Effects of hollow glass microspheres on the polybenzoxazine thermosets: Mechanical, thermal, heat insulation, and morphological properties

The growing need for high thermal and mechanical resistant lightweight syntactic foams demands the designing of new materials. Herein, we report the successful fabrication of lightweight and high thermal resistance syntactic foams with excellent thermal and good mechanical properties. For this end, 10–50 wt% hollow glass microsphere (HGMS) containing polybenzoxazine based syntactic foams were prepared by using bisphenol‐A‐aniline (BA‐a) and phenol‐diaminodiphenylmethane (P‐ddm) benzoxazine via curing at 10 MPa compression molding. The curing behavior, tensile, flexural, compressive, and impact strength, thermal properties, and fracture morphology of the syntactic foams were studied by DSC, universal material testing machine, and drop hammer impact testing machine, TGA, and SEM, respectively. The curing temperatures of BA‐a and P‐ddm benzoxazine resins were slightly increased after blending the HGMS. The highest decline (59%) in the density and highest void contains (13.17%) was recorded for the poly(P‐ddm/HGMS50) sample. The excellent specific mechanical properties of the syntactic foams were observed on the 30 wt% HGMS loading. The thermal conductivity of the foams was gradually decreased and the lowest values of 0.106 and 0.0985 W/m.K were observed for poly(BA‐a/HMGS50) and poly(P‐ddm/HGMS50) sample, respectively. Furthermore, a gradual improvement in the thermal properties was observed as the loading of HGMS increased. The polybenzoxazine/HGMS foams were prepared by blending the different wt.% loading of HGMS in the benzoxazine monomer. The loading reduced the density of produced foams. The fabricated syntactic foams showed lower thermal conductivity and higher thermal stability values, which suggest they can be used as insulation material.