Premium
Microstructure and melting behavior of a solution‐cast polylactide stereocomplex: Effect of annealing
Author(s) -
Hu Xiaodan,
Shao Jun,
Zhou Dongdong,
Li Gao,
Ding Jianxun,
Chen Xuesi
Publication year - 2017
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.44626
Subject(s) - materials science , differential scanning calorimetry , annealing (glass) , crystallite , amorphous solid , microstructure , lamella (surface anatomy) , enthalpy of fusion , melting point , composite material , fusion , polymer chemistry , chemical engineering , crystallography , thermodynamics , metallurgy , chemistry , linguistics , physics , philosophy , engineering
The effect of annealing on the microstructure and melting behavior of a solution‐cast polylactide (PLA) stereocomplex (sc) was systematically investigated by differential scanning calorimetry and small‐angle X‐ray scattering. A preorder state, an intermediate form between the amorphous and crystalline states, was found in the solution‐cast poly( l ‐lactide)–poly( d ‐lactide) blend. When the annealing temperature ( T a ) was below 220 °C, a part of the preorder state directly formed thicker sc crystallites; these corresponded to the second melting peak, which appeared around 250 °C during the heating process. Although the rest melted and became the amorphous phase, it formed a thinner lamella under the restriction of the unmelted initial sc crystallites during annealing; the melting process of this lamella was parallel to that of the new melting peak, which appeared around 220 °C. The melting of the initial crystal formed as the solvent volatilized corresponded to the range of the first melting temperature around 230 °C. When T a was above 220 °C, the preorder state melted completely, and the initial crystal experienced perfection process. Furthermore, the highest melting temperature of PLA sc (254.1 °C, with a fusion enthalpy of 125.5 J/g) was obtained when T a was 235 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44626.