Processabilities and mechanical properties of surlyn-treated starch/LDPE blends

The esterification of the hydroxyl group of starch with DuPont Surlyn was considered as pretreatment method of starch before blending with polyolefins. In treating starch with Surlyn, two different raction conditions were taken to optimize reaction conditions. First, the esterification reaction was carried out in 110°C xylene with oleic acid as a catalyst. Second, the reaction out in a 90°C mixture of deionized water and xylene with ceric ammonium nitrate(CAN) as an initiator. Starch granules would be swollen above the gelatinization temperature in water. In both cases starch was midified by Surlyn to have good compatibility with low-density polyethylene (LDPE). The mechanical and theological properties were examined for blends of the treated starch and LDPE. This system may be one of the biodegradable polymer blends that sufficiently retain properties as a packaging film.     

Effect of plasticizers on the thermal decomposition of chlorinated polyvinylchloride

Plasticized samples of chlorinated polyvinylchloride (CPVC) were investigated by using thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Three different plasticizers were studied, namely, dioctyl phthalate (DOP), alkyldiaryl phosphate ester (Santiciser 2148), and triaryl phosphate ester (Reofos 50). TG experiments in nitrogen showed one major decomposition stage, involving dehydrochlorination, and minor pyrolysis reaction of the hydrocarbon residue. In contrast to the three stages previously reported to occur in the nonplasticized‐stabilized CPVC, TG analyses in air showed two distinctive decomposition stages for the plasticized CPVC samples. The DOP system provided a suggestion of a third stage. The first decomposition stage was due not only to the loss of all the chlorine present, but also to loss of the plasticizer or its decomposition products. The second decomposition stage was mostly due to char oxidation, the char being formed almost exclusively from the DCE and VDC units in CPVC polymer. DSC results showed that in the presence of nitrogen, there was no significant plasticizer effect on the thermal decomposition behavior of CPVC up to about 330°C, while in air the DSC traces also show no significant differences below 400°C. The two phosphate plasticizers showed no significant differences in their effect on the thermal decomposition behavior of CPVC under the same experimental conditions. It is believed that P₂O₅ and polyphosphoric acid are among the main constituents of the residua. These would impart a protective glassy surface to the char. This will facilitate effective flame retardant action. This preliminary conclusion is based on the premise that the more stable the char layers are, the more resilient will be the protective layer, and consequently, the better the flame retardant effect. J. VINYL ADDIT. TECHNOL., 11:21–27, 2005. © 2005 Society of Plastics Engineers     

Random-effects regression analysis of correlated grouped-time survival data

Random-effects regression modelling is proposed for analysis of correlated grouped-time survival data. Two analysis approaches are considered. The first treats survival time as an ordinal outcome, which is either right-censored or not. The second approach treats survival time as a set of dichotomous indicators of whether the event occurred for time periods up to the period of the event or censor. For either approach both proportional hazards and proportional odds versions of the random-effects model are developed, while partial proportional hazards and odds generalizations are described for the latter approach. For estimation, a full-information maximum marginal likelihood solution is implemented using numerical quadrature to integrate over the distribution of multiple random effects. The quadrature solution allows some flexibility in the choice of distributions for the random effects; both normal and rectangular distributions are considered in this article. An analysis of a dataset where students are clustered within schools is used to illustrate features of random-effects analysis of clustered grouped-time survival data.     

Thermophysical properties of polyamide yarn-air composite systems

Conclusions By use of methods of nonstationary heat flow, thermophysical characteristics (thermal conductivity, , thermal diffusivity,a, and specific heat capacity, C) have been obtained and the character of the temperature dependence, =f(T), has been established for a yarn-air composite system with a parallel disposition of elementary filaments.The character of the temperature dependence, =f(T), is supported by the results of studies of PA yarn-air composite systems having an unordered disposition of the elementary filaments, which were obtained by the method of a stationary heat flux.The dependence of the change in specific heat capacity coefficient of a composite system with an unordered disposition of elementary filaments on temperature, C = f(T), has been determined by the nonstationary heat flux method.Equations for the temperature dependences of the coefficient of specific heat capacity and the thermal conductivity coefficient of PA complex yarns have been obtained in the temperature range from 300 to 423 K.Translated from Khimicheskie Volokna, No. 4, pp. 46–48, July–August, 1987.     

Hydrosilylation and dehydrocondensation reactions of methylhydridesiloxane to acrylic and methacrylic acids

The hydrosilylation of α,ω‐bis(trimethylsiloxy) methylhydridesiloxane (degree of polymerization ≈ 53) with acrylic and methacrylic acid with various ratios of the initial compounds, in the presence of platinum hydrochloric acid, has been investigated. In the presence of platinum hydrochloric acid, competitive dehydrocondensation reactions take place with the formation of various oligomers with various chemical links. In the later stages of the reaction, three‐dimensional systems have been obtained. During dehydrocondensation, the reaction order, reaction rate constants, and activation energy have been determined. The structures of the synthesized oligomers have been determined with IR and NMR spectroscopy data. Gel permeation chromatography, differential scanning calorimetry, and X‐ray analyses of the synthesized oligomers have been carried out. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3243–3252, 2007     

High resolution STEM/EDX spectral imaging to resolve metal distributions within ∼100 nm combustion generated ash particles

Ultrafine ash particles play an important role in establishing a sticky inner deposit layer on heat transfer surface for power plants, but it is still unclear whether a thin surface alkali coating on these ultrafine particles might control this deposition behavior. In this research, we used a high resolution FE-TEM/STEM equipped with twin SDD EDX detectors for high X-ray detection efficiency, to determine the presence and absence of surface enrichment of alkali metals on ultrafine solid fuel ash samples that had low bulk alkali compositions but high deposition rates. Results from two types of combustion generated nano-sized ash particles are presented. One was from the oxy-combustion of pulverized bituminous coal, the other from oxy-combustion of pulverized rice husks, both being burned in a 100?kW rated down-flow laboratory combustor. Elemental mapping results from STEM/EDX uncovered some surface enrichment of alkali metals in ultrafine ash particles, where it existed, as it did for combustion of rice husks. However, it was not able to discern similar alkali metal surface enrichment for the bituminous coal ultrafines that had resulted in even higher deposition rates. Since deposition rates from both of these cases lie on the same correlation with PM₁, one can conclude that although surface enrichment of alkali metals is present for some ～100?nm particles, it is not a prerequisite to achieve high inner surface deposition rates. This is in contrast to prevailing theories that point to alkali metals as “bad actors” as far as the sticky inner deposition rate is concerned.

Copyright © 2019 American Association for Aerosol Research     

Electrochemical promotion of Rh catalyst in gas-phase reduction of NO by propylene

The concept of non-faradaic electrochemical modification of catalytic activity (NEMCA) has been applied for the in situ control of catalytic activity of a rhodium film deposited on YSZ (yttria stabilized zirconia) solid electrolyte towards reduction of 1000 ppm NO by 1000 ppm C₃H₆ in presence of excess (5000 ppm) O₂ at 300 °C. A temporary heating at this feed composition results in a long-lasting deactivation of the catalyst under open circuit conditions due to partial oxidation of the rhodium surface. Positive current application (5 A) over both the active and the deactivated catalysts gives rise to an enhancement of N₂ and CO₂ production, the latter exceeding several hundred times the faradaic rate. While active rhodium exhibits a reversible behaviour, electrochemical promotion on the deactivated catalyst is composed of a reversible and an irreversible part. The reversible promotion results from the steady-state accumulation of current-generated active species at the gas exposed catalyst surface whereas the irreversible effect is due to the progressive reduction of the catalyst resulting in an increased recovery rate of lost catalytic activity. The results are encouraging with respect to application of rhodium for the catalytic removal of NO from auto-exhaust gases under lean-burn conditions.     

Alternative hydrocarbon solvents for cottonseed extraction

Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane. Presented in part at the AOCS Annual Meeting & Expo, Atlanta, Georgia, May 1994.     

The Polymorphism of Low Erucic Rapeseed Oil with High Content of Palmitic Acid

A new type of low erucic acid rapeseed oil containing high amount (11%) of palmitic acid (C₁₆-LOBRA) was studied, both in labscale and in pilot-plant equipment. The polymorphic behaviour of fat blends and margarine emulsions consisting of C₁₆-LOBRA, LOBRA and soybean oil and their hydrogenated fats were examined. The results clearly show the potential in the hydrogenated C₁₆-LOBRA. The time before the stable ß-form is developed is much longer for the hydrogenated C₁₆-LOBRA compared with the hydrogenated LOBRA and in fact similar to a hydrogenated soybean oil. The hydrogenated C₁₆-LOBRA is therefore well suited to be used in e.g. margarine systems.     

Combined XPS and TPR study of sulfur removal from a Pt/BaO/Al2O3 NO x storage reduction catalyst

Pt/Al₂O₃ and Pt/BaO/Al₂O₃ catalysts (1 wt% Pt, 10 wt%BaO) were sulfated under conditions simulating a real NSR catalyst operation. Comparative TPR and XPS studies of sulfur removal from Pt/Al₂O₃ and Pt/BaO/Al₂O₃ catalysts indicate that the sulfur removal from Al₂O₃ surface precedes reductive decomposition of BaSO₄ (250–400 °C). Barium sulfate decomposition started with further increase in desulfation temperature at the point of surface atomic ratio Ba:S = 1 (~450^o). Simultaneously, an intensive formation of sulfide species on the catalyst surface was observed. Thermodynamic analysis of the desulfation process allows us to hypothesize that barium sulfide formation may hinder sulfur removal under reducing conditions.