Probing the effect of post-curing and halloysite nanotube reinforcement on thermo-mechanical properties of lightweight epoxy syntactic foam composites

This paper deals with an investigation of the post-curing effect of halloysite nanotubes (HNTs) reinforced syntactic foam (HRSF) containing cenosphere as hollow inclusion at 0, 20, and 40 vol% in an epoxy matrix. Compression, flexural, and thermal properties of HRSF (1 vol% HNTs) and cenosphere/epoxy syntactic foam (CESF) composites without HNTs are studied under the influence of post-curing. Further, the post-cured HRSF containing 40 vol% cenosphere (NSF40_H) exhibited a compressive modulus of 33.2% higher than room temperature cured neat epoxy due to improved crosslinking. Addition of HNTs in NSF40_H augments the flexural modulus up to 26.9% compared to post-cured neat epoxy. Additionally, the glass transition temperature (T-g) of CESF composites with 40 vol% cenosphere was increased by 24.3 degrees C compared to the room temperature cured sample. This positive shift in T-g can be attributed to the beneficial impact of post-curing, as indicated by differential scanning calorimetry study. Thermogravimetric results demonstrated better thermal stability of HRSF relative to CESF and neat epoxy composites. Transmission electron microscopy illustrated the structure-property correlations of nanotube reinforcement. The improved properties of syntactic foams could be viewed as a potential material for lightweight constructions, especially in the marine and automobile industries.