The effect of lanthanum oxide (La₂O₃) on the structure and crystallization of poly(vinylidene fluoride)

Rare earth polymers, due to their excellent luminescence, fluorescence, laser protective, optical and magnetic properties, have attracted much research attention in recent years. However, little attention has been paid to the effect of rare earths on the structure and crystallization of polymers, which is of important significance in the development of functional polymers. X-ray diffraction and differential scanning calorimetry were used to investigate the structure and crystallization behavior of a poly(vinylidene fluoride) (PVDF)/lanthanum oxide (La₂O₃) composite. The results showed that the degree of perfection, crystal size, crystallization rate and isothermal crystallization activation energy of PVDF in the composite decreased, compared with pure PVDF. The spherulite nucleation and growth for PVDF and PVDF composite were analyzed in detail using the Lauritzen-Hoffman equation. The modified Avrami equation and the Mo equation were used to study the non-isothermal crystallization kinetics. The addition of La₂O₃ did not change the crystal structure and nucleation process for PVDF, but it decreased markedly the crystal growth rate and led to the formation of unstable crystals. This was attributed to the fact that too much La₂O₃ prevented PVDF molecular chains from moving and arranging in an orderly manner into crystals.