Effect of hexagonal boron nitride (h-BN) inclusion on thermal characteristics of disc brake friction composites

Abstract

Friction materials are developed keeping other ingredients constant and varying the weight percentage (wt%) of functional filler hexagonal boron nitride (h-BN) from 0 to 8 wt% and decreasing the space filler barite from 35 to 27 wt% in friction composites BN0, BN1, and BN2 respectively. Physical properties of these materials are measured as per Indian Standard (IS), and friction performance is studied using tribotester. Thermogravimetric analysis (TGA) with Differential scanning calorimetry (DSC) is carried out to find out the thermal behavior of friction composites at a higher temperature. The thermal conductivity values of these materials are measured using double-sided guarded hot plate apparatus. The addition of h-BN content enhances thermal conductivity from 0.86 W/mK to 1.40 W/mK. Effective thermal conductivity values of these multicomponent friction composites are also determined by analytical models and compared with experimentally measured values. Finally, to find out the thermal conductivity values of friction composites by the analytical method, the geometric mean model is modified with the introduction of the correction factor, which is based on the volume fraction of h-BN and temperature. Effective thermal conductivity values obtained by the modified geometric mean model agree well with measured values. The inclusion of h-BN improves physical properties, friction performance and thermal behavior of brake friction materials.