Hydrolytic degradation of isosorbide-based polycarbonates: Effects of terminal groups, additives, and residue catalysts
2021
Yan, Shengdi | Wu, Guozhang
The hydrolysis degradation of bisphenol-A polycarbonate (BPA-PC), isosorbide (ISB)-co-1,4-cyclohexanedimethanol (CHDM) polycarbonate (IcC-PC), and BPA-PC/IcC-PC reactive blends were systematically investigated. The terminal hydroxyl groups of BPA-PC, thermally derived chemical structure on IcC-PC chains, and derivatives from phosphite antioxidants trigger severe hydrolysis degradation. ¹H-NMR analysis shows that carbonate groups connected to the BPA unit are most susceptible to hydrolysis, followed by ISB and CHDM units, demonstrating that the acidity of monomers plays a key role in the hydrolysis degradation of polycarbonates. Residual catalysts may cause significant hydrolysis in BPA-PC/IcC-PC reactive blends. Hydrolysis prefers to occur on the exo position of ISB unit with a low steric hindrance rather than on the endo position with a high electrophilicity, indicating that the residual catalyst acts as a Lewis acid and likely promotes hydrolysis through coordination mechanism. The hydrolysis resistance of BPA-PC/IcC-PC blends with a Na-based catalyst is lower than that of blends with K- and Cs-based catalysts because of the strong coordination ability.
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