Abstract
Differential scanning calorimeter was used to extensively investigate the non-isothermal crystallization of polypropylene (PP)/layered double hydroxides (LDHs) nanocomposites prepared through wet solid-state shear milling. The corresponding crystallization kinetics was further investigated by using Ozawa, modified Avrami and combined Avrami–Ozawa method, respectively. The results showed that the Ozawa method could not well describe the crystallization kinetics of pure PP and its nanocomposites. Comparatively, the modified Avrami method as well as the combined Avrami–Ozawa method gives the satisfactory results. Under the effect of pan-milling, the produced LDH nano intercalated/exfoliated particles exhibit the inhibitive effect on the PP nucleation but more remarkable promotion effect on the spherulite growth, leading to enhancement in the overall crystallization rate. This is reflected in increase of the calculated fold surface free energy σe and also the supercooling degree ΔT required for crystallization nucleation. In addition, the polarized optical microscopy observation also verifies the higher spherulite growth rate of PP/LDHs nanocomposites than that of pure PP.
Highlights
For many years, so much work has been done on the modification of polymers [1,2,3,4,5], because this would endow the polymer with the enhanced mechanical properties and the2018 The Authors
Differential scanning calorimeter was used to extensively investigate the non-isothermal crystallization of polypropylene (PP)/layered double hydroxides (LDHs) nanocomposites prepared through wet solid-state shear milling
The results showed that the Ozawa method could not well describe the crystallization kinetics of pure PP and its nanocomposites
Summary
Much work has been done on the modification of polymers [1,2,3,4,5], because this would endow the polymer with the enhanced mechanical properties and the. There have been many studies on polymer crystallization by addition of different nanoparticles or nucleating agents to various polymer matrices [24,25,26] In these studies, calcium carbonate [27], silicon dioxide [28], halloysite nanotubes [29], clay [26] and silicon nitride [30] are found to have the potential to act as nucleating agents for PP chain, which contributes to great improvement in the mechanical and thermal properties of the prepared PP composites. In our previous work [39], PP/LDHs nanocomposites were prepared successfully through wet solid-state shear milling (S3M) method without using any compatibilizer and organic modifier, which are generally required in the conventional preparation method such as melt intercalation, solution intercalation, in situ polymerization, exfoliation– adsorption process and template synthesis. The crystalline structure, morphology and spherulite growth rate of nanocomposites are investigated by using polarized optical microscopy (POM)
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