Study of Optimum Process Conditions for Production of Thermally Conductive Polymer Compounds Using Boron Nitride
Year: 2010
Type: article
Abstract: Boron Nitride (BN) is widely used in thermal management applications involving thermoplastic polymeric articles.BN platelet agglomerates give higher through-plane thermal conductivity and more isotropic thermal conduction than single crystal powder grades.However, the agglomerates are relatively weak and susceptible to attrition when subjected to aggressive shearing in processing flows.Thus, it is imperative that compounding of BN with polymer and subsequent processing of the compounds should be carried out below a critical shear stress level in order to preserve the agglomerate structures and to obtain isotropic thermal conduction.This study focuses on identification of the critical hydrodynamic stress level for BN agglomerate attrition and its effect on the thermal conductivity of the composites produced by extrusion compounding and injection molding.Two agglomerate grades of BN viz.PT350 and CF400 with different mean particle sizes were used as fillers in polycarbonate (PC) at different filler loadings.Shear experiments were carried out in rotational and capillary rheometers and the status of BN particle breakdown was analyzed using Scanning Electron Microscopy (SEM) images.The results of shear experiments in rheometric flows revealed that morphology of BN particles and thermal conductivity of the composites strongly depended on the shear stress encountered.The particle size distribution and thermal conductivity measurements revealed that considerable breakage of agglomerates occurred during extrusion and injection molding which affected through iv plane conductivity of the composites.The in-plane conductivity was seen to increase with injection speed due to particle orientation during injection molding.The in-plane thermal conductivity as high as 2.47 W/mK around twelve times higher than neat polycarbonate was obtained with 35 wt% loading of boron nitride.It was also found that polycarbonate filled with 35 wt%PT350 and 25 wt%CF400 showed an increase in modulus by 87% and 53% respectively.However, the impact strength and elongation at break decreased by more than an order of magnitude.vDEDICATION Dedicated to my parents -Vidhi and Mahinder Bahl and my brother -Varun Bahl for their everlasting love and support….. vi
Author: Kushal Bahl
Institution: University of Akron
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2616028362