Halogen-Free Flame Retardant Polypropylene Fibers with Modified Intumescent Flame Retardant: Preparation, Characterization, Properties and Mode of Action

Composite Flame Retardants Based on Conjugated Microporous Polymer Hollow Nanospheres with Excellent Flame Retardancy

The development of polymer materials with excellent flame retardancy has been paid increasing attention for their valuable applications in saving energy in modern architecture. Herein, conjugated microporous polymers hollow nanospheres (CMPs-HNS) were prepared by Sonogashira-Hagihara cross-coupling reaction with 1,3,5-triacetylenebenzene, 3-amino-2,6-dibromopyridine, and 2,4,6-tribromoaniline as building blocks using SiO2 nanoparticles as hard templates. To enhance the flame-retardant performance of the CMPs-HNS, antimony pentoxide solution (Sb2O5) and bisphenol A-bis (diphenyl phosphate) (BDP) were coated onto the as-prepared CMP-HNS (CMPs-HNS-BSb) by a simple immersion method. The peak heat release (pHRR) from microscale combustion colorimeter (MCC) of CMPs-HNS-BSb was 76.5 and 73.05 W g-1, respectively. By introducing CMPs-HNS-BSb into the epoxy resin (EP) matrix, the CMP2-HNS-BSb/EP (0.5) composites show that the pHRR values were 809.3 and 645.2 kW m-2, reduced by 21% as measured by conical calorimetry (CC), and total heat release (THR) reduced by 29.7%, going from 101 to 70.8 MJ/m2 when compared to the pure sample. Besides, total smoke production (TSP) reduced about 23.7%. The hollow structure can enhance the thermal insulation performance. As measured, the thermal conductivity of CMP1-HNS-BSb and CMP2-HNS-BSb is 0.044 and 0.048 W m-1 K-1. Based on the advantages of simple manufacture, superior thermal insulation, and flame retardancy, our CMPs-HNS-BSb/EP composites may find useful applications in various aspects such as building energy saving in future development.

Synergistic Effects of DOPO-Based Derivative and Organo-Montmorillonite on Flame Retardancy, Thermal Stability and Mechanical Properties of Polypropylene

Polypropylene (PP), as a general thermoplastic polymer, is broadly used in different fields. However, the high flammability, melt dripping and poor mechanical properties of PP are a constraint to the expansion of its applications. In this paper, PP composites containing a combination of a phenethyl-bridged DOPO derivative (PN-DOPO) and organic montmorillonite (OMMT) were prepared via melt blending. The synergistic effects of PN-DOPO and OMMT on the flame retardancy, thermal stability and mechanical properties of PP composites were investigated systematically. The results showed that 20 wt% addition of PN-DOPO with OMMT improved the flame retardancy of PP composites. In particular, the introduction of 17 wt% PN-DOPO and 3 wt% OMMT increased the LOI values of the PP matrix from 17.2% to 23.6%, and the sample reached the V-0 level and reduced the heat release rate and total heat release. TGA indicated that OMMT could improve the thermal stability of the PP/PN-DOPO blends and promote the char residues of PP systems. Rheological behaviour showed a higher storage modulus, loss modulus and complex viscosity of PP/PN-DOPO/OMMT composites, suggesting a more effective network structure. In addition, the tensile strength, flexural properties and impact strength of the PP/PN-DOPO/OMMT composites actually increased for a good dispersion effect. Combined with the char layer analysis, the introduction of OMMT promoted more continuous and compact structural layers containing an aluminium-silicon barrier and phosphorus-containing carbonaceous char in the condensed phase. OMMT can improve the flame retardancy, thermal stability and mechanical properties of PP, and, thus, PN-DOPO/OMMT blends can serve as an efficient synergistic system for flame-retarded PP composites.

Preparation of flame retardant glass fiber via emulsion impregnation and application in polyamide 6

As a commonly used reinforcement, glass fiber (GF) can improve the mechanical properties of thermoplastics. However, previous studies have suggested that GF was not good for the flame retardancy of thermoplastics because of “wick effect.” Herein, a novel flame retardant emulsion was synthesized, containing film-former, lubricant, silane coupling agent, and ammonium polyphosphate modified by 3-aminopropyltriethoxysilane (mAPP). The GF impregnated with flame retardant emulsion and aluminum diethlyphosphinate (ADP) were blended with polyamide 6 (PA6) to prepare flame retardant GF reinforced PA6 (FRGFPA6/ADP). The LOI of FRGFPA6/ADP-15 can reach 34.7%, which is much higher than that of GF reinforced PA6 (GFPA6) and it also pass the UL-94 test and reach V-0 rating without dripping. The mHRR, pHRR, and THR of FRGFPA6/ADP-15 are reduced by 44.2, 121.0, and 26.3% compared to GFPA6. After burning, the surface of flame retardant GF can form a carbon layer, which improved the efficiency of interfacial flame retardancy between GF and PA6 and weakened the “wick effect.” At the same time, ADP is added to the matrix to release free radicals to capture oxygen in the air, and carbon layer is formed to isolate the air. The synergistic effect of ADP and mAPP increased the flame retardancy of GFPA6.

The Reuse of Municipal Solid Waste Fly Ash as Flame Retardant Filler: A Preliminary Study

The growing increase in the production of municipal solid waste incinerator (MSWI) ashes has led to the research of new possibilities to reuse these by-products. This work aims to use MSW fly ash (FA) as a flame retardant filler. The FA was stabilized according to a simple stabilization process involving the mixing of only different ashes: bottom ash (BA), flue gas desulphurization (FGD) residues and coal fly ash (CFA). Stabilized FA, calcite and commercial flame retardants were compared as additives in an epoxy resin or polypropylene (PP) matrix. The self-extinguish performance of fillers was evaluated by fire resistance tests: the vertical burning test (UL94-V) and glow wire test (GWT) at 750 °C and 850 °C. A life cycle assessment (LCA) evaluation was also performed to estimate the reduction in environmental impact related to the production of the flame retardant with stabilized FA. The results show that this new filler is a promising alternative to traditional flame retardant. The ignition time of composites with calcite was lower than the corresponding sample with FA. From an environmental point of view, the replacement of calcite in an epoxy resin matrix or commercial flame retardant in a PP matrix with stabilized FA allows for a reduction in the impact of about 24.1% and 49.5%, respectively.