Synergistic effects of carbon fillers on tensile and flexural properties in liquid‐crystal polymer based resins

Abstract

One emerging market for thermally and electrically conductive resins is bipolar plates for use in fuel cells. Adding carbon fillers to thermoplastic resins increases the composite thermal and electrical conductivity. These fillers have an effect on the composite tensile and flexural properties, which are also important for bipolar plates. In this study, various amounts of three different types of carbon (carbon black, synthetic graphite particles, and carbon fibers) were added to Vectra A950RX liquidcrystal polymer. In addition, composites containing combinations of fillers were also investigated via a factorial design. The tensile and flexural properties of the resulting composites were then measured. The objective of this study was to determine the effects and interactions of each filler with respect to the tensile and flexural properties. The addition of carbon black caused the tensile and flexural properties to decrease. Adding synthetic graphite particles caused the tensile and flexural modulus to increase. The addition of carbon fiber caused the tensile and flexural modulus and ultimate flexural strength to increase. In many cases, combining two different fillers caused a statistically significant effect on composite tensile and flexural properties at the 95% confidence level. For example, when 40 wt % synthetic graphite particles and 4 wt % carbon black were combined, the composite ultimate tensile and flexural strength increased more than what would be expected from the individual additive effect of each single filler. It is possible that linkages were formed between the carbon black and synthetic graphite particles that resulted in improved ultimate tensile and flexural strength.

Effects of carbon fillers on tensile and flexural properties in polypropylene‐based resins

“…Because prior tensile and flexural strength tests were performed using carbon black and synthetic graphite in a Vectra liquid crystal polymer matrix (LCP) for use in fuel cell bipolar plate applications,35 a comparison is made in Figures 6 and 7. The filler volume fractions used in the LCP matrix are summarized in Table VIII 35.…”

“…Because prior tensile and flexural strength tests were performed using carbon black and synthetic graphite in a Vectra liquid crystal polymer matrix (LCP) for use in fuel cell bipolar plate applications,35 a comparison is made in Figures 6 and 7. The filler volume fractions used in the LCP matrix are summarized in Table VIII 35. The tensile modulus increased as a function of the filler volume percent with increasing filler concentration for both carbon black and synthetic graphite in the polypropylene, as indicated in Figure 6.…”

“…Vectra is a highly ordered thermoplastic copolymer consisting of 73 mol % hydroxybenzoic acid and 27 mol % hydroxynaphtoic acid. Properties of Vectra are shown elsewhere 35…”

“…As part of a larger project, research work in our laboratory has proposed the addition of higher concentrations of carbon fillers to a liquid crystal polymer (LCP) matrix33–36 and a polypropylene matrix37, 38 to achieve a large enhancement of the thermal and electrical properties of the materials produced while maintaining good strength properties. As such, the focus of this article will be on the tensile and flexural properties and tensile modulus modeling of injection molded carbon/polypropylene composites.…”

The effects of particle size and content on the thermal conductivity and mechanical properties of Al2O3/high density polyethylene (HDPE) composites

“…Zhou et al [16] used Al 2 O 3 with different size to fill silicone rubber, and reported that nanosized Al 2 O 3 composite exhibited higher thermal conductivity and mechanical properties than the micro-sized one. The influence of hybrid fillers was also investigated [17,18]. However, reports on how to enhance the thermal conductivity and mechanical properties of the polymer composites simultaneously are still quite limited.…”