A Comparative Study of Impact Fracture Toughness of Epoxidized Poly(1, 4 Cis-Isoprene) Compatibilized PLA Binary and Ternary Blends

Poly(lactic acid) (PLA) is a biodegradable polymer with limited application because of its intrinsic brittleness, low toughness, and low elongation at break. Melt blends were prepared by mixing a natural rubber (NR, poly(1,4-cis-isoprene) in the form of liquid NR (LNR), liquid-epoxidized NR (LENR), and polypropylene (PP) in the PLA matrix. Four blend systems were designed and prepared, i.e., PLA-PP, PLA-PP-LNR, and PLA-LNR or PLA-LENR. The composition of PP in the blend was fixed at 10 % PLAPP (90/10). Results showed that PLA-PP mixed with LNR improved impact and elongation at break. The binary blend of PLA-LNR (90/10) significantly enhanced impact strength and elongation at break properties. In contrast, the binary blends of PLA-LENR (90/10) showed a lower value of elongation at break (9.5 % vs. 37.3%) and impact strength (4.56 kJ m(-2) vs. 6.44 kJ m(-2)). The melting temperature (T-m) and the glass transition temperature (T-g) were measured by differential scanning calorimetry, which recorded slight changes in the glass temperatures and melting temperatures. Scanning electron microscopy images of the tensile fracture of the PLA-LNR (90/10) blend showed the presence of large fibrils associated with the ductile failure related to neat PLA. Finally, the fracture toughness (K-IC) of PLA-LNR (90/10) showed an increase of 39 % over neat PLA (2.94 MPa.m(1/2) vs. 4.08 MPa.m(1/2)).