Effects of UV Exposure on the Thermo-Mechanical Properties of Cactus Based Biopolymers

The viability of renewable biopolymers as sustainable alternatives to synthetic plastics is promising, however ultra-violet (UV) radiation can lead to premature degradation and reduction in the material’s performance. Biopolymers comprised of nopal cactus juice, animal protein, natural wax, and glycerin in differing percentages were studied to obtain thermo-mechanical data in relation to UV exposure. To quantify degradation, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy, goniometry and gravimetric measurements were performed. Each formulation experienced mass loss as a result of UV exposure, which could be attributed to water evaporation. The thermogravimetric analysis indicated a reduction in the second onset of degradation for each formulation, but insufficient data prevented validation of conclusive theories. The mechanical testing illustrated minor changes in relation to UV exposure, and indicated that the formulation without glycerin has a significantly higher modulus of elasticity in comparison to the other formulations. The minimal changes observed during the thermo-mechanical analysis did not suggest a decrease in material performance for each formulation up to four weeks of accelerated UV exposure. It is recommended that the UV exposure time be increased, mass measurements be taken during the first few days of exposure, and a more consistent method of sample production be developed.