The effect of the titanium dioxide nanoparticles on the morphology and degradation of polyamide 6 prepared by anionic ring-opening polymerization

Thermoplastic Resin Transfer Molding can be used to produce polyamide 6-based composites from epsilon-caprolactam by anionic ring-opening polymerization. However, the service life and applicability of these composites are limited because polyamide 6 is sensitive to UV radiation. Therefore, we analyzed the effect of nanosized titanium dioxide on the UV stability of polyamide 6 produced from epsilon-caprolactam. Despite the very low viscosity of caprolactam, we dispersed nanoparticles homogeneously in it before producing polyamide 6 from it. We have shown that both structural and chemical changes occur in the material under UV exposure. We proved that UV irradiation increases the crystalline fraction of the samples. This is caused by the shortening of the polymer chains. The crystalline fraction increases less with the addition of TiO2, which shows its UV protective effect. The particles prevent the rays from reaching the inside of the sample, producing a chalking effect on the surface. We analyzed and proved the chemical change in the samples by FTIR and color measurement. Our results showed that surface-treated titanium dioxide was more stable, and the ideal filler content was about 0.6 w/w%, above which photodegradation accelerated. This can be attributed to the photocatalytic activity of the titanium dioxide particles.