Hindered Phenol Research Articles

Synthesis of a novel organic-inorganic hindered phenol antioxidant derived from polyhedral oligomeric silsesquioxane and its anti-oxidative behavior in polypropylene

To explore antioxidants with high anti-aging efficiency and admirable anti-extraction ability, a novel organic-inorganic hindered phenol antioxidant (AO-POSS) derived from polyhedral oligomeric silsesquioxane (POSS) was successfully synthesized via a nucleophilic substitution reaction. Chlorinated polyhedral oligomeric silsesquioxane with 8 silicon cores was first synthesized by hydrolysis-polycondensation of (3-chloropropyl)trimethoxysilane and further used for preparing AO-POSS by reacting with the sodium salt of hindered phenolic precursor 3-(3,5-Di‑tert‑butyl‑4-hydroxyphenyl)propionic acid (AO). According to the 29Si-NMR spectra, the T8 cores of Cl-POSS occurred cage-rearrangement under the catalytic effect of propionate anion to produce a thermodynamically stable mixed product, AO-POSS (T8, T10, and T12: 23.8 %, 60.5 %, and 15.7 %). When AO-POSS was incorporated into polypropylene (PP), the oxidation induction time (OIT) of the PP/AO-POSS compound (15.8 min) was slightly longer than that of the PP/1010 compound (13.8 min) at the same molar amounts of hindered phenols. Furthermore, the OIT value of PP/AO-POSS/168 (50.7 min) was obviously higher than that of PP/1010/168 (38.1 min), pointing out the enhanced levels of positive synergism between AO-POSS and secondary antioxidants in inhibiting PP oxidation degradation. Hence, it is apparent that AO-POSS possesses high thermo-oxidative stability and anti-aging efficiency in PP. Notably, even after 48 h of Soxhlet extraction, the OIT value of PP/AO-POSS was retained at 69.5 %, while that of PP/1010 was only 32.2 %, indicating the much better anti-extraction ability of AO-POSS.

A calixarene antioxidant C-undecylcalix[4]resorcinarene for endothermic hydrocarbon fuels

The antioxidation performance of small molecule antioxidants in high temperature environments is often limited due to insufficient thermal stability. Thus, macromolecular calixarene compounds were developed as thermal stable antioxidants to overcome the shortcomings of conventional small molecular hindered phenol antioxidants. In this work, C-undecylcalix[4]resorcinarene (C11C[4]R), with hydrocarbon soluble alkyl chain and hindered phenol structure, was used as antioxidants for endothermic hydrocarbon fuels. Thermogravimetric analysis shows C11C[4]R has better thermal stability than 2,6-di-tert-butyl-4-methylphenol (BHT), the commercial small molecular antioxidant, which made it suitable for intensively thermal-stressed conditions. Further tests shows that the radical scavenging activity of C11C[4]R is significantly better than BHT with a larger capacity and higher capture rate. C11C[4]R also presents a satisfactory antioxidation inhibition improvement in view of the oxidative stability of the model fuels in accelerated oxidation experiments. In addition, computational works were also conducted, by which the results suggest an improved H atom donation ability also contributes to the excellent antioxidation performance of C11C[4]R.

Synthesis of the reactive hindered phenol antioxidant 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl methyl isobutylene ester and its application in ABS resin

AbstractIn this study, a reactive hindered phenol antioxidant, 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl methyl isobutylene ester (DBHMIE), was synthesized and used to improve the antioxidant performance of ABS (acrylonitrile‐butadiene‐styrene terpolymer) resin. The chemical structure of DBHMIE was determined with Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopy. Moreover, the effects of the DBHMIE content on the antioxidant capabilities, thermal stabilities, tensile strengths, impact strengths, and morphologies of the ABS/antioxidant systems were investigated. The results indicated that the oxidation induction temperatures of the systems increased from 229.7 to 245.4°C as the DBHMIE content was increased from 0 to 0.5 wt%. The 5% mass loss temperature of the system was increased from 338.4 to 347.8°C by the addition of 0.3 wt% DBHMIE. The impact strengths of the systems increased with increasing DBHMIE content up to 0.1 wt% and then decreased. The addition of DBHMIE did not significantly affect the tensile strength of the ABS resin. SEM images showed that the DBHMIE was uniformly distributed in the ABS resin at low DBHMIE contents and agglomerated at high DBHMIE contents.

Bio-based polyurethane/hindered phenol AO-80 composites for room temperature high damping properties

Elastomeric damping materials are essential in modern life. Apart from natural rubber, conventional elastomers are mostly based on petroleum-based sources. Moreover, elastomers exhibit excellent damping properties in the glass transition region, the glass transition temperature (Tg) of elastomers is lower than room temperature, resulting in poor damping properties at room temperature. However, because of limited and unsustainable petrochemical resources and environmental pollution, sustainable development and green environmental protection have become important principles in the design of damping materials, and most damping materials are used at room temperature. Therefore, designing bio-based materials with high damping properties at room temperature to replace conventional cross-linked rubber materials is crucial. Herein, we prepared bio-based millable polyurethane (bio-MPU)/hindered phenol 3,9-bis-{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl-)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro (Wang et al., 2016; Wang et al., 2016) [5,5]-undecane (AO-80) composites to overcome the challenge of sustainable development and high damping properties at room temperature. Bio-MPU samples with high Tg were synthesized from bio-based modified polylactic acid-based polyols, 4, 4′-diphenylmethane diisocyanate, and unsaturated chain extender 3-allyloxy-1, 2-propanediol. AO-80 was mixed with bio-MPU to further increase the Tgand enhance the damping properties of the bio-MPU/AO-80 composites. The properties of the bio-MPUs and bio-MPU/AO-80 composites were systematically evaluated. This study proposes a strategy to design high damping properties from bio-based raw materials and reduce our dependence on fossil resources.

Bio-Based Polyurethane and Its Composites towards High Damping Properties.

The operation of mechanical equipment inevitably generates vibrations and noise, which are harmful to not only the human body but also to the equipment in use. Damping materials, which can convert mechanical energy into thermal energy, possess excellent damping properties in the glass transition region and can alleviate the problems caused by vibration and noise. However, these materials mainly rely on petroleum-based resources, and their glass transition temperatures (Tg) are lower than room temperature. Therefore, bio-based materials with high damping properties at room temperature must be designed for sustainable development. Herein, we demonstrate the fabrication of bio-based millable polyurethane (BMPU)/hindered phenol composites that could overcome the challenges of sustainable development and exhibit high damping properties at room temperature. BMPUs with a high Tg were prepared from modified poly (lactic acid)-based polyols, the unsaturated chain extender trimethylolpropane diallylether, and 4,4′-diphenylmethane diisocyanate, and 3,9-Bis-{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl-)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro [5,5]-undecane (AO-80) was added to prepare BMPU/AO-80 composites. Finally, the properties of the BMPUs and BMPU/AO-80 composites were systematically evaluated. After adding 30 phr of AO-80, the Tg and maximum loss factor (tan δmax) of BMPU/AO-80 composites increased from 7.8 °C to 13.5 °C and from 1.4 to 2.0, respectively. The tan δmax showed an improvement of 43%. Compared with other polyurethanes, the prepared BMPU/AO-80 composites exhibited higher damping properties at room temperature. This study proposes a new strategy to reduce society’s current dependence on fossil resources and design materials featuring high damping properties from sustainable raw materials.

Enhancements in damping properties and thermal conductivity of acrylonitrile‐butadiene rubber by using hindered phenol modified alumina

AbstractHighly integrated electronic components used under mechanical vibration usually require the vibration‐reduction and heat‐dissipation protection from rubber composites. But it is still a challenge to simultaneously improving damping properties and thermal conductivity of rubber. Herein, hindered phenol modified alumina is prepared and filled to acrylonitrile‐butadiene rubber (NBR), leading to NBR/modified alumina composites with strong interfacial interaction. The composites exhibit superior damping properties. They have higher hysteresis ratio, damping coefficient, damping factor at 25°C, and effective damping temperature ranges than NBR and its unmodified alumina composites. The NBR/modified alumina composites also have higher thermal conductivity and lower relaxation rate than NBR and its alumina composites. The modification of alumina by the hindered phenol is an effective method for preparing NBR composites with extraordinary combination of good damping properties and high thermal conductivity. The composites have a great application potential for vibration‐reduction and heat‐dissipation protection of electronic components.

Synthesis and application of new macromolecular hindered phenol antioxidants of polyamide 6

AbstractThe two macromolecular antioxidants, P(3,5‐di‐tert‐butyl‐4‐hydroxy cinnamic acid‐alt‐N‐phenylmaleimide) (PCN) and P(3‐butene‐1‐yl‐3,5‐di‐tert‐butyl −4‐hydroxyphenyl propionate‐alt‐N‐phenylmaleimide) (PPN) were designed and synthesized via free radical copolymerization. The structures of the resulting PCN and PPN antioxidants were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography. In addition, the effect of the two macromolecular antioxidants on the thermal oxidation aging resistance of polyamide 6 (PA6) was studied. According to the analysis of differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, dynamic viscosity, and the mechanical property of PA6 and its blends, these two types of macromolecular antioxidants protected the molecular chain of PA6 from breaking, protected the crystallization of PA6 and maintained the stability of PA6 crystal form, improved the activation energy of thermal degradation and thermal stability of PA6, enhanced the strength and elasticity of PA6 and maintained the mechanical properties of PA6 during aging to a certain extent.

Improving electric thermal stability of polypropylene by chemically linking small amount of hindered phenol groups.

Thermal stability of polypropylene (PP) over a broad temperature is critical for many applications. Hindered phenol (HP) groups have been utilized in PP for thermal-oxidative protection. This paper studies thermal stability of the electret property of PP linked with 0.2 mol% HP. It is observed that small amount of chemically linked HP groups improves electret thermal stability as reflected by the higher peak temperature of the thermally stimulated discharge curve and about 65% increase in the trap level. In addition, the HP groups in PP generate “rigid backbones” which maintain the PP film shapes to temperatures near the melting (~ 150 °C), compared with pristine PP at 70 °C.Supplementary InformationThe online version of this article (10.1557/s43580-021-00016-1) contains supplementary material, which is available to authorized users.

High‐temperature stabilization of polypropylene using hindered phenol–thioester stabilizer combinations, Part 2: Optimization and efficacy via encapsulation with silicate fillers

AbstractThe thermal degradation of unstabilized polypropylene has been investigated under long‐term thermal aging at 150°C, with additive concentration studies on combinations of an established hindered phenolic antioxidant (pentaerythritol tetrakis (3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate) [S1010] and two popular thioesters (distearyl‐3,3′‐thiodipropionate [DSTDP] and didodecyl‐3,3′‐thiodipropionate [DLTDP]) using melt flow rate (MFR), carbonyl index (Fourier transform spectroscopy [FTIR]) and differential scanning calorimetry (DSC) (oxidation induction time [OIT]) and ultimate embrittlement time (fracture) on injection‐molded test pieces. It was found in part 1 that 20:80 phenol:thioester ratios provided the best long‐term thermal stability (LTTS). Part 2 investigates potential improvements in stabilization, involving the use of controlled release systems in which the stabilizers are melt blended in the PP together with high surface area inorganic substrates. Here, a calcined gel silica SD3128 and two layered silicates Rockwood Additives Fulcat® 800 and Laponite® B were incorporated into the polymer formulations in order to limit stabilizer mobility at 6000 ppm through potential surface adsorption and subsequent controlled release. Additional hindered amine light stabilizers were also added as long‐term heat stabilizers and to act as displacing agents that promote controlled release via competitive adsorption on processing due to the strongly adsorbing amine functionalities. In some instances, the LTTS showed improvement. Flow micro calorimetry was used to investigate the stabilizer–substrate interactions. It was found that as a result of its small pore structure, Laponite B could only adsorb smaller molecules such as that of DLTDP while Fulcat® 800 was a more strongly adsorbing substrate with larger pores able to accommodate even the largest of the hindered amine light stabilizer (HALS) molecules. The gel silica SD3128 had overall the most adsorbing ability with each of these characteristics supporting the aging data studied in parallel. The data are discussed in relation to the long‐term stabilization of polypropylene in high‐temperature applications such as under the bonnet of automobiles where minimizing stabilizer losses and maximizing synergy are important.

High‐temperature stabilization of polypropylene using hindered phenol–thioester stabilizer combinations, Part 1: Optimization and efficacy via nondust blends

AbstractThe thermal degradation of unstabilized polypropylene has been investigated under long‐term processing (twin extruder) and thermal aging at 150°C, with additive concentration studies on combinations of an established hindered phenolic antioxidant (pentaerythritol tetrakis (3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate) [S1010] and two popular thioesters (distearyl‐3,3′‐thiodipropionate [DSTDP] and didodecyl‐3,3′‐thiodipropionate [DLTDP]) using melt flow rate, carbonyl index and powder diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (FTIR), and differential scanning calorimetry (DSC) (oxidation induction time [OIT]) and ultimate embrittlement time (Fracture) on injection‐molded test pieces. It was found that 20:80 phenol:thioester ratios provided the best long‐term thermal stability (LTTS); however, this was the reverse for processing stabilization (80:20), underlining the antioxidant nature of the two stabilizers (long term vs. melt). Melt preblending of the stabilizers (to form a no‐dust blend) gave rise to improved LTTS. DRIFTS FTIR indicated that there was an improvement in preblending the additives, which removed any volatile impurities. Increased additive dispersion and localized potential efficacy in the stabilization cycle is important, as well as possible improved addition of the additives to the extruder rather than fine powder. The data are discussed in relation to the long‐term stabilization of polypropylene in high‐temperature applications such as under the bonnet of automobiles where minimizing stabilizer losses and maximizing synergy are important.

New and novel stabilisation approach for radiation-crosslinked Ultrahigh Molecular Weight Polyethylene (XL-UHMWPE) targeted for use in orthopeadic implants

There is a substantial evidence to show that oxidative degradation has a negative impact on the properties and performance of radiation-crosslinked ultra high molecular weight polyethylene (XL-UHMWPE) used as articulating components in orthopaedic joint implants and is the primary cause for their premature failure. In general, high energy radiation is required not only for sterilising the articulating surfaces but also for crosslinking the polymer to improving its mechanical properties and wear resistance thus minimising the extent of formation of wear-particles which are implicated in the aseptic loosening and failure of the implant. To address the oxidative stability of the XL-UHMWPE bearing surfaces, the natural hindered phenol antioxidant, vitamin E, which has been approved by FDA for use in this application, is used to enhance the oxidation resistance of orthopaedic implants, e.g. in tibial bearings. Further, a purified grade of the commercial antioxidant Irganox 1010Ⓡ (pentaerythritol tetrakis(3-[3,5-di tertiary butyl‑4‑hydroxy phenyl]propionate) has also been FDA approved and used in some knee-based systems. In the case of vitamin E, its effectiveness as a potent free radical scavenger, however, presents some issues in respect of the polymer crosslinking process and the homogeneity of its distribution especially during manufacturing processes that involve the infusion of the vitamin into the polymer. The novel approach adopted in this study for the stabilisation of XL-UHMWPE bearing surfaces makes use of graftable polymer-reactive antioxidants (r-AOs) bearing a hindered phenol and also hindered amine moieties. Potentially, these r-AOs can be chemicaly grafted in-situ on the polymer backbone during the radiation-crosslinking process without the need for any additional manufacturing step. The results obtained have demonstrated a substantive stabilisation which can be achieved with these r-AOs. This was shown to be the case in all the XL-UHMWPE samples tested here which were manufactured according to a methodology typically used in the commercial production and crosslinking (by gamma- or electron-beam) of UHMWPE-based implants.

Methyl oleate derived multifunctional additive for polyol based lubricants

A novel multifunctional lubricant additive was synthesized by thiol‒ene coupling of methyl oleate (Mo) with thioglycolic acid (Tga) to obtain intermediate compound Mo−Tga {(S)-2-(18-methoxy-18-oxooctadecan-9-ylthio)acetic acid} followed by esterification with 2,6-di-tert-butyl-4-(hydroxymethyl)phenol to obtain the final additive Mo−Tga−Bz {(S)-methyl 10-(2-(3,5-di-tert-butyl-4-hydroxybenzyloxy)-2-oxoethylthio)octadecanoate} in the second step. Since the sulfur and steric hindered phenol was introduced in methyl oleate framework, so the Mo−Tga−Bz was evaluated for anti-oxidant, anti-wear, anti-friction and anticorrosion characteristics in polyol lube base oil at the varying concentrations after confirming the molecular structure by FT-IR and NMR spectroscopic techniques. The anti-oxidant property was evaluated by DPPH (2, 2-diphenyl-1-picrylhydrazyl) method which showed a maximum free radicals %inhibition of 73.06 % at 0.5% (w/v) additive concentration; tribological properties were evaluated by four-ball test method which showed a reduction of 19.61% in average wear scar diameter (AWSD) at 0.2% (w/v) and 37.71% reduction in average friction coefficient at 0.3% (w/v) additive concentration comparative to polyol base oil. The anticorrosion activity test result revealed that Mo−Tga−Bz shows the concentration‒effect but at 0.3% concentration the values for the weight loss, corrosion rate and penetration rate were decreased to a value of 1.39 ± 0.07 mg, 1.44 ± 0.07 mdd and 0.26 ± 0.01 mpy respectively from 11.34 ± 0.07 mg, 11.72 ± 0.07 mdd and 2.16 ± 0.01 mpy for polyol.

Synthesis of Triazole Derivatives with Sterically Hindered Phenol Fragments

In recent decades, the chemistry of functionally substituted 1,2,4-triazoles and the fused heterocyclic systems based on them have received significant attention due to their structural and biologi...

Acyl-chloride functionalized graphene oxide chemically grafted with hindered phenol and its application in anti-degradation of polypropylene

In this study, graphene oxide (GO) nanosheets were first functionalized by the acyl-chloride reaction and then reacted with hindered phenol (HP) to obtain HP grafted GO (GO-g-HP). The GO-g-HP prepared under the optimized condition exhibited a high efficiency against both thermal and photo oxidation of isotactic polypropylene (iPP). GO-g-HP exhibited a much better anti-aging efficiency than that of HP and GO used individually or that of their physical mixture. The outstanding anti-aging effect of GO-g-HP was attributed to the excellent synergistic effect produced between the chemically bonded GO and HP, which resulted in an improved oxygen barrier property of GO and excellent utilization of the free radical scavenging capability of GO and HP. Also, thanks to the grafting of HP on GO, the physical loss of HP, which was one of the main shortcomings for traditional small molecular antioxidants, was largely suppressed. It is expected that the GO-g-HP prepared can well meet the requirement of long-term applications of polymers in some harsh service conditions.

Effects of chain polarity of hindered phenol on the damping properties of polymer-based hybrid materials: insights into the molecular mechanism

Abstract For hindered phenol (HP)/polymer-based hybrid damping materials, the damping properties are greatly affected by the structure variation of HPs. However, the unclear relationship between them limits the exploitation of such promising materials. Therefore, three HPs with different chain polarity were synthesized to explore the relationship in this paper. The structures of the HPs were firstly confirmed by Nuclear Magnetic Resonance Spectrum, Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Diffraction (XRD). For further prepared HP/polyurethane hybrids, FT-IR and XRD were also adopted to confirm the hydrogen bonding interactions and micromorphologies. And, Molecular dynamics simulation was further used to characterize the effects of polarity variation on the hydrogen bonding interactions and chain packing of the hybrids in a quantitative manner. Then, combined with dynamic mechanical analysis, the relationship between the chain polarity variation of the hindered phenols and the damping properties was established.

Electrical properties of polypropylene-bonded hindered phenol blends

Polypropylene (PP) film is the most commonly used dielectric film in power capacitor applications, thanks to its high breakdown strength combined with low dielectric losses. Today, antioxidants based on hindered phenol (HP) are mixed into the PP resin during manufacturing to provide thermal-oxidative protection during melt processing, however they increase the dielectric losses. Recently, a new PP-HP copolymer has been synthesized containing a few comonomer units with HP moieties, which are homogeneously distributed along the PP polymer chain. Addition of new PP-HP copolymer to PP dramatically improve the thermal-oxidative stability under elevated temperatures compared to neat PP. In the current study the electrical properties of this novel PP-HP copolymer and PP/PP-HP blends are investigated using dielectric spectroscopy and direct current (DC) breakdown strength. By adding lower amounts (2–5 wt%) of the PP-HP copolymer in PP, the dielectric constant and loss remains similar to that of neat PP. The short-term DC breakdown strength of the PP/PP-HP blends is equal or higher than the neat PP reference, combined with a reduced scatter in breakdown data. As a next step, long-term ageing tests of the PP/PP-HP blends are required. These findings may bring an advanced PP dielectric material into the market which is highly beneficial for high voltage power capacitor applications.

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.

Molecular Insights Into Chain Length Effects of Hindered Phenol on the Molecular Interactions and Damping Properties of Polymer‐Based Hybrid Materials

For hindered phenol (HP)/polymer‐based hybrid damping materials, the unclear relationship between the structure of HP and the damping properties limits the application of such promising materials. Herein, three kinds of HPs with different chain lengths were synthesized to explore the mechanism. The structures of the HPs were confirmed by nuclear magnetic resonance spectrum, the Fourier Transform Infrared Spectroscopy (FT‐IR), and X‐ray Diffraction (XRD). For further prepared HP/polyurethane hybrids, FT‐IR and XRD were adopted to confirm the hydrogen bonding interactions and micromorphologies. Moreover, molecular dynamics simulation was used to characterize the effects of chain length variation on the inter‐ and intramolecular hydrogen bonds (HBs) and the chain packing of the hybrids in a quantitative manner. Subsequently, combined with the dynamic mechanical analysis, the relationship between the chain length variation and the damping properties was established. The results showed that with the increasing of chain length, the intramolecular HBs between HPs can be prevented, and the loose HP chain within tight polymer matrix can be achieved, which results in a maximum increase of loss factor. While the homogeneity of the chain packing increases with the chain length increasing, which results in a decrease of the temperature range of loss factor ≥ 0.3. POLYM. ENG. SCI., 60:446–454, 2020. © 2019 Society of Plastics Engineers

Preparation of novel damping layered silicates and its application in chlorinated butyl rubber (CIIR) composites

ABSTRACTOn the basis of layered silicates, montmorillonite (MMT) with lamellar structure was selected to realize the design of constrained damping materials. A novel type of organically modified MMT (MD-OMMT) containing -OH groups was prepared by introducing of organic hindered phenol groups. This novel filler, MD-OMMT, was then applied into chlorinated butyl rubber (CIIR) composites. After addition of different amounts of MD-OMMT, their tensile strength and elongation at break were improved. In addition, the damping factor was increased compared with that of pure CIIR. Moreover, the damping temperature was shifted to the room temperature and its damping temperature range was widened.

Towards a Stable and High-Performance Hindered Phenol/Polymer-Based Damping Material Through Structure Optimization and Damping Mechanism Revelation.

Although hindered phenol/polymer-based hybrid damping materials, with excellent damping performance, attract more and more attention, the poor stability of hindered phenol limits the application of such promising materials. To solve this problem, a linear hindered phenol with amorphous state and low polarity was synthesized and related polyurethane-based hybrid materials were prepared in this study. The structure and state of the hindered phenol were confirmed by nuclear magnetic resonance spectrum, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The existence of intermolecular hydrogen bonds (HBs) between hindered phenol and polyurethane was confirmed by FT-IR, and the amorphous state of the hybrids was confirmed by XRD. Moreover, by a combination of molecular dynamics simulation and dynamic mechanical analysis, the relationship between the structure optimization of the hindered phenol and the high damping performance of the hybrids was quantitatively revealed. By constructing the synthetic hindered phenol, the intramolecular HBs between hindered phenols were restricted, while the strength and concentration of the intermolecular HBs increased by increasing the amount of hindered phenol. Thus, intermolecular interactions were enhanced, which lead to the compact chain packing of polyurethane, extended chain packing of hindered phenol, and good dispersion of hindered phenol in polyurethane. Therefore, the stability of the hindered phenol and the damping properties of the hybrids were both improved. The experiment results are expected to provide some useful information for the design and fabrication of high-performance polymeric damping materials.