Stabilization and Carbonization of Rayon Fabrics and PAN-Based Nanofiber Webs, Characterization, and The Composites Chae Wook Cho Department of Polymer Science and Engineering, Graduate School Kumoh National Institute of Technology Abstract Although PANbased and pitchbased carbon fibers have been ...
Stabilization and Carbonization of Rayon Fabrics and PAN-Based Nanofiber Webs, Characterization, and The Composites Chae Wook Cho Department of Polymer Science and Engineering, Graduate School Kumoh National Institute of Technology Abstract Although PANbased and pitchbased carbon fibers have been dominantly used, rayonbased carbon fibers have been critically utilized in many key material components in military and aerospace applications due to their unique advantages in less thermal conductivity and good interfacial adhesion with thermosetting resins, especially with phenolic resins. Stabilization process, which is normally conducted in the temperature region below 400°C, is an extremely important step to convert the precursor fibers into chemically and physically stable carbon fibers during subsequent carbonization processes. It may be a determining stage for successful production of the carbon fibers because rayon precursor fibers lose their weight a lot and thermally shrink tremendously during the stabilization process, causing significant changes of chemical, physical, microstructural and thermal characteristics. An isothermal stabilization process performing much below than 400℃, for example at 200℃, may be useful as a longterm batch process for obtaining acceptable rayonbased stabilized fibers and then the carbon fibers. Consequently, the objectives of the present study are first to explore the isothermal stabilization processes at below 200℃ using rayon precursor fabrics in the absence and presence of chemical pretreatment and also to examine the chemical, physical, thermal and microstructural characteristics of the stabilized and the carbonized rayon fabrics. The study is extended to investigate the effect of nitric acid treatment on the thermal stability, thermal expansion behavior, dynamic mechanical property, flexural property, and fracture surfaces of carbon fabric/phenolic composites. During the last years, a few studies have reported on preparing and characterizing carbon nanofiber webs from electrospun PANbased nanofiber webs. PAN nanofiber webs have the greater specific surface area with a much smaller fiber diameter in comparison with conventional PAN fibers. Stabilization and carbonization processes of electrospun PANbased nanofiber webs are critically important to obtain useful carbon nanofiber webs. No reports on fabricating and characterizing polymer composites interleaved with layers of carbon nanofiber web (CNFW) have been found. Consequently, the objectives of the second part of the present work are, for the first time, to fabricate novel PANbased carbon nanofiber web/polymer composites and also to investigate their electrical resistivity and the thermal properties like thermal stability, dynamic storage modulus and coefficient of thermal expansion. The composites consist of electrospun, stabilized and then carbonized PANbased nanofiber webs and high density polyethylene (HDPE), polypropylene (PP) and polycarbonate (PC) as thermoplastic polymer matrices. The most interesting result is that both the surface and volume resistivites of HDPE, PP and PC were remarkably reduced by the introduction of threedimensionally networked carbon nanofiber webs uniformly dispersed in each polymer matrix of the composite system, as well as the improved thermal properties.
Stabilization and Carbonization of Rayon Fabrics and PAN-Based Nanofiber Webs, Characterization, and The Composites Chae Wook Cho Department of Polymer Science and Engineering, Graduate School Kumoh National Institute of Technology Abstract Although PANbased and pitchbased carbon fibers have been dominantly used, rayonbased carbon fibers have been critically utilized in many key material components in military and aerospace applications due to their unique advantages in less thermal conductivity and good interfacial adhesion with thermosetting resins, especially with phenolic resins. Stabilization process, which is normally conducted in the temperature region below 400°C, is an extremely important step to convert the precursor fibers into chemically and physically stable carbon fibers during subsequent carbonization processes. It may be a determining stage for successful production of the carbon fibers because rayon precursor fibers lose their weight a lot and thermally shrink tremendously during the stabilization process, causing significant changes of chemical, physical, microstructural and thermal characteristics. An isothermal stabilization process performing much below than 400℃, for example at 200℃, may be useful as a longterm batch process for obtaining acceptable rayonbased stabilized fibers and then the carbon fibers. Consequently, the objectives of the present study are first to explore the isothermal stabilization processes at below 200℃ using rayon precursor fabrics in the absence and presence of chemical pretreatment and also to examine the chemical, physical, thermal and microstructural characteristics of the stabilized and the carbonized rayon fabrics. The study is extended to investigate the effect of nitric acid treatment on the thermal stability, thermal expansion behavior, dynamic mechanical property, flexural property, and fracture surfaces of carbon fabric/phenolic composites. During the last years, a few studies have reported on preparing and characterizing carbon nanofiber webs from electrospun PANbased nanofiber webs. PAN nanofiber webs have the greater specific surface area with a much smaller fiber diameter in comparison with conventional PAN fibers. Stabilization and carbonization processes of electrospun PANbased nanofiber webs are critically important to obtain useful carbon nanofiber webs. No reports on fabricating and characterizing polymer composites interleaved with layers of carbon nanofiber web (CNFW) have been found. Consequently, the objectives of the second part of the present work are, for the first time, to fabricate novel PANbased carbon nanofiber web/polymer composites and also to investigate their electrical resistivity and the thermal properties like thermal stability, dynamic storage modulus and coefficient of thermal expansion. The composites consist of electrospun, stabilized and then carbonized PANbased nanofiber webs and high density polyethylene (HDPE), polypropylene (PP) and polycarbonate (PC) as thermoplastic polymer matrices. The most interesting result is that both the surface and volume resistivites of HDPE, PP and PC were remarkably reduced by the introduction of threedimensionally networked carbon nanofiber webs uniformly dispersed in each polymer matrix of the composite system, as well as the improved thermal properties.
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