Study of Coffee Grounds Oil Action in PVC Matrix Exposed to Gamma Radiation: Comparison of Systems in Film and Specimen Forms

<div><p>The poly (vinyl chloride), PVC, undergoes changes in its physicochemical properties when it is exposed to gamma radiation. Thus, the radiolytic stabilization of PVC is one way for obtain a material with radiation resistance. In this work, we studied the coffee grounds oil as PVC radiolytic protection in two systems forms: PVC film and PVC specimen. The systems were irradiated at sterilization dose of medical devices and viscosity measurements were performed. According to viscosity assays of PVC films, there was a 67% protection in polymer matrix promoted by the oil. On the other hand, the mean viscosity molar mass (Mv) of PVC specimens increased about 13%, indicating predominance of crosslinking effect, however samples containing the oil showed no Mv significant changes. Therefore, the oil can be considered a PVC radio stabilizing substance and open a way for use of sustainable additive in PVC industry.</p></div

ZnS Nanocrystals as an Additive for Gamma-Irradiated Poly (Vinyl Chloride)

<div><p>Zinc sulfide (ZnS) was synthesized by sonochemical method and nanoparticles with crystallite size around 2 nm were obtained. PVC containing ZnS nanoparticles at concentrations of 0.10; 0.30; 0.50; 0.7 and 1.00 wt% were gamma irradiated (60Co) at room temperature in air. No appreciable decrease in PVC Viscosity-Average Molar Mass (Mv) was observed for samples containing 0.7 wt% of ZnS nanocrystals. It was demonstrated that the addition of ZnS nanocrystals imparted molecular protection to the polymer matrix while improving flexibility, by decreasing the Young Modulus of PVC films. These results suggest the use of sonochemically synthesized ZnS nanocrystals as a new additive for radiation-grade PVC materials.</p></div

ZnS Nanocrystals as an Additive for Gamma-Irradiated Poly (Vinyl Chloride)

<div><p>Zinc sulfide (ZnS) was synthesized by sonochemical method and nanoparticles with crystallite size around 2 nm were obtained. PVC containing ZnS nanoparticles at concentrations of 0.10; 0.30; 0.50; 0.7 and 1.00 wt% were gamma irradiated (60Co) at room temperature in air. No appreciable decrease in PVC Viscosity-Average Molar Mass (Mv) was observed for samples containing 0.7 wt% of ZnS nanocrystals. It was demonstrated that the addition of ZnS nanocrystals imparted molecular protection to the polymer matrix while improving flexibility, by decreasing the Young Modulus of PVC films. These results suggest the use of sonochemically synthesized ZnS nanocrystals as a new additive for radiation-grade PVC materials.</p></div

Self-Supported Biopolymeric Films Based on Onion Bulb (<i>Allium cepa</i> L.): Gamma-Radiation Effects in Sterilizing Doses

Sterilization is a fundamental step to eliminate microorganisms prior to the application of products, especially in the food and medical industries. γ-irradiation is one of the most recommended and effective methods used for sterilization, but its effect on the properties and performance of bio-based polymers is negligible. This work is aimed at evaluating the influence of γ-radiation at doses of 5, 10, 15, 25, 30, and 40 kGy on the morphology, properties, and performance of bioplastic produced from onion bulb (Allium cepa L.), using two hydrothermal synthesis procedures. These procedures differ in whether the product is washed or not after bioplastic synthesis, and are referred to as the unwashed hydrothermally treated pulp (HTP) and washed hydrothermally treated pulp (W-HTP). The morphological analysis indicated that the film surfaces became progressively rougher and more irregular for doses above 25 kGy, which increases their hydrophobicity, especially for the W-HTP samples. In addition, the FTIR and XRD results indicated that irradiation changed the structural and chemical groups of the samples. There was an increase in the crystallinity index and a predominance of the interaction of radiation with the hydroxyl groups—more susceptible to the oxidative effect—besides the cleavage of chemical bonds depending on the γ-radiation dose. The presence of soluble carbohydrates influenced the mechanical behavior of the samples, in which HTP is more ductile than W-HTP, but γ-radiation did not cause a change in mechanical properties proportionally to the dose. For W-HTP, films there was no mutagenicity or cytotoxicity—even after γ-irradiation at higher doses. In conclusion, the properties of onion-based films varied significantly with the γ-radiation dose. The films were also affected differently by radiation, depending on their chemical composition and the change induced by washing, which influences their use in food packaging or biomedical devices