Mechanical characterisation of hybrid GNPS and functionalised BN as a thermal interface material

Electronic industries are continually striving to miniaturise electronic devices that have high power density in many current technologies. This development has caused significant challenges in the removal of heat generated from the small devices, which gradually caused overheat, especially for the electronic components that have a high working temperature like aircraft, Electric Vehicle (EVs), oil and gas and many more. The heat produce will cause damage which affected its life span. Thermal Interface Material (TIM) with high thermal conductivity is one of the methods to reduce the heat generated. From the past decade, the rapid development of new TIM by using high intrinsic thermal conductivity fillers like Boron Nitride (BN) and Graphene nanoplatelets (GNPs) in polymer composite has surged as a novel Thermally Conductive Adhesive (TCA). The focus on improving the thermal conductivity of TIM of polymer composite has heightened the need to hybridise both BN and GNPs filler at different filler sizes. Besides, modification of filler, especially BN filler, can also improve the properties of composites. However, to the best of author knowledge, very few studies have reported on the mechanical properties of the hybrid GNPs/f-BN polymer composite, especially at high temperature, to which these findings have wider relevance remains unclear. This thesis focuses on determining the thermal conductivity of GNPs/f-BN polymer composites at different filler sizes (GNPs-5 μm and BN-10 μm) and silane coupling agents (KH550 and KH560); to study the mechanical properties of hybrid GNPs/f-BN polymer composites at elevated temperatures. Prior to commencing this study, the thermal conductivity of the polymer composite was done using KD2 Pro Thermal Properties Analyzer before undergoing lap shear test for mechanical analysis by using Instron 8872 Universal Testing Machine (UTM). RT, 150ºC, 200ºC and 250ºC was selected as heating temperatures for mechanical analysis. Field Emission Scanning Electron Microscope (FESEM) was used to examine fillers dispersion because it often affects the thermal and mechanical properties of the polymer composite. The result of thermal conductivity for modified BN fillers shows significant improvement for both single and hybrid polymer composite with the value enhancement up to 37% and 86.4%, respectively. Hybridising GNPs with KH560 modified BN (f_BN_KH560) shows the highest thermal conductivity obtained at 0.37 ± 0.060 W/mK, especially at the ratio of 75-GNPs and 25-BN (75/25). The mechanical strength (shear strength and Young’s modulus) of f-BN has further shown a good improvement than pristine BN, especially for f_BN_KH560 composite, whose shear strength is 0.80 ± 0.02 MPa, while hybrid GNPs/f_ BN_KH560 is 1.20 ± 0.10 MPa. The silane treated on BN was observed to successfully forms a chemical bond between the inorganic particles and the resin, allowing for more efficient stress transfer from the matrix to the fillers. GNPs/f-BN_KH560 that has good filler dispersion reported the highest shear strength and reveals a cohesive failure. However, when the hybrid composites were exposed to a high temperature, the mechanical strength of the modified hybrid composite starts to degrade due to softening effect and shows partial cohesive adhesion. The knowledge gained was believed would be beneficial to extend the use of functionalised BN with GNPs/BN as TIM

Preparation of GNPs thermally conductive adhesive at different epoxy resin/curing agent ratio and mixing method

Reinforcement of GNPs fillers to polymer composite show remarkable improvement in thermal conductivity. However, high aspect ratio of GNPs attributes to agglomerate during the preparation process, which limits its performance. A proper step methodology is in urgent need to improve the interfacial reaction between the polymer matrix and fillers. The factors that play a significant role during preparation are controlling the epoxy resin/curing agent ratio (stoichiometry ratio) to ensure complete curing reaction and an appropriate mixing and processing method to improve dispersion and distribution of fillers. This study focuses on the effect of varying the ratio of polymer/curing agent to its curing reaction and combining the mixing method with solvent-free approach on the performance of the polymer composite. The results show that a complete curing reaction was observed at its stoichiometry ratio, which is ratio 3:1. The GNPs fillers also founded distribute and disperse well, especially when using BS+PCTM at the ratio of 3:1. This mixing method can avoid agglomeration of fillers and improve the interfacial reaction with good contact between filler-filler interface. As a result, the thermal conductivity of BS+PCTM was enhanced compared to BS+UH. The results presented perhaps facilitated improvement in the preparation of high performance of TC

Interface Thermal Resistance And Thermal Conductivity Of Polymer Composites At Different Types, Shapes, And Sizes Of Fillers: A Review

The growing demand toward miniaturization and power device packaging required new die-attach materials with high thermal conductivity (TC). Multitudinous attention is being paid to enhance the TC of thermally conductive polymer composites as it is easy to fabricate and environmentally friendly and has low-cost processability. However, after years of extensive research, it can be concluded that reinforcing different morphologies of fillers (types, sizes, and shapes) into polymer composite creates interfacial thermal resistance (ITR) that greatly constrains the TC value. Thus, this article presents an exhaustive review in minimizing the ITR effect by optimizing the types, sizes, and shapes of the fillers used. This literature also seeks to review the use of different morphologies of fillers in single and hybrid polymer composites. It was found that hybridizing two different fillers shows remarkable TC enhancement due to its synergistic effect and formation of three-dimensional network/conduction path. The size and shape of fillers used play a vital role in improving the TC of the polymer composite compared with the type of filler used due to more contact area created, which significantly reduces the ITR. The results presented here may facilitate improvement in the development of future work for new die attach of the thermally conductive polymer composite