Jasmee, Solehah (2023) Characterisation of hybrid graphene nanoplatelets with functionalised boron nitride as thermal interface material. Doctoral thesis, Universiti Teknikal Malaysia Melaka.
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Abstract
Conductive fillers with a polymer matrix or Thermal Conductive Adhesive (TCA) have met most of the ideal criteria due to being ecologically friendly, reliable, and affordable. However, this effort may not yet lead to a significant technology breakthrough due to the low thermal conductivity of the polymer and the high filler loading used in a single-filled composite. Hence, it has heightened the need for hybrid fillers with extraordinary properties, such as boron nitride (BN) and graphene nanoplatelets (GNPs), at varying sizes with the incorporation of silane-modified BN (fBN) to improve composite’s properties. Yet, the affirmative review shows very few studies have reported on the hybrid composite GNPs with fBN at different filler sizes and lower filler loading (<20 wt.%), as well as its suitable processing parameter and important characterization such as rheological, water absorption, and adhesion strength with and without moisture. Thus, this study seeks to determine the curing time, temperature, and mixing method of the composite, percolation threshold of thermal conductivity of single composite GNPs, BN, and fBN, and thermal conductivity of hybridized GNPs with BN or fBN below filler loading of single composite and also to characterize the rheological properties, adhesion strength (single lap joint (SLJ) approach) and failure mechanism of hybridized GNPs with BN or fBN composite at ambient and 100% humidity conditions. The hybrid composites were prepared by hybridizing different ratios of GNPs (5 μm and 15 μm) with BN or fBN (10 μm) that were modified using silane coupling agents (KH550 and KH560). KD2 Pro and Anton Paar Rheometer MCR 72 were used to measure thermal conductivity and rheological properties, while the SLJ test was prepared and accordance with ASTM D1002, ASTM D 1151, ASTM D 5229/D 5229M, and EN ISO 10365 standards. The result indicates that hybrid GNPs15/fBN_KH560 composites exhibit the highest thermal conductivity (1.16 ± 0.02 W/mK) at a GNPs15 ratio 0.75. However, hybrid GNP5 composites have a higher shear strength than hybrid GNP15 composites at all GNPs ratios, with the highest values reported being 1.20 ±0.10 MPa and 1.14 ± 0.15 MPa at GNPs ratio of 0.75 with fBN_KH560. The bigger filler size of GNPs may help to transfer heat, but smaller fillers are preferable to transfer stress. The failure mechanisms like plastic void growth, crack deflection, particle debonding, and pull-out mechanism also help promote cohesive failure in the hybrid composite. Hybrid GNP15 composites have high shear strength and absorb more water than hybrid GNP5 but can sustain for 30 days before reaching equilibrium. The larger filler particle fills the gaps between the epoxy, reducing the formation of cracks or voids. Nevertheless, moisture still caused the shear strength of composites to reduce (0.39 ± 0.05 MPa). In summary, the properties of hybrid composites containing fBN_KH560, especially at GNPs ratio of 0.75, show outstanding properties due to high compatibility between fBN_KH560 and the polymer matrix, proven by the lowest measured contact angle, and Hansen solubility parameter difference, well-dispersed filler, and better wetting properties (lowest viscosities varies shear rate) in rheological analysis.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | Materials, Thermal properties, Graphene, Boron nitride |
| Divisions: | Library > Tesis > FKM |
| Depositing User: | MUHAMAD HAFEEZ ZAINUDIN |
| Date Deposited: | 24 Apr 2024 16:20 |
| Last Modified: | 24 Apr 2024 16:20 |
| URI: | http://eprints.utem.edu.my/id/eprint/27298 |
| Statistic Details: | View Download Statistic |
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