Monitoring the degradation of stabilization systems in polypropylene during accelerated aging tests by liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry

Degradation pathways of three commonly used antioxidants were successfully studied by using accelerated aging tests for polymers. Additionally, thermal stability and resistance to discoloration of seven stabilizers were investigated by aging pure stabilizers dissolved in the polymer-mimicking solvent squalane. Methods based on high-performance liquid chromatography hyphenated with highly sensitive tandem mass spectrometric detection (HPLC-MS) were developed for structural elucidation of degradation products. Subsequent quantification was done using UV-detection. While Irganox 1330, Irganox 3114 and Cyanox 1790 showed a similar degradation mechanism with highly colored decomposition products, no corresponding oxidized species could be found for other stabilizers and less discoloration was observed. For Irganox 1010, hydrolysis was the preferred degradation mechanism, leading to products with an increased solubility in water. Therefore this stabilizer is less suitable for materials intended for water applications. In the aged materials previously unknown degradation mechanisms were observed for Irganox 1010 and Irgafos 168 which also contribute to the inhibition of autoxidation of the polymer.     

Chemiluminescence of polyethylene: The comparative antioxidant effectiveness of phenolic stabilizers in low‐density polyethylene

The thermal stabilizing efficiency of a range of phenolic antioxidants (Lowinox CA22, Lowinox WSP, Lowinox TBP6, Irganox 3114, Irganox 1330, and Cyanox 1790) was determined in polyethylene films with chemiluminescence and hydroperoxide analysis and compared with standard systems based on Irganox 1010 and 1076. Under both nitrogen and oxygen conditions, good correlations were obtained between the two methods, confirming the importance and role of the hydroperoxide functionality and its stability in the oxidative process. Chemiluminescence decay rates correlated well with the initial corresponding hydroperoxide contents, which were measures of the antioxidant efficiencies in the polymer. The antioxidant structure and volatility (melting points) were important parameters to consider in any such correlations and related very much to the methodology and conditions of analysis (i.e., the temperature and atmosphere). Some of the antioxidants themselves under nitrogen exhibited strong chemiluminescence, which appeared to be a legacy associated with their manufacturing history and the partial oxidation of their structures, which gave peroxide functionalities. This was more notable for the complex antioxidant structures. Under oxygen, higher levels of chemiluminescence were observed, and this was indicative of some level of oxidation associated with the antioxidant structures. With temperature‐ramping experiments, the chemiluminescence emission was significant and only observed at temperatures close to the melting points of the additives and/or polymer. Mobility was clearly an essential feature of this reaction emission because chemiluminescence was well observed when the molten state was reached. Under normal practical conditions, such levels of chemiluminescence, because of employed stabilizers, do not contribute significantly to the chemiluminescence emissions of stabilized polymer materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3312–3326, 2002     

耐辐射致色聚烯烃的研究

研究了在γ射线辐照条件下受阻胺光稳定剂 (简称HALS)、各种抗氧剂对聚丙烯 (PP)和聚乙烯 (PE)的黄度 (YI)的影响。结果表明五甲基HALS比相应的四甲基HALS更能有效地阻止聚烯烃的辐射致色。抗氧剂Irganox 10 76比Irgafos16 8或IrganoxPS 80 2更有效。当抗氧剂和HALS并用时显示出协同效应 ,10 76和PDS并用时聚丙烯的黄度比单独添加 10 76或PDS的聚丙烯的黄度都低。     

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.     

Determination of antioxidants in polyolefins using total dissolution methodology followed by RPLC

Antioxidants are added to polyolefins to improve the stability of the resin from oxidation and degradation during processing of the finished article and to increase product lifetime. Without antioxidants, polyolefins would quickly degrade during and after the extrusion or thermoforming process, which would cause inferior appearance and physical properties. The proper level must be added to protect the polymer and to minimize cost. Antioxidants are usually extracted from the resin and the extract is analyzed by RPLC, GC, or Fourier transform infrared spectroscopy. Unfortunately, many of these procedures require significant manual labor, time, and solvent, rendering them impractical for high-throughput work processes. In addition, they may not provide complete extraction of the additives depending upon the type of resin. A validated analytical method was needed for the determination of three common antioxidants, Irganox(?) 1010, Irganox(?) 1076, and Irgafos(?) 168 in polyolefin resins. This paper shows the determination of these antioxidants using dissolution followed by precipitation with o-xylene and methanol. Direct analysis of the solution is achieved in 8?min using RPLC.     

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.     

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     

Polymer-additive extraction via pressurized fluids and organic solvents of variously cross-linked poly(methylmethacrylates)

Variously cross-linked poly(methylmethacrylates) (PMMAs) are synthesized with three additives incorporated at theoretically 1000 microg of the additive per gram of prepared polymer. The additives are Irganox 1010, Irganox 1076, and Irgafos 168. The in-house" synthesized polyacrylates are then subjected to supercritical fluid extraction (SFE) to determine if additive recovery is a function of percent cross-linking. Although considerable work in this regard has been performed with non-cross-linked polyolefins, the literature is lacking regarding polyacrylates. Some additive degradation apparently occurs during the synthesis, as judged by the increased complexity of the extract high-performance liquid chromatographic trace and the low percent recoveries observed especially for the Irganoxes. For low polymer cross-linking (1%), it appears that both PMMA synthetic reproducibility and readily observed polymer swelling during SFE are serious issues that adversely affect additive percent recovery and precision of results. Higher percent cross-linking yields more consistent analytical data than low percent cross-linking, even though the amount of additive extracted in all PMMA samples (regardless of cross-linking percentage) is essentially the same whether the extraction is via SFE or liquid-solid extraction with methylene chloride. Results for comparably cross-linked poly(ethylmethacrylate) and poly(butylmethacrylate) are similar to PMMA.     

气相色谱-质谱联用法测定PC塑料粒子中的2种抗氧剂

基于溶解沉淀-气相色谱-质谱联用技术,建立了一种同时测定PC塑料粒子中十八烷基3-(3,5-二叔丁基-4-羟苯基)丙酸酯(抗氧剂1076)和三[2,4-二叔丁基苯基]亚磷酸酯(抗氧剂168)含量的方法。通过研究不同沉淀剂对抗氧剂提取率的影响,确定了最优沉淀剂。处理后的上清液采用HP-5 MS分离,选择离子模式检测,外标法定量。在优化实验条件下,抗氧剂1076在2~50 mg/L、抗氧剂168在0.1~50 mg/L质量浓度范围内相关系数(r2)均大于0.99,抗氧剂1076和抗氧剂168的方法检出限(LOD)分别为50 mg/kg和0.75 mg/kg,定量限(LOQ)分别为166.7 mg/kg和2.5 mg/kg,回收率为80.3%~119.8%,相对标准偏差(RSDs,n=6)为5.8%~9.2%。该方法适用于PC塑料粒子中抗氧剂1076和抗氧剂168含量的测定。     

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.     

Solvent exchange using hollow fiber prior to separation and determination of some antioxidants by high performance liquid chromatography

This study presents a simple and rapid solvent exchange procedure using a hollow fiber. Antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) and solvents such as tetrahydrofuran (THF), carbon tetrachloride and toluene were selected as model compounds and sample solvents, respectively. After injection of the sample solution into the hollow fiber and solvent evaporation, the precipitated analytes in lumen and pores of the fiber were washed with methanol (the mobile phase for separation and determination by HPLC-diode array detection) and good chromatographic peaks were obtained. The effect of different parameters such as fiber length, volumes of sample and washing solvents were investigated and the optimum conditions were selected. The repeatability of the method was tested and it was found that the relative standard deviation (R.S.D.) was less than 10% for all analytes. Also enrichment factors of 3.03, 2.21 and 1.19 times were obtained for Irganox 1010, Irganox 1076 and Irgafos 168, respectively, when 200 μL sample and 50 μL methanol (washing solvent) were used.     

Extraction and quantification of antioxidants from low-density polyethylene by microwave energy and liquid chromatography

In this paper a experimental design is applied to optimize the quantification of hindered phenol Irganox 1076, phosphite antioxidant Irgafos 168 and their oxidized product tri[2,4-di-tert-butylphenyl]phosphate from low-density polyethylene (LDPE). The developed analytical method consists of two steps: microwave-assisted extraction and reversed-phase liquid chromatography (LC) coupled with ultraviolet diode-array detector. A Plackett-Burman design was carried out in order to find the significant experimental parameters affecting the antioxidants extraction by microwave energy. These parameters were subsequently optimized by a central composite design. The performed method allows extracting the studied antioxidants at low temperature in a short time without degradation of phosphite antioxidant Irgafos 168.     

Extraction of polypropylene additives and their analysis by HPLC

Summary The polypropylene additives were extracted by dissolution-precipitation and Soxhlet. The Soxhlet method was adapted for the extraction of phosphorous antioxidants. The RP HPLC method with quaternary gradient elution separated five chemical groups of additives: lower molecular mass di-tert-butyl phenol (D.T.B.P.), hindered amine light stabilizers (Tinuvin 326), hindered phenolic antioxidants (Irganox 1010) and phosphorous antioxidants (Irgafos 168 and Ultranox 626) with their degradation products.     

Quantitative molecular depth profiling of organic delta-layers by C60 ion sputtering and SIMS

Alternating layers of two different organic materials, Irganox1010 and Irganox3114, have been created using vapor deposition. The layers of Irganox3114 were very thin ( approximately 2.5 nm) in comparison to the layers of Irganox1010 ( approximately 55 or approximately 90 nm) to create an organic equivalent of the inorganic 'delta-layers' commonly employed as reference materials in dynamic secondary ion mass spectrometry. Both materials have identical sputtering yields, and we show that organic delta layers may be used to determine some of the important metrological parameters for cluster ion beam depth profiling. We demonstrate, using a C(60) ion source, that the sputtering yield, S, diminishes with ion dose and that the depth resolution also degrades. By comparison with atomic force microscopy data for films of pure Irganox1010, we show that the degradation in depth resolution is caused by the development of topography. Secondary ion intensities are a well-behaved function of sputtering yield and may be employed to obtain useful analytical information. Fragments characteristic of highly damaged material have intensity proportional to S, and those fragments with minimal molecular rearrangment exhibit intensities proportional to S(2). We demonstrate quantitative analysis of the amount of substance in buried layers of a few nanometer thickness with an accuracy of approximately 10%. Organic delta layers are valuable reference materials for comparing the capabilities of different cluster ion sources and experimental arrangements for the depth profiling of organic materials.     

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.     

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.     

The hydrolysis mechanism of bis(2,4-di-tert-butyl)pentaerythritol diphosphite (Alkanox P24): An atmospheric pressure photoionisation mass spectrometric study

Alkanox P24 is a commercial phosphite antioxidant, well known in the literature for its excellent processing stability. As in the case of many processing phosphites, however, Alkanox P24 might undergo hydrolysis when exposed to small amounts of water. A number of products proposed recently in the hydrolytic pathway of the phosphite [Ortuoste N, Allen NS, Papanastasiou M, McMahon A, Edge M, Johnson B, et al. Polym Degrad Stab; 2006;91:195-211] are investigated in this study by atmospheric pressure ionisation-mass spectrometry (API-MS). The applicability of atmospheric pressure photoionisation (APPI) and atmospheric pressure chemical ionisation (APCI) ion sources is tested and the ion formation characteristics of Alkanox P24 are compared in both sources. In positive ion mode, ionisation of the parent phosphite occurred by protonation. In negative ion mode no pseudo-molecular ion peak was detected and the deprotonated species were more dominant in APPI. This source was employed further for the investigation of the hydrolysis products, since it exhibited lower limits of detection. High performance liquid chromatography (HPLC) with single ion monitoring (SIM) detection was used for the separation of the species formed. Hydrolysis of the phosphite proceeded via the scission of the two P-O_phenol bonds exclusively to give 2,4-di-tert-butyl phenol quantitatively as a final product.     

Development of Synergistic Stabilizing Compositions for Polyolefins and Evaluation of Their Performance

A series of new synergistic polyfunctional stabilizing compositions phenol-phosphite for polyolefins were developed. Their performance as antioxidants, color stabilizers, and agents preventing thermomechanical degradation was quantitatively evaluated.     

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.     

ANTIOXIDANT DEPLETION AND OIT VALUES OF HIGH IMPACT PP STRANDS

The service life of a polyolefin product depends to large extent on the type and amount of the antioxidants added. During the manufacturing,storage and use of the product the antioxidants are depleted by physical processes and chemical degradation,and this impairs its long-term performance.The initial and in-use oxidation stability is often characterized and monitored by the measurement of the oxidative induction time(OIT),and service life predictions are based on the rate of decrease of the OIT value.To...