Mechanical properties of polybenzoxazine syntactic foams

Abstract

Syntactic foams of polybenzoxazine, containing moderately high volume percentage of glass microballoons, were prepared. The specific gravity decreased with increase in microballoon content. The disproportionate decrease in specific gravity was ascribed to entrapment of air voids during compaction. The high content of microballoon increased the possibility for air voids that tended to get accumulated. The effect of microballoon concentration on tensile, compressive, and flexural strengths of the foams was studied. Tensile and compressive properties were optimized at about 68% by volume of microballoon while flexural strength decreased marginally on increasing the microballoon content. Althought the specific tensile and compressive strength showed a maximum followed by a decrease, the specific flexural strength systematically increased with microballoon content. The increased packing density of syntactic foam of a given constituent composition increased the compressive strength. The property variation was corroborated by morphological features, as evidenced in scanning electron micrographs. The syntactic foams showed ''multiple resin-neck formation'' and ''disc-shaped microballoon regions.'' The crushing of microballoons during molding was inevitable when compaction was effected to achieve a density beyond the theoretical one. Low-density syntactic foams tend to fail at lower loads because of fracturing of microballoons.

Effects of griseofulvin on in vitro porcine oocyte maturation and embryo development

“…The lower storage modulus of composite C‐1S is attributed to the shorter length of ultrasonically treated CNFs. The same influences of fiber length on modulus have also been reported in microfiber‐reinforced polymers in previous studies [19, 21].…”

“…With increasing loading of CNFs, the interface area also increases which results in more structural flaws within the composites and further impaired flexural properties. However, at some point the increasing CNF loading also leads to the spatial entanglement of unagglomerated CNFs in the composite, which could resist fracture and increase the plastic deformation [19]. This may account for the sudden brittle‐ductile transition of PEI/1.0 wt%CNF (pristine) composites (composite C‐1L).…”

Mechanical and dynamic mechanical properties of epoxy syntactic foams reinforced by short carbon fiber

“…Syntactic foams have been extensively studied in the past several decades and numerous studies are reported in literature concerning the mechanical properties of syntactic foams under compressive , flexural and tensile . These studies have helped in understanding the significant factors affecting the mechanical properties of syntactic foams, which are mainly guided by the volume fraction, wall thickness and size of microspheres .…”

Foaming behavior, cellular structure and physical properties of polybenzoxazine foams

“…Limited work has been done regarding the study of polybenzoxazine foams 19, 20. Santhosh et al 19. prepared and characterized syntactic foams using a bisphenol‐A‐based benzoxazine containing a high weight percentage of hollow glass microspheres (from 30 to 70 wt%).…”

“…Limited work has been done regarding the study of polybenzoxazine foams. [19,20] Santhosh et al [19] prepared and characterized syntactic foams using a bisphenol-A-based benzoxazine containing a high weight percentage of hollow glass microspheres (from 30 to 70 wt%). Lorjai et al [20] also prepared bisphenol-A-based benzoxazine foams and their related carbon foams using ADC as a blowing agent.…”