James C. Tou

Thermal hazard evaluation by an accelerating rate calorimeter

Abstract An accelerating rate calorimeter was developed for thermal hazard evaluation to provide time—temperature—pressure data for chemical reactions taking place under adiabatic conditions. The data interpretation is illustrated with an n th-order reaction. An approximate analytical solution for the time-to-maximum-rate is formulated, and its accuracy and utility are discussed. The technique was applied to a study of the thermal decomposition of N -methyl- N -nitroso- p -toluene sulfonamide, commonly known as Diazald®, and a complex runaway reaction taking place in a monomer system.

The correlation of membrane permselectivity with Hildebrand solubility parameters

Abstract Experimental and theoretical permselectivities for a filled elastomeric membrane have been correlated utilizing Hildebrand solubility parameters in a solution-diffusion model. Equilibrium partitioning of substances between the feed and membrane phases may be modelled as solutions. These two phases may be thermodynamically characterized by means of the Hildebrand solubility parameters. In addition, the effect on diffusive transport of the partitioning of a substance between a filler and polymer phase in a membrane may be correlated to solubility parameters. A variety of substances was examined in this study using a silicone elastomer membrane, composed by 69 wt% poly (dimethylsiloxane) and 31 wt% fumed silica. The model is demonstrated to have good predictive value over three or four orders of magnitude for the permselectivities of substances including permanent gases, alkanes, chlorinated and brominated hydrocarbons, alcohols, and aromatic hydrocarbons.

THE THERMOKINETIC PERFORMANCE OF AN ACCELERATING RATE CALORIMETER

Abstract The Arrhenius parameters of the thermal decomposition of pure di-t-butyl peroxide in toluene were measured to be E = 37.8 ± 1.1 kcal mole−1 and log A (sec−1) = 16.15 ± 0.61 from a series of accelerating rate calorimetric experiments covering a broad range of thermal inertia, from 3.1 to 17. The values are comparable to E = 37.78 ± 0.06 kcal mole−1 and log A (sec−1) = 15.80 ± 0.03 recommended by Shaw and Pritchard from a least-squares treatment of 177 data points obtained by various workers with different techniques. The highest self-heat rates that the calorimeter can follow without deviation from the expected self-heat rate curve were found to be dependent on the types of the sample bombs and the nature of the sample. They are ≈70°C min−1 for the Ti bombs (≈9 g), ≈20°C min−1 for the light-weight Hastelloy C bombs (≈19 g) and only about ≈2°C min−1 for the heavy-weight Hastelloy C bombs (≈70 g) for the reaction system studied.

Computation of Statistical Complexions by the Method of Steepest Descent

The approach of the steepest descent method to the calculation of the totality of states is extended to the cases of a collection of harmonic oscillators coupled with rigid rotors, and of a collection of anharmonic oscillators. The equations derived are applied to a selected model and to cyclopropane.

Study of Aqueous HCI and Formaldehyde Mixtures for Formation of Bis (Chloromethyl) Ether

The reaction of aqueous HCI and formaldehyde at concentrations up to 2000 ppm were carried out at ambient temperature for 18 hours to investigate the possible formation of bis(chloromethyl)ether. Bis(chloromethyl)ether was not observed either in the aqueous phase or the gas phase above the reaction mixture, with detection limits of 9 ppb and 1 ppb, respectively. Strong inferential evidence shows that bis(chloromethyl)ether cannot be present at even a much lower level than 9 ppb in aqueous solution.

Sampling system for mass spectrometric monitoring of a stream of reaction liquid

Abstract Reaction liquid is continuously circulated between the reactor and an automated Bendix liquid injection valve. A well defined volume of liquid is injected into a hot zone. The liquid injected is then vaporized and the resulting sample gas is swept with a stream of helium into a series of dilution chambers. The analyte concentration-time profile at the exit of the last chamber was mathematically modelled. It was found that the degree of symmetry of the profile increases when the number of chambers increases. The design and performance of the system are discussed together with results of a kinetic study of a chemical reaction.

A cradle-glass ampoule sample container for differential scanning calorimetric analysis

Abstract A sample container system was developed, which consists of a sealed micro-ampoule as the sample pressure vessel and a special ampoule cradle designed to optimize heat detection efficiency, reproducibility, baseline stability, and thermal responses. The heat detection efficiency and thermal responses of the sample container system were determined and compared to those of others. The reproducibility of heat measurements has been assessed using several common thermal standards and other chemicals. The interpretation of heat measurements by differential scanning calorimetry is also discussed.

Analysis of a Non-crosslinked, Water Soluble Anion Exchange Resin for the Possible Presence of Parts Per Billion Level of Bis (Chloromethyl) Ether

No evidence was found for the presence of bis-chloromethyl ether (bis-CME) in the resin at the detection limit ∼10 ppb with use of the hollow fiber probe-mass spec-trometric technique. The kinetic data indicate that bis-CME hydrolyzes rapidly and, therefore, cannot exist in any extended period of time in the resin solution.

Correlated electron spin‐resonance and infrared spectroscopic study of the postformation auto‐oxidation phenomenon in plasma‐polymerized 4‐vinyl pyridine films

Plasma polymerization of 4-vinyl pyridine (4-VP) proceeds through a gas-phase free radical mechanism to yield a film that retains much of the organic functionality of the monomer. During the deposition process, free radicals, which have been shown to quickly react with oxygen, are trapped to yield a film with a nascent peroxy radical density of 2.9 × 1018 spins/gas quantified by electron spin resonance (ESR) spectroscopy. In air at room temperature, peroxy radicals in the film react to produce carbonyl, hydroxyl, and ether structures in the polymer that was monitored using infrared (IR) spectroscopy. The free radical population was found to decay rapidly at first and then reach an apparent steady state after 30 hr. As the spin density decreases, a concomitant growth of vibrational modes associated with oxygen-containing functional groups was observed in the IR spectrum of the film. The relative population of oxygen-containing groups continued to increase even after the free radical population reached steady state. This slow, auto-oxidative effect may be attributed, in part, to free radical centers that are anchored to the polymer chain in regions of high crosslinking. In such regions, limited segmental mobility may limit the rate of radical-radical recombination (termination) proceses relative to oxidative radical-center.

Atmospheric-pressure ionization mass spectrometric and photoionization techniques for evaluation of barrier film permeation properties

Abstract Barrier films are mainly used as food packaging materials to protect food from oxygen and also to retain food flavor and aroma constituents. Since the packaging materials must exhibit very low permeation rates to these constituents, the measuring apparatus must have high sensitivity to the parts-per-billion concentration range. It is also desirable that the permeation rate measurements be conducted at packaging conditions, i.e., both sides of the films at ambient pressure. Two techniques, which are based on atmospheric-pressure ionization mass spectrometry and photoionization, are developed for the permeation rates measurements of flavor and aroma constituents. The film holders are also temperature controlled, which allows one to study the temperature effect on the permeation rates. In this paper, both the techniques and their applications to the study of the permeation rates and the permeabilities of a commercial film will be presented.