Linear low‐density polyethylene (LLDPE) crosslinks under irradiation in the range of up to 250 kGy. Crosslinking leads to better chemical and thermal resistance but causes reduction in mechanical performance. To counter this reduction, compounds of LLDPE with thermoplastic elastomers (TPV) were made. Specimens were irradiated with doses reaching from 99 to 231 kGy. Gel content shows a decrease of around 12% for compounds with 20 wt% of TPV compared to pure LLDPE. It is also found that compounds containing 10 wt% TPV experience a 4% higher gel content than predicted. For higher amounts of TPV elongation at break increases from 689% for pure LLDPE to 769% and tensile strength decreases from 31.9 to 30.5 MPa. Under irradiation, a trend to lower elongations and tensile strengths is observed. Elongation at break decreased around 200% and tensile strength around 5 MPa under irradiation. Thermal analysis of TPV showed that while the melting temperature decreases, its crystallinity first rises for doses up to 165 kGy before decreasing. Infrared spectroscopy was used to identify changes in the chemical structure, where evidence of surface oxidation under irradiation is found for all compounds with LLDPE.

When applying electron or gamma irradiation to poly-3-hydroxybutyrate (P3HB), main chain scissions are the dominant material reactions. Though propositions have been made that crosslinking in the amorphous phase of P3HB occurs under irradiation, a conclusive method to achieve controlled additive free irradiation crosslinking has not been shown and no mechanism has been derived to the best of our knowledge. By applying irradiation in a molten state at 195 °C and doses above 200 kGy, we were able to initiate crosslink reactions and achieved gel formation of up to 16%. The gel dose D_gel was determined to be 200 kGy and a range of the G values, the number of scissions and crosslinks for 100 eV energy deposition, is given. Rheology measurements, as well as size exclusion chromatography (SEC), showed indications for branching at doses from 100 to 250 kGy. Thermal analysis showed the development of a bimodal peak with a decrease in the peak melt temperature and an increase in peak width. In combination with an increase in the thermal degradation temperature for a dose of 200 kGy compared to 100 kGy, thermal analysis also showed phenomena attributed to branching and crosslinking.

Biopolyesters such as poly(butylene succinate) (PBS) show great potential to be used as biobased alternatives to conventional petroleum-based polyolefins. To access technical applications, biobased materials are mostly stabilized using conventional additives, which impair their biobased character. Wine grape pomace (WP), a largely unused, low-value by-product of winemaking, shows great potential to improve the thermo-oxidative stability. Since WP is a natural material, annual variations must be considered for its use as stabilizing bio-filler on an industrial scale. This study investigates the impact of annual variations of WP on the stabilizing effects in PBS. WP of two different varieties and three vintages were studied. The composition and properties of the native by-products were analyzed, and WP-based functional fillers were prepared by industrial mill-drying. The bio-fillers obtained were analyzed regarding their physical, thermal, biochemical, and antioxidant properties and blended into PBS with filler contents up to 20 wt.-% by twin-screw extrusion. The biocomposites’ thermal and thermo-oxidative properties were investigated subsequently. All WP varieties and vintages increased the thermo-oxidative stability of PBS by at least 24% at a filler content of 3 wt.-%, demonstrating the potential of WP as a reliable stabilizer. However, the maximum stabilization effect achieved varied slightly. The results of this study showed that minor differences in the bio-filler properties can be related to meteorological data, while the antioxidant activity, pH, and fat content could be used as bioanalytical indicators to evaluate the thermo-oxidative stabilization effects of WP-based functional fillers to enable reliable industrial applications of WP as a polymer stabilizer.

The present study analyses the changes in antioxidative behavior of biodegradable Poly(lactic acid) (PLA)-based composite films with bioactive additives derived from pomegranate peel, an abundant agricultural by-product rich in antioxidants and antimicrobials. PLA-based composites were prepared by incorporating industrial-grade pomegranate peel powder (PoP) via melt extrusion at concentrations of 1–5 percent by weight (wt.%). For mechanical characterization, the resulting films were subjected to tensile testing. Their thermal properties were further characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic oxidation induction temperature measurements (OIT), complemented by Fourier-transform infrared spectroscopy (FT-IR), color analysis, rheology, scanning electron microscopy (SEM), and UV-Vis spectroscopy. Results show that the incorporation of PoP had no significant impact on the characteristic transition temperatures (Tg, Tm, and Tc) of PLA, indicating that the thermal behavior of the polymer matrix was largely preserved. However, while the thermo-oxidative stability of PLA was improved in the presence of PoP, with a maximum at 3 wt.% of PoP, increasing the OIT by 30 °C, the mechanical performance of the composite films was adversely affected, as evidenced by decreased tensile strength and elongation at break indication embrittlement, especially for ≥3 wt.% of PoP. Significant changes were observed in the films’ surface properties, as well as in their color parameters and UV transmittance values. Consequently, while PoP offers potential bioactive functionality for use as a sustainable additive, its content must be carefully optimized to maintain an acceptable balance between functionality and mechanical integrity.