Development of highly conductive graphite-/graphene-filled polybenzoxazine composites for bipolar plates in fuel cells

Superior conductive fillers reinforced polymer composites are ideal alternatives to graphitic and metallic materials in proton exchange membrane fuel cells (PEMFCs) for high thermal and electrical conductive bipolar plates. Polymer composites are known to be adversely influenced from high contact resistance thus to minimize such resistance, highly graphite-/graphene-filled polybenzoxazine (PBA) composites are developed in this work. A very low melt viscosity of benzoxazine resin with graphite loading as high as 83 wt % is used for the samples. With an addition of graphene platelet, thermal and electrical conductivities of the specimens having 75.5 wt % of graphite in a combination of 7.5 wt % of graphene are significantly enhanced to 14.5 W mK⁻¹ and 323 S cm⁻¹, respectively. Properties of highly graphite-/graphene-filled PBA composites exhibit most values exceed those requirements by the U.S. Department of Energy for PEMFCs applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47183.     

Highly filled graphene‐benzoxazine composites as bipolar plates in fuel cell applications

This research emphasizes on the development of highly filled graphene‐polybenzoxazine composites and investigates thermal, electrical, and mechanical properties of the obtained composites for bipolar plate applications. The composition of graphene loading was achieved to be in the range of 10–60 wt%. The experimental results revealed that at the maximum graphene content of 60 wt% (44.8 vol%) in the polybenzoxazine, storage moduli at room temperature of the composites were considerably enhanced with the amount of the graphene, that is, from 5.9 GPa of the neat polybenzoxazine to about 25.1 GPa at 60 wt% of graphene. Glass transition temperatures (T_g) of the obtained composites were observed to be 174–188°C and the values substantially increased with increasing the filler contents. At 60 wt% of graphene content, thermal conductivity, as high as 8.0 W/mK, is achieved for the graphene‐filled polybenzoxazine. Furthermore, the flexural modulus and flexural strength of the composites were found to be as high as 18 GPa and 42 MPa, respectively. Water absorption of graphene filled‐composite is relatively low with the value of only about 0.06% at 24 h of water immersion. Additionally, electrical conductivity was measured to be 357 S/cm at maximum loading of the graphene. Therefore, the graphene‐filled composites based on polybenzoxazine are highly attractive as bipolar plates for polymer electrolyte membrane fuel cells applications. POLYM. COMPOS., 37:1715–1727, 2016. © 2014 Society of Plastics Engineers     

Synthesis and characterization of sequential interpenetrating polymer networks of polyurethane acrylate and polybenzoxazine

High‐performance ultraviolet (UV) curable polyurethane acrylate (PUA) coating alloyed with thermally curable polybenzoxazine (PBA) is developed. The hybrid polymer networks of PUA and PBA‐a were prepared by sequential cure methods, i.e., UV cure of the PUA followed by thermal cure of the PBA fraction. The effects of sequential cure were investigated in terms of mechanical, thermal, and physical properties of the resulting polymer alloys. The fully cured PUA/PBA‐a alloy films showed only single glass transition temperature (T_g) suggesting high compatibility between the two polymer networks, possibly of an interpenetrating polymer network type. The storage modulus in a glassy state and T_g of PUA/PBA‐a alloys were found to substantially increase with increasing PBA‐a content. Furthermore, degradation temperature at 10% weight loss of the PUA/PBA‐a alloy films was relatively high whereas the char yield at 800°C was found to increase with a PBA‐a component. Hardness was enhanced, whereas water absorption and water vapor permeation rate of the alloy were suppressed by the incorporation of the PBA‐a into the polymer alloys. As a consequence, the properties of UV curable PUA networks can be positively tailored and enhanced by forming hybrid network with PBA‐a. POLYM. ENG. SCI., 54:1151–1161, 2014. © 2013 Society of Plastics Engineers     

Improvement of polyimide/polysulfone composites filled with conductive carbon black as positive temperature coefficient materials

In this study, polyimide (PI)/polysulfone (PSF) blends filled with carbon black (CB) were developed for the use as positive temperature coefficient (PTC) materials in order to achieve the volume resistivity as lower than 10⁴ Ω.cm at room temperature. The weight ratios of PI/PSF were various from 100/0 to 10/90 with CB varied from 0 to 20 wt%. The use of conductive filler was reduced when PSF was blended with PI; the blends clearly possessed a percolation threshold decreased by 90%. The electrical conductivity of the CB-filled blends was higher than those of CB-filled pure PI. The transition temperature for PTC material was reported in the range of 180 to 210 °C. The preferential location of CB filler in PI domains could be observed using the optical microscope. In addition, the composites met the standards for the obtained mechanical and thermal properties, exhibiting the potential use as PTC materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48482.