William Hertl

Surface Modification of Polystyrene by Gamma-Radiation

The effect of gamma-radiation on the surface chemical properties of polystyrene was studied by ESCA and FT-IR. Gamma-radiation produces surface >C=O and C-O containing functional groups only, and also causes oxidation to depths >10 nm as detected by ESCA. FT-IR spectra showed that below the top few molecular layers ester, acid, and carbonyl groups of various types were present. The α,β-unsaturated carbonyl/acid groups form a higher proportion of the total carbonyls with increasing depth. Surface oxidation follows pseudo-first-order kinetics; the extent of interior oxidation is linear with dose.

Solubilization of corona discharge- and plasma-treated polystyrene

Abstract Polystyrene tissue culture vessels are commercially treated by corona discharge or plasma surface oxidation to provide a hydrophilic surface, with 15–20% surface oxygen. ESCA and FTIR showed that oxidation forms hydroxyl, carbonyl, and carboxyl groups. We have discovered that water washing removes about half the oxidized species. It is believed that reaction with the vinyl polymer backbone to form carboxyl groups results in CC bond scission to form soluble fragments; addition and ring reactions would not yield soluble species. This functional group removal could affect the desired properties, such as the use of these groups as anchors in chemical coupling.

Amine-reactive surface chemistry of zinc phosphate glasses

Surface chemical studies on zinc phosphate glasses were carried out with an ammonia probe using FTIR and XPS. Low softening point zinc phosphate glasses can be co-extruded with high softening point polymers to form polymer filled blends. NH 3 reacts with P-OH groups (Br⊘nsted acid sites) to form bound NH 4 + and with the zinc ions (Lewis acid sites) to form coordinately bound NH 3 . Bulk nitridation reactions, forming various P-N bonds to >100 nm, occur concurrently. The glass surfaces were depleted in Zn compared to the batch compositions. Exposure to ambient water vapor removed Lewis acid bound ammonia; aqueous washing removed both types. Di- and tri-methyl amines also reacted with surface Br⊘nsted and Lewis acid sites. These amine reactions have the potential for binding polymer chains to the glass surface.

In-Line Hydrocarbon Adsorber System for ULEV

An in-line hydrocarbon (HC) adsorber system was developed to reduce cold start HC emissions. The system comprises a first catalyst, adsorber unit, and a second catalyst for oxidation of desorbed HC. During cold start, exhaust gas is directed to the hydrocarbon adsorber using a fluidic flow diverter unit without any mechanical moving parts in the exhaust system. After the first catalyst lights off, the diverter is shut off and the major portion of the exhaust gas then flows directly to the second catalyst without heating the adsorber unit. After the second catalyst reaches light-off temperature additional air was added to oxidize the desorbed HC. The system attributes are: NMHC emissions in ULEV range; straight line axial flow; reliable design; and limited back pressure penalty. The system was tested on a 3.8L US vehicle.

Hydrocarbon adsorber system for cold start emissions

A new adsorber concept has been tested. A zeolite adsorber with a central hole is mounted below the first catalyst, with a second catalyst downstream. During the cold start, when the adsorber is cool and the HC concentration high, HCs are adsorbed from the gas fraction passing-through the channels. The small fraction of exhaust gas passing through the hole impinges directly on and heats the second catalyst. The rationale is to design the hole to maximize the second catalyst heating rate, minimize desorption during heat-up and simultaneously keep the HCs which pass through the hole at an acceptably low level. FTP test results on the 3.8 L engine give 0.081 g/mi NMHC with no hole (same as base line) and decrease to 0.056 g/mi NMHC with the hole. This concept exhibits NMHC performance in the LEV range.

By-pass hydrocarbon absorber system for ULEV

A by-pass zeolite adsorber system consisting of a first catalyst, a by-pass loop containing the zeolite adsorbers followed by a downstream second catalyst was FTP tested using a US vehicle equipped with a 3.8 L, V6 engine. The system exhibited ULEV emissions performance with hydrocarbon adsorption and regeneration (desorption and oxidation) within the FTP cycle and required only a single diversion valve within the exhaust line. Adsorption takes place during the initial 70 seconds of the FTP cycle. The adsorbers were regenerated with the exhaust gas plus injected air.

ANEROBIC SPECIMEN TRANSPORT SYSTEM

Degassed dimethyl silicone oil may be used as a transport medium for specimens containing anaerobic microorganisms.

Rapid Assay for Polystyrene Surface Oxidation

Polystyrene surfaces are often corona-discharge or plasma treated to oxidize the surface, which enhances the wettability. X-ray photoelectron spectroscopy (XPS), which requires time and an ultra-high vacuum, is generally used to measure this surface oxidation. A rapid, simple method for measuring polystyrene surface oxidation is described. The surface is soaked in a solution of Azure A dye, which adsorbs only to oxidized sites on the polystyrene. The excess dye is flushed away and the bound dye is desorbed with a detergent; an absorbance measurement at 635 nm is used to determine the quantity of desorbed dye. This value correlates with the polystyrene surface oxygen concentration and gives r2 = 0.93.

Vanadia-induced transformations in yttria-stabilized zirconia

Abstract The earliest stages of the corrosion of ceramic therma-barrier coatings were analyzed during a model transmission electron microscope experiment designed to simulate the degradation of Y2O3-stabilized ZrO2 in the presence of V2O5. Thin films of Y2O3-stabilized ZrO2, previously prepared for examination in the transmission electron microscope, were exposed to the vapor emitted by a small quantity of V2O5 at 810–950°C. Morphological, chemical and structural transformations of the Y2O3-stabilized material were then characterized V2O5 reacts preferentially with Y2O3 to form YVO4 and ZrO2-enriched phases which possess inferior thermal and mechanical properties. The growth of YVO4 was monitored and a special orientation relation between Y2O3-stabilized ZrO2 and YVO4 is discussed.