Hindered Phenol Antioxidant Research Articles

Thermo-oxidative aging resistance and mechanism of a macromolecular hindered phenol antioxidant for natural rubber

Macromolecular antioxidant due to its low physical loss, high thermal stability, and good compatibility has been considered to be a promising candidate to inhibit polymer aging. In this study, thermo-oxidative aging resistance and antioxidative mechanism of a macromolecular hindered phenol antioxidant, namely, polyhydroxylated polybutadiene containing thioether binding 2, 2′-thiobis (4-methyl-6-tert-butylphenol) (PHPBT-b-TPH) for natural rubber (NR) vulcanizate was studied in detail by oxidation induction time and accelerated thermal aging tests. The results showed that the antioxidative efficiency of PHPBT-b-TPH was very high. When the amount of PHPBT-b-TPH was only 1 phr, the NR vulcanizate could exhibit excellent thermo-oxidative aging resistance, obviously higher than that of NR vulcanizate with low-molecular-weight antioxidant TPH. After aged at 100°C for 168 h, the retentions of tensile strength and elongation at break of NR vulcanizate with PHPBT-b-TPH were 43.6% and 58.6%, respectively. However, those of NR vulcanizate with TPH were 35.6% and 54.5%. In addition, it was found that both thioether and urethane groups in PHPBT-b-TPH had antioxidative ability and had synergistic effect with hindered phenol. Through our findings, new strategy to design and synthesize the macromolecular antioxidant with multi-antioxidative groups for rubber materials and other polymer materials could be developed.

Novel strategic approach for the thermo- and photo- oxidative stabilization of polyolefin/clay nanocomposites

Polyolefin/clay nanocomposites were prepared by melt mixing and their oxidative stability was studied under long-term thermo- and photo-oxidative test conditions in the absence and presence of a modified organo montmorillonite clay (OM-MMt) containing a chemically-bound hindered phenol antioxidant function, (AO)OM-Mt. It was found that nanocomposites based on both polyethylene (PE) and polyethylene-grafted-maleic anhydride (PEgMA) containing the (AO)OM-Mt gave a higher oxidative stability, along with better clay dispersion, compared to analogous PE or PEgMA-based nanocomposites containing an added (free) conventional antioxidant with a similar hindered phenol function (using the commercial hindered phenol Irganox® 1076). These findings can be explained in terms of the ability of the organo-modifier containing the in-built antioxidant function to act locally at the interface between the clay silicate layers and the polymer macromolecules thus contributing to the improved stability of the polymer observed both during long-term thermal- and photo-oxidative treatments.

Reactive antioxidants for peroxide crosslinked polyethylene

Three synthesised reactive (graftable) antioxidants, r-AO, with hindered phenol and hindered amine antioxidant functions, were examined for their grafting efficiency in polyethylene and their retention and stabilising performance in peroxide-crosslinked polyethylene pipe material. Their level of grafting in un-crosslinked high density polyethylene, HDPE, and the extent of their retention in highly peroxide-crosslinked HDPE (PEXa) material (both laboratory prepared samples and PEXa pipes produced by commercial processes) were determined after stringent solvent extraction methodologies. The uniformity of distribution of the r-AOs in the PEXa pipes (across the length and thickness of the pipes) were examined using infrared-microscopy and compared with similarly produced PEXa pipes containing commercial antioxidants having the same antioxidant functions. The extent of interference of the graftable hindered phenol and hindered amine antioxidants with the peroxide crosslinking process in the PEXa materials was assessed by comparing the level of crosslinking achieved against analogously prepared samples containing a conventional hindered phenol antioxidant (Irganox 1076).The results obtained showed that the presence of the graftable (r-AOs) antioxidants did not affect the level of crosslinking of the PEXa pipes which remained high (>85%) and that they were retained to a very high extent in the PEXa material after solvent extraction, and are very uniformly distributed across the length and thickness of PEXa pipes. The long-term stabilising performance of the graftable r-AOs in the PEXa material (in both laboratory prepared samples and in peroxide crosslinked pipes produced by commercial processes) was also examined using complimentary methods: oxidative induction time (OIT) before and after solvent extraction, physical embrittlement following oven ageing at 125 °C, as well as by a hydrostatic pressure tests conducted (with water inside and air outside) at 115 °C and 2.5 MPa pressure. The stabilising efficacy of the r-AOs was compared with that of conventionally stabilised PEXa material containing analogous antioxidant functions produced in the same way. The level of retention (in the pipes) of the graftable antioxidants and their long-term stabilising performance was shown to be significantly higher than that of the conventional AOs under all the test conditions used here.

Thermo‐oxidative stabilization of poly(lactic acid)‐based nanocomposites through the incorporation of clay with in‐built antioxidant activity

ABSTRACTIn this work, an innovative approach to overcome the issue of the poor thermo‐oxidative stability of polymer/clay nanocomposites is proposed. Specifically, biodegradable poly(lactic acid) (PLA)‐based nanocomposites, containing organo‐modified clay with in‐built antioxidant activity, were prepared. Through a two‐step chemical protocol, a hindered phenol antioxidant was chemically linked to the ammonium quaternary salt which was then intercalated between the clay platelets [(AO)OM‐Mt]. The nanocomposites were characterized and their thermo‐oxidative stability during melt processing and under long‐term thermal test conditions was investigated. PLA nanocomposites containing the (AO)OM‐Mt showed higher oxidative stability, along with better clay dispersion, compared to PLA‐nanocomposites containing commercial clay and a free hindered phenol antioxidant. Obtained results can be explained considering that (AO)OM‐Mt may act locally, at the interface, between the silicate layers and the polymer macromolecules, thus contributing to the observed improved stability of the polymer both during processing and under long‐term thermal‐oxidative conditions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44974.

Extraction resistance and mechanism of a macromolecular hindered phenol antioxidant in natural rubber

ABSTRACTDue to low thermal stability, poor migration, and extraction resistances, the antioxidant with low molecular weight is easy to physically lose during processing and long‐term service, and its applications are severely restricted. To increase the molecular weight of antioxidant is one of the promising methods to overcome such drawbacks. In this study, the extraction resistance of a macromolecular antioxidant, namely polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was investigated by extraction resistance test and equilibrium swelling experiment. The results exhibited that the PHPBT‐b‐TPH offered much better extraction resistance in natural rubber (NR) than the low molecular weight antioxidant TPH. In addition, the extraction resistance of hydroxyl‐terminated polybutadiene (HTPB), polyethylene glycol (PEG), and polypropylene glycol (PPG) in NR were also compared to study the extraction mechanism of the PHPBT‐b‐TPH. It was found that the higher molecular weight of PHPBT‐b‐TPH and the co‐vulcanization between PHPBT‐b‐TPH and NR were the main reasons for the excellent extraction resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44905.

Developing Polypropylene Bonded Hindered Phenol Antioxidants for Expanding Polypropylene Applications in High Temperature Conditions

Polypropylene (PP) represents about a quarter of commercial plastics produced around the world. Despite its huge commercial success, PP polymer is not suitable for the applications that require long-term exposure to high temperatures (>80°C), due to its chemical and physical stability. The PP chain is prone to the oxidative chaindegradation and exhibits a relatively low material softening temperature. This paper discusses a new research approach by developing the PP-bonded hindered phenol (PP-HP) antioxidants to address this scientifically challenging issue. We have investigated two PP-HP structures, one with two methylene units adjacent to the hindered phenol group (HP-L) and one without this spacer (HP-S). In general, PP-HP polymers are advantaged with the ability to incorporate a suitable concentration of HP antioxidant groups with homogeneous distribution along the polymer chain, which provide effective protection to the PP chains from oxidative degradation. In addition, the specific PP-HP-L structure can also engage in a facile crosslinking reaction to form a 3-D network during the oxidation reaction. In one accelerated oxidation test in air at 190-210°C, the regular commercial PP polymer (containing common antioxidants and stabilizers) degrades within a few minutes; a PP-HP-L copolymer with about 1 mol% HP-L group shows almost no detectable weight loss after 24 hrs. In an ASTM endurance test at 140°C in air, the commercial PP shows 1% weight loss within about 10 days. On the other hand, the PP-HP-L polymer lasts for more than 30 years. Overall, the experiment results present the potential of expanding PP applications into a much higher temperature range (>140°C) under oxygen oxidative environments

The influence of processing aids on the melt stability and mobility of poly(arylene sulfide sulfone)

The phosphorous antioxidant bis[2,4-bis(1-methyl-1-phenylethyl)phenyl] pentaerythritol diphosphite (s-9228), hindered phenol antioxidant N, N′-hexane-1,6-diylbis-[3,5-di-tert-butyl-4-hydroxyphenylpropionamide] (1098), and zinc acetate (ZnAc) were chosen as processing aids to improve the melt stability and mobility of poly(arylene sulfide sulfone) (PASS). Different contents and components of the processing aids were discussed. The capillary rheometer test demonstrated that 3 wt% ZnAc showed better effect with the change of the shear rates. In contrast, the parallel-plate rheometer test proved that the complex antioxidant, including 0.8 wt% s-9228 and 1.6 wt% 1098, showed better effect with the change of temperature. Both the capillary rheometer and parallel-plate rheometer test showed that the compounding aid consisting of 0.8 wt% s-9228, 1.6 wt% 1098, and 3 wt% ZnAc showed the best effect with the dramatically improved melt stability and mobility. Also, PASS could be processed successfully by extruding and through an injection machine with the help of the compounding aid. Meanwhile, the effects of the applied processing aids on melt complex viscosity and modulus were also discussed.

New genre of antioxidants from renewable natural resources: Synthesis and characterisation of rosemary plant-derived antioxidants and their performance in polyolefins

Several ester derivatives of rosmarinic acid (rosmarinates) were synthesised, characterised (1D and 2D NMR, UV and FTIR spectroscopy) and tested for their potential use as antioxidants derived from a renewable natural resource. The intrinsic free radical scavenging activity of the rosmarinates was assessed, initially using a modified DPPH (2, 2-diphenyl-1-picrylhydrazyl radical) method, and found to be higher than that of commercial synthetic hindered phenol antioxidants Irganox 1076 and Irganox 1010. The thermal stabilising performance of the rosmarinates in polyethylene (PE) and polypropylene (PP) was subsequently examined and compared to that of samples prepared similarly but in the presence of Irganox 1076 (in PE) and Irganox 1010 (in PP) which are typically used for polyolefin stabilisation in industrial practice. The melt stability and the long-term thermo-oxidative stability (LTTS) of processed polymers containing the antioxidants were assessed by measuring the melt flow index (MFI), melt viscosity, oxidation induction time (OIT) and long-term (accelerated) thermal ageing performance. The results show that both the melt and the thermo-oxidative stabilisation afforded by the rosmarinates, and in particular the stearyl derivative, in both PE and PP, are superior to those of Irganox 1076 and Irganox 1010, hence their potential as effective sustainable bio-based antioxidants for polymers.The rosmarinic acid used for the synthesis of the rosmarinates esters in this study was obtained from commercial rosemary extracts (AquaROX80). Furthermore, a large number of different strains of UK-grown rosemary plants (Rosmarinum officinalis) were also extracted and analysed in order to examine their antioxidant content. It was found that the carnosic and the rosmarinic acids, and to a much lesser extent the carnosol, constituted the main antioxidant components of the UK-plants, with the two acids being present at a ratio of 3:1, respectively.

Biodiesel oxidative stability from Rancimat data

It is conventional to quantify the oxidative stability of oils and biodiesel through an induction time determined by a Rancimat instrument. European Standard EN 14112 for the Rancimat method describes two procedures for determining this induction period. The automated method relies on finding the position of the peak in the second derivative of the conductivity vs. time curve. The manual method is based on the intersection of two tangents lines. It is shown that this method can also be automated by a curve fitting approach based on a novel Rancimat response function. This analysis demonstrates that the induction period values determined by the two methods differ with the second derivative method returning slightly higher estimates for the induction period.Biodiesel was prepared using base-catalysed methanolysis of sunflower oil. It was stabilized using the hindered phenol antioxidant tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane. It was found that stability increases linearly with stabiliser concentration and that the effect of the measurement temperature follows Arrhenius kinetics. The effectiveness of the antioxidant stabiliser diminished with increasing temperature.

Lignin as a green primary antioxidant for polypropylene

ABSTRACTLignin and Irganox 1010, a hindered phenol antioxidant, are compared as a primary stabilizer in formulations for polypropylene (PP) by exposition to accelerated aging. The concentration of lignin was adjusted to match the concentration of hindered phenolic groups of the commercial stabilizer. Upon aging, lignin formulation retains the initial mechanical properties longer than the formulation with Irganox 1010. The ratio of the areas of the carbonyl and the hydroxyl infrared absorption bands is proposed as a method to evaluate the photodegradation process. In this aspect, the formulation with lignin also presents better results than the formulation with Irganox 1010. There are two hypotheses for the best performance of lignin in the studied conditions: lower leaching of lignin, due to its crosslinked nature, and leaching of low molar mass products of Irganox 1010 hydrolysis. These results indicate lignin, from the Kraft process of Eucalyptus wood, as a promising green substituent to synthetic hindered phenol stabilizers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43558.

Development of high-throughput chemiluminescence imaging instrument for parallel evaluation of polymer lifetime

A high-throughput chemiluminescence imaging instrument is developed to realize facile and systematic data accumulation in degradation and stabilization of polymer. The instrument works based on imaging chemiluminescence of 100 oxidatively degrading polymer samples that are placed in a multi-cell with arrayed wells being flushed with atmospheric gas, and thereby enables simultaneous acquisition of 100 chemiluminescence curves. The present study reports validation and demonstrative application of the instrument for the oxidative degradation of stabilized polypropylene with a variety of hindered phenol anti-oxidants. Based on quantitatively accurate and large-volume data on oxidative induction time, not only the feasibility of the new instrument but also a number of useful aspects of stabilizers are demonstrated.

Novel organo-modifier for thermally-stable polymer-layered silicate nanocomposites

A new novel approach for the stabilisation of polymer-clay nanocomposites has been investigated based on reacting chemically an antioxidant function, a hindered phenol moiety, with an organic modifier based on a quaternary ammonium salt. The chemically linked antioxidant-containing organic modifier (AO-OM) was then introduced into natural montmorillonite (MMt) through a cation-exchange reaction resulting in antioxidant-containing organo-modified clay (AO-OM-MMt). The new antioxidant-containing modified clay, along with other organo-modified clays having a similar organo-modifier but without the reacted antioxidant, were characterised by spectroscopic, thermogravimetric and x-ray diffraction techniques and tested for their thermo-oxidative stability.PA11-based clay nanocomposites samples containing the AO-OM-MMt and the other organo-modified clays, both without and with an added (i.e. not chemically reacted) hindered phenol antioxidant (similar to the one used in the AO-OM) were prepared by melt processing and examined for their processing and long-term thermal-oxidative stability at high temperatures. It was shown that although the new organo-modifier, AO-OM, was also susceptible to the Hoffman elimination reaction, the nanocomposites containing this newly modified clay (PA11/AO-OM-MMt) showed higher melt processing and long-term thermo-oxidative stability, along with excellent clay dispersion and exfoliation, compared to the other PA11-nanocomposites examined here (with and without the conventionally added antioxidant). It is suggested here that the excellent overall performance observed for the PA11/AO-OM-MMt nanocomposites is due to an in-situ partial release of low molecular weight antioxidant species having stabilising functionalities that are capable of acting locally at the interface between the inorganic clay platelets and the polymeric matrix which is a critical area for the onset of degradation processes.

Synthesis and antioxidative properties in natural rubber of novel macromolecular hindered phenol antioxidants containing thioether and urethane groups

Two novel macromolecular hindered phenol antioxidants containing thioether and urethane groups were synthesized by the combination of thiol-acrylate Michael addition and nucleophilic addition. First, a hindered phenol with hydroxyl (GM-ME) was synthesized by Michael addition between 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylphenyl) methyl-4-methylp-henyl acrylate (GM) and 2-mercaptoethanol (ME). Then macromolecular antioxidants GM-ME-IPDI and GM-ME-TDI were obtained after GM-ME reacted with isophorone diisocyanate (IPDI) and toluene diisocynate (TDI), respectively. The structures of the macromolecular antioxidants were confirmed by FT-IR, 1H NMR and MALDI-TOF-MS. TG analysis showed that the thermal stability of the GM-ME-IPDI and GM-ME-TDI were higher than that of the GM. The oxidation induction time (OIT) and accelerated thermal aging tests of natural rubber vulcanizates showed that the thioether and urethane groups of GM-ME-IPDI and GM-ME-TDI played an important role in improving antioxidative efficiency. In addition, it was found that the urethane group connected with benzene ring had better antioxidative ability than that connected with alicyclic ring.

Enzymatic oxidative polymerization of pyrogallic acid for preparation of hindered phenol antioxidant

ABSTRACTA novel antioxidant with high molecular weight was successfully synthesized via horseradish peroxide‐catalyzed oxidative polymerization of pyrogallic acid. As‐synthesized poly(pyrogallic acid), a black powder completely soluble in common organic solvents, has a number‐averaged molecular weight of about several thousand and consists of phenylene and oxyphenylene units. Besides, as‐prepared poly(pyrogallic acid) exhibits much better thermal stability and antioxidant capacity than butylated hydroxyanisole (denoted as BHA) and butylated hydroxytoluene (denoted as BHT), two kinds of commercial antioxidants. And it was also found that the higher phenolic content the pyrogallic acid polymer possess, the better antioxidant activity the poly(pyrogallic acid) shows. More importantly, poly(pyrogallic acid) could effectively inhibit the oxidation degradation of polypropylene (denoted as PP) during plastic processing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41591.

Synthesis and Characterization of A Novel Macromolecular Hindered Phenol Antioxidant and Its Thermo-Oxidative Aging Resistance for Natural Rubber

A novel macromolecular hindered phenol antioxidant with high antioxidative efficiency, polyhydroxylated polybutadiene (PHPB)-bound 2, 2′-thiobis (4-methyl-6-tert-butylphenol) (PHPB-b-TPH), was prepared by binding 2, 2′-thiobis (4-methyl-6-tert-butylphenol) (TPH) onto PHPB with isophorone diisocyanate (IPDI), using dibutyltin dilaurate (DBTDL) as catalyst, via a two-step nucleophilic addition reaction. The PHPB was first synthesized from hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol via a thiol-ene click reaction. The PHPB-b-TPH was characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), and thermal gravimetric analysis (TGA). The thermo-oxidative aging resistance of natural rubber (NR) with PHPB-b-TPH was evaluated by an accelerated thermal aging test and the oxidation induction time (OIT). The results showed that the −OH groups of PHPB first reacted with highly active secondary −NCO groups of IPDI at 35°C to form the adduct PHPB-NCO, and the PHPB-b-TPH was successfully obtained by one of the phenolic −OH in TPH reacting with the primary −NCO groups of PHPB-NCO at 70°C. The PHPB-b-TPH had better thermal stability and thermo-oxidative aging resistance for NR than TPH.

Synthesis and characterization of polyhydroxylated polybutadiene binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) with isophorone diisocyanate

ABSTRACTA macromolecular hindered phenol antioxidant, polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was synthesized via a two‐step nucleophilic addition reaction using isophorone diisocyanate (IPDI) as linkage. First, the OH groups of PHPBT reacted with secondary NCO groups of IPDI to form the adduct PHPBT‐NCO, then the PHPBT‐b‐TPH was obtained by one phenolic OH of 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (TPH) reacting with the PHPBT‐NCO. The PHPBT‐b‐TPH was characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (1H‐NMR), 13C‐NMR, and thermogravimetric analysis, and its antioxidant activity in natural rubber was studied by an accelerated aging test. Influences of reaction conditions on the two nucleophilic reactions between OH group and NCO group were investigated. In addition, catalytic mechanism for the reaction between PHPBT‐NCO and TPH was discussed. The results showed that the adduct PHPBT‐NCO could be obtained by using dibutyltin dilaurate (DBTDL) as catalyst, and the suitable temperature and DBTDL amount were 35°C and 3 wt %, respectively. However, triethylamine (TEA) was more efficient than DBTDL to catalyze the reaction between PHPBT‐NCO and TPH because of steric hindrance effect. In addition, it was found that the thermal stability and antioxidant activity of PHPBT‐b‐TPH were higher than those of the low molecular weight antioxidant TPH. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40942.

Thermo Oxidative Degradation Behavior of Jatropha Curcass L. Oil in the Presence of Antioxidant

Seed oils were used as base oil since long time ago. However their usage is limited due to its thermo oxidative and cold flow properties. Chemical modification and addition of proper additives are known to be able to improve these limitations. In this work, the effect of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate as potential hindered phenol antioxidant (HPAO) on thermo-oxidative degradation of jatropha oil was investigated. 1, 3, 5 wt% of antioxidant was dissolved into jatropha oil and their thermo-oxidative behavior was studied by using thermo-gravimetric analysis method under oxidative environment. The addition of the HPAO was found to accelerate the occurrence of thermal degradation first onset of jatropha oil. This factor corresponds to reaction of the compound during heating that reduces the peroxides formation to a less-reactive alcohol which is more volatile, thus making the first onset temperature occurred at a lower temperature.

Structural Changes in the Choroidoretinal Complex of the Eye in Total Transient Cerebral Ischemia and Their Correction

Electron microscopy and morphometric analysis were used to study structural changes in the choroidoretinal complex of the eye in 40 adult white mongrel male rats in conditions of total transient cerebral ischemia, and the effects of the sterically hindered phenol antioxidant dibornol was evaluated. Total transient cerebral ischemia was found to lead to thrombosis of capillaries in the capillary vascular lamina of the choroid sheath, structural alterations to the hematoretinal barrier, and degeneration of neurons and the radial glia of the retina. Courses of dibornol improved the microcirculation and had protective effects on the neuronal apparatus of the retina, the pigment epithelium, and the radial glia.

Assessment of hindered phenol antioxidants on processing stability of peroxide‐cure LDPE by rheology and DSC analysis

AbstractInfluence of commercial phenol antioxidants Irganox 300, 1010, 1035, and 1076 on peroxide‐cure reaction of low‐density polyethylene (LDPE) was evaluated through isothermal dynamic rheological and nonisothermal differential scanning calorimetry (DSC) testing. The results indicated that phenol antioxidants could reduce storage modulus of LDPE completely crosslinked at 175°C while they have a neglectable effect on gel fracture and activity energy of crosslinking reaction. On the other hand, time sweep dynamic rheological test revealed the antioxidants 1035 and 1076 with low molecular weight and low melting point could significantly depress scorch of crosslinkable LDPE at 135°C. The isothermal time sweep dynamic rheology test method was more sensitive than nonisothermal DSC test for characterizing the influence of phenol antioxidants on crosslinking kinetics of peroxide‐cure reaction of LDPE. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation of raspberry-like polystyrene/carbon black composite microsphere via π–π interactions

Polystyrene (PS)/carbon black (CB) composite microspheres were prepared using a modified CB, which was prepared by blending CB with a hindered phenol antioxidant Irganox 1330 in an internal mixer. Scanning electron microscopy indicated that the modified CB adsorbed on the surface of PS microspheres homogenously to form a raspberry-like morphology composite. The non-covalent binding of Irganox 1330 on the surface of PS microsphere was observed from the UV-Vis absorption spectrum in ethanol, while the fluorescence of PS was almost totally quenched by the binding of Irganox 1330. These results implied there were aromatic interactions between Irganox 1330 and the PS microspheres, which played a crucial role in the formation of composite microspheres.