Influence of molecular orientation direction on the in‐plane thermal conductivity of polymer/hexagonal boron nitride composites

Abstract

The effect of the molecular orientation direction of a polymer matrix on the in‐plane thermal conductivity (TC) of injection‐molded polymer/hexagonal boron nitride (h‐BN) composites is investigated. In this system, the h‐BN platelets align in the in‐plane direction owing to injection shear flow. Three molecular orientations (perpendicular, random, and parallel to the h‐BN plane) are achieved using liquid crystalline polyesters and the in‐plane TCs are compared. Although a parallel orientation of the polymer chains provides the highest TC of the matrix in the injection direction, the TC of the composites is the lowest of the three systems for this orientation. The highest in‐plane TC is found in the perpendicularly oriented system, irrespective of the in‐plane direction. These results reveal that perpendicularly oriented molecular chains serve as effective heat paths between h‐BN platelets that are arranged one above the other, and consequently, a continuous thermal network is created in the in‐plane direction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39768.

Modeling of anisotropic thermal conductivity of polymer composites containing aligned boron nitride platelets: Effect of processing methods

“…The model results well fit with the experimental results from two independent references [ ], in which the composites were prepared by either tape casting or spin casting. However, for the composites prepared by injection molding , large deviation between the model and experimental results was observed. Therefore, in this work, special attention was paid to the filler–matrix structure in the unit cell, which is physically related to the processing methods.…”

“…Different from fillers such as metals and carbon materials, which also possess high electric conductivity, hexagonal boron nitride (h‐BN) has high TC and low electric conductivity , making it a promising filler for preparing thermally conductive and electrically insulative composites. Many studies have been carried out for the preparation and characterization of h‐BN containing polymer composites . Due to the rigid 2D platelet shape and the anisotropic TCs of h‐BN, polymer/h‐BN composites generally have anisotropic TCs, especially when the h‐BN platelets are aligned in the composites with much higher TC along the in‐plane direction than the through‐plane direction.…”

“…For the composites containing the flake‐type h‐BN with the median diameter of 8 μm, the in‐plane and through‐plane TCs achieved 17.5 and 2.2 W/mK at the filler loading of 60 vol%, respectively. Yoshihara et al prepared liquid‐crystalline polyesters (LCPs)/h‐BN composites by injection molding . The in‐plane TC was as high as 23 W/mK at the h‐BN content of 50 vol%, while the corresponding through‐plane TC was only 4 W/mK.…”

Magnetic filler alignment of paramagnetic Fe3O4 coated SiC/epoxy composite for thermal conductivity improvement

“…However, this procedure is not suitable for compounding because of prohibitive manufacturing costs and the thermal damage inflicted on the composite at high temperatures. Yoshihara et al achieved molecular orientation along the injection direction and studied its effect on thermal conductivity [15]. However, this method is not broadly applicable because of the very particular synthesis method, namely extrusion from a processable melt mix thermoplastic matrix.…”

Thermal Conductivity Performance of Polypropylene Composites Filled with Polydopamine-Functionalized Hexagonal Boron Nitride

“…Among them, boron nitride (BN) is one of the most promising ones because it is both thermally conductive and electrically insulative [7, 10–14]. So far, BN has been used in the composites based on various matrices including rubber [15, 16], silicone gel [17], epoxy [18], polyvinyl alcohol (PVA) [13], polyimide (PI) [10], liquid crystalline polyester (LCP) [19], polybenzoxazine [20], polysiloxane[21], polyethylene (PE) [22] and polypropylene (PP) [23]. …”