Highly thermally conductive boron nitride@UHMWPE composites with segregated structure

Abstract

Highly thermally conductive boron nitride (BN)@ultra-high molecular weight polyethylene (UHMWPE) composites with the segregated structure were fabricated by powder mixing and hot pressing. Scanning electron microscopy and polarizing optical microscopy were used to analyze the dispersion of BN particles in the UHMWPE matrix. The morphology observation shows that BN particles are selectively located at the interfaces of UHMWPE particles and form continuous thermally conductive networks after the compression molding process. As a result, the thermal conductivity of the BN@UHMWPE composite increases to 3.37 W m−1 K−1 with 38.3 vol% BN, which is seven times larger than that of the pure UHMWPE. Furthermore, the incorporation of BN also influences the crystallinity and thermal properties of UHMWPE.

Enhancement of mechanical properties of ultra‐high molecular weight polyethylene nanocomposites without losing thermal stability

“…The translucent spaces among the dark lines are the polymeric grains, as previously reported by many authors. 3,5,18,27,29,30,34,36,44 This image demonstrates that the mixture between the polymer and the nanoparticles does not occur at the molecular level. As previously shown in the scanning electron microscopy images (Figure 2), the images from the optical microscope also evidenced that the nanoparticles only covered the polymer grains during the mixing process.…”

“…The structure and properties of the materials are susceptible to the processing methods; therefore, a large number of references [3][4][5]9,12,[18][19][20][21][22][23][24][28][29][30] were used to adopt a procedure similar to commonly published approaches. A hydraulic hot press was used to make specimens with dimensions of 10 mm  10 mm  1 mm.…”

“…This observation agrees with previous works, which show the same behavior when mixing UHMWPE powder with boron nitride particles and graphene nanoplatelets. 5,11,18,34…”

“…2 On the other hand, these particular structural characteristics cause the low processability of this polymer due to extremely high viscosity. Its processing temperature is frequently 70 C, over its melting temperature [3][4][5] ; otherwise, the macromolecules could not flow, and the polymer would not be molded. Furthermore, these molding processes are not fast and require the thermal stability of the polymer to keep its structure during the molding process.…”

“…As previously said, UHMWPE requires specific processing conditions under relatively high temperatures, which may lead to thermal degradation of the macromolecular chains when combined with other materials. On this point, it is worth noting that, in most investigations, many authors [3][4][5]9,[18][19][20][21][22][23][24] performed a thermal analysis of composite polymers but reached conclusions on thermal performance without considering a series of relevant details concerning the production route and the measurement and characterization methods. Some works in the literature have already shown changes in the thermal stability of the UHMWPE matrix by adding Al 2 O 3 microparticles and B 4 C nanoparticles individually.…”