Experimental and computational investigation on performances of the thermoplastic elastomer SEBS/Poly(lactic acid) blends

Poly(lactic acid) (PLA) was toughened by the thermoplastic elastomer of poly(styrene-ethylene-butadiene-styrene) (SEBS) and SEBS-grafted-maleic anhydride (SEBS-MAH). The toughening effect, the compatibility, as well as the corresponding mechanism with different content of SEBS or SEBS-MAH were investigated using experimental and simulation methods. As a result, the toughness effect became obvious with the increase of SEBS or SEBS-MAH content. Especially, for the PLA, SEBS/PLA(30/70), and SEBS-MAH/PLA(30/70) blends, the Shao D hardness decreased from 84.5 to 78.6 and 75, respectively. The tensile strength decreased from 51.0 MPa to 35.3 MPa and 31.3 MPa, while the breaking elongation increased from 13.0 % to 28.6 % and 31.9 %, the impact strength increased from 3.2 kJ/m2 to 4.0 kJ/m2 and 8.0 kJ/m2, respectively. Except that, the results of IR, DSC, and SEM revealed the addition of SEBS-MAH improved the toughness and compatibility more effectively than SEBS, on the basis of chemical bonding between SEBS-MAH and PLA molecular chains (SEBS-MAH-PLA). Moreover, according to molecular dynamics simulation results, the movement ability and flexibility of the molecular chains gradually increased with the increase of SEBS-MAH content, on the basis of Mean square displacement and Radius of gyration results. The compatibility between PLA and SEBS-MAH-PLA also got improved, as reflected by the solubility parameter, which increased from 13.982 +/- 0.034 (J/cm3)0.5 for SEBS to 15.931 +/- 0.087 (J/cm3)0.5 for SEBS-MAH-PLA. Further, the mechanical properties of each group of the sample were clarified from the characteristic parameters including E, B, G, B/G, as well as Poisson's ratio upsilon.