Influence of irradiation crosslinking on the flame-retardant properties of polyolefin blends

In the presence of flame retardants and other additives, halogen-free flame retardant (HFFR) shape-memory polymers were prepared using blends of ethylene vinyl acetate, ethylene propylene diene monomer, and low-density polyethylene. The HFFR compounds were irradiated using electron beam up to an absorbed dose of 150 kGy and characterized based on their mechanical, thermal, and electrical properties. Both the tensile strength (TS) and elongation at break (Eb) were found to increase as the levels of irradiation increased. This contrasted fact that, generally, Eb decreases as radiation doses increases because of polymer crosslinking capability. However, both TS and Eb decreased as the flame retardant content increased. The optimum mechanical properties were 13 MPa for TS and 200-350% for Eb. The versatile glass transition temperature greatly influenced the shape-memory impact. Nevertheless, the variable rubbery modulus had no significant influence. The limiting oxygen index was found to increase as the total flame retardant contents increased to values over the range of 30-35%. Hardness was about 92, and the retentions of TS and Eb after thermal aging at 136 degrees C for 168 h were between 93-112 and 75-93%, respectively. UL94 ratings of V-0 and a volume resistivity of 3.21 x 10(15) to 3.49 x 10(15) omega cm were obtained using these HFFR compounds. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48649.