Immobilization of antioxidant on nanosilica and the antioxidative behavior in low density polyethylene

On the Use of Phenolic Compounds Present in Citrus Fruits and Grapes as Natural Antioxidants for Thermo-Compressed Bio-Based High-Density Polyethylene Films

This study originally explores the use of naringin (NAR), gallic acid (GA), caffeic acid (CA), and quercetin (QUER) as natural antioxidants for bio-based high-density polyethylene (bio-HDPE). These phenolic compounds are present in various citrus fruits and grapes and can remain in their leaves, peels, pulp, and seeds as by-products or wastes after juice processing. Each natural additive was first melt-mixed at 0.8 parts per hundred resin (phr) of bio-HDPE by extrusion and the resultant pellets were shaped into films by thermo-compression. Although all the phenolic compounds colored the bio-HDPE films, their contact transparency was still preserved. The chemical analyses confirmed the successful inclusion of the phenolic compounds in bio-HDPE, though their interaction with the green polyolefin matrix was low. The mechanical performance of the bio-HDPE films was nearly unaffected by the natural compounds, presenting in all cases a ductile behavior. Interestingly, the phenolic compounds successfully increased the thermo-oxidative stability of bio-HDPE, yielding GA and QUER the highest performance. In particular, using these phenolic compounds, the onset oxidation temperature (OOT) value was improved by 43 and 41.5 °C, respectively. Similarly, the oxidation induction time (OIT) value, determined in isothermal conditions at 210 °C, increased from 4.5 min to approximately 109 and 138 min. Furthermore, the onset degradation temperature in air of bio-HDPE, measured for the 5% of mass loss (T_5%), was improved by up to 21 °C after the addition of NAR. Moreover, the GA- and CA-containing bio-HDPE films showed a high antioxidant activity in alcoholic solution due to their favored release capacity, which opens up novel opportunities in active food packaging. The improved antioxidant performance of these phenolic compounds was ascribed to the multiple presence of hydroxyl groups and aromatic heterocyclic rings that provide these molecules with the features to permit the delocalization and the scavenging of free radicals. Therefore, the here-tested phenolic compounds, in particular QUER, can represent a sustainable and cost-effective alternative of synthetic antioxidants in polymer and biopolymer formulations, for which safety and environmental issues have been raised over time.

Novel Hybrid Biomass Anti-Aging Filler for Styrene-Butadiene Rubber Composites with Antioxidative and Reinforcing Properties

Antioxidants are normally utilized to extend the service life of polymers due to the strong reducibility of the phenolic hydroxyl group of the hindered phenol structure. Inspired by this characteristic, we have introduced green tea polyphenol (TP) supported on a silica surface containing considerable phenolic hydroxyl groups to obtain a novel biomass anti-aging filler (BAF, denoted as silica-s-TP) to reinforce and improve the anti-aging property of rubber composites. The applying of silica-s-TP to enhance the thermal-oxidative stability and ultraviolet light (UV) aging resistance of styrene-butadiene rubber (SBR) was evaluated. The hybrid biomass anti-aging filler could not only uniformly disperse in the rubber matrix, giving rise to the excellent mechanical properties, but also enhance the properties of thermal-oxidative stability and UV aging resistance with the increasing silica-s-TP content of SBR distinctly. This study provides a mild and environmentally friendly strategy to prepare the functional biomass filler, which could be applied as not only a reinforcement filler but also an anti-aging additive in "green rubber".

On the Use of Gallic Acid as a Potential Natural Antioxidant and Ultraviolet Light Stabilizer in Cast-Extruded Bio-Based High-Density Polyethylene Films

This study originally explores the use of gallic acid (GA) as a natural additive in bio-based high-density polyethylene (bio-HDPE) formulations. Thus, bio-HDPE was first melt-compounded with two different loadings of GA, namely 0.3 and 0.8 parts per hundred resin (phr) of biopolymer, by twin-screw extrusion and thereafter shaped into films using a cast-roll machine. The resultant bio-HDPE films containing GA were characterized in terms of their mechanical, morphological, and thermal performance as well as ultraviolet (UV) light stability to evaluate their potential application in food packaging. The incorporation of 0.3 and 0.8 phr of GA reduced the mechanical ductility and crystallinity of bio-HDPE, but it positively contributed to delaying the onset oxidation temperature (OOT) by 36.5 °C and nearly 44 °C, respectively. Moreover, the oxidation induction time (OIT) of bio-HDPE, measured at 210 °C, was delayed for up to approximately 56 and 240 min, respectively. Furthermore, the UV light stability of the bio-HDPE films was remarkably improved, remaining stable for an exposure time of 10 h even at the lowest GA content. The addition of the natural antioxidant slightly induced a yellow color in the bio-HDPE films and it also reduced their transparency, although a high contact transparency level was maintained. This property can be desirable in some packaging materials for light protection, especially UV radiation, which causes lipid oxidation in food products. Therefore, GA can successfully improve the thermal resistance and UV light stability of green polyolefins and will potentially promote the use of natural additives for sustainable food packaging applications.

Preparation of nano-SiO2 compound antioxidant and its antioxidant effect on polyphenylene sulfide

Polyphenylene sulfide (PPS) is easily oxidized at high temperature, which greatly limits its applications. In this study, a nano-SiO2 compound antioxidant (SiO2-g-AO) was prepared and incorporated into PPS by melt compounding to obtain PPS/SiO2-g-AO composites. SiO2-g-AO was prepared by reacting 3-(3,5-di-tert-butyl-4-hydroxyphenyl) (antioxidant AO) with an aminosilane coupling agent (KH792). Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA) confirmed that the antioxidant AO was successfully immobilized on the surface of SiO2 and the thermal stability was improved. Scanning electron microscopy (SEM) images showed that SiO2-g-AO was uniformly dispersed in PPS. It has been found that the crystallinity and mechanical properties of PPS composites improved, and the dynamic oxidation induction temperature (OIT) increased in the range of 16.7°C–21.1°C. A synergistic anti-oxidation model of nanoparticles and antioxidants, namely a multi-stage antioxidant system, was established by comprehensive analysis of experimental results. The synergistic anti-oxidation model provides a new idea for the antioxidant modification of polymer composites.

DBHP-Functionalized ZnO Nanoparticles with Improved Antioxidant Properties as Lubricant Additives

In this article, 3-(3,5-di- tert-butyl-4-hydroxyphenyl) propionic acid (DBHP)-functionalized ZnO (DBHP-ZnO) nanoparticles were synthesized by decomposing the organometallic precursor Zn(DBHP)₂ under alkaline conditions. This in situ surface modification method can induce small-sized ZnO nanoparticles (5 nm) and form strong linkage between DBHP and ZnO nanoparticles. DBHP as an organic compound hindered phenol antioxidant that not only improved the dispersion stability of the prepared DBHP-ZnO nanoparticles in the lubrication oil but also scavenged free radicals produced during the oxidation process of oil. Compared with DBHP, the thermal stability of the prepared composite antioxidant was greatly enhanced by introducing inorganic ZnO nanoparticles, which was proved by the results of the thermogravimetric analysis test. A rotary oxygen bomb test, pressurized differential scanning calorimetry, and free-radical-scavenging method all showed that DBHP-ZnO nanoparticles had better antioxidant properties than DBHP under high temperature in the base oil of di- iso-octylsebacate (DIOS). The activation energy of the oxidation process was used to analyze this result by the model-free methods, including the Flynn-Wall-Ozawa method and the Kissinger equation. The calculated results showed that DIOS containing DBHP-ZnO nanoparticles have the lowest reaction constant and the longest half-life period compared to those of individual DBHP and ZnO nanoparticles, which is attributed to the combined action of the organic-inorganic composites. Besides, DBHP-ZnO nanoparticles as the additive are able to improve the antiwear ability of DIOS to some extent. Therefore, the as-prepared DBHP-ZnO nanoparticles with desired dispersibility as well as better thermal stability and antioxidant ability than DBHP in the DIOS base oil could be a potential high-performance nanocomposite additive for a synthetic lubricant base oil like DIOS.

A Comprehensive Study on The Accelerated Weathering Properties of Polypropylene-Wood Composites with Non-Metallic Materials of Waste-Printed Circuit Board Powders

In this study, non-metallic materials of waste-printed circuit board powders (WPCBP) were successfully used as reinforcing filler to produce polypropylene (PP)–wood composites, and their effect on the weathering properties of PP composites were fully evaluated via oxidation induction time (OIT), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry, vicat softening point (VST), scanning electron microscopy, and mechanical properties analysis. The OIT analysis confirmed that the anti-thermal oxidative aging properties of PP–wood composites were decreased with the loading of WPCBP. Apart from that, the PP composite, reinforced with 30 wt.% of WPCBP, exhibited the highest value of active energy, which suggests that it is more sensitive to temperature and oxygen when compared with other PP composites. The mechanical properties analysis revealed that neat PP exhibited the poorest weathering properties after being subjected to UV exposure, and its retention rate of tensile strength and notched impact strength were only 70.6% and 59.6%, respectively, while WPCBP and wood flour (WF) could efficiently improve the retention rates of the mechanical properties of the PP composites when subjected to UV exposure. The visual appearance of the PP composites after being subjected to UV exposure showed more and smaller cracks with the loading of WPCBP and WF. The ATR-FTIR results revealed that the carbonyl index increased for all the weathered samples, and the more WPCBP was added into the PP composites led to a higher carbonyl index value, which might be due to the multivalent transition metals in WPCBP, which accelerate the photo-oxidation of the PP composites. The VST results show that both WPCBP and WF can effectively enhance the heat deformation resistance of the PP composites that have been subjected to UV exposure.

Grafting of Hindered Phenol Groups onto Ethylene/α-Olefin Copolymer by Nitroxide Radical Coupling

The covalent immobilization of hindered phenol groups, with potential antioxidant activity, onto an ethylene/α-olefin (EOC) copolymer was carried out by the nitroxide radical coupling (NRC) reaction performed in the melt with a peroxide and the 3,5-di-tert-butyl-4-hydroxybenzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (BHB-T). Functionalized EOC (EOC-g-(BHB-T)) was exposed to photo- and thermo-oxidation. By comparison with some model compounds bearing the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) moiety or the hindered phenol unit, it was observed that the grafted BHB-T could effectively help the stabilization of the polymer matrix both under photo- and thermo-oxidation. In addition, the immobilization of BHB-T can effectively increase the service life of the functionalized polymers when polymer films were put in contact with ethanol solution thus simulating a possible application of the modified polymer.

Synthesis and oxidative stability of hyperbranched macromolecule-bridged hindered phenols

The oxidative stability of hyperbranched macromolecule-bridged hindered phenols was investigated using the DPPH method and the oxygen uptake method.

The synthesis of graphene-based antioxidants to promote anti-thermal properties of styrene-butadiene rubber

An immobile antioxidant (GO-RT) was successfully synthesized and possessed outstanding anti-oxidation performance in an SBR matrix.

Morphology, mechanical and thermal oxidative aging properties of HDPE composites reinforced by nonmetals recycled from waste printed circuit boards

In this study nonmetals recycled from waste printed circuit boards (NPCB) is used as reinforce fillers in high-density polyethylene (HDPE) composites. The morphology, mechanical and thermal oxidative aging properties of NPCB reinforced HDPE composites are assessed and it compared with two other commercial functional filler for the first time. Mechanical test results showed that NPCB could be used as reinforcing fillers in the HDPE composites and mechanical properties especially for stiffness is better than other two commercial fillers. The improved mechanical property was confirmed by the higher aspect ratio and strong interfacial adhesion in scanning electron microscopy (SEM) studies. The heat deflection temperature (HDT) test showed the presence of fiberglass in NPCB can improve the heat resistance of composite for their potential applications. Meanwhile, the oxidation induction time (OIT) and the Fourier transform infrared (FTIR) spectroscopy results showed that NPCB has a near resistance to oxidation as two other commercial fillers used in this paper. The above results show the reuse of NPCB in the HDPE composites represents a promising way for resolving both the environmental pollution and the high-value reuse of resources.

Thermal oxidative and ozone oxidative stabilization effect of hybridized functional graphene oxide in a silica-filled solution styrene butadiene elastomer

Modification of fGO and preparation of SSBR nanocomposites; the thermal oxidative stability mechanism of the fGO sheets-filled SSBR nanocomposites.

Antioxidation efficiency and reinforcement performance of precipitated-silica-based immobile antioxidants obtained by a sol method in natural rubber composites

This precipitated-silica-based immobile antioxidant (P-RT) possesses outstanding reinforcement and anti-oxidation performance in an NR matrix. E.g. the NR/P-RT composite is far longer than NR composites containing the general antioxidant 4010NA.