Synthesis and Characterization of Liquid Natural Rubber as Impact Modifier for Epoxy Resin

Thermal and Adhesion Properties of Fluorosilicone Adhesives Following Incorporation of Magnesium Oxide and Boron Nitride of Different Sizes and Shapes

Thermally conductive adhesives were prepared by incorporating magnesium oxide (MgO) and boron nitride (BN) into fluorosilicone resins. The effects of filler type, size, and shape on thermal conductivity and adhesion properties were analyzed. Higher thermal conductivity was achieved when larger fillers were used, but smaller ones were advantageous in terms of adhesion strength. Bimodal adhesives containing spherical MgOs with an average particle size of 120 μm and 90 μm exhibited the highest conductivity value of up to 1.82 W/mK. Filler shape was also important to improve the thermal conductivity as the filler type increased. Trimodal adhesives revealed high adhesion strength compared to unimodal and bimodal adhesives, which remained high after aging at 85 °C and 85% relative humidity for 168 h. It was found that the thermal and adhesion properties of fluorosilicone composites were strongly affected by the packing efficiency and interfacial resistance of the particles.

Enhanced mechanical and thermal properties of electrically conductive TPNR/GNP nanocomposites assisted with ultrasonication

Thermoplastic natural rubber (TPNR) was compounded with graphene nanoplatelets (GNP) via ultrasonication and melt blending. The effects of ultrasonication period (1-4 hours) and GNP weight fraction (0.5, 1.0, 1.5 and 2.0 wt.%) on the mechanical, thermal and conductivity properties were investigated. Results showed that the 3 hours of ultrasonic treatment on LNR/GNP gave the greatest improvement in tensile strength of 25.8% (TPNR/GNP nanocomposites) as compared to those without ultrasonication. The TPNR nanocomposites containing 1.5 wt.% GNP exhibited the highest strength (16 MPa for tensile, 14 MPa for flexural and 11 kJm-2 for impact) and modulus (556 MPa and 869 MPa for tensile and flexural, respectively). The incorporation of GNP had enhanced the thermal stability. It can be concluded that the GNP had imparted the thermally and electrically conductive nature to the TPNR blend.

Morphology and micromechanics of liquid rubber toughened epoxies

In the present work, a diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin was modified with the help of a liquid rubber (LR) obtained from the pyrolysis of rubber. Tensile tests on samples of rubber modified epoxy resins (REs) containing varying rubber volume fractions (RVF) were conducted to obtain their tensile properties. Fractographic analysis of fractured samples using field emission scanning electron microscopy (FESEM) revealed the presence of phase separated rubber zones characterized by microvoids, distributed uniformly in the epoxy domain. Young’s modulus and yield strength of REs were observed to drop with RVF. A three-dimensional (3D) finite element model was employed to predict the elastic properties and stress distributions in REs. Various stress distributions and their dependence on the properties of rubber were examined in detail through the model. The effect of rubber properties on bulk elastic properties of the REs were also studied. Lastly, the effective stress-strain relationship was predicted with the help of an elastic-plastic analysis. Predicted results showed coherence with experimental results.