The effect of carbon black on the oxidative induction time of medium-density polyethylene

An extensive series of: (i) oxidative induction time (OIT) measurements derived from differential scanning calorimetry experiments, and (ii) stabilizer analyses by high performance liquid chromatography were conducted on medium-density polyethylene (MDPE) stabilized with various levels of Irganox 1010 (penta-erythrityl-tetrakis-(3,5-di-tert-butyl-4-hydroxyphenyl propionate), Irgafos 168 (tris-(2,4-di-tert-butyl-phenyl)-phosphite), and carbon black (CB). The OIT data were analyzed using a novel interpretation method, which is described and applied. It was found that: (i) addition of CB to base-stabilized MDPE increases stability and reduces OIT variability; (ii) the optimum effective concentrations of Irganox 1010, Irgafos 168 and CB are 1690 ppm, 1580 ppm and 2.5% w/w, respectively; and (iii) interactions between CB and the base co-stabilizers may occur at high loadings of the latter but CB does not affect the extraction of the base co-stabilizers which are extracted with efficiencies of ca. 80% and 100% for Irganox 1010 and Irgafos 168, respectively.     

新型三元复配抗氧体系的设计及其在煤基均聚PP中的应用

设计了一系列由主抗氧剂、辅助抗氧剂、碳自由基捕捉剂组成的不同种类、不同配比抗氧剂体系,并将其用于煤基均聚聚丙烯（PP）的抗热氧老化性能改性中。其中以巴斯夫抗氧剂 Irganox®1010、Irgafos®168主辅抗氧剂质量比1∶1为对比基准,通过测试并对比添加新型三元复配抗氧体系改性 PP的氧化诱导时间（OIT）、黄色指数、熔体流动速率、力学性能等性能指标,从而开发煤基均聚PP的最佳耐热氧老化助剂配方。结果表明,当主抗氧剂为Irganox®1010、辅抗氧剂为 Irgafos®168质量比为 1∶1并与羟胺类抗氧剂 Revonox®420复合使用时,改性 PP的 OIT最长为 9. 8 min,黄色指数为 1. 3,熔体流动速率为 10. 7 g/10 min,综合性能最佳;当主抗氧剂为 Irganox®1010、辅抗氧剂为 Irgafos®168质量比为1∶2时,改性PP的抗黄变效果最好,由此设计并优化的抗氧剂体系及其配比对煤基均聚PP的耐长期热氧老化 改性配方设计具有重要的启示。     

Structural effect of secondary antioxidants on mechanical properties and stabilization efficiency of polyamide 6/halloysite nanotube composites during heat ageing

Hindered phenol (Irganox 1010) was combined with two kinds of secondary antioxidants [i.e., tris(2,4‐di‐tert‐butylphenyl) phosphite (Irgafos168) and tris(nonylphenyl) phosphite (TNPP)] to form antioxidant mixtures, and their influences on mechanical properties and thermo‐oxidative degradation of polyamide 6 (PA6) and halloysite nanotube (HNT) filled composites were investigated. The results showed that the antioxidant combinations provided an improvement in the oxidative induction time, decomposition temperature (T_d), processability, and tensile properties of PA6. Irganox/TNPP (1:1) was found to exhibit the best thermal oxidative resistance. The study of heat ageing in the air oven at 130 °C showed that the stabilized composites with 5 wt % of HNT could retain 92% of strength without loss of modulus. The physical characteristics of antioxidants such as low volatility and possible interaction with filler in the composites played a crucial role in stabilizing efficiency during heat ageing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45360.     

A new approach to quantitatively assessing the effects of polymer additives

A novel approach involving stability parameter mapping and stability vector analysis is developed for assessing the effect of an additive on polymer performance. The potential usefulness of the method is illustrated by applying it to (i) DSC oxidative induction time (OIt) data for medium-density polyethylene (MDPE) formulations made using two levels of carbon black and base-stabilized with Irgafos 168™ (tris-(2,4-di-tert-butylphenyl)-phosphite) and Irganox 1010™ pentaerythrityl-tetrakis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), and (ii) chemiluminescence OIt data for low-density polyethylene (LDPE) containing 0.2% (w/w) of Chimassorb 944™ and 0.5% (w/w) or 1.0% (w/w) of dicumyl peroxide cross-linking agent and base-stabilized with 0.2% (w/w) of various commercial antioxidants. The proposed method is validated using data from a previous study on MDPE and is applied to a preliminary investigation of LDPE destabilization by dicumyl peroxide. The results suggest that a styrenated phenolic stabilizer blended with zinc dibutyldithiocarbamate and zinc stearate is an effective system for stabilizing LDPE in the presence of dicumyl peroxide.     

复配型受阻酚类抗氧剂对聚甲醛的稳定作用

将受阻酚类抗氧剂Irganox245和Irganox1010进行复配并加入聚甲醛中，通过将物料在设定温度下多次挤出，测定挤出物料的黄色指数、拉伸强度、冲击强度、熔体质量流动速率、热失重率等方法对单剂和复配抗氧剂在聚甲醛中的稳定作用进行了研究。结果表明：将抗氧剂Irganox245和Irganox1010复配后，提高了聚甲醛的分解温度，较好地保持了聚甲醛的各项性能，没有发生劣化现象，作用效果介于两种抗氧剂单独作用效果之间；在聚甲醛的热氧稳定性能方面起到一定的协同作用。     

Influence of binary combined systems of antioxidants on the stabilization of peroxide‐cured low‐density polyethylene

The secondary antioxidants Irganox 168 and 242 and dilaurylthiodipropionate (didodecyl‐3,3′‐thiodipropionate) (DLTP) were chosen to be combined with the primary phenol antioxidants Irganox 300, 1010, 1035, and 1076, and the effects of the binary combined systems of antioxidants on the peroxide curing reaction and the long‐term stability of crosslinked low‐density polyethylene (XLPE) were studied through isothermal dynamic rheological and mechanical testing. The results show that the primary phenol antioxidants with lower melting points had better resistance to scorching and exhibited good synergistic effects with the secondary antioxidants. Irganox 168 had little resistance to scorching, whereas Irganox DLTP had moderate resistance, and Irganox 242 had the greatest resistance. Irganox 168 and DLTP guaranteed the mechanical properties well, whereas Irganox 242 reduced the tensile strength obviously. Irganox 300 and 1035 combined with secondary antioxidants performed poorly in long‐term thermal aging test, whereas Irganox 1076 in combination with secondary antioxidants displayed a moderate effect of aging resistance, and Irganox 1010 showed the best effect. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012     

环氧化苯乙烯-异戊二烯-苯乙烯嵌段共聚物的热氧老化研究

采用FI-IR研究了环氧化苯乙烯-异戊二烯-苯乙烯嵌段共聚物（ESIS）热氧老化前后的结构变化,并通过力学性能的测试考察了抗氧剂对ESIS抗热氧老化性能的影响。结果表明,ESIS在热氧老化过程中,环氧基和C=C双键减少,而由环氧基开环生成的羰基和羟基则显著增多。抗氧剂Irganox1010和Irgafos168的复合体系能够有效提高ESIS的抗热氧老化性能。     

Synthesis and performance of phenolic polybutadiene‐bound stabilizers

An antioxidant derivative, 6‐sulfanylhexyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propanoate, was synthesized and examined. With a radical initiator, the addition of this compound to pending vinyls of OH‐telechelic, low molecular weight liquid polybutadiene (LBH) was performed to various degrees of conversion to form polymeric antioxidants (PAOs) in which the phenolic moiety was separated from the main chain by a spacer [? CH₂CH₂? S? (CH₂)₆? O? CO? ]. Pure, unstabilized LBH was mixed in several ratios with PAOs, Irganox 1520, and Irganox 1076, and the oxidation stabilities of these mixtures, determined by thermogravimetric analysis and differential scanning calorimetry, were compared. Probably because of their good compatibility with LBH, PAOs exhibited equal or better effectiveness than commercial antioxidants of the Irganox type. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 885–889, 2003     

An approach to assess the synergistic effect of natural antioxidants on the performance of the polypropylene stabilizing systems

A study on the efficiency of natural antioxidants from agri‐food industry wastes as long‐term antioxidants for polypropylene (PP) is reported. Special attention is paid to the usage of vegetal wastes as a source of natural antioxidants such as alternatives to synthetic long‐term antioxidants. The potential of the lignin‐derived fractions generated during autoydrolysis processing of lignocellulosic agricultural, forestal, and food wastes was assessed. The measurements of oxidation induction time were used for obtaining information on long‐term antioxidant effectiveness, showing the protective effect of natural extracts. The protective effect was improved in combinations of natural extracts with 0.1% and 0.2% of Irgafos 168 (short‐term antioxidant) besides a synergistic effect was exhibited when 0.4% of Irgafos 168 is added. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermo-Oxidation of Polyethylene Stabilized with Irganox 1010 and Tinuvin 622

Abstract

Thermal oxidation of polyethylene stabilized with the mixture of Irganox 1010 and sterically hindered amine Tinuvin 622 confirmed that the occurrence of synergism or antagonism in the effect of sterically hindered amines towards antioxidants is concentration dependent. Provided that the concentration of phenolic antioxidant Irganox 1010 in polytheylene exceeds that of Tinuvin 622, synergism is observed at 185 and 190°C. Chemiluminescence, oxygen absorption method, nonisothermal differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were used for testing of stabilizing efficiency of mixtures of stabilizers and the mutual correspondence of the results have been pointed out.     

Effect of different additives and their mixtures on thermal stability of polyethylene synthesized using iron and titanocene hybrid catalysts

Traditionally, additives are introduced into a polymer matrix via extrusion process which consumes a high amount of energy. In this study, the use of different additives including antioxidants for the in‐reactor stabilization of polyethylene has been investigated in order to provide an energy saving system. Particular attention was dedicated to the efficiency of antioxidant influencing the catalysts activity and properties of polymers. The effect of the addition of Irganox 1330 and Irgafos 168 antioxidants and zinc stearate on the activities of metallocene, post‐metallocene, and their supported hybrid were studied. In addition, the effect of different additives on the thermal characteristics of the synthesized polymers and oxidative induction time (OIT) was evaluated. Our polymerization results exhibited that the factors such as chemical structure of antioxidant and its steric hindrance, type of catalysts, and their hybrid could affect the catalyst performance and OIT contents. The use of antioxidants mixture and hybrid of catalysts is a way that can increase oxidation resistance of polymers considerably. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45482.     

Synthesis and antioxidant activities in polyolefin of dendritic antioxidants with hindered phenolic groups and tertiary amine

Two novel primary antioxidants with dendritic structure and hindered phenolic groups were synthesized using 3‐(3,5‐diter‐butyl‐4‐hydroxyphenyl) propionic acid as raw material and dendritic poly(amidoamine) (PAMAM) as linker in chloroform. The antioxidant activities of the dendritic antioxidants were evaluated in polyolefin by melt flow index (MFI), yellowness index (Y.I.), and oxidation induction time (OIT). The dendritic antioxidants had excellent processing property and oxidation resistance behavior in polyolefin. At the same weighed amount of antioxidant, the MFI and Y.I. values of mulitiple‐extruded polyethylene (PE) stabilized with the dendritic antioxidants were smaller than those of the commercial antioxidants, as well as the OIT values of polyethylene (PE) stabilized with the dendritic antioxidants were larger. Applying to polypropylene, the antioxidant ability of the second‐generation dendritic antioxidant (G2.0 dendritic antioxidant) with larger molecular weight was superior to the commercial antioxidants and that of the first‐generation dendritic antioxidant (G1.0 dendritic antioxidant) was equal to the commercial antioxidants. The dendritic antioxidants can prevent polyolefin from breaking of macromolecular chain in processing and had stabilizing effect in polyolefin in service life by donating H‐atoms and electron to free radicals. The dendritic antioxidants combined with Irgafos 168 had improvement of antioxidant activities of the dendritic antioxidants in polyolefin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of the oxidative stability of multiextruded polypropylene as assessed by physicomechanical testing and simultaneous differential scanning calorimetry–chemiluminescence

Common physicomechanical tests comprising impact strength, the melt flow index (MFI), and the yellowness index (YI) were used to study the thermooxidative stability of polypropylene (PP) following multipass extrusion. Differential scanning calorimetry (DSC) coupled with chemiluminescence (CL) monitoring was also used to assess the stability. Three PP formulations were studied: (i) PP‐1 containing 0.050% w/w of the phenolic antioxidant Irganox 1010^™, (ii) PP‐2 containing 0.028% w/w Irganox 1010, 0.056% w/w of the phosphite costabilizer Irgafos 168^™ and 0.014% w/w of the lactone processing stabilizer HP 136^™, and (iii) PP‐3 containing 0.050% w/w Irganox 1010 and 0.100% w/w of the phosphite Ultranox 641^™. All formulations contained 0.045% w/w of the hydrotalcite acid scavenger DHT‐4A^™. The results suggest that physicomechanical tests cannot reliably detect the small difference in the stability between PP‐2 and PP‐3 but can detect the larger difference between these and the less stable PP‐1. The oxidative induction time (OIT) determined by CL monitoring (i.e., CL– OIT) is consistent with the OIT determined by DSC but has better reliability. The CL–OIT data suggest that PP‐3 has superior oxidative stability to PP‐2 in the early stages of multipass extrusion. However, PP‐2 exhibits a better resistance to yellowing. A correlation between the CL–OIT data and each of the MFI and YI data was found. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 733–741, 2001     

Natural extracts as potential source of antioxidants to stabilize polyolefins

Several natural matrices were investigated as potential sources of antioxidants to be used as plastic additives. Extracts of four matrices obtained under the same experimental conditions were initially considered: green tea, black tea, Lippia citriodora and Hypericum androsaemum. Both, the antioxidant activity of the extracts and their content in flavanols and quercetin, were compared. The antioxidant activity was determined by DPPH analysis and the phenolic composition by high performance liquid chromatography (HPLC) using ultraviolet (UV) diode array and fluorescence (FL) detectors. Concentration of the flavanols reduced in the same way as their antioxidant activity starting with green tea, through black tea, Hypericum androsaemum, and Lippia citriodora. The performance of polypropylene samples stabilized with green tea extract, or its individual components catechin and epicatechin, was compared with samples stabilized with a mixture of the synthetic antioxidants Irganox 1076 and Irgafos 168. Each sample was extruded and consecutively reextruded up to four times. The melt flow index (MFI) and the oxidation induction time (OIT) of the samples were measured after each step. The obtained results showed the interest of this natural matrix as a potential source of antioxidants for plastics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Process efficiency and long‐term performance of α‐tocopherol in film‐blown linear low‐density polyethylene

α‐Tocopherol was compared with a commercial phenolic antioxidant (Irganox 1076) as a long‐term and process antioxidant in film‐blown and compression‐molded linear low‐density polyethylene. The antioxidant function of α‐tocopherol was high in the film‐blown material, especially in the processing, according to oxygen induction time measurements with differential scanning calorimetry. The residual content of α‐tocopherol after processing, determined with chromatographic techniques, was less than that of the commercial phenolic antioxidant in both the film‐blown and compression‐molded materials. The process stabilizing efficiency was nevertheless higher for the material containing α‐tocopherol. During the long‐term stabilization, the efficiency of α‐tocopherol was less than that of the commercial phenolic stabilizer Irganox 1076 in the thin films, according to chemiluminescence and infrared measurements. The long‐term efficiency in the compression‐molded samples stabilized with α‐tocopherol or Irganox 1076 was equally good because of the low loss of both α‐tocopherol and Irganox 1076 from the thicker films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2427–2439, 2005     

Investigating effect of ferric stearate on stabilization efficiency of a phenolic antioxidant during thermal oxidation of polyethylene

This study aimed to achieve a formulation for an additive to produce oxo-biodegradable films that accelerates oxidative degradation of the films after preservation of properties over a span of desired service life. Thermal oxidation behavior of high-density polyethylene (HDPE) films (approximately 250 μm thick) containing various weight ratios of a commercially used phenolic antioxidant (Irganox 1010) to ferric stearate as pro-oxidant has been studied in both melt and solid states. Thermo-oxidative stability in melt state was studied using differential scanning calorimetry. The rate of thermal oxidation in solid state was investigated via oven aging experiments at 90 °C followed by measuring changes in tensile properties, gel content, carbonyl index and density. Comparing thermo-oxidative stability of the HDPE samples containing a combination of Irganox 1010 and ferric stearate with the samples containing Irganox 1010 alone confirmed that ferric stearate reduces the stabilization efficiency of the phenolic antioxidant in the polymer either in melt or in solid state. It was also shown that the efficiency of the phenolic antioxidant in thermo-oxidative stabilization of the polymer in both melt and solid states could be changed by altering weight ratio of Irganox 1010/ferric stearate. On the basis of the obtained results, it was concluded that weight ratio of 0.1/0.1 wt% of the antioxidant to the pro-oxidant is suitable for attaining desired stability during melt processing as well as retaining properties during a reasonable service life when is used as a film and a favorable rate of thermal oxidation after the service life.     

Optimization of experimental parameters for the quantification of polymer additives using SFE/HPLC

Analysis of low concentration additives; for example, antioxidants, in polymeric materials remains a difficult task. In the usual analytical methods, additives are extracted using large quantities of solvents first followed by concentrating the resulting solution for making possible the analysis. The supercritical fluid extraction (SFE) technique eliminates the use of large quantities of solvents and simplifies the analytical procedure. This work has been done with the goal of extracting the antioxidants Irganox 1010 and Irgafos 168 from a polypropylene matrix by using the SFE technique and by subsequent analysis using high‐performance liquid chromatography (HPLC). The experimental parameters; that is, temperatures, pressure, and modifiers have been varied to find the best extraction conditions. The optimum temperature and pressure for extraction of above‐mentioned polymer additives were found to be 120°C and 384 bar, with methanol as the modifier. The quantitative extractions are significantly faster than those reported earlier in the literature. The results point out that the technique used in these experiments—SFE combined with HPLC—is a reliable and environmentally friendly alternative to the commonly used liquid extraction and analytical methods. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 938–946, 2000     

A rapid microwave‐assisted solvent extraction method for assessment of stabilizer concentration in crosslinked polydimethylsiloxane

Crosslinked polydimethylsiloxanes were prepared containing 0.05 to 0.2 wt % of either a phenolic antioxidant (Irganox® 1010) or a hindered amine stabilizer (Tinuvin® 144). The stabilizer concentration was assessed by HPLC and UV‐Vis spectroscopy of Soxhlet and microwave‐assisted solvent extracts. Almost complete recovery of stabilizer was achieved with Soxhlet extraction. High stabilizer recovery was achieved when acetone was used as the solvent in the microwave‐assisted extraction. HPLC was shown to be an efficient method for determining the concentration of Irganox 1010. For Tinuvin 144 the selectivity of both UV‐Vis spectroscopy and HPLC was poor, leading to imprecise evaluation of the antioxidant concentration. The loss of stabilizer by migration from polymer to hot water (75 and 95°C) was monitored for the systems stabilized with Irganox 1010 and the diffusion coefficient of the antioxidant in the polymer was determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2185–2192, 2004     

Effects of chemical structure of phenolic antioxidants on Ziegler–Natta catalyst performance during propylene polymerization

Present work studied the synthesis of in-reactor stabilization of polypropylene via introducing antioxidant into polymerization media. Special attention was dedicated to assess the efficiency of antioxidant in catalyst deactivation. Three different types of antioxidants (Irganox 1076, Irganox 1010 and Irganox 1330) which contain ester and/or phenolic OH functional groups were chosen to investigate their impact on Ziegler–Natta catalyst performance during slurry propylene polymerization. Our Results indicated that not only phenolic OH groups but also esteric bond of antioxidants are capable of interacting with active center of catalyst and consequently decreasing the catalyst activity. Our propylene polymerization results showed that determining factors such as antioxidant chemical structures and its steric hindrance effect and the number of functional groups (phenolic and esteric groups) affected on the Ziegler–Natta catalyst performance. Therefore, effects of these three types of antioxidants on polymer characteristics such as particle size distribution, morphology, T _m , T _c , X _c , and isotacticity were evaluated. Morphological analysis using scanning electron microscopy (SEM) showed that introducing antioxidant during propylene polymerization did not destroy the spherical morphology of the polypropylene particles. Conclusively, due to the negative effect of esteric bond of antioxidant on Ziegler–Natta catalyst performance, the use of antioxidant without ester groups (Irganox 1330) is more recommended during propylene polymerization.     

Performance and synergistic effect of phenolic and thio antioxidants in ABS graft copolymers

The synergistic effect of phenolic and thio antioxidants on the stabilization of acrylonitrile-butadiene-styrene (ABS) graft copolymers has been studied. Three commercial antioxidants Irganox245, Irganox1076 and dilauryl thiodipropionate (DLTP) were selected. Formulations based on hindered phenols and secondary antioxidant DLTP were prepared. Stabilization was monitored in terms of changes in the functional groups (oxidation products), tensile properties and yellowness index. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were also used to assess the stability. The results indicated that the combination of Irganox245 and DLTP showed much better stabilization effect than the individual components due to the strong synergistic effect. Only weak synergism could be observed in the formulation that contained Irganox1076 and DLTP. Irganox1076 and Irgnox1076/DLTP exhibited similar behaviors between antioxidants with the highest and lowest efficiencies.