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Thermal properties and flame retardancy of novel epoxy based on phosphorus‐modified Schiff‐base
Author(s) -
Liu Huan,
Xu Kai,
Cai Hualun,
Su Jiangxun,
Liu Xin,
Fu Zien,
Chen Mingcai
Publication year - 2012
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.1832
Subject(s) - thermogravimetric analysis , epoxy , limiting oxygen index , materials science , differential scanning calorimetry , diglycidyl ether , fourier transform infrared spectroscopy , polymer chemistry , imine , schiff base , thermosetting polymer , nuclear chemistry , char , organic chemistry , composite material , chemistry , chemical engineering , pyrolysis , bisphenol a , physics , thermodynamics , engineering , catalysis
Through addition reaction of Schiff‐base terephthalylidene‐bis‐( p ‐aminophenol) ( DP‐1 ) and diethyl phosphite (DEP), a novel phosphorus‐modified epoxy, 4,4'‐diglycidyl‐(terephthalylidene‐bis‐( p ‐aminophenol))diphosphonate ether ( EP‐2 ), was obtained. An modification reaction between EP‐2 and DP‐1 resulted in an epoxy compound, EP‐3 , possessing both phosphonate groups and CN imine groups. The structure of EP‐2 was characterized by Fourier transform infrared (FTIR), elemental analysis (EA), 1 H, 13 C, and 31 P NMR analyses. The thermal properties of phosphorus‐modified epoxies cured with 4,4'‐diaminodiphenylmethane (MDA) and 4,4'‐diaminodiphenyl ether (DDE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The activation energies of dynamic thermal degradation ( E d ) were calculated using Kissinger and Ozawa's methods. The thermal degradation mechanism was characterized using thermogravimetric analysis/infrared spectrometry (TG‐IR). In addition, the flame retardancy of phosphorus‐modified epoxy thermosets was evaluated using limiting oxygen index (LOI) and UL‐94 vertical test methods. Via an ingenious design, phosphonate groups were successfully introduced into the backbone of the epoxies; the flame retardancy of phosphorus‐modified epoxy thermosets was distinctly improved. Due to incorporation of CN imine group, the phosphorus‐modified epoxy thermosets exhibited high thermal stabilities; the values of glass‐transition temperatures ( T g s) were about 201–210°C, the values of E d were about 220–490 kJ/mol and char yields at 700°C were 49–53% in nitrogen and 45–50% in air. These results showed an improvement in the thermal properties of phosphorus‐modified epoxy by the incorporation of CN imine groups. Copyright © 2010 John Wiley & Sons, Ltd.