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Concerning inorganic flame retardants, the facile fabrication and high-efficiency fire safety without compromising the mechanical property of matrix are still significant challenges. Here, nano-layered double hydroxide containing boron constructed on the surface of ammonium polyphosphate complexes (B-LDH@APP) is prepared by a simple in-situ coprecipitation technology to reduce the fire hazard and improve mechanical performances of epoxy resin (EP). The as-obtained 4B-LDH@APP/EP achieves the UL-94 V-0 rating and presents superior flame-safety performance. With respect to the 4APP/EP, the fire growth rate, the peak heat release rate, and the peak smoke production rate of 4B-LDH@APP/EP decrease by 77.8%, 57.3%, and 52.6%, respectively. The reason is mainly contributed to excellent synergistic flame-retardant effect among boron, LDH, and APP, which can accelerate the generation of compact charring residual with good microstructure during combustion of B-LDH@APP/EP composites. Furthermore, B-LDH@APP slightly affects the mechanical performances of EP matrix due to the upgraded interfacial interaction.

The construction of novel semiaromatic polyamides (SaPAs) combining all advantages of aliphatic and aromatic polyamides is of particular importance in both academia and industrial circles. To study...

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.

Semi-aromatic polyamides (SaPAs) combining each advantages of aliphatic and aromatic polyamides received ever-increasing development in both academia and industrial circles. In this work, four kinds of SaPAs with fluorenyl pendent and different length of aliphatic spacers, named P–FPB, P–FPH, P–FPO and P–FPD respectively, were designed and synthesized via the aromatic nucleophilic substitution (SNAr) polycondensation. The effects of both the rigid pendent and flexible methylene (4, 6, 8, 10) spacers on the comprehensive properties of the SaPAs were comprehensively investigated. At the presence of the rigid fluorenyl pendent and the intermolecular π–π stacking thereof, the resulting SaPAs exhibited enhanced glass transition temperature (Tg), thermal stability, solubility in typical organic solvents and mechanical properties compared with the commercially available 6T based SaPa. Also with increasing the number of the methylene units of the SaPAs, their Tg, Vicat softening temperature, tensile strength and modulus gradually decreased; while the initial decomposition temperature and impact strength anomalously increased. Rheological investigations and solubility tests further confirmed that the resulting SaPAs were suitable for processing either in melt or in solution. In addition, these polyamides displayed favorable dielectric properties for potential availability in electric and electronic applications.

Here zinc borate@ZIF-8 (ZB@ZIF-8) hybrid nanorods were constructed through self-template strategy using zinc borate as the template, so as to realize the multifunctionalization of epoxy resins. By virtue of this smart design, it rationally combined the structural and functional advantages of the curing capability of ZIF-8 and the flame-retardant efficiency of ZB into core-shell nanoarchitecture, which could facilitate the curing of epoxy resins, improve the fire safety and enhance the physical-mechanical property of epoxy thermosets. Benefiting from this design, the apparent activation energy for ZB@ZIF-8 nanorods to cure epoxy resins is lower than ZIF-8, and epoxy thermosets cured by ZB@ZIF-8 presented lower flammability and higher mechanical properties as compared to epoxy thermosets cured by ZIF-8 individually.

In this work, a flame-retardant polypropylene (PP)/ramie fiber (RF) composite was prepared. The ramie fibers were wrapped chemically by a phosphorus- and nitrogen-containing flame retardant (FR) produced via in situ condensation reaction so as to suppress their candlewick effect. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) demonstrated that the ramie fibers wrapped chemically by FR (FR-RF) were obtained successfully. Thermogravimatric test showed that the PP/FR-RF composite had more residue and better thermal stability at high temperatures than the PP/RF composite. Cone calorimeter (CC) results indicated that the peak of heat release rate (PHRR) and total heat release (THR) correspondingly decreased by 23.4% and 12.5% compared with the values of neat PP/RF. The PP/FR-RF composite created a continuous and compact char layer after the combustion. Combining FTIR analysis of char residue after CC test with heat conduction coefficient results, it could be concluded that the charring of FR on RF greatly weakened the candlewick effect of RF, and more char residue in the RF domain facilitated the formation of more continuous and compact char layer in the whole combustion zone, consequently protected PP composites during combustion, resulting in the better flame retardancy of PP/FR-RF composite than that of PP/RF composite.

A novel phosphorus-nitrogen flame retardant named as melamine phenyl phosphate (MAPPO) was synthesized successfully via the neutralization reaction between phenylphosphonic acid (PPOA) and melamine (MA). The chemical structure of MAPPO was characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR) and element analysis (EA). MAPPO was introduced into epoxy resin by blending to improve the flame retardancy. Flame retardancy and combustion behavior of EP/MAPPO were investigated by limiting oxygen index (LOI) test, vertical burning (UL-94) test and cone calorimeter test. UL-94 and LOI tests results showed EP containing 18 wt% MAPPO passed the UL-94 V-0 rating and got a high LOI value of 33%. In the cone calorimeter test, compared with that of EP, the values of peak of heat release rate (HRR), total heat release (THR), peak of smoke production rate (PSPR) and total smoke production (TSP) of modified EP were reduced by 58.7%, 40%, 49% and 61.6%, respectively. By analyzing the volatile pyrolysis products of MAPPO, it was known that MAPPO mainly produced CO2, NH3, H2O and other nitrogen-containing compounds, which diluted the concentration of fuel gases and oxygen during combustion. Meanwhile, the char residue of EP/MAPPO system after combustion was also analyzed by scanning electron microscope (SEM), FT-IR and Raman tests, and the results showed MAPPO was able to promote the crosslinking of EP leading to the formation of compact char layer containing P–O–C, P O and C C, etc. In a word, the enhancement in flame retardancy was attributed to both dilution effect of non-combustible gases and barrier effect of compact char.