Bio‐inspired low dielectric phenol formaldehyde laminates for electrical insulation applications

In this research work, the effect of individual and hybridized reinforcement of sisal fibrils with randomly distributed short sisal fibers has been investigated. The sisal fibrils (SP) and sisal fibers (SF) were reinforced with phenol formaldehyde matrix using hot stage compression molding technique. Composite laminates were prepared keeping the total wt% of the fibrils/fibers to be 40. The mechanical strength of SP reinforced phenol formaldehyde laminates was found to be superior as compared to sisal fiber and sisal fibril/fiber hybrid reinforced laminates. The 40 wt% sisal fibril reinforced composite laminates (SP40PF60) showed 73% and 25% increase in tensile strength, 78% and 23% increase in flexural strength, and 174% and 44% increase in impact strength as compared to 40 wt% sisal fiber reinforced laminates (SF40PF60) and 40 wt% hybrid reinforced (having equal proportion of fibrils and fibers) laminates (SF20SP20PF60). The dielectric properties of SP40PF60 increased by 14% and 9% as compared to SF40PF60 and SF20SP20PF60 laminates. Thermo‐gravimetric analysis analysis also showed higher thermal stability for sisal fibril phenol formaldehyde laminates than pure fiber and fibril/fiber hybrid laminates. Scanning electron microscopy was carried out to understand the nature of fibril/fiber/matrix interface. These laminates have been specially designed for press boards used in transformer assembly as environment friendly high mechanical strength and electrical insulating material. Additionally, these laminates can be useful for various fields such as electrical and aerospace industry.