Design of Highly Thermally Conductive Hexagonal Boron Nitride-Reinforced PEEK Composites with Tailored Heat Conduction Through-Plane and Rheological Behaviors by a Scalable Extrusion

Abstract

The challenge of developing highly thermally conductive polymeric composites to meet the growing thermal management demands has recently attracted a lot of attention. To achieve a through-plane thermal conductivity higher than 2 W/mK, a high filler concentration within the poly(ether ether ketone) (PEEK) matrix is required, thus adding to the complexity of polymer processing. In this study, an optimized twin-screw extrusion melt-compounding technique was developed by tuning the melt flow of unfilled PEEK, feeding zones, and process cycles for dispersion of hexagonal boron nitride (h-BN) in the PEEK polymer. The prepared composites demonstrated exceptionally high in-plane and through-plane thermal conductivity of 12.451 and 2.337 W/mK, respectively, at 60 wt % h-BN loading. This improvement of thermal conduction in both directions can be attributed to two factors: (1) formation of through-thickness surface contacts between h-BN particles due to shear-driven exfoliation during compounding stage and (2) high degree of alignment of h-BN platelets achieved during molding stage. The calorimetric and thermogravimetric analyses indicated that the prepared composites possess enhanced crystallinity compared to unfilled PEEK and are thermally stable in elevated temperature ranges. The rheological characterization exhibited a progressive increase in viscosity and shear-thinning behavior of composite melts proportional to the h-BN concentration. Using the temperature and time-dependent rheological results, viscosity buildup profiles were constructed to outline allowable melt viscosity ranges for each composite composition. These profiles can be utilized to tailor the residence time of a composite melt by varying the filler concentration and process temperature during advanced manufacturing processes such as extrusion-based additive manufacturing and powder bed fusion. Hence, we provide a facile and industrially scalable method for development of h-BN-filled PEEK composites with high thermal dissipation characteristics aimed for thermal management in various harsh environment applications.

Dimension effect on thermal conductivity of hexagonal boron nitride/titanium dioxide reinforced hybrid PEEK composites developed with a scalable compounding approach

“…In hBN/PEEK composites, our previous investigation has shown that at 60 wt% loading, a 4880% improvement in thermal conductivity of composite comes at an expense of a 30% reduction in the mechanical strength compared to neat PEEK. This reduction in strength is attributed to the undesired aggregation of hBN filler inside the polymer 15 . A similar reduction in mechanical strength of the 60 wt% hBN loaded elastomer polymeric composite was reported by Yu et al, 16 which they ascribed to the presence of stress concentration at the hBN/matrix interfaces.…”

“…A bespoke screw configuration was established during compounding by optimization of the number of mixing, kneading, and reverse elements to accommodate the high filler amount (i.e., 60 wt%) in the PEEK polymer based on our previous publication. 15,30 Prior to extrusion, PEEK granules, hBN powder, and TiO 2 powder were dried at 150 C for 4-6 h in vacuum. A 26 mm screw diameter and L/D ratio of 40 was used in the extrusion line.…”

“…3,46 Furthermore, compared to the 60 wt% hBN loaded non-hybrid counterpart, the current specimens exhibit an increase of 22.6% in terms of tensile strength. Meanwhile, the through-plane thermal conductivity performance of this non-hybrid hBN/PEEK sample (1.9 W/(m.K) 15 ) and the hybrid 50B-10T specimen (1.78 W/(m.K)) remain comparable. Thus, by utilizing hybrid compositions, we can achieve enhanced mechanical performance while simultaneously lowering costs for the PEEK-based thermal management materials.…”

Improvement of “point‐plane”‐like hetero‐structured fillers on thermal conductivity of poly(vinyl alcohol) composites

“…Nevertheless, excessively high‐BNNS loading results in a loss of mechanical characteristics and increases the complexity and cost of processing composites. [ 31 ]…”

“…Nevertheless, excessively high-BNNS loading results in a loss of mechanical characteristics and increases the complexity and cost of processing composites. [31] In order to take advantage of the anisotropic heat conduction of BNNSs, various strategies have been dedicated to obtaining the well-ordered arrangement of BNNSs, such as magnetic field, [32] ice template, [33] vacuum-assisted, [34] doctor blading, [35] electrospinning [36] and 3D Printing. [37] Recent research has drawn considerable attention to hetero-structured fillers due to the synergistic improvement effects of avoiding the introduction of interfacial thermal resistances between different fillers and establishing an effective thermal conduction network.…”