Preparation Characterization of Modified Poly(Lactic Acid) Using Dicumyl Peroxide and Tetraglycidyl Diamino Diphenyl Methane

Abstract

Poly(lactic acid) (PLA) was modified using dicumyl peroxide (DCP) and tetraglycidyl diamino diphenyl methane (TGDDM) to improve its melt viscosity and molecular weight for a variety of industrial applications. The PLA was branched or crosslinked with DCP at 180 °C, and gel content was detected as the DCP concentration was over 0.6 phr. However, for TGDDM, it was observed that only chain extension or branching occurred; the number- and weight-average molecular weights and polydispersity index (PDI) increased. The melt flow index decreased as the concentration levels of DCP and TGDDM increased. However, when the TGDDM was over 0.5 phr, the opposite results were observed. The variations in the mechanical properties of modified PLA were marginal; however, the elongation at break slightly decreased. The onset value of the decomposition temperature of the DCP-modified PLA slightly decreased. In contrast, with TGDDM, the onset value slightly increased. As the branching and crosslinking of the modified PLA increasingly occurred, relatively low relaxation enthalpy was detected. However, the glass transition temperature (Tg) was not influenced. An increase in the storage modulus (G′), loss modulus (G″), and complex viscosity (η*), and a decrease in tan δ at low frequencies showed that the rheological behavior of the modified PLA turned from liquid-like to solid-like because of the modifications achieved using DCP and TGDDM.