Prevention of degradation of γ-irradiated EPDM using phenolic antioxidants

The mitigation of oxidative degradation under γ-irradiation promoted by eight commercial antioxidants: Ethanox 330, Hostanox O3, Irganox 1010, Topanol OC, Ionox 220, Santonox R, Santowhite, Cyanox 2246 loaded onto ethylene-propylene terpolymer at the concentration of 0.5 phr in respect of a pristine polymer was studied. The polymer samples were exposed to various doses up to 500 kGy. The kinetic parameters of oxidations: oxidation induction times, onset oxidation temperature, oxidation rates were evaluated by CL measurements. They validated the differences in the stabilisa-tion activities by limitation of the oxidation gradient. The high efficiency of some of the antioxidants studied, such as Ionox 220 and Santowhite, ensured the delay in degradation even at a high irradiation dose (500 kGy). For the environments with γ-radiation exposure, a relevant sequence in the increasing protection efficiency could be established: Topanol OC; Hostanox O3; Irganox 1010; Cyanox 2246; Santonox R; Ionox 220; Santowhite. The FT-IR spectra were recorded for the calculation of the radiochemical yields resulting from the modifications occuring in the concentrations of oxygenated structures. The accumulations of hydroxyl- and carbonyl-containing products were calculated to evaluate the irradiation effects in EPDM-based products during a severe accident. The options for EPDM stabilisation are discussed based on chemiluminescence and FTIR analyses.     

The effects of gamma irradiation on the fate of hindered phenol antioxidants in food contact polymers. Analytical and 14C-labelling studies

The extractable levels of two hindered phenol antioxidants (Irganox 1076 and Irganox 1010) present in PVC, polyethylene and polypropylene, have been monitored by HPLC techniques following progressive exposure of the polymers to ⁶⁰Co γ radiation. There is a gradual diminution in the extractable levels of each antioxidant as irradiation progresses as a result of transformation of the antioxidants in the oxidation reactions ensuing during irradiation. Experiments involving the use of a ¹⁴C-labelled sample of Irganox 1076 in polyolefins have provided evidence of covalent binding of antioxidant degradation products to the polymer following gamma irradiation. However, there is also evidence of the formation of extractable degradation products, the identity of which is as yet unknown.     

Thermal oxidation and molding feasibility of cycloolefin copolymers (COCs) with high glass transition temperature

Cycloolefin copolymers (COCs) with high glass transition temperature (T_g = 203 °C) have been synthesized and pelletized by extrusion molding. However, their colors change from transparent to yellow during extrusion molding because of thermal oxidation and generation of alkene groups. We have successfully blended several antioxidants (Irganox 1010, Irgafos 168, Irganox HP2225 and Irganox HP2921) into lab-made COCs to avoid the discoloration. The experimental results show that Irganox HP2921 is the best antioxidant among the antioxidants used and can effectively not only suppress thermal oxidation but also eliminate the color stain.     

HALS和抗氧剂对PE辐射致色的影响

聚乙烯;稳定剂;HALS和抗氧剂对PE辐射致色的影响     

Gel permeation chromatography – Atmospheric pressure chemical ionization – Mass spectrometry for characterization of polymer additives

The study presents the possibility to use gel permeation chromatography (GPC) with atmospheric pressure chemical ionization (APCI)-mass spectrometry for the analysis of polymer additives having molecular weights up to 2,000?g?mol^?1. Irganox 1010, Irganox 1035, Irganox 1076, and Irganox 3114 were analyzed in chloroform using 2.1-mm-internal-diameter GPC columns at the optimum flow rate of 50?µL min^?1. Based on the chemical formula, the APCI interface combined with chlorine ionization enabled us to predict the expected mass spectrum and to build libraries without needing to inject each additive separately. Quantification limits of about 100?µg of additive in 1?g of polymer (100?ppm) can be reached using single-ion-monitoring methods based on the calculated isotope distribution.     

Saponification then GC for Determination of Irganox 1010 and Irganox 1076 in a Polymer Matrix

A gas chromatographic method has been established for determination of Irganox 1010 and 1076 after saponification. The analytes were saponified with methanolic potassium hydroxide, acidified with hydrochloric acid, and the solvent was removed by rotary evaporation. The dry residue was dissolved in xylene and analyzed by GC with flame-ionization detector (FID). Compounds were separated on a polar (Carbowax 20 M) capillary column and nitrogen was used as carrier gas and make-up gas. This method has a relatively large linear dynamic range, 50–3,000 and 100–1,600 mg L⁻¹ for Irganox 1010 and 1076, respectively, and limits of detection (LOD) were 20 and 40 mg L⁻¹, respectively. The effect of conditions such as saponification temperature, and concentration and volume of potassium hydroxide were studied.     

Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene

Effect of various antioxidants on the thermal oxidation stability of LDPE and X-LDPE has been investigated. To achieve this purpose, miscellaneous commercial grade antioxidants such as Irganox 1010, Irganox1076, Irgafos168, Irganox B225, and Chimassorb 944 were selected. Then, formulations based on different content of antioxidant were prepared. The samples were crosslinked by exposure to electron beam irradiation. To assess the thermal oxidation stability of samples, oxidation induction time (OIT) test was accomplished on both the irradiated and unirradiated specimens. Ageing tests were carried out in order to evaluate the thermal oxidation stability of irradiated X-LDPE. The results indicate that Irganox 1010 is the most effective antioxidant amongst the selected ones, concerning thermal oxidation stability of LDPE, before and after aging test.     

A simple spectrophotometric technique for determination of Irganox 1010 in polymeric samples

A simple spectrophotometric method is presented for the determination of tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhyrocinnamate)] methane (Irganox 1010) in polymeric samples. To a solution of Irganox 1010 in acetone is added concentrated sodium hydroxide solution and then it is shaken for a short time. The 2-phase system produced in the upper phase (acetone) is yellow colored. Absorbance of the colored phase is recorded in a quartz cell at 440 nm. Different parameters such as temperature, time after mixing solutions of Irganox 1010 and sodium hydroxide, and concentration of sodium hydroxide are studied. The linear dynamic range, limit of detection and correlation coefficient (r) are 25–1000 mg·L⁻¹, 10 mg·L⁻¹ and 0.996, respectively. The repeatability of this method is good (n = 6, C = 250 mg·L⁻¹, RSD = 3.26%). Correspondence: Mir Ali Farajzadeh, Department of Analytical Chemistry, Faculty of Chemistry, Tabriz University, Tabriz, Iran     

Polyethylene stabilization against thermal oxidation by a trimethylquinoleine oligomer

The thermal oxidation at 110 and 120 °C of polyethylene (PE) films stabilized by 0.1, 0.2 and 0.5% of a trimethylquinoleine (TMQ) oligomer has been studied by IR spectroscopy (carbonyl build-up) and by DSC (measurement of the oxidation induction time at 200 °C). The induction period increases almost proportionally to the TMQ concentration and the TMQ efficiency (as estimated by the ratio t_ind/[TMQ]₀) increases when lowering the temperature. Some features of stabilizer consumption kinetics and the dependence of maximum oxidation rate with initial stabilizer concentration were compared to experimental results obtained for stabilization by hindered phenols (Irganox 1010) and to literature data for sacrificial (e.g. hindered phenols) and regenerative (Hindered Amine Stabilizers) antioxidants. These comparisons led to classify TMQ in the category of Hindered Amine Stabilizers (HAS), which was confirmed by a kinetic analysis. Only the scheme taking into account the specific features of HAS (role of NO radicals, regeneration from alkoxyamines) was able to correctly simulate the oxidation behaviour of TMQ stabilized PE.     

Synergistic effect of combination of Irganox 1010 and zinc stearate on thermal stabilization of electron beam irradiated HDPE/EVA both in hot water and oven

Thermo-oxidative stability of HDPE/EVA blends can be considerably increased by combination of a high-molecular weight phenolic antioxidant and zinc stearate. In this work, the post-irradiation thermal stability of HDPE/EVA blends has been studied. High-density polyethylene and its blends with ethylene-vinylacetate copolymer in both pure form and mixed with Irganox 1010 and zinc stearate were exposed to electron beam radiation at doses between 80 and 150 kGy, at room temperature, in air. In order to evaluate the thermal stability of the samples, post-irradiation heat treatments were done in both hot water bath at 95 °C and in an oven at 140 °C. The mechanical properties and changes in the chemical structure were determined during thermal aging in hot water and oven. The gel content was enhanced by increasing EVA concentration in all applied doses. The stabilized blends have lower gel content than the unstabilized samples. From the results of heat aging treatments it was observed that the thermal stability of the unstabilized blend samples was lower than HDPE. Thermal stability of the samples has been improved by incorporation of Irganox 1010 and zinc stearate. Formation of hydroxyl group was insignificant for stabilized samples during heat aging in both conditions. Also, the changes in the value of oxidation induction time (OIT) for the stabilized samples were negligible after prolonged immersion in hot water.     

Kinetic Evaluation of Reactivity of Phenolic Derivatives as Antioxidants for Polypropylene

Reactivity of commercial phenols as antioxidants for plastics, especially polypropylene, was examined under kinetic considerations. Inhibitive rate constants, k_inh, were found to decrease in the order: SWP ? Topanol CA ? BMP > Ionox 330 > Irganox 1076 > Irganox 1010, while numbers n′ of free radicals trapped by the phenolic moiety decreased in the order: Irganox 1076 > Irganox 1010 ? Ionox 330 > BMP ? Topanol CA > SWP (the structures of these antioxidants are given in the text). In practical use of phenols for polypropylene, it was found that effective phenols are not those having higher values of of k_inh., but n′ values nearly two. The effect of substituents, especially para substituents, of phenols on their activities was elucidated.     

Measurement and correlation of solid–liquid equilibria of Irganox 1010 with n-hexane

Solid–liquid equilibria (SLE) for the binary mixtures of Irganox 1010 with n-hexane have been measured using a method in which an excess amount of solute was equilibrated with the alkane solution. The liquid concentrations of the Irganox 1010 in the saturated solution were analyzed by UV spectrometry. Activity coefficients for Irganox 1010 have been calculated by means of the Wilson, NRTL and UNIQUAC models and with them were correlated solubility data that were compared with the experimental ones. The best correlation of the solubility data has been obtained by the Wilson model, by which the average root-mean-square deviation of temperature for the system is 0.33 K.     

Optimization of Dispersive Liquid–Liquid Microextraction of Irganox 1010 and Irgafos 168 from Polyolefins Before Liquid Chromatographic Analysis

A new dispersive liquid–liquid microextraction method has been established for extraction of two antioxidants, Irganox 1010 and Irgafos 168, from polyolefins. The extracts were analyzed by liquid chromatography. Carbon tetrachloride at microliter levels and acetonitrile at milliliter levels were used as extraction and dispersive solvents, respectively. Central-composite design and response-surface methodology were used as experimental strategies for modeling and optimization. The effects of experimental conditions on extraction were investigated by modeling extraction recovery as the response. The experimental design was performed at five levels of the operating conditions. Nearly the same results for optimization were obtained by using the one-variable-at-a-time and central-composite-design methods: sample size 5–10 mg, dispersive solvent acetonitrile (2 mL), extraction solvent carbon tetrachloride (200 μL); extraction temperature 100 °C, and extraction time 3 h. Under the optimum conditions the calibration plots were linear over the range 50–2,000 μg L^?1 in solution. The relative standard deviation of the method for six replicate experiments was 7.0 and 4.9% for Irganox 1010 and Irgafos 168, respectively.     

Depth profiling of Irganox‐3114 nanoscale delta layers in a matrix of Irganox‐1010 using conventional Cs+ and O2+ ion beams

Depth profiling of an organic reference sample consisting of Irganox 3114 layers of 3 nm thickness at depths of 51.5, 104.5, 207.6 and 310.7 nm inside a 412 nm thick Irganox 1010 matrix evaporated on a Si substrate has been studied using the conventional Cs⁺ and O₂⁺ as sputter ion beams and Bi⁺ as the primary ion for analysis in a dual beam time‐of‐flight secondary ion mass spectrometer. The work is an extension of the Versailles Project on Advanced Materials and Standards project on depth profiling of organic multilayer materials. Cs⁺ ions were used at energies of 500 eV, 1.0 keV and 2.0 keV and the O₂⁺ ions were used at energies of 500 eV and 1.0 keV. All four Irganox 3114 layers were identified clearly in the depth profile using low mass secondary ions. The depth profile data were fitted to the empirical expression of Dowsett function and these fits are reported along with the full width at half maxima to represent the useful resolution for all the four delta layers detected. The data show that, of the conditions used in these experiments, an energy of 500 eV for both Cs⁺ beam and O₂⁺ beam provides the most useful depth profiles. The sputter yield volume per ion calculated from the slope of depth versus ion dose matches well with earlier reported data. Copyright © 2013 John Wiley & Sons, Ltd.     

The extractability of phenolic antioxidants into water and organic solvents from polyethylene pipe materials - Part I

Three commercial anti-oxidant systems have been studied regarding migration and chemical reaction in different polyethylene pipe materials during extraction in organic solvents and in hot water, 95-100 °C, under anaerobic and aerobic conditions. Materials made of crosslinked and non-crosslinked high density polyethylene, low density polyethylene and blends thereof were stabilized with different phenolic antioxidants: Irganox 1330, Irganox 1010, and Irganox 1076. The loss in stability with increasing extraction times was followed by oxidation induction time (OIT) measurements and by measuring the residual amounts of anti-oxidant by extraction. A gradual decrease in OIT and amount of anti-oxidant with increasing treatment time in water was observed for all samples. However, the behaviour of the three antioxidants was dissimilar. For materials containing Irganox 1330 three new species, possibly transformation products of the anti-oxidant, were found within the material. Larger decrease in anti-oxidant content in the polymer compared to corresponding loss in OIT indicates that the new species still have anti-oxidant capacity. On the other hand, corresponding transformation species could not be found within materials stabilized with Irganox 1010 or 1076. It is suggested that these antioxidants, which both contain ester groups, are hydrolyzed and that the new species migrate out into the surrounding water. Solvent extractions showed that crosslinking did not affect the extractability of the antioxidants. Actually, even with water as the extracting media, the network did not show any obstructive effect of the migration of the anti-oxidant. For peroxide crosslinked samples part of the anti-oxidant could not be extracted with solvent but we believe that grafting of antioxidants onto the polymer backbone is the most plausible explanation in this case. Additionally, we see a clear decrease in anti-oxidant loss with increasing crystallinity.     

Burning of thermally thin polyethylene mixtures

The burning of polyethylene in the mixture with aluminium hydroxide, aluminium oxide, cellulose and Irganox 1010 has been examined by cone calorimeter under non-standard sizes of the sample. The time to ignition of pure polyethylene decreases with decreasing initial amount of polyethylene powder. The subtraction of the mass of water released from the total mass lost for polyethylene with aluminium hydroxide give the same values of effective heats of combustion as for pure polyethylene up to the load about 50 mass% of aluminium hydroxide. The mean heats of combustion determined from the cone calorimeter software are higher than those determined from the total oxygen consumed and mass lost multiplied by the factor 13.1. The additivity rule was found for effective heat of combustion and total smoke released for polyethylene with cellulose. The free radical scavenger Irganox 1010 does not show a significant effect on the flammability of polyethylene except for the increase of the total smoke released. The equation describing the heat release rate evolution in time has been proposed showing a good fit to the experimental runs.     

Effect of stabilizers on the preparation of poly(ethylene terephthalate)

Previous investigators have indicated that stabilizers will block the transesterification catalyst in the preparation of PET by the DMT process. This was not the case when triphenyl phosphate (TPP) or Irganox 1010 was used as the stabilizer and manganous acetate as the catalyst. Stabilizers in this study included TPP, trimethyl phosphate (TMP), tetraethylammonium hydroxide (TEAOH), Irganox 1010, and Irganox 1222. Their effect on the properties of PET made by the TPA process was investigated. It was observed that TPP and TMP greatly reduced the carboxyl content of PET and that the others had little or no effect. All stabilizers lowered the diethylene glycol content of PET. The rate of polycondensation was slightly increased when a small amount of Irganox 1010, Irganox 1222, or TMP was added. Proper concentration of stabilizer should be chosen to obtain good stability and low diethylene glycol content. Among the five stabilizers studied TPP was the best with respect to carboxyl and diethylene glycol content and thermal stability. The concentration of TPP should be kept under 0.04% by weight of PET.     

Chemiluminescence and inhibited oxidation of polypropylene

The efficiency of mixtures of the commercial antioxidants, Hostanox OSP 1, Irganox 1010 and distearylthiodipropionate was examined by chemiluminescence and oxygen uptake methods. Lower induction periods of oxidation, observed by the chemiluminescence method at 190°C, were found with samples which contain more of the less volatile additives. In accordance with earlier findings this is due to the surface nature of chemiluminescence which yields results close to those of the kinetic region.     

Dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-diode array detection as an efficient and sensitive technique for determination of antioxidants

Dispersive liquid-liquid microextraction (DLLME) and high performance liquid chromatography-diode array detection (HPLC-DAD) was presented for extraction and determination of Irganox 1010, Irganox 1076 and Irgafos 168 (antioxidants) in aqueous samples. Carbon tetrachloride at microliter volume level and acetonitrile were used as extraction and dispersive solvents, respectively. The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at μL level. Limit of detection for analytes is between 3 and 7 ng mL⁻¹. One variable at a time optimization and response surface modeling were used to obtain optimum conditions for microextraction procedure and nearly same experimental conditions were obtained using both optimization methods. Recoveries in the ranges 78-86% and 84-110% were obtained by one variable at a time and response surface modeling, respectively. Using tap water and packed water as matrices do not show any detrimental effect on the extraction recoveries and enrichment factors of analytes.     

Photooxidation of Selected Polycyclic Aromatic Hydrocarbons in Aqueous Organic Media in The Presence of Ti(IV)Oxide

Abstract

We have studied the photooxidation of selected polycyclic aromatic hydrocarbons (PAH) in the presence of Ti(IV)oxide in a mixed solvent system consisting of N-methylpyrrolidinone (NMP) and water. Reaction rates for the photooxidation of acenaphthylene and pyrene were investigated by monitoring the disappearance of the PAH substrate from the reaction mixture as a function of time. For both compounds plots of In C_o/C_t, as a function of time yielded straight lines, indicating first order kinetics with respect to the substrate. With an initial acenaphthylene concentration of 1.0 gL^?1 the first order reaction rate constant was 0.19 hr^?1 and the half life was 3.7 hr. With an initial pyrene concentration of 0.2 gL^?1 the first order reaction rate constant was 0.0285 hr^?1 and the half life was 24 hr. The photoproducts were characterized by high performance liquid chromatography with diode-array detection (HPLC/DAD) and by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (APCI/LC-MS). Although a number of simple oxidation products were identified the bulk of the photoproducts consisted of the parent PAH substituted with one or more solvent (NMP) molecules. The product mixtures from the photooxidation of the non-mutagens acenaphthylene and pyrene were found to be also non-mutagenic in our Salmonella typhimurium forward mutation assay.