Simultaneous crystallization and decomposition of PVA/MMT composites during non-isothermal process

• PVA/MMT decomposition during melting–crystallization is firstly confirmed.
• MMT can slow down the crystallization and degradation of PVA/MMT composites.
• PVA/MMT composite crystallization is severely affected by its degradation.
• PVA/MMT crystallization can still be corroborated well with classical models.

Decomposition of poly(vinyl alcohol)/montmorillonite clay (PVA/MMT) composites during melting–crystallization was experimentally confirmed by morphology and molecular structure changes. In particular, FTIR spectra show the shift of OH stretching band as well as enhanced intensities of CO stretching and CH2 rocking vibrational modes. Furthermore, Raman deconvolution indicates that CH wagging, CH2CH wagging, CHCO bending and CH2 wagging modes in amorphous domains were all decreased greatly. Moreover, this decomposition leads to decreased melting enthalpy, melting point, crystallization enthalpy and crystallization temperature. Crystallization analysis shows that the MMT incorporated slows down the crystallization process in the PVA matrix regardless of the nucleation capability of MMT. Despite the severe decomposition, the crystallization kinetics still corroborated well with common classical models. As a result, molecular structure changes and crystallization retardation observed in this study clearly indicate the strong effects of the thermal degradation on the non-isothermal crystallization of PVA/MMT composites.

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