Time‐dependent properties of epoxy resin with imidazolium ionic liquid

Enhanced Electrical Properties and Impact Strength of Phenolic Formaldehyde Resin Using Silanized Graphene and Ionic Liquid

In this study, to improve the electrical properties and impact strength of phenolic formaldehyde (PF) resin, PF-based composites were prepared by mixing graphene and the ionic liquid 3-decyl-bis(1-vinyl-1H-imidazole-3-ium-bromide) (C10[VImBr]2) via hot blending and compression-curing processes. The graphene surface was modified using a silane coupling agent. The synergistic effect of graphene and C10[VImBr]2 on the electrical properties, electromagnetic shielding efficiency, thermal stability, impact strength, and morphology of PF/graphene and PF/graphene/C10[VImBr]2 composites was then investigated. It was found that the electrical conductivity of the composites significantly increased from 2.3 × 10-10 to 4.14 × 10-3 S/m with an increase in the graphene content from 0 to 15 wt %, increasing further to 0.145 S/m with the addition of 5 wt % C10[VImBr]2. The electromagnetic shielding efficiency of the composite increased from 4.70 to 28.64 dB with the addition of 15 wt % graphene, while the impact strength of the composites rose significantly from 0.59 to 1.13 kJ/m2 with an increase in the graphene content from 0 to 15 wt %, reaching 1.53 kJ/m2 with the addition of 5 wt % C10[VImBr]2. Scanning electron microscopy images of the PF/GNP/C10[VImBr]2 composites revealed a rough morphology with numerous microcracks.

High-performance acetosolv lignin-incorporated DGEBA cured with aprotic imidazolium-based ionic liquid: Polymerization, chemical, thermal and combustion aspects of the thermosetting materials

The lignin valorization constitutes a chemical platform for several segments of chemical industry. The aim of this work was to evaluate the potential of acetosolv coconut fiber lignin (ACFL) as an additive to DGEBA, curing it using an aprotic IL ([BMIM][PF₆]) and analyze the properties of the obtained thermosetting materials. ACFL was obtained by mixing coconut fiber with 90 % acetic acid and 2 % HCl at 110 °C during 1 h. ACFL was characterized by FTIR, TGA and ¹H NMR. The formulations were fabricated by mixing DGEBA and ACFL at different concentrations (0-50 % wt.). The curing parameters and [BMIM][PF₆] concentrations were optimized by DSC analyses. The cured ACFL-incorporated epoxy resins were characterized by gel content (GC), TGA, MCC and chemical resistance in different media. ACFL undergone a selective partial acetylation that favored its miscibility with DGEBA. High GC values were obtained at high curing temperatures and ACFL concentration. The crescent ACFL concentration did not affect the T_onset of the thermosetting materials significantly. ACFL has increased the resistance of DGEBA to combustion and different chemical media. ACFL has shown a great potential to be used as a bio-additive for enhancing the chemical, thermal and combustion properties of high-performance materials.

Modelling of Environmental Ageing of Polymers and Polymer Composites—Durability Prediction Methods

Polymers and polymer composites are negatively impacted by environmental ageing, reducing their service lifetimes. The uncertainty of the material interaction with the environment compromises their superior strength and stiffness. Validation of new composite materials and structures often involves lengthy and expensive testing programs. Therefore, modelling is an affordable alternative that can partly replace extensive testing and thus reduce validation costs. Durability prediction models are often subject to conflicting requirements of versatility and minimum experimental efforts required for their validation. Based on physical observations of composite macroproperties, engineering and phenomenological models provide manageable representations of complex mechanistic models. This review offers a systematised overview of the state-of-the-art models and accelerated testing methodologies for predicting the long-term mechanical performance of polymers and polymer composites. Accelerated testing methods for predicting static, creep, and fatig ue lifetime of various polymers and polymer composites under environmental factors’ single or coupled influence are overviewed. Service lifetimes are predicted by means of degradation rate models, superposition principles, and parametrisation techniques. This review is a continuation of the authors’ work on modelling environmental ageing of polymer composites: the first part of the review covered multiscale and modular modelling methods of environmental degradation. The present work is focused on modelling engineering mechanical properties.