Ye Ji Noh

Ultra-high dispersion of graphene in polymer composite via solvent freefabrication and functionalization

The drying process of graphene-polymer composites fabricated by solution-processing for excellent dispersion is time consuming and suffers from a restacking problem. Here, we have developed an innovative method to fabricate polymer composites with well dispersed graphene particles in the matrix resin by using solvent free powder mixing and in-situ polymerization of a low viscosity oligomer resin. We also prepared composites filled with up to 20 wt% of graphene particles by the solvent free process while maintaining a high degree of dispersion. The electrical conductivity of the composite, one of the most significant properties affected by the dispersion, was consistent with the theoretically obtained effective electrical conductivity based on the mean field micromechanical analysis with the Mori-Tanaka model assuming ideal dispersion. It can be confirmed by looking at the statistical results of the filler-to-filler distance obtained from the digital processing of the fracture surface images that the various oxygenated functional groups of graphene oxide can help improve the dispersion of the filler and that the introduction of large phenyl groups to the graphene basal plane has a positive effect on the dispersion.

Silica Aerogel/Polyimide Composites with Preserved Aerogel Pores Using Multi-Step Curing

Abstract

Carbon nanotube mat reinforced thermoplastic composites with a polymerizable, low-viscosity cyclic butylene terephthalate matrix

A fabrication method was developed to enhance the processability of a thermoplastic composite reinforced with a carbon nanotube (CNT) mat using an in situ polymerizable low-viscosity cyclic butylene terephthalate (CBT) oligomer. We obtained excellent electrical, thermal, and mechanical properties in the in-plane direction of the prepared CNT mat composites. For the CNT mat composites, the highest thermal diffusivity of 1.53×10−5 m2/s was obtained in the in-plane direction due to the continuously and fully connected CNTs within the CNT mat filler and the value was higher than that of alumina. The properties depended on the internal structure of the composites, such as the development of the morphology, waviness, and weight fraction of the CNT mat within the composites. These excellent properties were revealed under optimum processing conditions with combined high compression pressure, short processing time, and quenching to induce an ideal structure in the CNT mat within the composites.

Improved Electrical Conductivity of a Carbon Nanotube Mat Composite Prepared by In-Situ Polymerization and Compression Molding with Compression Pressure

A fabrication method to improve the processability of thermoplastic carbon nanotube (CNT) mat composites was investigated by using in-situ polymerizable and low viscous cyclic butylene terephthalate oligomers. The electrical conductivity of the CNT mat composites strongly depended on the compression pressure, and the trend can be explained in terms of two cases, low and high compression pressure, respectively. High CNT mat content in the CNT mat composites and the surface of the CNT mat composites with fully contacted CNTs was achieved under high compression pressure, and direct contact between four probes and the surface of the CNT mat composites with fully contacted CNTs gave resistance of 2.1 Ω. In this study the maximum electrical conductivity of the CNT mat composites, obtained under a maximum applied compression pressure of 27 MPa, was 11 904 S m -1 , where the weight fraction of the CNT mat was 36.5%.

High-speed fabrication of thermoplastic carbon fiber fabric composites with a polymerizable, low-viscosity cyclic butylene terephthalate matrix for automotive applications

A weight savings of approximately 30% of the total weight of an automobile can be achieved if high-speed mass production of the continuous carbon fabric reinforced composites (CCFRCs) is possible. In this study, we analyzed the high-speed production of thermoplastic CCFRCs with a 2 min processing time using a polymerizable, low-viscosity thermoplastic cyclic butylene terephthalate (CBT) resin. Along with the reduced processing time, superior mechanical properties were obtained in the CCFRC specimen, such as a tensile strength of 440 MPa and an impact strength of 44 KJ m−2. This could be achieved because a high carbon fiber content of 70% volume could be reached with few pores or defects in the CCFRC. The proposed high-speed production of the thermoplastic CCFRC can compete with metal pressing due to its short processing time of only a few minutes, which is the time limit currently accepted by the automotive industry.