Original and/or functionalized nanosilica particles (NSI^x, FNSI^x_(my)) with a quoted specific surface area of 100, 300 and 600 m^2/g, respectively, were used to investigate the influence of specific surface areas of nanosilica particles on ultradrawing and ultimate tensile properties of UHMWPE (F100), UHMWPE/nanosilica (F_(100)NSI^x_z) and UHMWPE/functionalized nanosilica (F_(100)FNSI^x _(my-z)) fibers. The specific surface areas of well dispersed FNSI^x _(my) nanofillers in F_(100)FNSI^x_(my-z) fibers can positively affect their ultradrawing, orientation, ultimate tensile properties and “micro-fibrils” morphologies. Excellent orientation and ultimate tensile properties of UHMWPE/nanofiller fibers can be prepared by ultradrawing the F_(100)FNSI^x _(my-z) as-prepared fibers with optimal contents of the best prepared FNSI^x _(my) particles well dispersing in the as-prepared fibers. The ultimate tensile strength (σ_f) value of the best prepared F_(100)FNSI^(600)_(m9-0.0375) drawn fiber reaches 7.6 GPa, which is about 1.7 and 2.3 times of those of the F_(100)FNSI^(100)_(m3-0.075) and the best prepared F_(100) drawn fibers without addition of any nanofiller. Specific surface area, morphological and Fourier transform infrared analyses of NSI^x, FNSI^x_(my) particles and/or investigations of thermal, orientation factor and ultimate tensile properties of as-prepared and/or drawn F_(100)FNSI^x_(my-z) fibers were performed to understand the above improved ultradrawing and ultimate tensile properties of the F_(100)FNSI^x _(my-z) as-prepared and/or drawn fibers.
