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Crystallization and flame‐retardant properties of polylactic acid composites with polyhedral octaphenyl silsesquioxane
Author(s) -
Jia Lin,
Tong Bin,
Li Dinghua,
Zhang Wenchao,
Yang Rongjie
Publication year - 2019
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.4501
Subject(s) - materials science , polylactic acid , differential scanning calorimetry , silsesquioxane , thermogravimetric analysis , composite material , cone calorimeter , fire retardant , fourier transform infrared spectroscopy , thermal stability , crystallization , scanning electron microscope , thermal decomposition , polymer , chemical engineering , char , pyrolysis , organic chemistry , physics , engineering , thermodynamics , chemistry
To develop environmental‐friendly and flame‐retarded polymer composites, bio‐based polylactic acid (PLA) was loaded with thermally stable polyhedral octaphenyl silsesquioxane (OPS). Pure PLA and PLA/OPS composites with the OPS of 1, 3, 5, and 10 wt% were prepared by extrusion and injection molding, respectively. The scanning electron microscopy (SEM), polarized optical microscope (POM), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and thermal gravimetric analysis (TGA) were used to analyze the dispersion of the OPS in the PLA matrix and the effects of OPS on the crystallization and thermal stability properties of PLA/OPS composites, respectively. Limited oxygen index (LOI) and cone calorimeter (CONE) measurements were used to study flame retardancy of PLA and PLA/OPS composites. In order to study the flame‐retardant mechanism, the char residues were investigated by SEM, Fourier transform infrared spectra (FTIR), and X‐ray photoelectron spectroscopy (XPS). TGA‐FTIR was used to analyze the gaseous products of their thermal decomposition. The results show that the OPS particles were submicron in the PLA and could increase the crystallization rate of PLA and form small‐sized secondary α‐form crystalline compared with the pure PLA spherulite. The PLA and OPS decomposed individually in the PLA/OPS composites by TGA. According to the LOI tests, the PLA with the OPS loading exhibited very small reduction of LOI. However, the CONE tests indicated that the OPS could improve the flame retardancy of the PLA by means of low peak heat release rate and average heat release rate. It was obtained that the degree and type of the PLA crystalline for the pure PLA and PLA/OPS affect their flame retardancy. In the max thermal decomposition stage of PLA and PLA/OPS, their gaseous products were similar; at high temperatures, the PLA/OPS produced simple and clear gaseous products of PLA with solid SiO 2 in the gas phase.