Miscibility and Double Glass Transition Temperature Depression of Poly(l-lactic acid) (PLLA)/Poly(oxymethylene) (POM) Blends

Abstract

The poly(l-lactic acid)/poly(oxymethylene) (PLLA/POM) blends have been prepared by simply melt blending. The phase diagram, miscibility, glass transition temperatures, and physical properties have been investigated systematically. The PLLA/POM blends exhibit typical lower critical solution temperature (LCST) behaviors. PLLA and POM are miscible in the melt state at low temperature and become phase-separated at elevated temperatures. It was found that the weak interactions between the carboxyl groups of PLLA and methylene groups of POM (weak C–H...O hydrogen bonding) account for the miscibility of the two components. Although the PLLA/POM blends are homogeneous at the melt state in the miscible temperature region, two distinct glass transition temperatures are observed for the all blends when quenched from the homogeneous state. More surprisingly, both POM and PLLA exhibit the apparent glass transition temperature (Tg) depression in the blends, compared with Tgs of the neat polymers. The behaviors are tota...