Carbon nanotubes (CNTs) were synthesized by a chemical vapor deposition technique at a broad range of temperatures, i.e. 550ºC to 950ºC (at 100ºC intervals). CNTs were synthesized by flowing source and carrier gases (ethane, argon, and hydrogen) over Fe catalyst in a quartz tubular reactor. CNTs were melt-mixed with a polyvinylidene fluoride (PVDF) matrix in the 2mL APAM mixer. The resulting nanocomposites were then compression molded, and electrically and morphologically characterized. Moreover, a wide range of characterization techniques were employed to obtain detailed information about the physical and morphological characteristics of CNTs. It was surprisingly observed that, despite the ascending trend of powder conductivity with synthesis temperature (11.0 - 40.3S∙cm-1), the nanocomposites made with (CNT)650ºC had significantly lower percolation threshold (around 0.5wt.%) and higher electromagnetic interference shielding (20.3dB over the X-band for 1.1mm thickness), compared to the other temperatures. The characterization of nanofillers showed that the synthesis yield and quality of (CNTs)650ºC were superior to CNTs synthesized at 550ºC. At 750ºC and higher, most of the carbonaceous materials synthesized had planar rather than tubular graphitic structure. These findings were attributed to sintering and coalescence of catalyst particles at high synthesis temperatures. It was also observed that dispersion state of (CNT)650ºC within the PVDF matrix was much better than that of CNTs made at the other temperatures. Superior electrical properties of (CNT)650ºC can be attributed to a combination of high synthesis yield, aspect ratio, and crystallinity of CNTs coupled with good state of dispersion within the PVDF matrix. Moreover, it was found that the inferior electrical properties of the nanocomposites made with planar graphitic materials synthesized at high temperatures were due to lack of intercalation and exfoliation of the more platelet-like nanomaterials.