Showing papers on "Chemical decomposition published in 1995"
TL;DR: In this paper, the authors examined the starting material and fractured membranes using a combination of X-ray diffraction and thermogravimetric analyses and found that the first type of fracture was the consequence of an oxygen gradient in the membrane, pointing from the reaction side to the air side, leading to fracture.
Abstract: In the course of generating synthesis gas (H2, CO) from methane, we have observed two types of fractures occurring on the Sr(Co, Fe)Ox-type oxygen membrane reactors The first type occurred shortly after the reaction started and the second type often occurred days after the reaction To determine the causes of these fractures, we have examined the starting material and fractured membranes using a combination of X-ray diffraction and thermogravimetric analyses We found that the first type of fracture was the consequence of an oxygen gradient in the membrane, pointing from the reaction side to the air side This causes a lattice mismatch inside the membrane, leading to fracture The second type of fracture, however, was the result of a chemical decomposition We found that the Sr(Co, Fe)Ox-type membrane had been reduced to SrCO3, and elemental Co and Fe by the synthesis gas generated in the reaction The decomposition causes enormous expansion leading to a large crack along the axis of tube
292 citations
TL;DR: Careful screening of chelating agents has been shown to be an alternative method for preventing metal-catalyzed oxidation, a site-specific process, in which the addition of antioxidants may accelerate the oxidation reaction.
Abstract: Oxidation is one of the major chemical degradation pathways for protein pharmaceuticals. Methionine, cysteine, histidine, tryptophan, and tyrosine are the amino acid residues most susceptible to oxidation due to their high reactivity with various reactive oxygen species. Oxidation during protein processing and storage can be induced by contaminating oxidants, catalyzed by the presence of transition metal ions and induced by light. Oxidative modification depends on the structural features of the proteins as well as the particular oxidation mechanisms inherent in various oxidative species, and may also be influenced by pH, temperature, and buffer composition. Protein oxidation may result in loss of biological activity and other undesirable pharmaceutical consequences. Strategies to stabilize proteins against oxidation can be classified into intrinsic methods (site-directed mutagenesis and chemical modification), physical methods (solid vs. liquid formulations) and use of chemical additives. The optimum choice of chemical additives needs to be evaluated on the basis of the specific oxidation mechanism. Oxidation induced by the presence of oxidants in the system is referred to as a non-site-specific mechanism. Under such conditions, oxidation can be effectively inhibited by the appropriate addition of antioxidants or free radical scavengers. metal-catalyzed oxidation is a site-specific process, in which the addition of antioxidants may accelerate the oxidation reaction. Careful screening of chelating agents has been shown to be an alternative method for preventing metal-catalyzed oxidation. (c) 1995 John Wiley & Sons, Inc.
273 citations
TL;DR: In this article, the electrochemical degradation of 100 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between 10.1 and 12.7 has been studied at constant current intensity using a Pb/PbO{sub 2} anode and a carbon-polytetrafluoroethylene O{ sub 2}-fed cathode.
Abstract: The electrochemical degradation of 100 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between 10.1 and 12.7 has been studied at constant current intensity using a Pb/PbO{sub 2} anode and a carbon-polytetrafluoroethylene O{sub 2}-fed cathode. Under these conditions, hydrogen peroxide was electrogenerated in the cell via a two-electron reduction of oxygen gas fed to the cathode. The current efficiency for H{sub 2}O{sub 2} generation depended on the applied current intensity and the background electrolyte used. The concentration decay for each contaminant with electrolysis time was followed by high pressure liquid chromatography (HPLC). Kinetic analysis of these data showed a pseudo first-order decomposition reaction for both substrates at anodic current densities of 30 mA cm{sup {minus}2} or higher, as well as a decrease, of their half-lifetimes when current intensity increased. A gradual decrease in total organic carbon (TOC) for 0.05 mol/dm{sup 3} NAOH solutions with electrolysis time was always found. Product analysis of these electrolyzed solutions by gas chromatography-mass spectroscopy (GC-MS) and HPLC allowed the detection of nitrobenzene and 1-chloro-4-nitrobenzene proceeding from the anodic decomposition of aniline and 4-chloroaniline, respectively. Maleic acid was also detected as intermediate and ammonia was found as final product. Destruction of initial pollutantsmore » and intermediates is explained by their oxidative reactions with OH and HO{sub 2} radicals at the anode reaction layer. The effect of HO{sub 2} upon decomposition pathways of anilines is discussed.« less
242 citations
TL;DR: In this article, the influence of the direction of ultraviolet irradiation upon the yields of the photocatalytic decomposition of pure water has been investigated in a Pt/TiO2 aqueous suspension system.
Abstract: The influence of the direction of ultraviolet irradiation upon the yields of the photocatalytic decomposition of pure water has been investigated in Pt/TiO2 aqueous suspension system. The yields of the photocatalytic decomposition irradiated from the top of the reaction cell are about 103 times higher than those irradiated from the bottom. The difference seems due to the reverse reaction of the formed H2 and O2 in the suspension.
137 citations
TL;DR: In this paper, the authors examined the relationship between hydrogen peroxide decomposition and contaminant degradation in the presence of subsurface materials and reported on batch and column studies examining this relationship using quinoline and a sandy aquifer material.
131 citations
TL;DR: In this paper, the phenol decomposition pathways and intermediates in ozonation and two advanced oxidation processes (e.g. UV/ozone, UV/hydrogen peroxide) were studied in a photochemical pilot reactor utilizing 5000 W low pressure mercury lamp.
100 citations
TL;DR: In this paper, the authors investigated the performance of different types of catalysts for NO adsorption and decomposition in a quartz microreactor and showed that the best catalysts were comparable to Co/ZSM-5 on a TOF basis.
96 citations
TL;DR: In this article, a series of Cu-based catalysts with and without ZnO have been studied for methanol decomposition in the absence of water, and the compositional study suggests that metallic Cu is the active species for methenolate decomposition, probably due to the dissolution of Zn into the Cu lattice.
Abstract: A series of Cu based catalysts with and without ZnO have been studied for methanol decomposition in the absence of water. CO and H2 are the major products. A significant amount of methyl formate is produced at low conversions and low reaction temperatures. Cu ZnO based catalysts show high initial activity but quickly deactivate. This may be attributed to the dissolution of Zn into the Cu lattice. Without the component ZnO, other Cu based catalysts show good activity and better stability. Cr increases the stability of the Cu based catalysts but slightly reduces the selectivity to CO. The composition of Cr correlates with the yield of dimethyl ether. Among many other components evaluated, a small amount of Ba, Mn and Si oxides strongly promote the Cu based catalysts in methanol decomposition. Cu, Cr, Si, O and Ba or Mn constitute the components of the highly active multicomponent catalyst. Characterizations of the catalysts combined with the compositional study suggest that metallic Cu is the active species for methanol decomposition. Silica enhances the activity probably by increasing the dispersion of Cu.
92 citations
TL;DR: In this paper, the reactions of ozone decomposition and CO oxidation by ozone on CeO2 have been investigated in a gradientless reactor, and it has been established that both oxygen species do not participate in CO oxidation.
Abstract: The reactions of ozone decomposition and CO oxidation by ozone on CeO2 have been investigated. Kinetic experiments were carried out in a gradientless reactor. Ozone decomposition and CO oxidation were found to proceed in the temperature range 10–70°C. Using EPR, TPD and XPS spectroscopy, two different kinds of oxygen species are observed on the oxide surface, one of them being identified as O−3. It has been established that both oxygen species do not participate in CO oxidation. The oxidant in the low-temperature oxidation of CO is highly reactive atomic oxygen (probably O−), which is produced by ozone decomposition on the oxide surface.
84 citations
TL;DR: In this article, the physicochemical properties of the working catalyst of the Cu-ZSM-5 have been evaluated under bona-fide catalytic conditions by X-ray absorption methods.
70 citations
TL;DR: In this article, the effect of sulfidation by H 2 S at 623 K of various metal oxides (MgO, TiO 2 rutile and anatase, ZrO 2, CeO 2, Al 2 O 3 ) on their catalytic properties towards isopropanol decomposition, cumene decomposition and methanol hydrosulfurization has been studied.
Abstract: The effect of sulfidation by H 2 S at 623 K of various metal oxides (MgO, TiO 2 rutile and anatase, ZrO 2 , CeO 2 , Al 2 O 3 ) on their catalytic properties towards isopropanol decomposition, cumene decomposition and methanol hydrosulfurization has been studied. The results are discussed according to the H 2 S adsorption modes. H 2 S coordination mainly occurs on TiO 2 samples and generates strong acid sites. The dissociative adsorption of H 2 S on alumina does not significantly influence its acidity. Replacement of O 2− by S 2− ions as in the case of MgO, ZrO 2 and CeO 2 mainly affects their basic or redox properties.
TL;DR: In this article, the promoted electro-oxidation of aqueous sulphur dioxide at platinum electrodes has been studied in acidic medium with the aid of cyclic voltammetry and in-situ FT-IR spectroscopy.
TL;DR: In this article, the kinetic aspects of the thermal decomposition of H2S in a flow reactor were investigated and it was shown that the reaction is essentially first-order in H 2S partial pressure.
TL;DR: Electrospray mass spectrometry was used in this study to confirm the two-step hydrolysis of chloranil to yield chloranilic acid, and the kinetics of each step were quantified as a function of pH.
Abstract: p-Chloranil (2,3,5,6-tetrachloro-2,5-cyclohexadiene-1,4-dione; tetrachloro-1,4-benzoquinone) has been observed as an oxidation product in processes used to oxidize pentachlorophenol (PCP), has known biocidal properties, and has been implicated in genotoxic effects associated with PCP. Chloranil undergoes displacement of chloride by hydroxide under highly alkaline conditions, but no previous work on chloranil decomposition has been conducted at environmentally relevant pH. Electrospray mass spectrometry was used in this study to confirm the two-step hydrolysis of chloranil to yield chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone), and the kinetics of each step were quantified as a function of pH. The half-life of chloranil at pH 7 is estimated to be slightly over 1 h, while that of its first hydrolysis product (trichlorohydroxyquinone) is about 21 d. Chloranil also reacts with hydrogen peroxide in a pH-dependent manner at rates substantially greater than the rate of spontaneous hydrolysis. The low yield of chloranilic acid from this reaction suggests that other, as yet unidentified, products are formed. Chloranilic acid has lower acute toxicity (as measured in the Microtox screening assay) than does chloranil, so that promoting the accelerated hydrolysis of chloranil may be advantageous in waste treatment or remediation processes in which it is formed.
Patent•
23 May 1995
TL;DR: In this article, a process for producing fine metal oxide particles comprising the step of heat-treating an aqueous solution of a metal salt at a temperature of not lower than 200° C. under a pressure of not less than 160 kg/cm2 for 1 second to 1 hour so as to bring into the decomposition reaction of said metal salt.
Abstract: Disclosed herein is a process for producing fine metal oxide particles comprising the step of heat-treating an aqueous solution of a metal salt at a temperature of not lower than 200° C. under a pressure of not less than 160 kg/cm2 for 1 second to 1 hour so as to bring into the decomposition reaction of said metal salt.
TL;DR: In this article, a commercial epoxy adhesive based on DGEBA cured with dicyandiamide (DDA) and containing fillers has been aged in water vapour (ca. 100% RH) at various elevated temperatures.
Abstract: A commercial epoxy adhesive based on DGEBA cured with dicyandiamide (DDA) and containing fillers has been aged in water vapour (ca. 100% RH) at various elevated temperatures. Viscoelastic characterisation was effected after ageing for various times up to saturation and after subsequent drying. Young's modulus in the glassy state is reduced after water sorption but returns virtually to its original value after drying, suggesting physical weakening due to plasticisation whereas, in the rubbery state, the observed diminution is only slightly restored on drying. An analysis based on the theory of rubber elasticity leads to the conclusion that chemical degradation is occurring by hydrolysis and chain scission. Gravimetric measurements effected on the polymer exposed to vapour for a fixed time and then dried to (virtual) equilibrium show an increase in weight followed by a decrease and finally a weight loss as exposure time is increased. A theory is proposed to explain the phenomena by initial chemical combination of water followed by leaching of severed chain segments. Calculations of average inter-crosslink molecular weight using both viscoelastic and gravimetric data are in good agreement. It is concluded that long-term exposure of the epoxy adhesive to water leads to both reversible (physical) and irreversible (chemical) degradation of the material.
TL;DR: In this article, the authors examined the relationship between contaminant degradation rate and the rate of hydrogen peroxide decomposition on filter media and found that the mass of contaminant removed depended on the amount of H peroxide decomposed, filter medium concentration, and filter medium characteristics.
TL;DR: The present work provides a reference for the development of an advanced oxidation process on the basis of a tunable plasma reactor, especially suitable for the treatment of air contaminated with chemical compounds that dissociatively attach electrons.
Abstract: The cold plasma decomposition of carbon tetrachloride (CCl 4 ) and trichloroethylene (C 2 HCl 3 ) at dilute concentrations in dry and wet air of atmospheric pressure was investigated. The cold plasma was generated in a tunable plasma reactor, where the electron concentration is controlled by an electron beam and the average electron energy is controlled by a superimposed sub-breakdown electric field. The energy expense for decomposition, i.e., the electron beam energy per molecule decomposed, as well as the intermediate and final decomposition products were determined. Moreover, likely reaction mechanisms for the decomposition of CCl 4 and C 2 HCl 3 are presented. These mechanisms are based on bimolecular dissociative electron attachment for both CCl 4 and C 2 -HCl 3 and additionally a chlorine chain reaction for C 2 HCl 3 . The present work provides a reference for the development of an advanced oxidation process on the basis of a tunable plasma reactor. Such a process would be especially suitable for the treatment of air contaminated with chemical compounds that dissociatively attach electrons.
TL;DR: In this article, the authors present a review of the mechanisms of the degradation of the solvent system in TBP and diluent radiation-chemical transformations occurring on decomposition of a solvent system.
Abstract: Reprocessing spent nuclear fuel is indispensable for the economical use of uranium in nuclear energy production, and has been used industrially for more than 40 years. These processes involve the use of an extractant/diluent (solvent) for separation of the reusable actinides from unwanted fission products. The most widely used processes employ tributyl phosphate (TBP) diluted with normal-paraffin hydrocarbon. However, on repeated use, the solvent becomes degraded due to thermal, radiolytic, and chemical attacks, resulting in chemical as well as physical damage. In view of the considerable expansion in the knowledge and understanding regarding the chemical and radiolytical decomposition of both TBP and the hydrocarbon diluent, an up-to-date review seemed appropriate. This review is concerned mainly with the mechanisms of the degradation of the solvent system. Schemes of TBP and diluent radiation-chemical transformations occurring on decomposition of the solvent system are presented.
TL;DR: In this paper, the authors investigated the oscillatory behavior of a BZ system with bromomalonic acid and bromate as substrates and with [Ru(phen)3] SO4 as a catalyst.
Abstract: We investigated the oscillatory behavior of a BZ system with bromomalonic acid and bromate as substrates and with [Ru(phen)3] SO4 as a catalyst. The observed oscillations can be well modeled with a theory based on two different feedback loops originally developed for a corresponding BZ system with [Ru(bipy)3] SO4 as a catalyst. Furthermore, we have reexamined the decomposition of acidic bromate. We conclude that the products of this reaction are HOBr and O2 rather than HOBr and perbromate; the rate constant for the decomposition reaction turns out to be 1000 times smaller for 1 M sulfuric acid solution than expected from earlier experiments performed with 3 M sulfuric acid solutions.
TL;DR: In this article, the adsorption, decomposition and oxidation of CH 3 Cl have been investigated on pure and chromiadoped SnO 2 catalysts by means of infrared spectroscopy, mass spectrometric and gas chromatographic analysis.
Abstract: The adsorption, decomposition and oxidation of CH 3 Cl have been investigated on pure and chromiadoped SnO 2 catalysts by means of infrared spectroscopy, mass spectrometric and gas chromatographic analysis. Catalyst samples have been characterized by X-ray photoelectron spectroscopy. It was found that the Cr 3+ ions incorporated in the surface layer of SnO 2 are oxidized to higher valent chromium ions. In harmony with the determination of active oxygen content, samples calcined at 873–973 K contained the largest concentration of higher valent chromium ions. Infrared spectroscopy showed that CH 3 Cl interacts with the OH groups of SnO 2 at 200–300 K to form H-bridge-bonded alkyl chloride. The decomposition of CH 3 Cl occurred slowly on pure SnO 2 above 573 K to give CH 4 , H 2 O, CO and HCl. The oxidation of CH 3 Cl on SnO 2 proceeded at a measurable rate at 400–440 K. Incorporation of a small amount of chromium ions into the SnO 2 increased the rate of both the decomposition and the oxidation by a factor of 10–16. The enhanced activity of chromia-doped SnO 2 is attributed to the high reactivity of chromium ions in the surface layer of SnO 2 .
TL;DR: In this paper, the authors used transmission infrared spectroscopy to monitor CCl x (a) intermediate surface species formed during the decomposition of CCl 4 on high surface area calcium oxide.
Abstract: Transmission infrared spectroscopy was used to monitor CCl x (a) intermediate surface species formed during the decomposition of CCl 4 on high surface area calcium oxide. Carbon tetrachloride was adsorbed on calcium oxide at 113 K During CCl 4 desorption, additional infrared bands at 801, 787, 775, 765, and 751 cm -1 were observed in the temperature range 110-250 K. These bands, which disappeared in the temperature range 150-250 K, were attributed to the formation and depletion of CCl x (a) species as C-Cl bonds are broken and Ca-Cl bonds are formed on the CaO surface. Carbon tetrachloride ( 13 C labeled) was employed to prove that the infrared bands of the surface intermediates were due to C-Cl vibrational modes. To compare carbon tetrachloride decomposition on different types of calcium oxides, both autoclave prepared (nanoscale particles) and conventionally prepared CaO were investigated.
TL;DR: In this paper, the thermal decomposition of low-density polyethylene was studied on samples containing a few per cent of polyvinyl chloride, poly(vinylbenzyl chloride) or poly(chlorostyrene).
TL;DR: In this article, the effect of Ru-loading on the performance of RuNaZSM-5 catalysts prepared by ion exchange (extent of ruthenium exchange: 20-100%) in the decomposition of nitrous oxide was studied in the temperature range of 40-700°C.
Abstract: The effect of Ru-loading on the performance of Ru-NaZSM-5 catalysts prepared by ion exchange (extent of ruthenium exchange: 20–100%) in the decomposition of nitrous oxide was studied in the temperature range of 40–700°C. The turnover frequency (TOF) for nitrous oxide decomposition (number of nitrous oxide molecules converted per ruthenium site per unit time) increased significantly with decreasing Ru-loading. Although lower Ru-loading resulted in higher TOF and lower apparent activation energy for nitrous oxide decomposition, this occurred at the expense of stronger inhibition by oxygen. Therefore, to obtain catalysts that remain active in the presence of excess oxygen, high Ru-loaded catalysts (close to 100% of exchange) are needed; whereas in the absence of oxygen, low Ru-loadings (close to 20% of exchange) are preferred. The high TOF observed in Ru-NaZSM5-20 was attributed to the interaction between ruthenium and sodium cations.
TL;DR: In this article, the ozone decomposition reaction to molecular oxygen was studied in a flow reactor on a MnO2 / γ-Al2O3 / cordierite catalyst.
Abstract: The ozone decomposition reaction to molecular oxygen was studied in a flow reactor on a MnO2 / γ-Al2O3 / cordierite catalyst. The rate expression is found to depend on ozone concentration, rO3 = k(O3)0.68, but not on O2 or H2O partial pressure. A reaction sequence based on an ionic type intermediate with superoxide (O2−) or peroxide (O22−) character is proposed to explain the kinetics.
TL;DR: The effect of alloying palladium supported on alumina with Group 1B metals was studied with the catalytic decomposition of nitric oxide into nitrogen and oxygen in this article, where it was shown that added gold and silver alloyed with palladium on the surface of Al 2 O 3 increased its catalytic activity towards the decomposition.
Abstract: The effect of alloying palladium supported on alumina with Group 1B metals was studied with the catalytic decomposition of nitric oxide into nitrogen and oxygen. Pd/Al 2 O 3 was inactive for the decomposition at low temperatures, but the activity increased rapidly when the system temperature was raised to 1023 K. TPO studies revealed that supported PdO became unstable at elevated temperatures and started to decompose to metallic palladium by desorbing oxygen also around 1023 K. Therefore, the desorption of oxygen is regarded as the rate determining step for the catalytic decomposition at T 2 O 3 increased its catalytic activity towards the decomposition. TPR and hydrogen chemisorption studies confirmed that added gold and silver alloyed with palladium on the surface of Al 2 O 3 . TPO studies also demonstrated that the enhanced activity on alloying palladium with gold and silver can be correlated with a decrease in the temperature required for the desorption of oxygen.
TL;DR: In this article, the effects of preparation of Cu-ZSM-5 catalysts on the activity of over-exchanged copper for NO decomposition were reported, which correlated very well with the amount of copper remaining in the channel.
Abstract: Effects of Cu-ZSM-5 catalyst preparation on the activity of “over-exchanged” copper for NO decomposition are reported. The Cu-ZSM-5 catalysts were prepared by incorporating Cu2+ cations into ZSM-5 zeolites from an aqueous cupric acetate solution adjusted to different pH values by adding either acetic anhydride or aqueous ammonia in the solution. The Cu2+ exchange levels increased with increasing pH level. STEM/EDX analysis identified CuO particles (5–6 nm) on the zeolite surface for the materials exchanged at pH>6. Conversion and kinetics measurements of NO decomposition to N2 over these catalysts showed that the “over-exchanged” copper was not active. Short-time wash with aqueous ammonia removed this copper. The catalyst activity correlated very well with the amount of copper remaining in the ZSM-5 channels.
TL;DR: In this article, the photo-oxidation of cationic, non-fashionic and amphoteric nitrogendash-containing surfactants (ndashdodecylpyridinium chloride (DPC) and benzyl-tetradecyldimethyl-ammonium chloride(BTDAC)) was examined in UV-illuminated, air-equilibrated aqueous titania suspensions.
Abstract: The photo-oxidation of cationic, nondashionic and amphoteric nitrogendashcontaining surfactants (ndashdodecylpyridinium chloride (DPC) and benzyl-tetradecyldimethyl-ammonium chloride (BTDAC); dodecanoyl-ndash(2-hydroxyethyl) amide (ndashDHA) adn dodecanoyl-N,ndashbis(2 hydroxyethyl) amide (N,ndashDHA); dodecyl-β-alanine (C12-β-Ala) and ndash(2-hydroxydodecyl)-ndash(2-hydroxyethy)- β-alanine (C12-βHAA)) was examined in UV-illuminated, air-equilibrated aqueous titania suspensions. Variations in the surface tension of the photo-oxidized surfactant solutions were monitored as a function of the irradiation time. The formation of ammonium and nitrate ions, together with the evolution of carbon dioxide, was investigated for the various surfactant chemical structures to obtain mechanistic information on the mineralization pathways. The yield of NH4+ ions was 4–13 times greater than yield of NO3+ ions. The amount of NH4+ ions formed depends on the structures of the surfactants. Mechanistic details of the photocleavage of the alkyl chains were inferred by probing the oxidation of sodium dodecanoate. The intermediates formed during the temporal photomineralization of the surfactant species were identified by high-frequency Fourier transform (FT) proton nuclear magnetic resonance (NMR) spectroscopy.
TL;DR: In this article, the authors investigated the desorption of OH radicals from Pt(111) at high temperature, ≳1000 K, during the water formation (H2+1/2) O2→H2O) and water decomposition reactions, respectively, using the laser-induced fluorescence technique.
Abstract: The desorption of OH radicals from Pt(111) at high temperature, ≳1000 K, during the water formation (H2+1/2 O2→H2O) and water decomposition reactions, respectively, was investigated using the laser‐induced fluorescence technique. The results are compared with corresponding data from our laboratory for polycrystalline Pt. The OH desorption rate in H2+O2 at 1–100 mTorr total pressure has its maximum at 8%–9% relative H2 concentration for surface temperatures between 1100 and 1400 K. With H2 replaced by D2, the OD desorption rate maximizes at somewhat higher relative hydrogen content. The apparent activation energy for OH desorption increases from about 1.4 eV at low relative hydrogen concentration to about 2.0 eV at hydrogen contents of 25% or more. For the water decomposition reaction, the apparent activation energy for OH desorption was found to be 1.7±0.2 eV at 0.5 Torr and 1.9±0.2 eV at 1 Torr. These differences in apparent activation energies are primarily due to kinetic effects. The results are analyz...
TL;DR: In this paper, peroxidase and iodide were used to study the thermal and redox decomposition of polypropylene and polyurethane films and polyester fibers by ozonization, UV irradiation, and plasma treatment.
Abstract: Polymer peroxides were generated onto polypropylene and polyurethane films, and polyester fibers by ozonization, UV irradiation, and plasma treatment. Their thermal and redox decompositions were studied using two assays: peroxidase and iodide. They may differ in the sensitivity to access the peroxides, depending on their localization in the polymer substrates. It was found that the generated peroxides are likely to be distributed not only on the outermost surface, but also in the subsurface of the polymer substrates. Plasma treatment provided polyurethane film with easily accessible peroxides, while UV irradiation and ozonization generated peroxides that were mostly incapable of reacting with aqueous solution of peroxidase. Redox decomposition of the peroxide groups by ferrous ions at 25°C showed that less than 50% of peroxides could react with ferrous ions with a rate constant similar to that of hydrogen peroxide in aqueous solution. Thermal decomposition of the peroxides did not obey the first-order kinetics, probably due to formation of not single peroxide species with different decomposition rate constants. The lowest decomposition rate constant observed at 65°C was 3 × 10−3 min−1, which did not depend on the polymer substrate nature and the method of peroxide generation. © 1995 John Wiley & Sons, Inc.