Abstract:To develop functional sustainable epoxy resins, we report a novel epoxy resin (DEU-EP) with high net biobased content (70.2 wt%) derived from renewable eugenol. We comparatively study DEU-EP with a commercial bisphenol A epoxy resin (DGEBA) in the presence of a most representative aromatic diamine curing agent, 4,4'-diaminodiphenyl methane (DDM).Differential scanning calorimetry reveals that DEU-EP can be sufficiently cured by DDM at a slower rate than DGEBA. By applying an autocatalytic reaction model, we adequately simulate the curing rate of DEU-EP/DDM, and reveal its detailed kinetic mechanisms from model-free isoconversional analysis. Dynamic mechanical analysis shows that DEU-EP/DDM takes higher storage modulus up to ~97 o C than DGEBA/DDM with the glass temperature of 114 o C. Nanoindentation and thermogravimetric analysis demonstrate that compared with DGEBA/DDM, DEU-EP/DDM exhibits a 20%, 6.7% and 111% increase in Young's modulus, hardness and char yield, respectively. Microscale combustion calorimetry data show that DEU-EP/DDM expresses 55% and 38% lower heat release rate and total heat release than DGEBA/DDM, respectively.Macroscopically, the horizontal burning test approves DEU-EP/DDM can self-extinguish in a short time. Our results demonstrate that the eugenol building blocks and their arrangement greatly affect the cure behaviors of DEU-EP/DDM, and contribute significantly to its enhanced mechanical properties, high-temperature charring ability and chain motions at glass state, as well as the reduced flammability. To summarize, DEU-EP exhibits a high promise as a new sustainable epoxy monomer for fabricating high biobased content, high rigid and low flammable epoxy materials.

A highly efficient phenylphosphonate based flame retardant epoxy resin (FREP) was firstly prepared from phenylphosphonic dichloride (PPDCl) and allylamine (AA). Functionalized graphite nanoplatelets (fGNPs) fillers were then performed to fabricate the fGNPs/FREP nanocomposites via mixing followed by casting method. The thermally conductive coefficient (l), thermal diffusivity (a), flame retardancy, electrical conductivities and thermal stabilities of the fGNPs/FREP nanocomposites were all enhanced with the increasing addition of fGNPs fillers. The l and a value of the fGNPs/FREP nanocomposite with 30 wt% fGNPs fillers was increased to 1.487 W/mK and 0.990 mm2/s, about 7 times and 6 times for that of pure FREP matrix (0.234 W/mK and 0.170 mm2/s), respectively. And the corresponding electrical con ductivity was also increased to 5.0 x 10 4 S/cm, far better than that of pure FREP matrix (1.0 x 10 12 S/ cm). In comparison with that of pure FREP, the THR and TSP value of the fGNPs/FREP nanocomposite with 15 wt% fGNPs fillers was decreased by 37% and 32%, respectively, char yield was increased by 13%, and LOI value was increased from 31% to 37%. However, the peak of heat release rate of the fGNPs/FREP nano composite became worse due to its high thermal conductivity. Nanoindentation revealed that there was negligible influence of fGNPs fillers on the hardness values and Young's modulus of the fGNPs/FREP nanocomposites.

A novel bio-epoxy resin, TPEU-EP, was developed. It possesses good intrinsic flame retardancy, low smoke production, and excellent mechanical properties, showing high promise for application.

Harvesting biobased epoxy resins with improved thermomechanical properties (e.g., glass transition temperature T g and storage modulus), mechanical and dielectric similar and even superior to that of bisphenol A epoxy resin (DGEBA) is vital to many applications, yet remains a substantial challenge. Here we develop a novel eugenol-based epoxy monomer (TEU-EP) with a branched topology and a very rich biobased retention (80 wt %). TEU-EP can be well cured by 3,3′-diaminodiphenyl sulfone (33DDS) and the resultant TEU-EP/33DDS system can be considered as a “single” epoxy component, exhibiting adequate reactivity at high processing temperatures. Importantly, compared with DGEBA/33DDS, TEU-EP/33DDS achieves a 33 °C, 39% and 55% increment in the glass transition temperature, Young’s modulus, and hardness, respectively, and shows the improved creep resistance and dimensional stability. TEU-EP/33DDS is also characterized by the considerably reduced permittivity, dielectric loss factor, and flammability with high yield of pyrolytic residual. Overall, TEU-EP endows the cured epoxy with a number of the distinguished properties outperforming its DGEBA counterpart, and therefore may find practical applications in demanding and even cutting-edge areas.

Individual Ni(3) Al nanocubes under pressure are investigated by comparing the compressive strength of both dislocation-free and irradiated Ni(3) Al nanocubes. The results are dicussed in light of the size-dependent and size-independent strength of face-centered cubic (fcc) nanocrystals in the framework of dislocation nucleation at free surfaces. This study sheds more light on the understanding of fundamental deformation mechanisms and size-affected strength in dislocation-free metallic nanocrystals.

a b s t r a c tA multiscale modeling strategy is presented to determine the effective mechanical properties of polycrystalline Ni-based superalloys. They are obtained by computational homogenization of a representative volume element of the microstructure which was built from the grain size, shape and orientation distributions of the material. The mechanical behavior of each grain was simulated by means of a crystal plasticity model, and the model parameters that dictate the evolution of the critical resolved shear stress in each slip system (including viscoplastic effects as well as self and latent hardening) were obtained from compression tests in micropillars milled from grains of the polycrystal in different orientations suited for single, double (coplanar and non coplanar) and multiple slip. The multiscale model predictions of the compressive strength of wrought IN718 were in good agreement with the experimental results.

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