Influence of nano-AlN particles on thermal conductivity, thermal stability and cure behavior of cycloaliphatic epoxy/trimethacrylate system

Recent Advances on Thermally Conductive Adhesive in Electronic Packaging: A Review

The application of epoxy adhesive is widespread in electronic packaging. Epoxy adhesives can be integrated with various types of nanoparticles for enhancing thermal conductivity. The joints with thermally conductive adhesive (TCA) are preferred for research and advances in thermal management. Many studies have been conducted to increase the thermal conductivity of epoxy-based TCAs by conductive fillers. This paper reviews and summarizes recent advances of these available fillers in TCAs that contribute to electronic packaging. It also covers the challenges of using the filler as a nano-composite. Moreover, the review reveals a broad scope for future research, particularly on thermal management by nanoparticles and improving bonding strength in electronic packaging.

Tailoring the Thermal Conductivity of Rubber Nanocomposites by Inorganic Systems: Opportunities and Challenges for Their Application in Tires Formulation

The development of effective thermally conductive rubber nanocomposites for heat management represents a tricky point for several modern technologies, ranging from electronic devices to the tire industry. Since rubber materials generally exhibit poor thermal transfer, the addition of high loadings of different carbon-based or inorganic thermally conductive fillers is mandatory to achieve satisfactory heat dissipation performance. However, this dramatically alters the mechanical behavior of the final materials, representing a real limitation to their application. Moreover, upon fillers’ incorporation into the polymer matrix, interfacial thermal resistance arises due to differences between the phonon spectra and scattering at the hybrid interface between the phases. Thus, a suitable filler functionalization is required to avoid discontinuities in the thermal transfer. In this challenging scenario, the present review aims at summarizing the most recent efforts to improve the thermal conductivity of rubber nanocomposites by exploiting, in particular, inorganic and hybrid filler systems, focusing on those that may guarantee a viable transfer of lab-scale formulations to technological applicable solutions. The intrinsic relationship among the filler’s loading, structure, morphology, and interfacial features and the heat transfer in the rubber matrix will be explored in depth, with the ambition of providing some methodological tools for a more profitable design of thermally conductive rubber nanocomposites, especially those for the formulation of tires.

Flexible Nanocomposites Based on Polydimethylsiloxane Matrices with DNA-Modified Graphene Filler: Curing Behavior by Differential Scanning Calorimetry

Novel silicone-based nanocomposites with varied elastic properties were prepared by blending standard polydimethylsiloxane (PDMS) with a lower viscosity component (hydroxyl-terminated PDMS) and integrating a graphene nanoplatelets (GNP) filler modified by strands of deoxyribonucleic acid (DNA). The curing behavior of these nanocomposites was studied by dynamic and isothermal differential scanning calorimetry. The activation energies of the polymerization reactions were determined using the Kissinger method and two model-free isoconversional approaches, the Ozawa-Flynn-Wall and the Kissinger-Akahira-Sunose methods. Results show that the complex trend of the curing behavior can be described using the isoconversional methods, unveiling lower activation energies for the nanocomposites with standard PDMS matrices. The role of the DNA modification of graphene on the curing behavior is also demonstrated. The curing reactions of the nanocomposites with the PDMS matrix are favored by the presence of the GNP-DNA filler. PDMS/PDMS-OH blends generate softer nanocomposites with hardness and reduced elastic modulus that can be tuned by varying the amount of the filler.

Thermal Conductivity and Cure Kinetics of Epoxy-Boron Nitride Composites-A Review

Epoxy resin composites filled with thermally conductive but electrically insulating particles play an important role in the thermal management of modern electronic devices. Although many types of particles are used for this purpose, including oxides, carbides and nitrides, one of the most widely used fillers is boron nitride (BN). In this review we concentrate specifically on epoxy-BN composites for high thermal conductivity applications. First, the cure kinetics of epoxy composites in general, and of epoxy-BN composites in particular, are discussed separately in terms of the effects of the filler particles on cure parameters and the cured composite. Then, several fundamental aspects of epoxy-BN composites are discussed in terms of their effect on thermal conductivity. These aspects include the following: the filler content; the type of epoxy system used for the matrix; the morphology of the filler particles (platelets, agglomerates) and their size and concentration; the use of surface treatments of the filler particles or of coupling agents; and the composite preparation procedures, for example whether or not solvents are used for dispersion of the filler in the matrix. The dependence of thermal conductivity on filler content, obtained from over one hundred reports in the literature, is examined in detail, and an attempt is made to categorise the effects of the variables and to compare the results obtained by different procedures.

Poly(methyl methacrylate) as an Environmentally Responsive Capping Material for Aluminum Nanoparticles

We present an investigation of the photochemistry of aluminum nanoparticles (Al NPs) capped with poly(methyl methacrylate) (PMMA). Powder X-ray diffraction and Fourier transform infrared spectroscopy with total attenuated reflection confirm the presence of crystalline aluminum cores and the PMMA cap and allow us to confirm the latter's photodegradation upon exposure to UV light. The PMMA-Al NPs were also characterized by differential scanning calorimetry coupled with thermogravimetric analysis to study the thermal profiles for polymer combustion and metal oxidation exotherms. Transmission electron microscopy confirms that the Al NPs, around 36 nm in diameter, are embedded in the PMMA matrix. Following UV irradiation, the PMMA-Al NPs react considerably faster with alkaline solutions, compared with unphotolyzed samples. Photoactivation of the nanocomposite induces partial decomposition of the PMMA capping layer, exposing the underlying reactive metal cores to the surrounding environment and accelerating its redox reactivity. Photolysis times of 1, 6, 24, and 52 h were investigated to establish a minimum UV exposure time for the activation of the PMMA-Al NPs toward hydrolytic hydrogen gas generation.

Sulphur and peroxide vulcanisation of rubber compounds – overview

Vulcanisation is a process of transforming a plastic rubber compound into a highly elastic product by forming a three-dimensional cross-linked network structure in the rubber matrix. Many systems have been developed to vulcanise rubber compounds, among which sulphur and peroxide curing systems remain the most desirable. The application of sulphur systems leads to the forming of sulphidic cross-links between elastomer chains, while carbon–carbon bonds are formed in peroxide-curing. Both vulcanisation systems provide certain benefits to the cross-linked rubber articles, but also some disadvantages. The present work seeks to provide an overview on both vulcanisation systems; their composition, possibilities of their application, reaction mechanisms, structure of the cross-links formed and the main feature of the final cross-linked materials – vulcanisates.

Enhanced thermal properties in a hybrid graphene–alumina filler for epoxy composites

The inclusion of hybrid LCPBI/RGO and Al₂O₃-APS fillers into a polymer matrix with formation of composites has proven to be an efficient way to improve thermal properties of the composites.

Peroxide vulcanization of natural rubber. Part II: effect of peroxides and co-agents

Four types of peroxides in combination with two types of co-agents were used as cross-linking agents for the preparation of rubber compounds based on natural rubber. The effects of Type I and Type II co-agents on cross-linking and physical-mechanical properties of vulcanizates were investigated. The correlation between mechanisms of the interaction of co-agents with the rubber matrix in relation to the characteristics of tested systems was discussed. The results showed that the Type I co-agent influenced the rate and the state of cure. Physical-mechanical properties were improved by addition of the Type I co-agent. By contrast, the Type II co-agent had no contribution to the rate and state of cure. Moreover, physical-mechanical properties of vulcanizates deteriorated in the presence of this type of co-agent.

Development of Thermally Conductive Polymer Materials and their Investigation

In the recent years a remarkable development can be observed in the electronics. New products of electronic industry generate more and more heat. To dissipate this heat, thermally conductive polymers offer new possibilities. The goal of this work was to develop a novel polymer based material, which has a good thermal conduction. The main purpose during the development was that this material can be processed easily with injection molding. To eliminate the weaknesses of the traditional conductive composites low-melting-point alloy was applied as filler. Furthermore in this work the effect of the filler content on thermal conductivity, on structure and on mechanical properties was investigated.