Influence of Graphene Nano Fillers and Carbon Nano Tubes on the Mechanical and Thermal Properties of Hollow Glass Microsphere Epoxy Composites

The present work aimed to analyze the roll of carbon nano tubes and graphene nano fillers on the mechanical and thermal characteristics of hollow glass microsphere reinforced epoxy composites. Composites with varying content of hollow glass microballoons (2, 4, 6, 8, and 10 wt %) reinforced in epoxy matrix were fabricated. Additionally, two more types of composites, one with graphene nano fillers and the other with carbon nano tube at a constant 0.5 wt %, were fabricated with varying weight percentages of hollow glass microballoons (2, 4, 6, 8, and 10%). The composites were fabricated using an open mold casting process. Composites were tested for thermal and mechanical properties. The tensile and flexural moduli were found to rise as the HGM concentration increased. Graphene-filled HGM/epoxy composites revealed the highest modulus compared with HGM/epoxy and HGM/CNT/epoxy composites. The impact strength of all composite types decreased as the HGM content increased. Neat epoxy specimens revealed low response as compared with all the composites tested. Further, the thermal conductivity of HGM/epoxy composites was lower as compared with other compositions and neat epoxy. Scanning electron microscopy was used to analyze the surface morphological behavior of the composites subjected to flexural test. It was found that HGM/G/E composites with 10% of HGM and 0.5% of graphene by weight in epoxy matrix were the optimum.

Effect of Composition on Impact and Flexural Properties of Hybrid Glass Microballoons/Fly Ash Cenosphere Filled Vinyl Ester Matrix Syntactic Foams

Syntactic foams are porous particulate composites fabricated by mixing hollow particles called micro-balloons into a matrix material such as metal, polymer, ceramic etc. Fillers i.e. micro balloons are used to decrease the amount of expensive matrix material and/or to enhance or tailor some properties of matrix materials. The different variations in density and properties of syntactic foam could be obtained by changing the material, volume fraction and/ or density of micro balloons. Here the hybrid syntactic foams were synthesized by adding two different filler materials that are hollow glass microballoons and flyash cenospheres into vinyl ester matrix. Two types of hybrid systems are created one with 50% total filler content and another with 60% total filler content in a matrix whereas, within these hybrid systems an internal composition of two fillers were varied in a step of 25 vol% with respect to each other. Hybridization of two different types of ceramic microballoons in vinyl ester matrix gives maximum 111% increase in impact strength with respect to plane hollow glass microsphere syntactic foam. Hybridization also causes lncrease in flexural strength and Flexural modulus by 39% and 58% respectively.

Epoxy-Glass Microballoon Syntactic Foams: Rheological Optimization of the Processing Window

In this paper, we discuss the chemorheology of epoxy based syntactic foams containing glass microballoons of varying density, with an aim of establishing the effect of microballoon loading on its processability. The primary objective is to determine the maximum microballoon loading that disperses uniformly in the resin without the aid of any diluent. The viscosity and dynamic mechanical properties of epoxy formulations containing varying amounts of glass microballoons were established by parallel plate rheometry. Our studies reveal that solventless processing of formulations with microballoon loading > 60% poses practical difficulties due to prohibitively high viscosities, although a packing efficiency of 74% is theoretically allowed in the case of hexagonal close packing. The presence of microballoons does not alter the curing mechanism. The mechanical properties of syntactic foams were inversely proportional to the loading and type of glass microballoons.