Effects of Hindered Phenol Organic Molecules on Enhancing Thermo-Oxidative Resistance and Damping Capacity for Nitrile Butadiene Rubber: Insights from Experiments and Molecular Simulation

Machine learning-assisted design of the molecular structure of p-phenylenediamine antioxidants

This study employed machine learning to predict the solubility parameter (δ) and bond dissociation energy (BDE) of antioxidant molecules, focusing on p-phenylenediamine derivatives with varying carbon chain lengths, side group positions, and functional groups (-CH3, -OH, and -NH2). The multilayer perceptron (MLP) model, enhanced by data augmentation and genetic algorithms, was developed to correlate the "molecular structure-descriptor-target parameter" relationship. The model achieved high prediction accuracy (coefficient of determination >0.86, relative percent difference >2.62). SHapley Additive exPlanations analysis revealed molecular polarity as the key factor influencing antioxidant performance. Molecules with -NH2 side groups exhibited lower BDE values. A p-phenylenediamine derivative with 'CH3[CH2]13CH(NH2)-' connected to an aniline group showed optimal properties (Δδ = 0.02 (J cm-3)0.5, BDE = 289.46 kJ mol-1). Molecular simulations confirmed that the proposed antioxidant has excellent compatibility, anti-migration, and antioxidant activity in triglyceride oil. This study demonstrates the utility of MLP models for designing high-efficiency antioxidants for edible oils.

Thermal Oxidative Aging and Service Life Prediction of Commercial Ethylene-Propylene-Diene Monomer Spacer Damping Composites for High-Voltage Transmission Lines

The aging behavior and life prediction of rubber composites are crucial for ensuring high-voltage transmission line safety. In this study, commercially available ethylene-propylene-diene monomer (EPDM) spacer composites were chosen and investigated to elucidate the structure and performance changes under various aging conditions. The results showed an increased C=O peak intensity with increasing aging time, suggesting intensified oxidation of ethylene and propylene units. Furthermore, the surface morphology of commercial EPDM composites displayed increased roughness and aggregation after aging. Furthermore, hardness, modulus at 100% elongation, and tensile strength of commercial EPDM composites exhibited a general increase, while elongation at break decreased. Additionally, the damping performance decreased significantly after aging, with a 20.6% reduction in loss factor (20 °C) after aging at 100 °C for 672 h. With increasing aging time and temperature, the compression set gradually rose due to the irreversible movement of the rubber chains under stress. A life prediction model was developed based on a compression set to estimate the lifetime of rubber composites for spacer bars. The results showed that the product's life was 8.4 years at 20 °C. Therefore, the establishment of a life prediction model for rubber composites can provide valuable technical support for spacer product services.

Influence of Alternating Multi-Layered Design on Damping Characteristics of Butyl Rubber Composites and a New Idea for Achieving Wide Temperature Range and High Damping Performance

This paper investigates the influence of an alternating multi-layered design on the material loss factor and effective temperature range of free/constrained-damping butyl rubber, and then proposes a new method of designing materials with high damping properties and a wide temperature range. First, the wide-temperature rubber IIR-0, the low-temperature rubber IIR-1, the medium-temperature rubber IIR-2, and the high-temperature rubber IIR-3 are prepared and characterized. Second, the influences of an alternating multi-layered design on the damping peak values and temperature range of free damping and micro-constrained damping of the rubber types are investigated. Finally, different methods for broadening the damping temperature range and improving the damping loss factor are discussed. The results show that the loss factor of the alternating multi-layered, constrained damping structure is increased to 0.488, while that of the free-damping structure is increased to 0.845. Their damping-temperature ranges are increased to 89.4 °C and 93.2 °C, respectively. A wide temperature range and high damping performance can be achieved by the alternating multi-layered design of rubber/plastic micro-constrained damping composites.

Bio-based, recyclable and self-healing polyurethane composites with high energy dissipation and shape memory

Rubber composites make an important contribution to eliminating vibration and noise owing to their unique viscoelasticity. However, it is important to find alternative bio-based products with high damping properties owing to the shortage of petrochemical resources and poor performance. The ability to self-heal is an additional characteristic that is highly desirable because it can further increase the service life and safety of such products. In this study, a bio-based polylactic acid thermoplastic polyurethane (PLA-TPU) and its composites (PLA-TPU/AO-80) were synthesized. The reversible sacrificial hydrogen bonds in the composites increased the peak value of the loss factor (tan δ_max ) from 0.87 to 2.12 with a high energy dissipation efficiency of 99% at 50% strain. After being heated for 15 min, the healed sample recovered 81.98% of its comprehensive mechanical properties due to the reorganization of the hydrogen bonds. Its tensile strength remained at 93.4% after recycling five times. Moreover, its shape memory properties showed a response temperature close to the human body temperature making it an ideal candidate for medical applications. This article is protected by copyright. All rights reserved.

Development of nitrile rubber/eucommia ulmoides gum composites for controllable dynamic damping and sound absorption performance

Aiming at enhancing the damping and sound absorption performances of nitrile rubber (NBR) incorporated Eucommia ulmoides gum (EUG), a series of NBR/EUG composites were successfully fabricated using an open mixing mill. The co-vulcanization behaviors, fracture surface morphology observations, mechanical and thermal properties and damping and sound absorption performances of NBR/EUG composites were investigated systematically. It was shown that the crystalline area and the amorphous area in NBR/EUG composites displayed a sea-island phase distribution and most of the EUG crystals were β-form crystals. Compared to that of neat NBR, the tensile strength and storage modulus of NBR/EUG composites increased dramatically with the increasing EUG content, owing to the gradually increasing number of crystals in the NBR/EUG composites. In addition, the incorporation of EUG into the NBR matrix distinctly improved the sound absorption performance of NBR/EUG composites. This work is expected to provide a new insight into the fabrication of other composite materials with controllable damping and sound absorption properties.

Nitrile rubber (NBR)/Eucommia ulmoides gum (EUG) composites were successfully fabricated with controllable dynamic damping and sound absorption performances, owing to the changeable EUG crystal number in different NBR/EUG composites.

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 (T_g) 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 T_g 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 δ_max) of BMPU/AO-80 composites increased from 7.8 °C to 13.5 °C and from 1.4 to 2.0, respectively. The tan δ_max 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.

Investigation of the Compatibility and Damping Performance of Graphene Oxide Grafted Antioxidant/Nitrile-Butadiene Rubber Composite: Insights from Experiment and Molecular Simulation

Rubber damping materials are widely used in electronics, electrical and other fields because of their unique viscoelasticity. How to prepare high-damping materials and prevent small molecule migration has attracted much attention. Antioxidant 4010NA was successfully grafted onto graphene oxide (GO) to prepare an anti-migration antioxidant (GO-4010NA). A combined molecular dynamics (MD) simulation and experimental study is presented to investigate the effects of small molecules 4010NA, GO, and GO-4010NA on the compatibility and damping properties of nitrile-butadiene rubber (NBR) composites. Differential scanning calorimetry (DSC) results showed that both 4010NA and GO-4010NA had good compatibility with the NBR matrix, and the T_g of GO-4010NA/NBR composite was improved. Dynamic mechanical analysis (DMA) data showed that the addition of GO-4010NA increased the damping performance of NBR than that of the addition of 4010NA. Molecular dynamics (MD) simulation results show GO-4010NA/NBR composites have the smallest free volume fraction (FFV) and the largest binding energy. GO-4010NA has a strong interaction with NBR due to the forming of hydrogen bonds (H-bonds). Grafting 4010NA onto GO not only inhibits the migration of 4010NA but also improves the damping property of NBR matrixes. This study provides new insights into GO grafted small molecules and the design of high-damping composites.