed to quantitatively evaluate the acid etch resistance of automotive clearcoats. Here we attempt to verify that the conditions used in the laboratory test reproduce the field degradation chemistry to assure that the test is evaluating realistic performance characteristics. In this study we applied X-ray photoelectron spectroscopy (XPS) as a tool to determine if degradation products are observable which can be used to verify the consistency of the field and laboratory degradation processes for acrylic melamine-based clearcoats.

The weakness of plastics at weld lines provides serious difficulties far the design and long term durability of injection molded parts. The goal of this work was to identify the cause of weld line weakness in polypropylene (PP) systems. The morphology of weld lines in a high molecular weight PP has been studied. It was found that the PP contains a hindered phenolic antioxidant additive that is not soluble in the polymer at the standard processing conditions. Transmission electron microscopy (TEM) pictures reveal the additive existing as a dispersed phase in the bulk polymer. Even though very small concentrations of this additive are normally used, (0.1-0.5%) large quantities were found at weld lines in a band approximately 100 nm wide and penetrating about 10 mu m into the surface of the part, hindering strength development at the weld line. X-ray photoelectron spectroscopy (XPS) results confirm enhanced concentrations of antioxidant on the now front and mold wall surface of short shot samples. The mechanical properties (Izod impact, tensile strength) are measured for samples molded at various processing conditions, varying amounts of antioxidant additive and with and without weld lines. The results are consistent with the presence of the additive playing a key role in strength development at PP weld lines.

In this study we evaluate the utility of using x-ray-excited valence band measurements for the determination of the surface composition of simple model thermoplastic olefin systems composed of binary blends of semicrystalline polypropylene (PP) and an amorphous ethylene–propylene copolymer (E-co-P). Blend compositions included combinations of high- and low-molecular-weight (MW) PP and E-co-P composed of 60 wt.% PP/40 wt.% E-co-P and 80 wt.% PP/20 wt.% E-co-P blends. Results demonstrate that experimental valence band spectra for the polyolefin blends can be approximated by a linear combination of the pure-component valence band spectra. Bulk compositions determined from spectra recorded from cryomicrotomed cross-sections were found to be consistent with the bulk component wt.%. The surface compositions of the binary blends were all found to be enriched in PP. Measurements taken from the 60/40 wt.% blends were 10–20% higher in PP concentration than the bulk compositions, and were found to vary depending on the MW combination of the components. No MW dependence was observed for the 80/20 wt.% blends, apparently due to a near saturation of the surface with PP. The development of methods for assessing the surface composition of these types of materials may prove useful in monitoring changes in composition with material formulation and process conditions. Information of this nature could be helpful in permitting an evaluation of potential influences of composition on adhesion. © 1997 by John Wiley & Sons, Ltd

Recently developed experimental techniques have allowed better characterization of lubricant-derived antiwear and antifriction surface films. These techniques and the information obtained in earlier studies are being applied to fully formulated engine oils with the objective of assisting implementation of advanced fuel efficient and emissions friendly oil technologies. Published results from those studies were combined with some new experimental results and with background information from related experiments and from experiments delineating the antioxidant chemistry of ZDTP to yield a more global view of antiwear film formation. This more global view has allowed us to propose an improved mechanism for the formation of lubricant-derived antiwear films, which accounts for a substantial body of experimental data, together with some unique observations resulting from our own investigations.

The surface films formed by a set of oils of related additive chemistry, but with differing detergent and dispersant contents, have been chemically characterized using a combination of surface analysis techniques. The films were formed in a cam/tappet friction apparatus with a direct acting bucket tappet geometry. In the absence of overbased detergent, the amorphous films were composed essentially of inorganic zinc phosphates formed by the ZDTP anti-wear additive, and evidence of higher molecular weight phosphates (e.g. metaphosphates) was found. Adding overbased detergent and dispersant resulted in partial replacement of zinc by the detergent metal and loss of the higher molecular weight phosphates in favour of ortho- and pyro-phosphates.

The interfacial chemistry of model systems consisting of two adhesion promoting primers and a single Thermoplastic Olefin (TPO) substrate was examined. Two commercial adhesion promoter (AP) materials were applied to a commercially-available TPO material and either flash dried at room temperature or baked at 100 degrees C. The surface composition of the AP films and TPO substrate, and the interfacial compositions of the AP/TPO systems were characterized using x-ray photoelectron spectroscopy (XPS). The AP films studied were based upon a chlorinated polyolefin (CPO). For one adhesion promoter film (AP-I), no chlorine was present at the surface suggesting a nonhomogeneous system. For the second adhesion promoter film (AP-2), the surface composition was about 15% CPO and 85% AP matrix. No changes in AP surface composition were evident for the different bake conditions for either AP. Interfacial compositions of the room temperature flashed materials were found to be very similar for both AP/TPO systems, with CPO being present for each and at similar concentrations. Interfacial compositions for the baked materials were also similar for the two systems, although the level of CPO at the interface increased for both the AP-1 and AP-2 relative to the unbaked materials. The relative increases observed were 46% and 41% for the AP-1 and AP-2 systems, respectively. The increase in the relative concentration of CPO at the interface with bake temperature suggests that there is a stronger interaction between the AP and TPO. The implication of these data is that a baked AP should result ih a more robust paint system with respect to AP/TPO adhesion.

X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been used to follow the effect of calcination temperature on CeO2 particle size, relative CeO2 concentration, and cerium oxidation state for CeO2 supported on γ-Al2O3. When the calcination temperature was increased from 500 to 900°C, XRD results indicated a decrease in the relative concentration of CeO2 at the highest loading (15 wt%), while XPS results reflected an apparent reduction of Ce4+toCe3+ at the lowest loading (5 wt%). Together these results suggest a transformation of a portion of the CeO2 particles to a more dispersed Ce3+-like species following high-temperature calcination. The reduction of ceria under these conditions is thermodynamically unfavorable. The apparent reduction of Ce4+ to Ce3+ upon calcination may be the result of an electronic effect, rather than a true reduction of the ceria.

The surfaces of tappet inserts subjected to lubricated, moving contact in a cam/tappet friction apparatus have been analyzed by IR reflection—absorption, X-ray photoelectron and Auger electron spectroscopies. The two lubricants used were similar fully formulated oils. One contained a soluble molybdenum friction modifier additive while the other did not. Thin inorganic films were formed across the contact area during the cam/tappet experiment. Regardless of the lubricant used, these films consisted of varying amounts of inorganic phosphates, sulfates, sulfides, and perhaps thiophosphates, with zinc and magnesium as cations. Molybdenum would also be a cation in the case of the friction modified oil. The films generated during the wear process differed in thickness, composition and surface coverage as a function of wear time, contact position and lubricant composition. The films formed by the friction modified oil were thinner and less continuous as compared with films formed from the unmodified oil.

X-ray photoelectron spectroscopy measurements indicate that the Ce3+ fraction in Al2O3-supported CeO2 can be decreased by the incorporation of La3+. If La3+ is incorporated into the Al2O3 before CeO2 is added, a higher CeO2 dispersion and a greater range of reversible reducibility of the CeO2 may also be obtained. These changes offer potential for improvement in the oxygen storage capacity provided by CeO2 in three-way catalysts.

Binding energies and reduction properties of palladium in commercial monolithic automotive catalysts were measured using X-ray photoelectron spectroscopy (XPS). It was shown that XPS in conjunction with temperature selective reduction can be used to associate palladium binding energies and reduction characteristic with varying degrees of palladium-support and palladium-support additive interactions. Good correlation was found for the palladium binding energies and reduction properties of the commercial catalysts, and those reported previously for model studies of γ-alumina supported palladium. In addition, a palladium state was observed consistent with that reported for a γ-alumina supported Pd-Ce system, suggesting the presence of Pd-Ce interactions in the commercial catalysts. This work indicates that with the combination of these techniques, dispersed and particulate palladium, as well as palladium-support additive interactions can be identified. The effects of thermal aging (sintering) on precious metal interactions were also investigated, with results demonstrating the utility of these techniques for assessing catalyst aging.

Die Röntgenkleinwinkel-Untersuchung des γ-Globulinmoleküls erfolgte an einer Konzentrationsreihe von 5 - 0,5-proz. Lösungen. Die Extrapolation der Kurvengestalt auf die Konzentration Null ergab den Streumassenradius des Teilchens (72 A) und im Verein mit der Absolutmessung, d. i. der Bestimmung der Streuintensität relativ zur Intensität des Primärstrahls, das Mol.-Gew. von 1,59 · 105. Die weitere Analyse basierte wesentlich auf der Querschnittsstreukurve. Die Zerlegung von deren Amplitude in zwei Anteile führte auf die Vorstellung eines langgestreckten Teilchens aus einem dichteren Kern und einer weniger dichten Hülle. Der Kernquerschnitt (Rq,K= 13,6 A) ist elliptisch mit den Halbachsen 10.9 und 25 Å und repräsentiert 76% der Masse. Die Hülle ist wesentlich ausgedehnter (Rq,H = 38,5 A). Dieses Ergebnis wird sowohl aus der Kurvengestalt als auch aus der absoluten Intensität des Querschnittsfaktors erschlossen. Der Kernanteil weist eine innere Solvatation auf, was aus dem Vergleich der experimentellen Invariante mit der theoretischen für eine kompakte Struktur zu erwartenden geschlossen werden kann. Auch hierfür ist die absolute Intensitätsmessung erforderlich.

Die Röntgenkleinwinkel-Untersuchung des γ-Globulinmoleküls erfolgte an einer Konzentrationsreihe von 5 - 0,5-proz. Lösungen. Die Extrapolation der Kurvengestalt auf die Konzentration Null ergab den Streumassenradius des Teilchens (72 A) und im Verein mit der Absolutmessung, d. i. der Bestimmung der Streuintensität relativ zur Intensität des Primärstrahls, das Mol.-Gew. von 1,59 · 105. Die weitere Analyse basierte wesentlich auf der Querschnittsstreukurve. Die Zerlegung von deren Amplitude in zwei Anteile führte auf die Vorstellung eines langgestreckten Teilchens aus einem dichteren Kern und einer weniger dichten Hülle. Der Kernquerschnitt (Rq,K= 13,6 A) ist elliptisch mit den Halbachsen 10.9 und 25 Å und repräsentiert 76% der Masse. Die Hülle ist wesentlich ausgedehnter (Rq,H = 38,5 A). Dieses Ergebnis wird sowohl aus der Kurvengestalt als auch aus der absoluten Intensität des Querschnittsfaktors erschlossen. Der Kernanteil weist eine innere Solvatation auf, was aus dem Vergleich der experimentellen Invariante mit der theoretischen für eine kompakte Struktur zu erwartenden geschlossen werden kann. Auch hierfür ist die absolute Intensitätsmessung erforderlich.