A Novel Organophosphorus Hybrid with Excellent Thermal Stability: Core-Shell Structure, Hybridization Mechanism, and Application in Flame Retarding Semi-Aromatic Polyamide.
An organophosphorous hybrid (BM@Al-PPi) with unique core-shell structure was prepared through hybridization reaction between boehmite (BM) as the inorganic substrate and phenylphosphinic acid (PPiA) as the organic modifier. Fourier transform infrared spectra (FTIR), solid state (31)P and (27)Al magic angle spinning nuclear magnetic resonance, X-ray diffraction, and element analysis were used to investigate the chemical structure of the hybrids, where the microrod-like core was confirmed as Al-PPi aggregates generated from the reaction between BM and PPiA, and those irregular nanoparticles in the shell belonged to residual BM. Compared with the traditional dissolution-precipitation process, a novel analogous suspension reaction mode was proposed to explain the hybridization process and the resulting product. Scanning electronic microscopy further proved the core-shell structure of the hybrids. BM exhibited much higher initial decomposition temperature than that of Al-PPi; therefore, the hybrid showed better thermal stability than Al-PPi, and it met the processing temperature of semi-aromatic polyamide (HTN, for instance) as an additive-type flame retardant. Limiting oxygen index and cone calorimetric analysis suggested the excellent flame-retardant performance and smoke suppressing activity by adding the resulting hybrid into HTN.
A hybrid flame retardant for semi-aromatic polyamide: Unique structure towards self-compatibilization and flame retardation
Abstract Construction of high performance flame-retardant engineering plastics is of particular interest both in academia and industrial circles for years. Herein, a novel organic-inorganic hybrid (BM@Al-BuPPi) with unique core-shell structure was prepared based on the reaction of isobutyl-phenylphosphinic acid (Bu-PPiA) and boehmite (BM) via analogue suspension in aqueous solution. The core from the self-aggregated microrod of Al-BuPPi brought a high flame-retardant efficiency to the hybrid, where the V-0 rating in UL-94 burning test and 42.5% of limiting oxygen index (LOI) were achieved. The shell composed of BM nanoparticles was responsible for the improvement of the compatibility between hybrid and semi-aromatic polyamide matrix by increasing the surface polarity and the wettability of the hybrid. Compared with the original Al-BuPPi, the hybrid was homogeneously wrapped by the matrix, and the tensile strength of semi-aromatic polyamide/hybrid composite was over twice higher than that of the flame-retardant composite containing Al-BuPPi. At last, cone calorimetric results revealed the hybrid combines both advantages of the organic phosphinate and the inorganic boehmite in flame inhibition and smoke suppressing activity.
Evolution of morphology in compatibilized vs uncompatibilized polyamide blends
Abstract The development of phase morphology in non-reactive vs reactive polyamide blends with a styrene acrylonitrile (SAN) copolymer and SEBS (a styrenic triblock copolymer with ethylene-butylene midblocks) in a co-rotating twin screw extruder was investigated using electron microscopy techniques. For the polyamide/SAN systems, significant differences were observed between the evolution of morphology in non-reactive binary blends vs blends compatibilized with a reactive imidized acrylic (IA) polymer which is miscible in the SAN phase and has functional groups which are capable of reacting with the amine end groups in the polyamide phase. While a steady decrease in the dispersed phase particle size was observed in general for the non-reactive nylon 6/SAN blends with both increasing screw length and speed, for the ternary nylon 6/SAN/IA blends a dramatic drop in the dispersed phase particle size was observed in the initial region of the screw almost immediately after melting of the pellets followed by some coalescence of dispersed phase in the latter stages leading to a dual population of particle at the exit of the extruder. The extent and onset of coalescence after attainment of minimum particle size in the initial region of the screw in reactive nylon 6/SAN blends was found to be strongly dependent on the screw speed and configuration. The extent of chemical reaction along the extruder screw for reactive nylon 6/SAN blends was dependent on the screw speed, extruder configuration and flow rate. While similar differences in the evolution of morphology were observed between non-reactive and reactive polyamide/SEBS systems, changing the polyamide type from monofunctional (nylon x , e.g. nylon 6) to difunctional (nylon x , y , e.g. nylon 6,6) revealed interesting differences even within these reactive blends. Significant differences in both the development of morphology and reaction profile along the screw were also observed between binary and ternary nylon 6/rubber blends containing similar concentrations of reactive maleic anhydride functionality in the rubber phase using a fixed screw speed and configuration.