A facile approach to prepare cage‐ladder‐structure phosphorus‐containing amino‐functionalized POSS for enhancing flame retardancy of epoxy resins

Abstract

AbstractThe cage‐ladder‐structure phosphorus‐containing amino‐functionalized polyhedral oligomeric silsesquinoxanes (CLNH2‐POSS) have been synthesized through a facile catalyst‐free hydrolytic condensation of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide‐vinyltrimethoxysilane (DOPO‐VTMS) with 3‐aminopropyl trimethoxysilane (KH540). The successful preparation of CLNH2‐POSS has been proven by the characterization of Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (1H‐NMR, 29Si‐NMR), matrix‐assisted laser desorption ionization time of flight (MALDI‐TOF), and X‐ray diffraction (XRD). Then flame retardant (FR) epoxy resins (EPs) were prepared by the addition of different content of CLNH2‐POSS into EPs with thermal curing technology. The CLNH2‐POSS showed good solubility in EP matrix. The well‐dispersed CLNH2‐POSS contributed to thermal, mechanical, and FR properties of EP. Dynamic scanning calorimetry nonisothermal curing scans showed that CLNH2‐POSS had accelerating effect on the curing of EP. With the addition of only 3 wt% CLNH2‐POSS (0.30% phosphorus loading), the limiting oxygen index value of the EP composite increased from 25.5 of pure EP to 31.8, and vertical burning (UL‐94) V‐0 ratings was achieved. In addition, the EP composites showed improved thermal and mechanical properties. The investigations on char residue and pyrolysis volatiles of cured EP further revealed that CLNH2‐POSS exerted FR effects in condensed and gas phase simultaneously.