Structure Changes and Thermal Behaviors of Polymer in PP/BaTiO₃ Nanocomposites during Solid State Shear Milling

Abstract

Polypropylene/barium titanate (PP/BaTiO₃) nanocomposites were prepared by a novel method—solid state shear milling (S³M). The effects of S³M on the structure changes and thermal behaviors of PP were investigated by X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) study. The results showed that PP underwent significant amorphization. The crystallinity of PP decreased from 50.29% to 35.65% after 20 cycles of milling. During the subsequent heating process, the destroyed crystalline structure of PP can readily be recovered, though incompletely. Double melting characteristics were detected by DSC in the milled samples. It was inferred that the milling process resulted in enhanced intimacy between PP and BaTiO₃, which would significantly influence the melting behavior of the polymer phase. The abnormal thermal behaviors can be interpreted using an inferred nanocrystalline morphology, during which residual lamellae fragments randomly distribute in the amorphous bulk PP. The conclusions were also strongly supported by quantitative analysis of the XRD.

Keywords:

• Barium titanate
• Mechanical milling
• Nanocrystalline
• Polypropylene
• Solid state shear milling
• Structure changes
• Thermal behaviors

Acknowledgments

This work was supported financially by the National Basic Research Program of China (No. 2005CB623808).