Polypropylene Copolymer Containing Cross-Linkable Antioxidant Moieties with Long-Term Stability under Elevated Temperature Conditions

Functional Polyolefins and Composites

Polyolefins are simple hydrocarbons that require additional chemical modifications or functional additives to give them custom functions. Recent research in the development of functional polyolefins has surpassed the traditional approach of simply improving surface properties by incorporating polar moieties. Creating custom functionalized polyolefins by using specific functional units has attracted increasing attention. This review summarizes advances in preparing custom functionalized polyolefin materials using functional units such as comonomers, chain-transfer agents, post-polymerization modification reagents, and functional fillers. Exploring new functional units and innovative synthetic strategies will further enhance the performance and expand the applications of functional polyolefins.

Superhydrophobic polypropylene sorbent derived from discarded face masks: A highly efficient adsorbent for oil spill sorbent

Globally, an estimated 130 billion face masks are used and disposed of every month. Thus, recycling or upcycling discarded face masks has attracted significant attention due to economic benefits and environmental concerns. To reduce the amount of used face masks going to waste, this study features a superhydrophobic face mask prepared by simple chemical modification with environmentally preferable alkane solvents (n-hexane, n-heptane, and n-decane), that is effective as a sorbent for oil spill cleanup. All alkanes examined increased the surface roughness of the face masks and improved face mask hydrophobicity. The heptane treated face mask (at 90 °C for 1 h), can adsorbed Arabian light crude oil up to 21 times of their weight on the water surface. In addition, chloroform, toluene, gasoline, and diesel were adsorbed 18, 13, 8 and 16 times, respectively. More importantly, heptane has a high recycling efficiency as a treatment solvent and is reusable for at least 10 cycles of mask surface treatment. Consequently, this inexpensive and easily fabricated material is a promising development in waste face mask (WFM) upcycling.

Waste-based nanoarchitectonics with face masks as valuable starting material for high-performance supercapacitors

Surgical face masks waste is a source of microplastics (polymer fibres) and inorganic and organic compounds potentially hazardous for aquatic organisms during degradation in water. The monthly use of face masks in the world is about 129 billion for 7.8 billion people. Therefore, in this contribution the utilization of hazardous surgical face masks waste for fabrication of carbon-based electrode materials via KOH-activation and carbonization was investigated. The micro-mesoporous materials were obtained with specific surface areas in the range of 460 - 969 m²/g and a total pore volume of 0.311 - 0.635 cm³/g. The optimal sample showed superior electrochemical performance as an electrode material in supercapacitor in the three-electrode system, attaining 651.1F/g at 0.1 Ag^-1 and outstanding capacitance retention of 98 % after a test cycle involving 50'000 cycles. It should be emphasized that capacitance retention is one of the most crucial requirements for materials used as the electrodes in the supercapacitor devices. In this strategy, potentially contaminated face masks, common pandemic waste, is recycled into highly valuable carbon material which can serve in practical applications overcoming the global energy crisis. What is more, all microorganisms, including coronaviruses that may be on/in the masks, are completely inactivated during KOH-activation and carbonization.

The synthesis and properties research of functionalized polyolefins

This work demonstrated a tandem ROMP/hydrogenation approach for the preparation of functionalized polyolefins and their properties were investigated.

Highly efficient and recyclable polyolefin-based magnetic sorbent for oils and organic solvents spill cleanup

The oil dispersants have been applied in a broad oil pollution area, but the dispersed oil caused environmental problems during sedimentation. Unlike oil dispersants, flake type polyolefin-based oil absorbent (PA) is not emulsified and shows excellent swelling characteristic for oil removal. However, the sprayed PA flakes cannot be fully collected due to its tiny architectures, the uncollected flakes can cause unintentional secondary pollution. In this study, we develop a kind of flake type polyolefin-based magnetic absorbent (PMA) hybridized with magnetic nanoparticle, to facilitate the collection process. The magnetic nanoparticle is uniformly dispersed in PMA due to the hydrophobic functionalization of iron oxide nanoparticle. This enables the convenient collection of isolated sorbent flakes even when they were placed in the marine system and show a desirable oil recovery performance up to about 37 times for organic solvent. Moreover, oil-soaked PMA flakes can be fully converted into refined oil via a pyrolysis process. After pyrolysis, the thermally undecomposed compounds, which comprise of carbon residue and magnetic nanoparticle, can be also separated by a magnet. The as-prepared flake type PMA possesses good oil recovery performance, fast magnetic response, and efficient oil recycling, thus representing an environmentally promising method for oil spill cleanup.

First-principles based theoretical investigation of impact of polyolefin structure on photooxidation behavior

Despite their mass production and large applications, polyolefins' stability and durability toward the air, moisture, and weather resistance is a challenge for the ecosystem. After long-term exposure to ultraviolet (UV) radiation or high-temperature or erosion, polyolefins undergo degradation generating microplastics (MPs). The MPs generated after the degradation of these polyolefins are hazardous for the ecosystem. In the present work, we have carried out density functional theory (DFT) studies to investigate the photodegradation of six different polyolefins ranging from polyethylene to polydecene, differing in side-chain. Herein, we have investigated photooxidized derivatives of different polyolefins and analyzed their relative stability, conformations, UV-visible spectral behavior, and carbonyl index. The photooxidized derivatives of various polyolefins formed during degradation are examined. The time-dependent density functional theory analysis confirms that the carbonyl groups of photooxidized products show absorption peak in Infrared (IR) and visible region, acting as light-absorbing species. The relative stabilities of hydroperoxide formed during photo/thermal oxidation of different polyolefins have been evaluated to explain the degradation behavior. The oligomerization and stabilization energies of their corresponding hydroperoxide's were computed and analyzed to explain the degradation behavior of the polyolefins. The computed results suggest that polyolefins in their pristine state are stable toward photooxidation, but chemical impurities like carbonyl, unsaturated carbonyl, carboxylic acid, and hydroperoxide derivatives make them prone to undergo degradation, a fundamental process leading to generation of MPs. The comparative results confirmed that the side-chain length affects the stability and degradation of different polyolefins toward photooxidation.

Enabling Superior Thermo-Oxidative Resistance Elastomers Based on a Structure Recovery Strategy

Thermo-oxidative process leads to the structure damage of elastomers, such as the scission of main chains and destruction of crosslinks. The problem that damaged structure brings about the deterioration of mechanical properties has not been solved by the conventional anti-aging methods. Inspired by self-healing process, a structure recovery strategy for recovering the damaged structure induced by thermo-oxidative process is proposed, which endows elastomers with superior thermo-oxidative resistance. The high reactivity between 1,3-diisopropenylbenzene and free radicals realizes high recovery efficiency (from 83% to 118%); the changes in topology structure during recovery process make much more rubber chains bear external stress and improve mechanical properties significantly (from 18.5 to 29.6 MPa). This work paves the way for the development of elastomers with superior thermo-oxidative resistance, meanwhile this work is helpful to push the theoretical research of self-healing to practical application.

MXene Enabling the Long-Term Superior Thermo-Oxidative Resistance for Elastomers

The ability of long-term thermo-oxidative resistance is very important for elastomers in application. However, many conventional antioxidants are difficult to realize the long-term thermo-oxidative resistance. To overcome this limitation, a design strategy is introduced by combing elastomers with MXene and natural rubber (NR) is chosen as a model material. MXene is efficient in absorbing oxygen and the generated free radicals in the NR matrix and can inhibit the diffusion of oxygen toward the interior. Moreover, MXene, like graphene and carbon black, absorbs molecular chains, inhibiting the migration of MXene toward the surface of the sample. Such characteristics of MXene endow NR/MXene with the long-term outstanding thermo-oxidative resistance. For example, after three days of the thermo-oxidative process for NR/MXene, the tensile strength is 19 MPa and the retention of tensile strength is 63%, which far exceeds the effects of conventional antioxidants. This work not only provides a good guide for the universal design of elastomers with long-term thermo-oxidative resistance but also expands the application of MXene.

Thermally Stable Low-Loss Polymer Dielectrics Enabled by Attaching Cross-Linkable Antioxidant to Polypropylene

Polymer dielectrics with low-loss and high-temperature tolerance are extremely desirable as electrical energy storage materials for advanced electronics and electrical power applications. They can allow fast switching rates during power conversion and therefore achieve high power densities without thermal issues. Here, we explore polypropylene (PP), the state of the art dielectric polymer, and present an innovative approach to substantially improve the thermal stability and concurrently reduce the dielectric loss of PP. In particular, cross-linkable antioxidant groups, hindered phenol (HP), are incorporated into PP via well-controlled chemical synthesis. The grafted HP can simultaneously serve as radical scavenger and cross-linker, thereby constraining thermally decomposed radicals and charge transport in the synthesized PP-HP copolymer. As a result, the upper-temperature limit of PP-HP is greatly extended to 190 °C and the electrical loss is even gradually reduced upon thermal annealing. The copolymer after heating under 190 °C exhibits better dielectric properties than the PP without any thermal treatment. The experimental results indicate that the PP-HP copolymers are promising materials for high-temperature, low-loss, and high-voltage dielectric applications.

Design, fabrication and anti-aging behavior of a multifunctional inorganic–organic hybrid stabilizer derived from co-intercalated layered double hydroxides for polypropylene

The concomitant presence of HALS/DBHP co-intercalated within the LDH structure strongly improved the anti-aging performance of PP, which opens the pathway for potential future research of high-performance PP associated with hybrid fillers.

Co-intercalated layered double hydroxides as thermal and photo-oxidation stabilizers for polypropylene

An elegant and efficient approach consisting in the co-intercalation of stabilizing molecular anions is described here. The thermal stabilizer calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (Irganox 1425, MP-Ca) and a photo-oxidation stabilizer (hindered amine light stabilizer, HALS) are co-intercalated into the interlayer regions of layered double hydroxides (LDH) in a one-step coprecipitation. These hybrid organic-inorganic materials are successively dispersed in polypropylene to form H _n M _{n '}-Ca₂Al/PP composite films (with H = HALS and M = MP) through a solvent casting method. The corresponding crystalline structure, chemical composition, morphology as well as the resistance against thermal aging and photo-oxidation are carefully investigated by various techniques. The results show that the powdered H _n M _{n '}-Ca₂Al-LDHs hybrid materials have a much higher thermal stability than MP-Ca and HALS before intercalation. In addition, the H _n M _{n '}-Ca₂Al/PP composites exhibit a higher overall resistance against thermal degradation and photo-oxidation compared to LDHs intercalated with only HALS or MP. This underlines the benefit of the co-intercalation. The co-intercalated LDH materials pave a new way in designing and fabricating high-performance multifunctional additives for polymers.

Polyolefin-based interpenetrating polymer network absorbent for crude oil entrapment and recovery in aqueous system

In this research, a series of different two polyolefin-based interlaced polymer network material was prepared with a semi-crystalline linear low density polyethylene (LLDPE, thermoplastic) and a crosslinked 1-decene/divinylbenzene (1-D/DVB, elastomer) having high crude oil absorption capacity. The prepared absorbents, LLDPE/D/DVB, were characterized by NMR, TEM, contact angle measurement and TGA analysis. It was observed that the mixing ratio of two interlaced polymer network played a crucial role in determining its crude oil absorption capacity. The swelling capacity of absorbent prepared from a 1:1 mixing of LLDPE and D/DVB (0.2 ml) exhibit high removal efficiency in crude oil absorption over 40 g/g at both 25 °C and 0 °C. The removal of the absorbed crude oil from the water surface is effective. As the absorbent made of polyolefin materials have pure hydrocarbon content, offer significant advantages such as high absorption capacity, simple recovery, and recyclability.