Preparation of photochromic isotactic polypropylene filaments: influence of drawing ratio on their optical, thermal and mechanical properties

In this research, metallocene catalyst isotactic polypropylene (miPP) filaments were produced with different concentrations of photochromic pigments to develop ultraviolet (UV) sensing materials. The produced miPP filaments showed good photochromic response under UV irradiation. In this work, six drawing ratios were applied to get the final product (miPP filament). Resultant filaments showed significant photochromic responses, such as Kubelka–Munk values (K/S). The interesting observation was that the photochromic response was indirectly proportional to the applied drawing ratio. The photochromic color build was found to be maximum with the highest concentration of pigment as well as the lowest drawing ratio. Overall, it was observed that the thermal properties were significantly dependent on the drawing ratio. The changes in thermal properties, such as T_m, ΔH_m and ΔS_m, for miPP filaments in dependence on photochromic pigment concentration was significantly less as compared to the drawing ratios. The thermal properties improved with the drawing ratio, which directly influenced the crystallinity of produced miPP filaments. The addition of photochromic pigment to the miPP filaments increased the crystallinity by 14%. Also, the lamella thickness increased with increasing the drawing ratio. However, there was no significant effect of pigment concentration on lamella thickness. In this experimental work, the impact of drawing ratio on the optical, thermal and mechanical properties of photochromic miPP filaments was investigated.