Textiles, with appropriate light absorbers and suitable finishing methods, can be used as ultraviolet (UV) protection materials. In this study, we investigated the effects of nano-TiO2 particles on the LTV-protective and structural properties of polypropylene (PP) textile filaments. Master batches of PP/TiO2 nanoparticles were prepared by melt compounding before spinning, and filaments incorporating 0.3, 1, and 3% TiO2 nanoparticles were spun in a pilot melt-spinning machine. The structural properties of the nanocomposite fibers were analyzed with scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and tensile tests. The UV-protection factor was determined to evaluate the UV-protective properties of the filaments. In conclusion, although the structure and mechanical properties of the nanocomposite filaments were slightly affected by the addition of nano-TiO2, the UV-protective properties of the PP filaments improved after treatment with nano-TiO2, and the nanocomposite filaments exhibited excellent UV protection. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 152-157, 2010