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Crystallization kinetics of poly ( L ‐lactic acid)/montmorillonite nanocomposites under isothermal crystallization condition
Author(s) -
Hwang JiunnJer,
Huang SuMei,
Liu HsinJiant,
Chu HawnChung,
Lin LiHuei,
Chung ChenSheng
Publication year - 2011
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.35254
Subject(s) - crystallization , materials science , montmorillonite , avrami equation , nanocomposite , isothermal process , chemical engineering , glass transition , polymer chemistry , melting point , composite material , polymer , enthalpy of fusion , thermodynamics , physics , engineering
Poly( L ‐lactic acid)/ o ‐MMT nanocomposites, incorporating various amounts of organically modified montmorillonite ( o ‐MMT; 0–10 wt %), were prepared by solution intercalation. The montmorillonite (MMT) was organically modified with dilauryl dimethyl ammonium bromide (DDAB) by ion exchange. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) reveal that the o ‐MMT was exfoliated in a poly( L ‐lactic acid), (PLLA) matrix. A series of the test specimens were prepared and subjected to isothermal crystallization at various temperatures ( T 1 – T 5 ). The DSC plots revealed that the PLLA/ o ‐MMT nanocomposites that were prepared under nonisothermal conditions exhibited an obvious crystallization peak and recrystallization, but neat PLLA exhibited neither. The PLLA/ o ‐MMT nanocomposites (2–10 wt %) yielded two endothermic peaks only under isothermal conditions at low temperature ( T 1 ), and the intensity of Tm 2 (the higher melting point) was proportional to the o ‐MMT content (at around 171°C). The melting point of the test samples increased with the isothermal crystallization temperature. In the Avrami equation, the constant of the crystallization rate ( k ) was inversely proportional to the isothermal crystallization temperature and increased with the o ‐MMT content, especially at low temperature ( T 1 ). The Avrami exponent ( n ) of the PLLA/ o ‐MMT nanocomposites (4–10 wt %) was 2.61–3.56 higher than that of neat PLLA, 2.10–2.56, revealing that crystallization occurred in three dimensions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012