The compatibility

thermal property

crystallization behavior and crystal morphology of the poly(lactic acid)/carboxylated polypropylene(PLA/EPP) blends were investigated by using scanning electron microscopy(SEM)

thermogravimetric analysis(TGA)

differential scanning calorimetry(DSC) and polarizing optical microscopy(POM)

respectively.The results suggest that the blends have better compatibility and thermal stability and exhibit no clear glass transition temperature when the content of the PLA component is lower than 50%.The crystal morphology of both components is spherulites

but PLA exhibits smaller and brighter Maltese crosses

while EPP shows bigger and darker Maltese crosses.Moreover

the spherulites of PLA component show regular discontinuous concentric circlelines surrounding the nuclear of the spherulite

which are cracks with a width about 1～2 μm in SEM micrograph caused by internal stress of the spherulite

and there are some microfibers within the cracks.All the blends exhibit three decomposition stages in the TG curves corresponding to the decomposition of the carboxy groups in EPP

PLA component and main chains of the EPP

respectively

and some content of PLA will improve the thermal stability of the EPP component.The DSC thermalgrams of blends exhibit three main melting peaks

while two lower-temperature melting peaks have been found for the carboxylated polypropylene

and the higher-temperature one is for the PLA.During the melt-crystallization process; the blends have two mainly crystallization peaks when the content of the PLA component is greater than 50%.The EPP component in blends acts as a diluent decreasing much of the cold-crystallization temperature of the PLA in melting process

and improves the melt-crystallization behavior of PLA in melt-cooling process.