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Polymers are known as thermally insulated materials with reported effective thermal conductivity (K eff ) in the range of 0.1 to 0.5 Wm À1 K À1 . However, increasing demand for smaller and more powerful electronics has created the need for thermally conductive polymers for use in heat exchangers and electronic packaging applications. Given this background, much research has been done over the past two decades to increase the K eff of polymers. Based on the strategy involved, those works can be divided into two main categories:(i) increasing the K eff of the neat polymer by aligning its chains orientation; and (ii) increasing polymer K eff by fabrication of polymeric composites with thermally conductive filler networks. Among these two strategies, the former is limited to nanoscale laboratory research and is difficult to scale up for mass production. Therefore, this work is mainly focused on the latter category, thermally conductive polymeric composites, which has a higher potential for large-scale production. This work aims to summarize, evaluate, and highlight the successful strategies of the recent efforts in enhancing the thermal conductivity of polymer composites. The major achievements, future challenges, and the outlooks of high thermally conductive polymeric composites are presented by analyzing the results of about 300 works.

A continuous extrusion devulcanization process has been developed by using supercritical CO2. Experiments have been carried out on an industrial scale twin screw extruder to study the effects of processing conditions on the properties of devulcanized rubber. Using a fractional factorial design in three levels, the effects of process temperature, screw speed, and feed rate on the sol fraction, degree of devulcanization, Mooney viscosity, and tensile properties of devulcanized rubber have been investigated. The significance of the effects of the processing conditions decreases in the following order: flow rate, screw speed, and process temperature. Similar trends are noted for different responses with the exception of tensile properties. The observed relationship between the sol fraction and the degree of crosslinking in the rubber samples before and after devulcanization points to a highly selective disruption of the sulfur crosslinks in the rubber network during devulcanization rather than a random network scission. Mooney viscosity has been found to be in excellent agreement with the network structure properties, sol fraction, and degree of devulcanization.

A growing concern of climate change and waste pollution is causing a shift in products towards green materials. The automotive industry is exploring environmentally friendly alternatives to glass fibers (GF). This research focuses on understanding interactions between constituents of biocomposites made up of basalt fiber (BF) and hemp hurd particle fiber (HF) reinforced polypropylene (PP), and statistically comparing the mechanical properties. The addition of a coupling agent has significantly improved the performance and fiber-matrix interactions in the biocomposite blends. The elastic modulus of some BF/HF/PP mixtures were comparable to the GF/PP composite; however, the GF still outperformed in strength. Rotational and capillary rheometer analysis determined the viscosities of all formulations displaying that basalt composites were consistently lower in viscosity than the glass fiber composite, indicating easier processing conditions.