Influence of E-beam irradiation on compounds from linear low density polyethylene and thermoplastic vulcanized rubber consisting of a polypropylene and ethylene propylene diene monomer rubber phase

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.

Automated summary

Linear low-density polyethylene (LLDPE) can be crosslinked through irradiation, which improves its chemical and thermal resistance but reduces its mechanical performance. To mitigate this reduction, compounds of LLDPE with thermoplastic elastomers (TPV) are prepared. Irradiation experiments show that compounds with 20 wt% TPV have a decrease of around 12% in gel content compared to pure LLDPE. It is also observed that compounds with 10 wt% TPV have a 4% higher gel content than predicted. Increasing the amount of TPV leads to an increase in elongation at break from 689% for pure LLDPE to 769%, and a decrease in tensile strength from 31.9 to 30.5 MPa. Under irradiation, both elongation at break and tensile strength decrease. Elongation at break decreases by around 200% and tensile strength decreases by around 5 MPa. Thermal analysis reveals that the melting temperature of TPV decreases, and its crystallinity initially increases before decreasing for doses up to 165 kGy. Infrared spectroscopy shows evidence of surface oxidation under irradiation for all compounds containing LLDPE.