Poly(para-dioxanone) and Poly(l-lactic acid) Blends: Thermal, Mechanical, and Morphological Properties

ABSTRACT: Blends of two semicrystalline polymers, poly(l-lactic acid) (PLLA) and poly-p-dioxanone (PPD) have been prepared by solvent casting in different compositions. Thermal, morphological, and mechanical properties of the blends were studied using modulated differential scanning calorimetry, wide-angle X-ray diffractometry, scanning elec-tron microscopy (SEM), polarizing light microscopy (PLM), and tensile tests. Thermal analysis showed two glass transi-tion temperatures nearly constant and equal to the values of the homopolymers and constant values of melting temper-ature (Tm) for all blend compositions, suggesting that both polymers are immiscible. The PLM and SEM observations validated these results, and showed the different morphol-ogy obtained by changing the composition of the blend. The blends 40/60, 50/50, and 60/40 presented a clearly mac-roseparated system, while the 20/80 and 80/20 blends pre-sented better homogeneity, probably due to the low amount of one component in the other. It was found by PLM that PPD is able to crystallize according to a spherulitic morphol-ogy when its content is above 40%. Under this content, the crystallization of PPD is hardly observed. The blend 20/80 is more flexible, and tough material and neck formation dur-ing elongation is also observed, due to PPD, which may ac