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.
UV absorber co-intercalated layered double hydroxides as efficient hybrid UV-shielding materials for polypropylene.
Two kinds of UV absorbers 2-hydroxy-4-methoxy-benzophenone-5-sulphonic acid (HMBA) and cinnamic acid (CA) were successfully co-intercalated into the interlayer of Mg2ZnAl layered double hydroxides (LDH) by a modified coprecipitation method to prepare novel UV-shielding material HMBA-CA-LDH for improving the anti-photoaging capability of polypropylene (PP). The characterization results reveal the presence of host-guest interactions between the LDH host layers and HMBA/CA guest anions as well as guest-guest interactions between guest anions in HMBA-CA-LDH, and the HMBA-CA-LDH has much stronger UV absorption capability than the HMBA intercalated LDH (HMBA-LDH) in the whole UV band and a much broader UV absorption band than the CA intercalated LDH (CA-LDH). A series of LDH/PP composites with evenly dispersed LDH nanosheets were prepared by incorporating the prepared LDHs into the matrix of PP via the solvent casting method. As expected, LDH/PP composites show higher thermal stability and better anti-photoaging ability than pristine PP. Interestingly, HMBA-CA-LDH/PP shows better anti-photoaging performance in comparison with HMBA-LDH/PP and CA-LDH/PP because of its better UV-shielding ability arising from the synergistic UV-shielding effects of both HMBA and CA, and the HMBA-CA-LDH can reduce the photodegradation of PP by about 85%. Hence, the prepared novel HMBA-CA-LDH has potential application in the field of PP as an efficient and promising UV-shielding material.
Effect of melamine polyphosphate on thermal degradation of polyamides: a combined X-ray diffraction and solid-state NMR study
Abstract The effect of melamine polyphosphate (MpolyP) on the thermal degradation of both polyamide 66 (PA66) and polyamide 6 (PA6) was studied using a combination of solid-state techniques. The mixtures of MpolyP with polyamides were heated for different times at 350 and 450 °C. The residues were then analyzed by X-ray diffraction and both solid-state 13 C NMR and 31 P NMR. The chemical structures formed in these oven experiments were used to study the chemical changes that take place during a standard flammability test. The mixtures of MpolyP with polyamides were also characterized by frequency-dependent rheological experiments. It was shown that MpolyP could induce significant cross-linking in PA66 and leads to dramatic depolymerization of PA6. These results were used to explain the performance of MpolyP as a flame retardant in these polyamides.