Application of high impregnation characterization of a cyclic butylene terephthalate oligomer resin for electrically and thermally conductive composites simultaneously reinforced with continuous fiber and nanocarbon fillers

Interests in polymerizable, low-viscosity oligomer resins are increasing in fibers and composites fields because high impregnation characteristics of polymer matrices are important for continuous fiber reinforced composites. In this presentation, applications of high impregnation characterization of the polymerizable, low-viscosity cyclic butylene terephthalate (CBT) oligomer resin to continuous carbon fiber fabric and carbon nanotube mat composites, respectively, are introduced. High-speed mass production of the continuous carbon fiber reinforced composites (CCFRCs) is required to achieve high-level weight savings by substituting metallic or ceramic automotive parts with CCFRCs. The high-speed production of thermoplastic CCFRCs with a processing time of only 2 min using the polymerizable, low-viscosity thermoplastic CBT resin is proposed. Since a high carbon fiber content of 70 vol % could be achieved with few pores and defects into the CCFRCs caused by the initial low molten viscosity and high impregnation characteristic of the CBT resin, excellent mechanical properties were obtained in the CCFRCs such as a tensile strength of 440 MPa and an impact strength of 44 KJ/m² despite the reduced processing time. Also, the electrically and thermally conductive CCFRCs simultaneously reinforced with nanocarbon fillers were successfully fabricated by modifying the proposed processing. To improve the processability of a thermoplastic carbon nanotube (CNT) mat composite (CNTMC) using the polymerizable, low-viscosity CBT resin, a fabrication method was suggested and the structure-property relationship of the prepared CNTMC were evaluated. Excellent electrical, thermal and mechanical properties were obtained in the in-plane direction of the CNTMC due to the continuously and completely connected CNTs incorporated into the CNT mat filler and composite. The thermal diffusivity in the in-plane direction was 15.3 × 10^-6 m²s^-1 for the CNTMC prepared under a compression of 36 MPa at 250 ℃ for 2 min and the result was larger than that of alumina, a ceramic material. The properties were influenced by the internal structure of CNTMC such as the development of the morphology, alignment and weight fraction of the CNT mat within CNTMC.