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.     

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     

Loss and transformation products of the aromatic antioxidants in MDPE film under long‐term exposure to biotic and abiotic conditions

The loss of a primary phenolic antioxidant Irganox 1010 and of a secondary phosphite antioxidant Irgafos 168 from a medium density polyethylene film (MDPE) was investigated after exposure of the film for 4 years to different environments such as aqueous media at pH5 and 7, open air, and compost, with an exposure of exposition of 25°C. An ultrasonic extraction technique using chloroform as extraction solvent was applied to recover the residual antioxidants from the polymeric matrix, and this was followed by High‐Performance Liquid Chromatography (HPLC) with acetonitrile as mobile phase and a quantitative analysis at a wavelength of 280 nm of the extracted antioxidants. The amount of antioxidant lost varied remarkably depending on the testing medium. The fastest loss of antioxidant was found on exposure to open air and sunlight while the slowest loss was observed in compost. Thermo‐analytical measurements were made to characterize the residual thermo‐oxidative stability of MDPE film in terms of oxidation temperature and oxidation induction time, to provide a greater insight into the underlying mechanisms of ageing in the different environments. Analysis by Gas chromatography–Mass Spectrometry (GC‐MS) revealed that degradation of the polymeric matrix resulted in the formation of hydrocarbons and oxygen‐containing compounds such as alcohols, carboxylic acids, aldehydes, and esters. The transformation products of the antioxidants formed as result of processing or exposure to the tested media were also identified. The transformation of the phenoxy radical of the Irganox 1010 produced the ester, acid, dealkylated cinnamate, and quinone products, whereas Irgafos 168 yielded oxidation products and the phenolic hydrolysis byproduct 2,4‐di‐tert‐butylphenol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 974–988, 2002     

Effects of phenolic antioxidants on ultrahigh molecular weight polyethylene/decalin solution

The degradation of ultrahigh molecular weight polyethylene (UHMW‐PE) during its dissolution into decalin is discussed. The stabilization of the solution by three phenolic antioxidants, octadecyl β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (1076), tetrakis[methylene‐β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate]methane (1010), and 1,1,3‐tris(2‐methyl‐4‐hydroxy‐5‐tert‐butylphenyl)butane (CA), and an auxiliary antioxidant, dilaurylthiodipropionate (DLTP) is also discussed. Among the three phenolic antioxidants, 1076 had the greatest effect. The auxiliary antioxidant was effective in stabilizing the solution when combined with one of the three phenolic antioxidants. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2877–2881, 2000     

Synthesis,characterization, and application of a hydrolytically stable liquid phosphite

Organic alkyl and aryl phosphites are effective antioxidants and photostabilizers with applications in a wide range of polymers. The primary role of phosphites is to decompose hydroperoxide. However, aryl phosphites are also capable of reacting as antioxidants by negatively affecting the kinetics. In particular, liquid phosphites have a greater effect on polymer degradation because of their high compatibility, reactivity, and solubility with almost all polymers, but they are sensitive to hydrolysis. In order to overcome this hydrolytic sensitivity in liquid phosphites, a novel hydrolytically stable liquid phosphite incorporating a sterically hindered aromatic alcohol (2,4‐di‐tert‐butyl‐6‐methylphenol) that gives hydrolytic stability to the phosphite was synthesized and characterized, and its performance as an antioxidant for polypropylene was investigated. J. VINYL ADDIT. TECHNOL., 22:163–168, 2016. © 2014 Society of Plastics Engineers     

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。     

Benefits of a high‐performance phosphite in the gamma irradiation of polyolefins

The highly active process stabilizer bis(2,4‐dicumylphenyl)pentaerythritol diphosphite (P1) was compared in a series of polyolefin formulations with tris(2,4‐di‐t‐butylphenyl) phosphite (P2). Because of its high activity, there was less polymer degradation during processing with P1 as compared to P2. As a result, improvements in color and other physical properties were observed for the polymers, not only during processing, but also after treatment with gamma radiation.     

Physical chemistry of a phosphite processing stabilizer in polypropylene. Part 1: Solubility

The solubility of a commercial aryl phosphite processing stabilizer for ployolefins, {tris (2,4‐di‐t‐butylphenyl)} (irgafos 168, Ciba Speciality Chemicals), has been measured in polypropylene over a range of temperatures. Measurements are complicated by hydrolsis of the phosphite, releasing 2,4‐di‐t‐butylphenol, which is much more soluble in the polymer. We have measured the solubility of this phenol, and of the phosphate oxidation product of the stabilizer. The result are interpreted on the basis of a regular solution model. They show that the phosphite has a very low solubility but that it is not particularly anomalous in comparison with other stabilizers of similar molecular weight and polarity. The phosphate is significantly more soluble than the phosphite at 70°C, but their solubiliies are comparable at 25°C. This is mainly due to the lower heat of fusion and melting point of the phosphate, whose compatibility is actually lower than that of the phosphite. The phenol is much more soluble because of its low melting point.     

Antioxidant mechanism of a 3‐arylbenzofuranone containing a 2′‐hydroxyl group

5‐Methyl‐7‐tert‐butyl‐3‐(2′hydroxyl‐5′‐methylphenyl)3H‐benzofuran‐2‐one (PCRBF2), is a better scavenger of 2,2‐diphenyl‐1‐picrylhydrazyl radicals than benzofuranone analogs without the 2′‐substituent, which indicates that PCRBF2 will cause good stabilization in polymers. To prove this further, antioxidation by PCRBF2 and other benzofuranone analogs, namely, 5‐methyl‐7‐tert‐butyl‐3‐(3′,4′‐dimethylphenyl)3H‐benzofuran‐2‐one (OXBF2) and 5‐methyl‐7‐tert‐butyl‐3‐(2′,5′‐dimethylphenyl)3H‐benzofuran‐2‐one (PXBF2), was comparatively studied in polypropylene. The resulting antioxidant activity order of these benzofuranones was PCRBF2 > OXBF2 > PXBF2, an observation showing that the hydroxyl group in the 2′‐position does not weaken the antioxidant activity of benzofuranone, but, on the contrary, increases it. Analyses by FTIR revealed intramolecular hydrogen bonding between the 3‐position hydrogen and the oxygen of the 2′‐hydroxyl group, which makes the 2′‐hydroxyl hydrogen of PCRBF2 more reactive than the 3‐position reactive hydrogen. Thus the hydroxyl group reacts with radicals first. J. VINYL ADDIT. TECHNOL., 19:198‐202, 2013. © 2013 Society of Plastics Engineers     

2′-羟基-3-芳基苯并呋喃酮在聚丙烯中的抗氧性能研究

采用多次挤出和高温加速老化的方法对2′-羟基-3-芳基苯并呋喃酮以及其与亚磷酸酯抗氧剂Irgafos168进行复配的二元体系在聚丙烯中的抗氧性能进行研究,并与受阻酚抗氧剂Irganox1010与亚磷酸酯抗氧剂Irgafos168的经典复配体系B225和B215进行比较,从而探究新的苯并呋喃酮-亚磷酸酯二元复配抗氧体系应用的可行性,结果显示:2′-羟基-3-芳基苯并呋喃酮具有优越于其他苯并呋喃酮的抗氧性能,其与羟基所引起的分子内氢键作用有关;此外,其与亚磷酸酯Irgafos168复配之后体现出优越于B225和B215的加工稳定性能以及与B225和B215的相当的长期热氧稳定性能,有望成为新的二元抗氧体系。     

Relationship between bridged groups and antioxidant activity for aliphatic diamine bridged hindered phenol in polyolefins

Four aliphatic diamine bridged hindered phenols were successfully synthesized with aliphatic diamine as the bridged group and 3‐(3,5‐di‐tert‐butyl‐4‐hydroxy‐phenyl)‐propionyl chloride as the material, and their structures were clarified by NMR, Fourier transform infrared spectroscopy, and mass spectrometry. Their performance as antioxidant for polypropylene (PP) and linear low‐density polyethylene (LLDPE) were investigated through the melt flow rate and the oxidation induction time. The thermooxidative stabilities of PP and LLDPE with different aliphatic diamine bridged hindered phenols were assessed by the measurement of the oxidation induction temperature and with long‐term aging testing. The results showed that aliphatic diamine bridged hindered phenols could protect two kinds of polyolefins from thermal oxidative degradation, and the mechanical properties and antioxidant activities of polyolefins stabilized with aliphatic diamine bridged hindered phenols were increased with increasing length of the bridged group for aliphatic diamine bridged hindered phenols at the same concentration of phenolic hydroxyl group. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45095.     

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.     

Photodegradation and stabilization of styrene–butadiene–styrene rubber

Photooxidative degradation and stabilization of a polystyrene–block–polybutadiene–block–polystyrene thermoplastic elastomer using a polychromatic UV light in air at 60°C has been studied by monitoring the appearance of the hydroxyl and carbonyl groups in Fourier transform infrared spectroscopy. The extent of photooxidative degradation in different samples has been compared. The rate of photooxidation was also estimated in the presence of different concentrations of 2,6‐di‐tert‐butyl‐4‐methylphenol [BHT], 2‐(2′‐hydroxy‐5′‐methylphenyl)benzotriazole [Tinuvin P] and tris(nonylphenyl) phosphite [Irgafos TNPP], and 1,2,2,6,6‐pentamethyl piperidinyl‐4‐acrylate was grafted onto the surface of the SBS film. The kinetic evolution of the oxidative reaction was determined. The morphological changes upon irradiation in the solution cast SBS films were studied by scanning electron microscopy. Based on the experimental data a suitable photooxidative degradation mechanism also has been proposed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1097–1102, 2000     

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,characterization, and application of oligomer‐type‐based phosphites

Organic alkyl and aryl phosphites are effective antioxidants and photostabilizers with applications in a wide range of polymers. The primary role of phosphites is to decompose hydroperoxide. However, aryl phosphites are also capable of reacting as antioxidants by affecting the kinetics. In particular, oligomer‐type phosphites have a greater effect on polymer degradation because of their high compatibility, reactivity, and solubility with almost all polymers. Generally, phosphites are sensitive to hydrolysis. In order to overcome this hydrolytic sensitivity in phosphites, a novel hydrolytically stable oligomeric phosphite incorporating a sterically hindered aromatic alcohol (2,4‐di‐tert‐butyl‐6‐methylphenol) that gives hydrolytic stability to the phosphite was synthesized and characterized, and its performance as an antioxidant for polypropylene was investigated. J. VINYL ADDIT. TECHNOL., 22:146–155, 2016. © 2014 Society of Plastics Engineers     

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     

Charge storage behavior of isotropic and biaxially‐oriented polypropylene films containing α‐ and β‐nucleating agents

A study on the influence of the crystal modification (α and β) of isotactic polypropylene (i‐PP) films on the resulting electret properties is presented. Two commercial nucleating agents, sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl)‐phosphate (NA11) and N,N′‐dicyclo‐hexyl‐2,6‐naphthalene‐dicarbox‐amide (NU100), were employed in this investigation. Isothermal charge decay was measured at 90°C. In hot pressed isotropic polypropylene films, no significant differences in the charge storage properties were observed for α‐ and β‐nucleated specimens. In addition, the article presents the influence of the nucleating agents at different concentrations on the PP‐film morphology of biaxially stretched films with respect to electret features. It was possible to prepare elongated cavities with the virtually insoluble NA11 additive during stretching, even at concentrations below 0.3 wt %. These films displayed slightly improved electret properties in comparison to stretched neat PP films due to generated cavities acting as barriers for the drift of charges. Various draw ratios were also studied for i‐PP films with 0.15 wt % NA11. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 650–658, 2006     

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     

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     

耐高温亚磷酸酯类抗氧剂的合成

以2,4-二叔丁基苯酚和自制的4,4'-联苯基双二氯化膦溶液为主要原料,在三乙胺的存在下制得亚磷酸酯型抗氧剂2,4-二叔丁基苯酚-4,4'-联苯基(P-EPQ)。实验表明:在一定的反应条件下,当三乙胺和4,4'-联苯基双二氯化膦的摩尔比为5∶1时,产品P-EPQ的收率达到最高值86%,纯度为99.7%。P-EPQ的受热分解温度高达350℃,因此它作为辅助抗氧剂,广泛应用于PP、ABS、PC等多种塑料材料的加工及应用中。