Polycarbonate (PC)/vapor‐grown carbon fiber (VGCF™) composite was prepared through melt compounding. It was unexpectedly found from differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) that the crystallization of PC was substantially accelerated in the presence of the ordered graphite surface of VGCF™. To make an aligned structure of PC crystallization together with the orientation of VGCF™, a magnetic field of 2.4 T was applied to the composite under several temperature profiles. The WAXD pattern revealed that not only dispersed VGCF™ but also matrix PC crystallization was magnetically aligned through the optimization of processes. The evidence for PC crystallization by VGCF™ with and without magnetic force is described.
ABSTRACT:The influence of filler types and concentration on the foaming structure was investigated using a batch method to penetrate CO 2 in ABS polymer matrix. Vapor grown carbon fiber (VGCF Ò , averaged diameter = 150 nm), and calcium carbonate (averaged particle diameter = 1.8 mm) were used as fillers and the concentration was changed from 5 to 15 wt %, respectively. Vapor grown carbon fiber or calcium carbonate was compounded with ABS using an extruder and samples were made by hot press method. Foamed samples, whose density reduction showed about 30-40%, were made by controlling preparation conditions. In the case of vapor grown carbon fiber/ABS systems, the average diameter of foaming cell decreased, and the cell density increased as a function of fiber concentration. On the other hand, by the incorporation of calcium carbonate, the diameter increased, and density decreased with higher concentration. The initial nucleation stages of foaming from fillers were carefully observed for fillers having large aspect ratio and particle shape. Based on the evidences from optical microscope observation, the different tendency of cell diameter between the two systems as a function of concentration was discussed.
ABSTRACT:It is known that polycarbonate (PC) is categorized as amorphous polymer and pure PC crystallizes extremely slowly. However, we have recently found that the crystallization of PC was substantially accelerated around 200 C in the presence of vapor grown carbon fiber (VGCF), having ultra thick multi-walled carbon nanotube (MWCNT) structure. To examine the accelerated crystallization by VGCF, the effect of pre-graphitized VGCF, carbon black, and mesophase pitch based carbon fiber (CF) on the crystallization was evaluated. In addition, polarized optical microscope observation was performed by using PC including magnetically oriented VGCF. It was suggested that the surface of ordered graphite structure from VGCF or CF induced the oriented crystallization of PC along the axial direction of VGCF or CF. To utilize the accelerated oriented crystallization of PC by CF, PC sheet having oriented crystallized surface PC layer was made by annealing the stacked structure of PC sheet and oriented CF sheet at 200 C.The PC sheet, whose surface was crystallized along CF axial direction, was successfully produced, showing retardation property by polarized optical microscope.
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