The performance of epoxy/cenosphere syntactic foams cured using phenalkamine (PA) were analyzed and characterized. The PA system was found to cure faster at room temperature, had lower density, and lower water absorption values. The thermogravimetric analysis result implied higher thermal stability. The cure studies using DSC inferred faster cure reaction in the ambient temperature conditions. The compression studies confirmed that unlike the epoxy system based on conventional triethylenetetramine curative, PA‐based system did not undergo brittle failure. This was also confirmed with the scanning electron microscope images. Dynamic mechanical analysis inferred the glass transition temperatures (Tg) as 81.4°C. The specific modulus and specific strength were higher for 40% cenosphere loading in PA‐based syntactic foams. As the need for light weight core materials is continually increasing, there is a great possibility for the utilization of this novel bio‐based curing agent to produce sustainable products. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44189.

Epoxy syntactic foams with different compositions of cenosphere were fabricated and characterised. The effect of loading cenosphere in epoxy syntactic foams was analysed. Good thermal stability of cenosphere–epoxy syntactic foams was established from the thermogravimetric analysis results. The completion of cure reaction at ambient temperature conditions was ascertained from differential scanning calorimetry results. Dynamic mechanical analysis revealed 114°C as the glass transition temperatures ( Tg) for neat epoxy sample, which increased to 132°C with 50% loading of cenosphere. Cenosphere-filled epoxy syntactic foams had low density and low water absorption values when compared to the neat epoxy sample. Homogeneous distribution of the cenosphere particles was confirmed using scanning electron microscopy. The compression studies confirmed brittle failure of the syntactic foams. This was also supported by the scanning electron microscopic images. The incorporation of hollow cenosphere particles led to a decrease in the flexural strength. Syntactic foams with 30% loading of cenosphere exhibited best specific modulus and specific strength. The specific strength increased by 24% for T30 sample and specific modulus increased by 36% for T30 samples when compared to the neat epoxy sample. As the need for strong but lightweight thermally stable products is continually increasing, there is a great possibility for the utilisation of these cenosphere–epoxy syntactic foams as lightweight core for sandwich composites.

Cenosphere-filled epoxidized cardanol syntactic foams were fabricated using stir-casting technique: 10–40 wt% of cenosphere was mixed gradually in several steps in order to avoid any damage of the cenosphere. The syntactic foams were cured at room temperature for a day followed by postcure for 3 h at 100°C. Completion of the cure reaction was ascertained using differential scanning calorimetry of the fresh sample and postcured sample. Homogeneous distribution of cenosphere was confirmed with the scanning electron microscopic (SEM) images. The fracture mechanism was also analysed using SEM image of the compression failed sample. Thermal, hygrothermal and compressive properties of the syntactic foams were studied. Epoxidized cardanol-based syntactic foams were found to have lower density, good thermal stability and higher char residue as revealed from the thermogravimetric analysis result. The yield strength decreased with the increase in cenosphere. The specific modulus was optimum for 30% loading of cenosphere and it increased by 42% in comparison to the neat sample. Hygrothermal studies conducted using deionized water and sea water at room and high temperature conditions revealed stability and lower water absorption. The bio-based syntactic foams derived from cardanol promised sustainable path for the preparation of light-weight foam core materials.