Effects of Mixing Ratio of Hybrid Carbonaceous Fillers on Thermal Conductivity and Mechanical Properties of Polypropylene Matrix Composites

Cation Bimetallic MOF Anchored Carbon Fiber for Highly Efficient Microwave Absorption

Carbon fiber (CF) is a potential microwave absorption (MA) material due to the strong dielectric loss. Nevertheless, owing to the high conductivity, poor impedance matching of carbon-based  materials results in limited MA performance. How to solve this problem and achieve excellent MA performance remains a principal challenge. Herein, taking full advantage of CF and excellent impedance matching of bimetallic metal-organic frameworks (MOF) derivatives layer, an excellent microwave absorber based on micron-scale 1D CF and NiCoMOF (CF@NiCoMOF-800) is developed. After adjusting the oxygen vacancies of the bimetallic MOF, the resultant microwave absorber presented excellent MA properties including the minimum reflection loss (RLmin) of -80.63 dB and wide effective absorption bandwidth (EAB) of 8.01 GHz when its mass percent is only 5 wt.% and the thickness is 2.59 mm. Simultaneously, the mechanical properties of the epoxy resin (EP)-based coating with this microwave absorber are effectively improved. The hardness (H), elastic modulus (E), bending strength, and compressive strength of CF@NiCoMOF-800/EP coating are 334 MPa, 5.56 GPa, 82.2 MPa, and 135.8 MPa, which is 38%, 15%, 106% and 53% higher than EP coating. This work provides a promising solution for carbon materials achieving excellent MA properties and mechanical properties.

Improved Dynamic Compressive and Electro-Thermal Properties of Hybrid Nanocomposite Visa Physical Modification

The current work studied the physical modification effects of non-covalent surfactant on the carbon-particle-filled nanocomposite. The selected surfactant named Triton™ X-100 was able to introduce the steric repelling force between the epoxy matrix and carbon fillers with the help of beneficial functional groups, improving their dispersibility and while maintaining the intrinsic conductivity of carbon particles. Subsequent results further demonstrated that the physically modified carbon nanotubes, together with graphene nanoplates, constructed an effective particulate network within the epoxy matrix, which simultaneously provided mechanical reinforcement and conductive improvement to the hybrid nanocomposite system. For example, the hybrid nanocomposite showed maximum enhancements of ~75.1% and ~82.5% for the quasi-static mode-I critical-stress-intensity factor and dynamic compressive strength, respectively, as compared to the neat epoxy counterpart. Additionally, the fine dispersion of modified fillers as a double-edged sword adversely influenced the electrical conductivity of the hybrid nanocomposite because of the decreased contact probability among particles. Even so, by adjusting the modified filler ratio, the conductivity of the hybrid nanocomposite went up to the maximum level of ~10^-1-10⁰ S/cm, endowing itself with excellent electro-thermal behavior.

Comparison of the Thermal and Mechanical Properties of Poly(phenylene sulfide) and Poly(phenylene sulfide)-Syndiotactic Polystyrene-Based Thermal Conductive Composites

Syndiotactic polystyrene (SPS) has attracted considerable attention recently due to its high melting temperature, low cost, and relatively low density value. The aim of the study is to reveal whether a blend of PPS and SPS (PPS-SPS) can be used instead of PPS for high thermal stability, high mechanical performance, and high thermal conductive material applications. For this aim, poly(phenylene sulfide)/syndiotactic polystyrene-based carbon-loaded composite materials were prepared using a twin screw extruder. Two carbon-based materials, carbon fiber (CF) and synthetic graphite (SG), were used to improve the mechanical properties and thermal conductivity of the PPS-SPS blends. Through-plane conductivity values of PPS-30SG-10CF and PPS-SPS-30SG-10CF were obtained to be 13.67 and 12.92 W/mK, with densities of 1.55 and 1.50 g/cm3, respectively. It was demonstrated that PPS-SPS blend-based carbon-loaded composites have great potential to be used in thermal management applications with the advantages of relatively low cost and lightweight compared to PPS-based composites.