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Biodegradable poly(butylene succinate) (PBS) is considered as promising material to replace conventional nondegradable polymers in various engineering fields, but the applications are limited by its inherent flammability and low electrical conductivity. In this study, the synergistic effect of carbon nanotube (CNTs) on improving thermal stability, flame retardancy, and electrical conductivity of poly(butylene succinate)/piperazine pyrophosphate (PBS/PAPP) composites was investigated. Thermogravimetric analysis (TGA) demonstrated that the addition of CNTs could improve the thermal stability of PBS/PAPP composites, where the maximum mass loss temperature (Tmax) of PBS/18PAPP-2CNT increased by 9.1 °C in comparison with that of PBS/20PAPP. Meanwhile, PBS/18PAPP-2CNT exhibited the optimal flame retardancy with limited oxygen index (LOI) of 30.1%, V0 rating in UL-94 vertical burning test, and 79.6% reduction on the peak of heat release rate (PHRR) in cone calorimeter test. The synergistic effect of CNTs and PAPP was beneficial to construct high-quality char layer, resulting in the enhanced flame retardancy of PBS. Furthermore, the CNTs could improve the electrical conductivity of PBS/PAPP composites with low percolation threshold of 1.75 wt%, which was ascribed to the "volume excluded effect" of PAPP. Thus, the current work provided an efficient strategy to prepare multifunctional PBS composites to meet various engineering applications. [ABSTRACT FROM AUTHOR]

Polyvinyl chloride (PVC) is the most widely used general flame-retardant plastic worldwide; however, the large number of plasticizers added during processing significantly reduces its flame-retardant property. To prepare a new type of PVC material with highly efficient flame retardancy and smoke suppression, antimony trioxide (Sb2O3), talc powder, hydromagnesite, and zinc borate were added in different proportions to PVC to explore the flame-retardant properties, thermal weight, smoke density (Ds), and mechanical properties of the composite materials. Results showed that the limiting oxygen index value of each group was higher than 27% after adding talc powder, magnesite, and zinc borate to replace part of the Sb2O3. This value was within the refractory-grade level and indicated a good flame retardancy performance. The replacement effect was in line with the experimental expectation. The lowest Ds peak value was 656.4 when the flame retardants were added with 10 wt% Sb2O3, 50 wt% hydromagnesite, 20 wt% talc, and 20 wt% Zn3BO6. Compared with pure Sb2O3 as a flame retardant, the Ds peak value decreased by 46.7%. The thermogravimetric decomposition temperature of the composites in each group was generally higher than that of the group with pure Sb2O3 as a flame retardant, increasing by 45.3 °C. The thermal stability of the composites was improved, and the elongation at the break and tensile strength were 234.9% and 25.8 MPa, respectively, indicating good mechanical properties. The results showed that using compound flame retardants to replace most of the Sb2O3 is an effective technique for obtaining good flame retardancy and mechanical properties of PVC. This study, not only reduced the manufacturing cost of flame-retardant PVC, but also effectively reduced its smoke density and the time to reach the highest smoke density, which provided a research reference for the application and promotion of flame-retardant PVC. [ABSTRACT FROM AUTHOR]

As a promising biodegradable polymer, poly(butylene succinate) (PBS) is limited by its inherent flammable and melt-dripping nature. In this study, the effect of molecular sieve 4A (MS4A) as synergist on thermal stability and flame retardancy of PBS/piperazine pyrophosphate (PAPP) composites was investigated. TGA results showed that the addition of MS4A could effectively improve the thermal stability of PBS/PAPP composites both in nitrogen and air atmospheres. Compared to PBS/20PAPP, PBS/17PAPP-3MS4A exhibited the optimal flame retardancy with limited oxygen index of 29.8%, V0 rating in UL-94 vertical burning test, and 86.6% reduction on the peak of heat release rate in cone calorimeter test. According to the analysis for char morphology and microstructure, the combination of PPAP/MS4A mainly imparted its flame retardancy through condensed phase. The enhancement mechanism was ascribed to their catalytic carbonization effect and the migration of MS4A to construct stronger char layer in out interface during combustion. This work provides a new intumescent flame-retardant system with high efficiency and low toxicity, which will greatly promote the widely applications of PBS composites. [ABSTRACT FROM AUTHOR]

Organically modified montmorillonite (OMMT) and Ni2O3 were simultaneously introduced into flame‐retardant linear low‐density polyethylene/ethylene‐vinyl acetate/magnesium hydroxide (LEM) composites. Compared with the LEM composite, the thermal stability, and tensile properties of LEM/ remained basically unchanged when 5 wt% of OMMT/Ni2O3 was substituted for MH. The LOI value increased a little from 27.2 to 27.7%. The data from cone calorimeter test showed that the first and second peak heat release rate was reduced by 19% and 67%, respectively. The total heat release and total smoke production showed a significant reduction by 18% and 36% after incorporation of OMMT/Ni2O3, respectively. The mechanism study indicated that the combination of OMMT/Ni2O3 cooperates promote the carbonization of the polymer itself into carbon naotubes, which form a more cohesive char layer with magnesium hydroxide during combustion. This is the core factor responsible for the synergistic effect on reducing the heat release and smoke production in the LEM composite. [ABSTRACT FROM AUTHOR]

In this study, a magnesium phosphate whisker (DPM‐H) was synthesized by the acid–base neutralization reaction between magnesium hydroxide and 10‐hydroxy‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐OH) at 120°C. A new synergistic intumescent flame retardant (IFR) for epoxy resin (EP), which was composed of DPM‐H and ammonium polyphosphate (APP) was thoroughly studied. When the IFR loading was 8%, with the DPM‐H to APP weight ratio at 1:7, the prepared flame‐retardant EP (EPDA‐2) passed the vertical burning tests (UL‐94) V‐0 rating and obtained the limiting oxygen index (LOI) value of 29.3%. Microscale combustion calorimetry (MCC) results showed that the total heat release (THR) of EPDA‐2 reduced by 32.1% compared with pure EP. Meanwhile, the addition of DPM‐H can partially solve the problem of the decrease of the EP mechanical property caused by the addition of APP. Compared with the flame‐retardant EP with the 8% loading of APP, the impact strength of EPDA‐2 increased 152.3%. [ABSTRACT FROM AUTHOR]

Although the rigid cross‐linked polyvinyl chloride (c‐PVC) foam has excellent mechanical properties, there are still problems of unsatisfactory thermal insulation performance, flame retardancy, and smoke suppression. So how to simultaneously improve the thermal insulation and flame retardant properties of c‐PVC foam is still a challenge. Herein, the combination of copper powder and molybdenum trioxide (Cu/MoO3) is used to prepare c‐PVC composite foams. The cell structure, thermal conductivity, thermal stability, limiting oxygen index (LOI), and smoke density of the c‐PVC composite foams are characterized. The results showed that, on the one hand, the cell density and thermal insulation performance are improved (31.24 mW m−1 K−1) due to the good heterogeneous nucleation and infrared reflection of the copper powder. On the other hand, when the mass ratio of Cu/MoO3 is 4/1, the best synergistic catalytic effect to promote char formation achieved the highest LOI value of 30.1, and the smoke density rating (SDR) is reduced by 27%. This work is beneficial to the design and application of c‐PVC foams with high performance. [ABSTRACT FROM AUTHOR]

In this paper, a bio-based flame retardant PA-AR is synthesized, which endows PLA with good flame retardant and crystallization properties, and at the same time promotes the biodegradability of PLA. Only 1 wt% PA-AR makes the LOI value of PLA reach 26.8% and reaches UL-94 V-0 level. In addition, 1 wt% PA-AR increases the crystallinity of PLA to 23.4%, which increased by 460% compared with PLA. Further, due to the increase of crystallinity, the tensile strength is also improved. Besides, the addition of PA-AR can greatly promote the degradation performance of PLA under specific biological conditions. This work proposed a novel method to obtain completely biodegradable flame retardant composites. [Display omitted] • A bio-based compound is synthesized in aqueous phase as a flame retardant for PLA. • 1 wt% addition of flame retardant can make PLA composite self-extinguish and enhance LOI value. • The flame retardant endows PLA with excellent crystallization. • The flame retardant significantly promotes the biodegradation rate of PLA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Imidazole-based liquid compounds containing different P oxidation states were synthesized for curing EP. • EP-DCPPI and EP-PPOAI show the combined flame-retardant mechanism of gas-phase and condensed-phase flame retardancy. • EP-DCPPI and EP-PPOAI show excellent flame-retardant, mechanical properties and heat resistance. In this work, two phosphorus-containing liquid imidazole compounds with different phosphorus oxidation states (1,1′-(phenylphosphanediyl)bis(1 H -imidazole) (DCPPI) with + 1 valence phosphorus, and imidazole-phenylphosphate (PPOAI) with + 3 valence phosphorus) were designed and synthesized. Both of DCPPI and PPOAI were used as curing agents to obtain intrinsic flame-retardant epoxy resin (EP-DCPPI and EP-PPOAI), in which the imidazole group was used as the curing group of EP, and the phosphorus-containing group was directly connected to the EP crosslinking network. On the one hand, the efficient flame-retardant groups containing + 1 or + 3 valence phosphorus were incorporated into the EP system to obtain excellent flame-retardant properties; on the other hand, the introduction of phenylphosphine or phenoxyphosphine groups in the molecular chain of EP greatly enhanced the interaction between molecular chains, adjusted crosslinking density and endowed EP with excellent tensile strength and toughness. Compared with imidazole cured EP (EP-MZ), the peak heat release rate (PHRR) of EP-15DCPPI and EP-15PPOAI decreased by 70 % and 68 %, and the total heat release rate (THR) decreased by 37 % and 36 %, respectively. Meanwhile, EP-15DCPPI passed UL-94 V-0 rating, and the limiting oxygen index (LOI) reached 36.1 %. EP-15PPOAI passed UL-94 V-1 rating and the LOI reached 29.1 %. The flame-retardant mechanism was analyzed and discussed. Compared with EP-MZ, the dynamic and static mechanical properties of EP-15DCPPI and EP-15PPOAI were enhanced simultaneously, and the glass transition temperature (T g) was obviously increased. [ABSTRACT FROM AUTHOR]

A reactive flame retardant containing DOPO and aromatic imine (DOPO-AI) is synthesized. Adding 20 wt% of DOPO-AI reduces heat release and increases mechanical properties of epoxy thermosets. The addition of DOPO-AI does not affect T g and toughness of epoxy thermosets. For improving the flame-retardant performance of epoxy thermosets without sacrificing other properties, a novel aromatic imine-containing DOPO-based bisphenol, DOPO-AI, was synthesized. Diglycidyl ether bisphenol F epoxy resin (DGEBF) reacted with DOPO-AI first, followed by curing with 4, 4′-diaminodiphenylmethane (DDM). When the mass of DOPO-AI was 25% of DGEBF, the resulting epoxy thermoset EP/20DOPO-AI exhibited the V-0 rating with the limiting oxygen index of 35.4%. In the cone calorimetry test, the peak heat release rate and total heat release of EP/20DOPO-AI showed the reduction of 26% and 27%, respectively, compared to those of DGEBF/DDM (EP). The mechanism of DOPO-AI in reducing heat release and increasing char-form ability of EP/DOPO-AI was studied. Interestingly, the mechanical and thermal mechanical properties of EP/20DOPO-AI were improved, although the crosslinking density was much lower than that of EP. The tensile strength and storage modulus of EP/20DOPO-AI were increased by 13% and 5%, while the glass transition temperature and the elongation at break were kept, compared with those of EP. The high rigidity of DOPO and aromatic imine was the reason for the improvement of the mechanical properties of EP/20DOPO-AI. Furthermore, EP/20DOPO-AI showed a small reduction in thermal stability, compared with that of EP. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, ammonium phosphomolybdate (AMP) and aluminum diethylphosphinate (ADP) acting as temperature-response microparticles, were incorporated into epoxy resin (EP) together to promote fire safety and dynamic mechanical performance of EP composites at the same time. Both ADP and AMP acted as chemical inertness fillers to enhance the EP matrix at the normal service temperature and processing temperature. When the temperature rose after heating or even burning, both ADP and AMP presented chemical functions. On one hand, AMP exhibited excellent catalytic charring activity and smoke suppression efficiency. On the other hand, the combination between AMP and ADP in the EP/AMP/ADP composites showed excellent synergistic effects in improving the flame retardancy of EP. Compared to the case of EP, the peak heat release rate (PHRR) of EP/AMP/ADP composites (1.2 wt% AMP and 3.6 wt% ADP) was decreased by 54%, the total heat release (THR) was reduced by 25%, and the total smoke production (TSP) was reduced by 25%. Meanwhile, the UL-94 V-0 rating was obtained, and the limiting oxygen index (LOI) of the composite was increased from 26.2 to 31.2%. The mechanism of flame retardancy was analyzed and discussed. In addition, compared with EP, EP/AMP/ADP composites showed a higher dynamic mechanical property without affecting the glass transition temperature. [Display omitted] • The combination of AMP/ADP as temperature-response microparticle shows a synergistic effect in improving fire safety of EP. • The introduction of AMP and ADP changes the degradation process and degradation products of EP. • Both ADP and AMP acted as chemical inertness fillers to enhance EP matrix at the normal service temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly intumescent char layer with core–shell structure was formed during combustion of PC/PBS composites. • The core–shell char layer is composed of an outer porous structure and an inner lamellar structure. • Linear PDMS with terminal Si-H is the key intermediate to join reaction for forming core–shell char. • The addition of 2 wt% PBS reduce the pSPR of PC by 63.2%, increase the LOI to 31.2% and pass the UL94 V-0 rating. A rare charring behaviour was found during the combustion of polycarbonate (PC) composites containing polyborosiloxane (PBS), in which a highly intumescent char layer with core–shell structure was formed. Particularly the core–shell structure is composed of an outer porous structure and an inner lamellar structure, which can effectively isolate external heat radiation and limit the diffusion of degradation products and oxygen. PC/PBS-X composites with 2 wt% PBS-X showed excellent flame retardancy without compromising mechanical properties, including passing the UL-94 V-0 rating and increasing the limiting oxygen index (LOI) to 31.2%. Compared to PC, the peak heat release rate (pHRR) and peak smoke production rate (pSPR) in the case of PC/PBS-1 composites were reduced by 63.2% and 45.5%, respectively. The mechanism for promoting the flame retardancy of PC by PBS-X was studied. The results showed that the PBS decomposed to form linear polysiloxane oligomer with terminal Si-H bond (L-PDMS-H), which reacted with the degraded products of PC to quickly form intumescent char layer with core–shell structure during the combustion. This is the reason why to PBS presented the striking effect on improving flame retardancy of PC. [ABSTRACT FROM AUTHOR]

It is still a great challenge to develop epoxy resin/glass fabric (EP/GF) composites with well-balanced enhancements on flame retardancy and mechanical properties. Herein, a novel strategy that polyhydric SiO 2 coating assistant to graft organophosphorus (DOPO) onto GF was developed for simultaneously improving flame retardancy and mechanical properties of EP composites. The grafting amount of DOPO could reach to 43.64 wt% via the helpful bridging of polyhydric SiO 2 , so that EP composites displayed excellent flame retardancy with the LOI of 37.2%, the V0 rating on UL-94 and a 63.3% decrease on PHRR in cone calorimeter test. According to the analysis of char morphology and structure, the flame retarded mechanism was mainly ascribed to the enhanced barrier effect of a continuous and intergrow char layer, which was composed of GF@SiO 2 as framework and P-containing condensed carbon as stuffing. Meanwhile, EP composites exhibited outstanding mechanical performances with 35% and 60% increases on tensile strength and impact strength respectively, which resulted from the special molecular structure of GF@SiO 2 - g -DOPO with strong interfacial adhesion with EP chains via hydrogen bond and chemical bond. In summary, this work will be favorable to design multifunctional polymer composites with well-balanced comprehensive performances, and expand their widespread applications in high-end fields. [Display omitted] • A novel polyhydric SiO 2 coating assistant to graft organophosphorus onto GF. • The grafting amount of DOPO could reach to 43.64 wt%. • Excellent flame retardancy with LOI of 37.2%, V0 rating on UL-94 and a 63.3% decrease on PHRR. • Outstanding mechanical performances with 35% and 60% increases on tensile strength and impact strength respectively. • The corresponding enhancement mechanisms on flame retardancy and mechanical performances were revealed. [ABSTRACT FROM AUTHOR]

In this work, we demonstrated a new method for rapidly forming a three-dimensional network porous char layer during the combustion of PP composite foam, based on the combination of intumescent flame retardant (IFR) with expandable graphite (EG) and carbon nanotubes (CNTs). The IFR was composed of pentaerythritol (PER) and ammonium polyphosphate (APP) with a mass ratio of 1:2. Compared to PP composite foams with 40% IFR (PP/40IFR), the PP/EG/CNTs/IFR composite foams we designed could preserve the original foam shape and show excellent flame retardancy after combustion due to the formation of a complete porous char layer. It was found that the EG aggregates violently expanded during combustion and offset the shrink of cellular structure, which can blocks the heat transfer from outside to inside and protect the inner material from the fire. At the same time, the CNTs could bind expanded EG aggregates tightly through the interaction between CNTs and EGs. Very interestingly, the IFR was found to form char residue on the surface of CNTs/expanded EG aggregates to not only improve the compactness of the porous char layer but also promote thermal oxidation resistance of this char layer. Owing to the synergistic effect of the IFR with expanded EG and CNTs, the flame retardancy of PP/EG/CNTs/IFR composite foams was dramatically improved, including delayed the flame spread and completely inhibited the droplet phenomenon, and reached the level of flame retardant HF-1 in the standard level combustion test. Moreover, the PP/10EG/5CNTs/25IFR composite foams prepared by this work also presented excellent ablation resistance in the case of a large-scale flame. [Display omitted] • A new method for rapidly forming a 3D network porous char layer during combustion of PP composite foam was demonstrated. • The synergistic action of ternary IFR/EG/CNTs combination enhanced heat insulation of PP composite foam during combustion. • The formation of a complete porous char layer of the foam during combustion maintains its original shape. • The PP/EG/CNTs/IFR foam shows excellent flame retardancy and ablation resistance in both small / large-scale flame tests. [ABSTRACT FROM AUTHOR]