Effect of functional filler morphology on the crystallization behavior and thermal conductivity of PET resin: A comparative study of three different shapes of BN as heterogeneous nucleating agents

Functional fillers play a vital role in thermally conductive polymer-based composites. However, little attention has been paid to how functional fillers with the same composition but different morphologies affect the crystallinity of the matrix and the final thermal conductivity of polymeric composites. In this work, two-dimensional boron nitride nanosheet (2-D BNNS), one-dimensional boron nitride whisker (1-D BNW) and one-dimensional boron nitride nanotube (1-D BNNT) acting as both nucleating agents and thermally conductive fillers were melt-mixed with Polyethylene terephthalate (PET) resin, respectively, and the effects of filler morphology on the crystallization behavior of PET and thermal conductivity of the PET/BN composites were investigated and compared. Results indicate that three kinds of BN all play a better heterogeneous nucleation role in crystallization of PET, which significantly accelerates the crystallization rate and improves the crystallinity of PET, but the modifying effect is not the same. The thermal conductivity of PET is improved by increasing the crystallinity of the polymer with a very low content of 0.5 wt% of BN in PET. The BNNT with regular shape and minimum size achieves the best effect in nucleation and improvement of thermal conductivity, followed by BNW and BNNS. Experimental fact illustrates that the functional fillers with the same composition but different shapes can produce different modification effects on both crystallinity of matrix and the final thermal conductivity of the polymeric composites.