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The flammability of unsaturated polyester resins (UPRs) limits their applications. Herein, a reactive P‐ and N‐containing flame retardant (DPET) having triazole and piperazine rings is reported. The 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) was used to introduce P atoms, and eugenol was used to import reactive double bonds to DPET. Different ratios of DPET were mixed with a commercial UPR and the thermal, mechanical, optical, and flame retardancy properties were measured. The addition of 15% of DPET into neat UPR led to a decrease in the water contact angle from 70° ± 2 to 61° ± 2. The gel content values of the UPRs were found to change between 97.5% and 89%. The optical properties of the UPR were adversely affected by the incorporation of DPET. The modulus of the DPET‐containing UPRs increased with increasing amount of DPET and 15% of DPET‐containing UPR displayed a modulus value of 1784 ± 86 MPa. When 15% DPET was added to neat UPR, char yields were increased (from 5.6% to 16.6%). Limiting oxygen index (LOI) values increased with increasing amounts of DPET and reached up to 23.4%. Micro cone calorimeter (MCC) test results showed up to a 20.5% reduction in the peak heat release rate (PHRR) of the UPR when 15% DPET was added. [ABSTRACT FROM AUTHOR]

Wooden fishing vessels are vulnerable to fire hazards that threaten vessel investment and security. This study proposes the use of fiberglass reinforced plastic (FRP) as a flame retardant laminate to coat wooden ship hulls. FRP consists of glass fibers reinforced with Unsaturated Polyester (UP). The addition of aluminum trihydrate (ATH) filler to the resin can increase FRP flame retardant. FRP laminated specimens of various ATH compositions are manufactured and tested for fire resistance using UL 94 Horizontal standard. The results showed that the addition of ATH increased fire resistance significantly, especially at a concentration of 40%, effectively reducing the burn rate to 8 mm / min. This research offers a solution for FRP lamination with ATH flame retardant filler to improve the safety of wooden fishing vessels without compromising other important properties. Proper use can minimize major damage to fishing vessels during fires and give firefighters more time to extinguish fires. [ABSTRACT FROM AUTHOR]

The ortho unsaturated polyester resin (UPR) was successfully synthesized from propylene glycol, and diethylene glycol in the presence of acids such as phthalic anhydride and maleic anhydride using polycondensation reaction, where styrene is used as a cross-linker, which is catalysed by triphenyl phosphate and accelerated by cobalt octate. The Fire-retardant properties were incorporated into UPR using fire-retardant additives such as Aluminium trihydrate and Ammonium polyphosphate resulting in efficient fire-retardant resin. The liquid and casted mechanical properties of UPR resin are studied and The UPR composite was manufactured through the hand layup method, with the Ecorrosion resistant glass fiber reinforcement with different stacking layers. The synthesized resin to the glass fiber ratio was less than other commercial resin to glass-fiber ratios. The final composite properties were found in the acceptable range. [ABSTRACT FROM AUTHOR]

The flammability levels, flame retardancy ratings, and reaction-to-fire (fire response) properties (under five radiant heat fluxes, i.e., 15, 25, 35, 50, and 75 kW m−2) for same real E-glass fiber-reinforced unsaturated polyester resin (UPR) composite wind turbine blade (WTB) samples were determined by experimental techniques like limiting oxygen index (LOI), vertical flame test (VFT), and cone calorimeter test (CCT). Based on typical CCT results (main test parameters), thermal and non-thermal hazard assessment index systems were selected, calculated, and compared to deduce corresponding hazard characteristics of the blade samples. The WTB shows a LOI value of 25.10% (combustible) and a non-rated (NR) UL (Underwriters Laboratories) 94 classification according to the after-flame time criterion. CCT analyses indicate that higher external heat fluxes correspond to increased peak heat release rate (PkHRR), total heat release (THR), and mass loss rate (MLR) values, and reduced ignition time (tig), flame duration (tfl), and overall flame (combustion) duration (FD) values. Meanwhile, CCT analyses indicate that higher external heat fluxes result in elevated specific extinction area (SEA), rate of smoke released (RSR), total smoke released (TSR), CO yield (COY), and CO production rate (COP) values, and relatively lower CO2 yield (CO2Y) and CO2 production rate (CO2P) values. These results reflect real WTB fires will pose severe situations with noticeable thermal and non-thermal hazards. Multiple physical and chemical evolution processes undergo in burning processes of such fires with higher PkHRR values through heat releases, transfers, exchanges, and feedback. Composite blade materials may be largely deformed and disintegrated in faster rates. Burning blade blocks may form spotting fires and cause secondary ground fires. Local air quality, visibility levels, working, and health conditions of related persons may be worsened. It is really urgent to develop mature, effective, novel, and even revolutionary fire protection and suppression technologies for such fires. [ABSTRACT FROM AUTHOR]

Fireproof coatings are the simplest, most efficient, and oldest method for protecting a wide range of flammable products, such as wood. Furthermore, surface ignition is the initial phase, so surface protection is essential to reduce fire propagation. Furthermore, delaying the spread of flames can help to save someone when a fire starts. This project synthesized flame-resistant resin starting from tetraallyloxysilane monomer as a halogen-free monomer, an intrinsic flame retardant co-curing agent. The following step synthesized polyester resin using terephthalic acid as a heat-resistant resin. Unsaturated polyester was used by bulk radical polymerization. FT-IR and 1H-NMR analysis showed the successful synthesis of the desired monomer and polymeric compound. The thermal degradation and flame retardancy of pure unsaturated polyester resin (UPE) and allyloxysilane-unsaturated polyester (AUPE) were investigated by thermogravimetric analysis (TGA/DTG/DSC). The burning test and the thermal stability of the coating layers were evaluated using standard UL 94. Physical properties of resins were evaluated using Heat Deflection Temp tests (HDT) ISO 75-A, ASTM 648, Hardness ASTM D2583, Volumetric shrinkage ASTM 3521, and Water absorption ASTM D570. The results of the tests show the successful synthesis and their flame retardant properties. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPR) are broadly applied in chemical, construction, transportation and electrical fields, etc. However, UPR materials are extremely flammable. Through radiation, conduction and convection, the released heat brings serious thermal hazards to surrounding life and the environment. Meanwhile, the combustion of UPR also releases a vast of toxic pyrolysis gases and smoke, causing extremely serious non-thermal hazards, endangering life and health, reducing fire visibility and hindering escape and rescue efforts. Therefore, the flame retardant modification of UPR materials is an inevitable measure to reduce its flammability and broaden its application breadth. In this review, the flammability of UPR materials is firstly analyzed from the perspective of their compositions and structures. Meanwhile, based on the differences in preparation methods of flame retardant UPR (FR-UPR) in literature research, it is divided into additive flame retardant, intrinsic flame retardant and interfacial flame retardant methods. The relationship between the highly efficient flame retardant structures and the properties, and the gaseous-phase flame retardant and condensed-phase mechanisms in FR-UPR composites are analyzed. Compared with traditional additive flame retardants, polymeric flame retardants, nanosheet flame retardants and intrinsic flame retardant method are important directions for the future development of FR-UPR composites. In addition, the interfacial flame retardant method can effectively improve the interfacial adhesion and flame retardant properties of fiber-reinforced UPR composites, and also has application prospects. This review analyzes the current challenges faced by FR-UPR, and looks forward to its possible future development directions to guide the preparation and application of high-performance FR-UPR. [ABSTRACT FROM AUTHOR]

I‐MXene with excellent dispersibility was successfully prepared using the chemical grafting method with 1‐butyl‐3‐methylimidazole hexafluorophosphate ([BMIM]PF6) onto MXene. It was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM), which was added to unsaturated polyester resin (UPR) as a synergistic agent, combined with ammonium polyphosphate (APP) to improve the flame retardancy of composites. Tensile strength of the composites was measured using the electronic universal material testing machine. The results showed that the incorporation of I‐MXene was able to increase the tensile strength and elongation at break of the composites. The flame retardancy and thermal stability of the composites were investigated through limiting oxygen index (LOI), cone calorimeter test (CCT), TG and Fourier‐infrared spectroscopy (FT‐IR). The experimental data showed that the LOI values of I‐MXene/APP/UPR composites increased to 29.1%, complying with UL‐94V‐0 rating. Its peak heat release rate (pHRR) and total heat release (THR) were 19.35% and 16.35% lower than those of APP/UPR composites, and the total smoke production (TSP) was reduced by 10.78%. When heated to 800°C, the amount of residual carbon increased by 7.71%. The catalytic effect of I‐MXene contributed to the formation of a compact and expanded carbon layer, resulting in further suppression of heat and smoke release. Highlights: A new type of modified MXene is obtained.It has good dispersivity and synergistic effects.It has good flame retardancy and smoke suppression effects. [ABSTRACT FROM AUTHOR]

For many years, efforts have been made to reduce the flammability of unsaturated polyester resins (UPRs), which are often used in the rail, shipbuilding, and construction industries. Without modification, they often fail to meet fire safety standards. Despite a rich history of flame retardants (FRs) applied to UPRs, researchers seek new solutions that will provide lower flammability and smoke density, as well as attaining a lower environmental impact from the composites. The objective of the study is to highlight the most important recent research on promising nano FRs in order to promote their further development. Mechanisms of action of several groups of nano FRs, such as clay-based, carbon-based, transition metal compounds, layered double hydroxides, polyhedral oligomeric silsesquioxanes, and others, including bio-based, have been studied. Particular emphasis has been laid on nano FRs applied to UPRs, and their influences on thermal stability, flammability, and mechanical properties. Moreover, the environmental impact and toxicity of nano FRs have been discussed. Results have proved that nano FRs applied at low loadings may significantly improve thermal stability, with a simultaneous increase or only a slight decrease in mechanical properties. However, attention on related environmental issues has highlighted the necessity of carefully selecting novel nano FRs. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resin (UPR) with excellent flame retardant is mainly obtained by adding large amounts of flame retardants, usually at the expense of mechanical properties. In this work, a reactive flame retardant containing phosphorus and nitrogen (DOPO-N) was successfully synthesized and incorporated in UPR as a crosslinker. The mechanical and flame-retardant properties of UPR composites were enhanced. UPR/30DOPO-N passed a UL-94 V-1 rating with a limiting oxygen index (LOI) of 30.8%. The tensile strength of UPR/30DOPO-N increased by 24.4%. On this basis, a small amount of modified HNTs (VHNTs) was added to further improve the flame-retardant properties of the composite. With the introduction of 3 wt% VHNTs, the composite passed the UL-94 V-0 rating. The peak of heat release rate (PHRR) and total heat release (THR) of it decreased by 60.7% and 48.3%, respectively. Moreover, the detailed flame-retarding mechanism of DOPO-N and VHNTs was investigated by thermogravimetric infrared spectroscopy (TG-IR), Raman spectra, and X-ray photoelectron spectroscopy (XPS). It was found that DOPO-N played a role in quenching the flame in the gas phase and cooperated with VHNTs to enhance the barrier effect in the condensed phase. [ABSTRACT FROM AUTHOR]

• A bottom-up grown nanoparticle (nSiO 2) composite was synthesized by reacting liquid unsaturated polyester resins (UPR), and substituted alkoxy silanes. • nSiO 2 reduced the overall heat and smoke released during the combustion of the composites by increasing the solid char residue formation. • 10 wt% nSiO 2 loaded composites showed 41 % reduction in total heat release (THR) and 52 % reduction in total smoke release (TSR). • The composites retained >90 % of their transparency in the 500-800 nm range. Achieving lower heat release rates (HRR) during combustion is one of the key steps toward obtaining flame retardant materials. UPR thermosets, while mechanically strong and chemically durable, show high HRR upon ignition. While most commercial applications focus on blending of metal oxide or other heterogeneous fillers to reduce HRR, they have significant drawbacks like phase segregation, drop in transparency and other features which disfavor their use in UPRs. Herein, a novel, green technique to generate nSiO 2 in-situ in UPRs is demonstrated. The method is designed such that the precursors act as nucleating agents covalently bonded to the UPRs and as growth fuel for the nSiO 2 production. Apart from major advantages like a uniform phase distribution in the thermoset and transparency, this technique also prevents direct handling of powdered micro or nanoparticles, leading to a safer working environment for the handling of UPRs. The physical, thermal, and mechanical properties analyzed show great promise towards flame retardant composites, as the formed nanocomposite material, with 10 wt% loading of nSiO 2 demonstrates a 41 % reduction in total heat release (THR) and a 52 % reduction in total smoke release (TSR), while retaining optical transmission >90 %. On combination with commercial phosphorus containing flame retardant, ammonium polyphosphate (APP), the composite shows an even greater reduction in THR and TSR, while also being self-extinguishing. These compelling features, coupled with the safe nature of generating nanoparticles in-situ, offer substantial benefits of using this nSiO 2 approach towards HRR reduction in UPR-based thermosets and advocate for their use in commercial formulations. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new flame retardant (DPPONSi) containing P, N and Si elements was synthesized by the facile Kabachnik-Fields reaction. • DPPONSi enhances the flame retardancy of UP with high efficiency. • DPPONSi can withstand the conditions of UP's recycling process. • The degradation product of UP/DPPONSi16.7 was recycled conveniently and used to prepare aerogels with high flame retardancy. Recycling thermosets presents significant economic benefits and social implications, and to date, a series of controllable recycling strategies have been proposed. However, prior research has primarily focused on neat polymers, neglecting the impact of the recycling process on composites whose additives may lose performance post-recycling. The paradigm shift towards sustainability necessitates the development of additives that not only exhibit high performance but also endure recycling conditions. Herein, taking flame-retardant unsaturated polyester (FRUP) as an example, we designed a new flame retardant (DPPONSi) with multiple flame-retardant elements and a low phosphorous oxidation state. FRUP with 16.7 wt% of DPPONSi achieves a V-0 rating in the UL-94 vertical burning test, and its limiting oxygen index (LOI) reaches 27.1%. Moreover, its peak heat release rate and total heat release are distinctively reduced by 65% and 42%, respectively. The high flame-retardant efficiency structure also protected DPPONSi from by-reactions. Without complex separation processes, FRUP degradation products were integrated with polyvinyl alcohol (PVA) to create flame-retardant aerogels with high flame retardancy. Additionally, we systematically studied the influence of flame retardants with varying oxidation states on FRUP, the corresponding flame-retardant mechanisms, and the degradation process of FRUP. This work realizes the organic combination of strategies to enhance the high efficiency of flame retardants with design methods for flame retardants that are resistant to existing unsaturated polyester degradation systems. [ABSTRACT FROM AUTHOR]

A new reactive flame retardant (DTA), containing phosphaphenanthrene and triazine-trione groups was synthesized and applied to improve the flame retardancy of unsaturated polyester resin. The thermal stability, flame retardancy and combustion behaviors of UP/DTA thermosets were detected by thermogravimeric analysis (TG), limited oxygen index (LOI), vertical burning (UL94) test and cone calorimeter test. According to the research results, the addition of DTA contributed to improving the flame retardancy of UP. After adding 20 wt% DTA, the LOI of UP composite increased from 19.0% of the neat UP to 26.6%, and UL94 rating reached V-0. In addition, compared with pure UP, the peak heat release rate (pk-HRR), average heat release rate (av-HRR) and total heat release rate (THR) of UP/DTA-20 thermosetting material decreased by 44.0, 26.2 and 29.5%, respectively. In the gaseous phase, DTA decomposed to generate nitrogen-containing fragments with diluting effect and phosphorus-containing free radicals with quenching effect to inhibit the combustion. In the condensed phase, phosphaphenanthrene group of DTA decomposed to generate phosphorus-based compounds, which promoted the carbonization of the UP matrix and cooperated with triazine-trione group to increase the char yield. Therefore, DTA plays an important role in flame retardancy in the gas and condensed phases. [ABSTRACT FROM AUTHOR]

Summary: Graphene oxide (GO) was prepared from graphite powder by the classic Hummers method, and modified by 1‐N‐butyl‐3‐methylimidazolium hexafluorophosphate (IL) and 3‐aminopropyltriethoxysilane (KH550) to obtain ionic liquid functionalized graphene oxide (ILGO). ILGO, compounded with traditional flame retardants (ammonium polyphosphate and expandable graphite), was used in unsaturated polyester resin (UPR) to enhance the flame retardancy. The flame retardant property and thermal degradation of the UPR composites were analyzed by limiting oxygen index (LOI), UL‐94, cone calorimeter test (CCT), and thermogravimetric analysis (TGA). The results show that there is an obvious synergism between ILGO and the traditional flame retardants. The LOI value of UPR‐4 containing ILGO reaches 28.2% and passes V‐0 of UL‐94, and UPR‐4's the initial temperature (Ti), maximum degradation temperature (Tmax), and residual carbon greatly increase. The experimental data shows that ILGO can promote UPR to form more residual carbon during combustion, enhance thermal stability, and make the material not easy to decompose. The morphology of carbon layer measured after CCT was observed by scanning electron microscope (SEM). SEM images show that the surface of char layer of UPR‐4 containing ILGO becomes smoother, flatter and denser, compared with UPR containing only flame retardants. The cohesiveness and compact structure residual carbon can effectively prevent the oxygen, combustible gas, and heat transfer between the flame zone and the base material to reduce flammability. [ABSTRACT FROM AUTHOR]

Currently, the issue of natural flammability of unsaturated polyester resin (UPR) severely restrains its application. In this study, polymeric flame retardant poly methyl vinyl di (1-thio-2,6,7-trioxal-1-phosphabicyclo [2.2] octane-4-methoxy) silane (PMVDOS) with P–S–Si-based cage unit was synthesized. The UPR/PMVDOS composites were prepared by adding different ratios of PMVDOS into UPR. The flame-retardant properties and the char layer structure of UPR samples were evaluated via the limiting oxygen index (LOI), vertical burning test, cone calorimeter test, scanning electron microscopy, laser Raman spectroscopy, and X-ray photoelectron spectroscopy. The results showed that UPR/PMVDOS composites reached the UL-94 V-0 rating with the LOI value of 27.8%, and the carbon residue increased from 4.9% for pure UPR to 14.9% when the content of PMVDOS was 18 wt%. The peaks of heat release rate, total heat release, and total smoke production were comparatively reduced. The flame-retardant mechanism of PMVDOS mainly acted on the condensed phase. The surface of the matrix was covered with the polymer containing phosphorous and silicon dioxide particles, preventing the escape of flammable volatiles and isolating the exchange of oxygen and heat, thus, the degradation of the matrix could be inhibited. This research provides a solution to improve the flame retardancy of UPR. [ABSTRACT FROM AUTHOR]

The thermal degradation behaviors of commercial flame-retardant unsaturated polyester glass fiber-reinforced plastic (polyester GFRP) containing aluminum trihydrate (ATH) were studied using thermogravimetric analysis and a combination of TG-Fourier transform infrared-gas chromatography/mass spectrometry (TG-FTIR-GC/MS). From the variation of derivative thermogravimetry curves, it is found that the degradation of polyester GFRP can be divided into two stages with the critical conversion rate of 0.35. Activation energies were calculated by Starink method, and then the kinetic triplet was further determined by Coats-Redfern method. The results show that the dehydration of ATH and breakage of ester linkages lead to the first major mass loss, and volatile products including H2O, dicyclopentadiene, benzaldehyde and dimethyl phthalate are generated. Consecutive reaction occurs in the second stage. The statistical rupture of polyester and polystyrene chains leads to the formation of toxic volatiles, especially styrene, α-methylstyrene, toluene, ethylbenzene, benzaldehyde, phenol and phthalic anhydride. Possible reaction mechanisms are discussed in order to explain the observed results. The experimental results could give guidance to the fire safety design of high-speed train and provide basic data for numerical simulation of fire accidents. [ABSTRACT FROM AUTHOR]

[Display omitted] Owing to the lack of research on structure-activity relationship and interaction mechanism between unsaturated polyester resins (UPR) and flame retardants, it has been a big challenge to prepare high-efficiency flame retardants for UPR in industry. In this research, to explore structural rules of high-efficiency flame retardants, several polymeric flame retardants were synthesized with varied main-chain, side-chain, phosphorus valence states and contents of flame retardant elements. The thermal stabilities of flame retardants and UPR composites were firstly assessed. It has been found the interaction existed between flame retardants and UPR, through transesterification reaction and β scission pathway in polyester and polystyrene chains. With only 15 wt% of PCH 3 -S, UPR composites can reach V0 rating in UL-94. The PHRR and THR values can be maximumly decreased by 71.66 % and 77.67 %, with 20 wt% of PB-S. It has been found flame retardants with sulfone group and + 3 valence state of phosphorus in molecular backbone can release SO 2 and phosphorus containing compounds in gaseous phase, which diluted fuel fragments and catalyzed H⋅ and HO⋅ radical removal. The mechanism for improved flame retardancy of UPR composites with various polymeric flame retardants were discussed in detail. Some general rules for highly efficient flame retardant UPR can be summarized: First, gaseous phase flame retardant mechanism plays the major role in improvement of flame retardant performance of UPR composites; Second, the combination of + 3 valence state of phosphorus structures, higher phosphorus contents and sulfone groups effectively improves the flame retardant efficiency of flame retardants. [ABSTRACT FROM AUTHOR]

The application of flame retardants in automobiles is extensive, and the existing flame retardants will cause some pollution to the environment. Therefore, environmentally friendly flame retardants need wide exploration. Natural fibers have been used in various fields for their environmentally friendly features. Thus, in this paper, hemp fiber (HF) was modified with phytic acid and then combined with melamine cyanurate to improve the fire safety of unsaturated polyester resins (UPRs). The fire behavior and thermal stability of UPR composites were evaluated using the limiting oxygen index (LOI), cone calorimeter test, and thermo-gravimetric analysis (TGA). With 3 wt. % modified HF (HF-P) incorporation, the LOI value of UPR/HF-P-3 composites increased from 18.9% of pure UPR to 22.1%, and the average heat release rate (AHRR) and total heat release were reduced to 401.9 kW/m2 and 150.6 MJ/m2, respectively. TGA revealed that UPR/HF-P-3 composites led to the increased amount of residual char and better thermal stability compared to UPR/HF composites. In addition, HF-P endowed a better enhancement on the flexural strength of UPR composites. [ABSTRACT FROM AUTHOR]

• Summarized the effects of APP and its derivatives on the performances of UPR. • Compared the advancement and challenges of different APP modification methods. • Highlighted the future research opportunities of APP for UPR. Ammonium polyphosphate (APP) is a common and commercially available flame retardant for various polymeric materials due to its low cost, ease of proccessing, low toxicity, and environmental friendliness. This mini review focuses on the application of APP in unsaturated polyester resin (UPR) and outlines the flame retardancy, thermal stability, and mechanical properties of the APP-containing UPR composites. As an effective acid source, APP can facilitate the dehydration and carbonization of the UPR matrix during combustion, forming a graphite char layer on the matrix surface to slow down heat exchange and volatile release, thus suppressing the burning reaction. Due to the inorganic properties of APP, microencapsulation and surface decoration are usually conducted on it to enhance its compatibility with UPR and its flame-retardant efficiency. Moreover, different flame-retardant synergists are also applied to strengthen the flame-retardant performance of APP in UPR. In this review, we briefly summarized the influences of microencapsulated APP, surface-decorated APP, and APP/synergist on the properties of UPR, respectively. Then, the advancement and challenges of these APP systems are highlighted, and future research opportunities are also proposed. [ABSTRACT FROM AUTHOR]

The impact of three phosphonate oligomers with different unsaturation degrees on the flame retardancy, mechanical properties and optical performance of unsaturated polyester resins (UPRs) were investigated. The three phosphonate oligomers were poly(2-butyne-1,4-diol phenylphosphonate) (PY) containing C C, poly(cis -2-butene-1,4-diol phenylphosphonate) (PE) containing C C and poly(1,4-butanediol phenylphosphonate) (PO) without unsaturated bonds. The flame retardancy and UV-shielding effect of UPRs were positively correlated with the unsaturation degree of oligomers. Specifically, only adding 20 wt% PY made UPR pass UL-94 V-0 rating and 22 wt% PE was needed, while 22%PO/UPR was still in UL-94 NR rating. Further, PE containing C C exhibited the highest efficiency in improving the toughness of UPR. The impact strength and elongation at break of 22%PE/UPR were significantly improved by 460 % and 200 % respectively, compared with pure UPR. Meanwhile, the high transparency of UPRs benefits from the good compatibility between oligomers and matrix. This work provides the basis for development and utilization of novel high-performance and multifunctional UPRs with potential versatile applications. [Display omitted] • Three multifunctional flame retardant/toughening oligomers were prepared. • The flame retardancy, toughness and UV-shielding effect of UPRs were greatly strengthened. • The unsaturated degree of oligomers exerted significant influence on all the properties of UPRs. [ABSTRACT FROM AUTHOR]

An unsaturated ladder phenyl/vinyl polysilsesquioxane (PhVPOSS) was synthesized and applied to vinyl ester resin (VER) thermosets. The compatibility, mechanical properties, thermal properties, and combustion behavior of the VER-PhVPOSS composites were further investigated. As a result, the PhVPOSS and VER had a good compatibility and interaction based on the solubility parameters and Flory–Huggins parameters. PhVPOSS provided the VER with a significantly enhanced bending strength, thermal stability, and smoke-suppression effect. When 20 wt% PhVPOSS was added, the bending strength, flexural modulus, and breaking force increased by195.6%, 260.6%, and 196.6% compared with pure VER. The peak heat release rate, total smoke release, and specific optical density decreased by 52.2%, 20.7%, and 15.7%, respectively. These favorable characteristics indicated that PhVPOSS had a good application prospect in unsaturated polyester resin. [ABSTRACT FROM AUTHOR]

A comparison of ammonium polyphosphate/montmorillonite nanocompound (AM) and a synergistic agent, boron/silicate‐based graphene oxide (B‐Si@GO), is performed in unsaturated polyester resins (UPR) on flammability and thermal properties. It is found that by the presence of 14.9 wt% AM and 0.1 wt% B‐Si@GO, the limiting oxygen indices value of 0.1 B‐Si@GO/flame‐retardant‐UPR (FRUPR) composites is increased to 28.5%, and the UL 94 rating of V‐0 is achieved. And, lower loading of B‐Si@GO is observed to improve char skeleton, resulting in better insulation of the char and decrease in heat release, and the synergism of AM and B‐Si@GO reduces the fire risk. Furthermore, by analyzing the pyrolysis behavior and mechanical properties of materials, B‐Si@GO significantly improves the effects of flame retardants on the thermal stability, decomposition activation energy, tensile strength, and elastic modulus of UPR. Finally, flame retardant mechanism and model are proposed on the basis of the analyses of thermal decomposition products and process, and residual char structural components. This work provides a solution to improve the flame retardancy of UPR without affecting its mechanical properties, and will be conducive to the development of its flame retardant mechanism. [ABSTRACT FROM AUTHOR]

In the present work, allylamine exfoliated alpha zirconium phosphate (AXZrP) reinforced unsaturated polyester (UP) nanocomposites were developed and characterized. Exfoliation of alpha zirconium phosphate (α-ZrP) was achieved through Brønsted acid–base interaction using allylamine in different mole ratios. The partially exfoliated α-ZrP possesses a higher concentration of α-ZrP than completely exfoliated. Subsequently, the partially exfoliated α-ZrP was reinforced with UP resin to enhance the thermal and mechanical properties of the resulting composite. Detailed studies using scanning electron microscopic and X-ray diffraction analysis suggest that the AXZrP/UP composite possesses a homogeneous distribution of α-ZrP within the UP matrices. For 10.0 wt% AXZrP/UP composite, the mechanical properties such as tensile and flexural strength were observed to enhance up to 56% and 61% respectively. Further, appreciable enhancement in the flame retardant behavior with V0 rating and high thermal stability with LOI value of 27.1% for 10.0 wt% AXZrP/UP composite was observed. Similarly, the catalytic effect of α-ZrP contributes to enhancing the flame retardant behavior along with rapid char formation. [ABSTRACT FROM AUTHOR]

Heat- and fire-resistant of the composite nanomaterials based on unsaturated polyester resins are produced. Using ZnO nanoparticles and water as fire retardants are found to reduce the combustion rate and to increase the formation of the carbonized residue of composite nanomaterial based on polyester resin. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPRs) are usually used in the field of automotive and electronic appliances, but their natural flammability severely constrain their wide application. In this research, a mono‐component intumescent flame retardant piperazine pyrophosphate (PPAP) was incorporated into the UPR matrix and the fire retardancy, thermal properties, combustion performance, and flame‐retarded mechanisms of UPR/PPAP were comprehensively investigated. With as low as 18 wt% PPAP introduced, UPR/18 wt% PPAP thermosets fulfilled UL‐94 V‐0 grade during vertical burning tests and the limiting oxygen index value reached 29.8%. Cone calorimeter tests shown that the peak of heat release and CO production were prominently declined with the decrease of 60.9% and 70.2% compared with those of UPR. The incorporation of PPAP efficaciously enhanced the fire safety of UPR thermosets. The investigation of flame‐retarded mechanisms for UPR/PPAP thermosets indicated that PPAP stimulated UPR thermosets to form sufficient, compact, partially graphitized, and expanded char layer on thermosets surface in advance and the char layer effectively exerted shielding effect in condensed phase. Thus, the total amount of heat of UPR/PPAP was suppressed with the reduction of 42.5% compared with that of UPR. Overall, the excellent fire safety performance promised the flame‐retardant UPR/PPAP thermosets crucial application values in some key areas. [ABSTRACT FROM AUTHOR]

To achive excellent fire resistance, new microcapsule flame retardants (DMCAD and DMPPD) were prepared using 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide combined with melamine cyanurate or melamine polyphosphate as the shell material and diatomite as the core material. The successful assembly of DMCAD and DMPPD was detailed characterized by Fourier transform infrared (FT‐IR) spectra, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Meanwhile, the flame retardancy and thermal stability of the unsaturated polyester resin (UPR)/DMCAD and UPR/DMPPD composites were also studied. The addition of DMCAD and DMPPD effectively improves the flame retardance properties of UPR, and the effect of DMPPD was better. The limiting oxygen index (LOI) of UPR/DMPPD‐3 increased by 11.6% when compared with that of UPR, and the sample achieved V‐0 rating. Moreover, the peak heat release rate (pHRR) and the total heat release (THR) rate of UPR/DMPPD‐3 were reduced by 67% and 26%, respectively. Under nitrogen condition and air condition, UPR/DMPPD showed better thermal stability and char‐forming ability from the thermogravimetric (TG) results. Residual char of the UPR composites was systematically analyzed with SEM and XPS. Finally, the flame retardant mechanism of DMPPD was proposed. [ABSTRACT FROM AUTHOR]

In this work, we were prepared a novel coating flame retardant APP@UiO and added it to UPR, the thermal stability, flame retardancy and impact properties of UPR composites were explored. [Display omitted] • A novel coating flame retardant APP@UiO was obtained by synthesizing UiO66-NH 2 on the surface of APP. The thermal stability of APP@UiO has been significantly enhanced when compared to both APP and UiO-66-NH 2. • APP@UiO has exhibited remarkable flame retardant capabilities in unsaturated polyester resin (UPR), reduced the emission of toxic gases during the combustion process of UPR and exhibited effective smoke suppression properties. • APP@UiO contributes to the enhanced mechanical properties of UPR affected by APP to a certain extent. A novel coating flame retardant named APP@UiO was successfully synthesized by in-situ synthesis of UiO-66-NH 2 on the surface of APP. Its structure was characterized by fourier transform infrared (FTIR) X-ray diffraction（XRD）, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The effects of APP@UiO on the flame retardant properties and mechanical properties of unsaturated polyester, as well as their flame retardant mechanism, were comprehensively analyzed. The flame retardant properties of UPR composites were studied through limiting oxygen index (LOI) and cone calorimeter test (CCT). When the addition amount of APP@UiO was 10 wt%, the peak heat release rate (pk-HRR) value and the maximum smoke yield (SPRmax) value of UPR composites decreased by 61.34% and 37.5%, respectively, compared with pure UPR, and the LOI value reached 31.2%. The impact performance test of UPR composite was carried out to explore its mechanical properties. The research data showed that the existence of organic ligands in APP@UiO can improves the deterioration of mechanical properties of UPR caused by APP. [ABSTRACT FROM AUTHOR]

A mussel-inspired intumescent flame-retardant (MIFR) was introduced into unsaturated polyester resin (UPR) to modify its flame retardancy. Its flame retardant and smoke suppression properties were studied by cone calorimetry test (CCT) and limiting oxygen index (LOI), UL-94, and the flame-retardant mechanism was studied by scanning electron microscopy and thermogravimetric analysis (TG). The LOI data showed that MIFR could greatly enhance the flame retardancy of UPR. The UPR composites with 10 mass% of MIFR have a LOI 27.8% and passes the UL-94 V-0 test without melt-dripping, while that for UPR-MAPP is only 25.5% with V-2 test at the same content. The mechanical properties of UPR-MIFR composites are higher than those of UPR-MAPP composites. The CCT revealed that MIFR can significantly decrease the heat release and the amount of smoke production. The TG test showed that MIFR could catalyze degradation of UPR composites and promote the char formation in the combustion process of UPR. In summary, the microencapsulation coating of the TA–Fe3+ modified the surface of MAPP enhanced the mechanical properties, flame retardancy and smoke suppression. [ABSTRACT FROM AUTHOR]

To obtain a novel multifunctional flame retardant material, Triphenyl phosphate (TPP) was used as the capsule material to microencapsulate diatomite/ammonium polyphosphate (Dia/APP). The novel multifunctional material Dia-APP-TPP could effectively improve the flame retardancy of unsaturated polyester resin (UPR). The desired structure of Dia-APP-TPP was clearly observed through Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Scanning electron microscopy (SEM). The combustion behavior, thermal property and mechanical performance of UPR/Dia-APP-TPP composites were also investigated. Incorporation of Dia-APP-TPP into UPR greatly enhanced the flame retardancy and thermal stability of the composites. Remarkably, with 20 wt% of Dia-APP-TPP, UPR-2 successfully achieved UL-94 V-0 rating and the LOI value increased from 19.2% to 26.6%. Besides, the CCT test showed that the THR value of UPR-2 decreased by 33.9% compared with that of pure UPR. The results of this study also confirmed that a novel and feasible strategy can be used to obtain a microencapsulation flame retardant. Unlabelled Image • A microencapsulated flame retardant (Dia-APP-TPP) was successfully fabricated. • Charring property of Dia-APP-TPP exceed the addition effect of Dia, APP and TPP. • The incorporation of Dia-APP-TPP endows UPR with excellent flame retardancy. [ABSTRACT FROM AUTHOR]

In this work, phosphorylated chitosan‐coated carbon microspheres (PCH@CMS) was successfully synthesized. Obtained PCH@CMS used as flame retardant was added into unsaturated polyester resin (UPR). Fourier infrared spectroscopy (FTIR) and X‐ray electron spectroscopy (XPS) results indicated that C═O, P─O, and P═O appeared on the surface of PCH@CMS. Compared with UPR, the residues of UPR/PCH@CMS‐10 at 800°C under nitrogen and air atmospheres increased by 9.0 and 3.9 wt%, respectively, and the peak heat release rate (pHRR) and the peak smoke release rate (pSPR) of UPR/PCH@CMS‐3 decreased by 18.9% and 23.5%, respectively. Limiting oxygen index (LOI), thermogravimetric analyzer (TG), and cone calorimeter test (CCT) results showed that the addition of PCH@CMS could enhance the flame retardancy and smoke suppression of the UPR composites. Moreover, the residues after CCT were characterized by scanning electron microscopy (SEM), XPS, and laser Raman spectroscopy (LRS). Based on the above results, the flame retardant mechanism of PCH@CMS was proposed. The carbon layer produced by the UPR/PCH@CMS composites was tortuous and could suppress the heat and pyrolysis product exchange with UPR matrix. [ABSTRACT FROM AUTHOR]

The unsaturated polyester resins (UPR) were usually applied in electronic equipment, but the intrinsic flammability severely retrained their application. A mono‐component flame retardant poly (piperazine methylphosphonic acid neopentylglycol ester) (PPMPNG) made in our lab was selected and applied to improve their flame retardant performance. The UPR thermosets achieved UL‐94 V‐0 grade during vertical burning tests and the limiting oxygen index was as high as 32.1% when 15 wt% PPMPNG was incorporated. PPMPNG promoted the decomposition and carbonization of UPR materials in advance during heating process, and the residual mass was effectively enhanced at high temperature. The flame retardant mechanism of UPR/PPMPNG thermosets was investigated by pyrolysis‐gas chromatography/mass spectrometry tests, and the measurement of the morphologies and chemical components of the char residue. The phosphine oxygen radical was generated and then quenched the active free radicals in gas phase. Moreover, the av‐EHC of FR‐UPR was declined from 15.8 MJ kg−1 of pure UPR to 8 9 MJ kg−1 corresponding a reduction of 43.6%, which also verified the flame retardant effect in gas phase. The compact, integrated, and graphitized char layer was produced on materials surface and then exerted excellent barrier effect in condensed phase. Thus, the UPR/PPMPNG composites were conferred superior flame retardant properties. [ABSTRACT FROM AUTHOR]

Abstract Ammonium dihydrogen phosphate (ADP) as a glass fiber (GF) coating is useful as a flame retardant for glass fiber reinforced composites (GFRC). Three different ADP weight fraction coatings on GF resulted in distinctly different behavior. Single fiber tensile tests were conducted and statistically evaluated by Weibull distribution, for the three different ADP coatings. The tensile strength of neat GF and ADP coated GFs was not significantly affected by the ADP weight fraction. GFRC was manufactured using ADP coated GF mat reinforcement in unsaturated polyester (UP). The flame retardant test was used to access and compare the flame retardant property for the different composite specimens. The GFRC with the 20 wt% ADP coating exhibited the best flame retardant property. Interfacial/wettability properties were determined using static contact angle measurements. The static contact angle increased with increasing ADP weight fraction. Interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) were measure using the short beam and microdroplet pull-out tests respectively. Both ILLS and interfacial adhesion decreased somewhat in the ADP coated GF, while the flame retardant property markedly improved in GFRC, for ADP coated GF mat. [ABSTRACT FROM AUTHOR]

Modified montmorillonite‐containing phytic acid (PA‐MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA‐MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL‐94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA‐MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA‐MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA‐MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame‐retardant mechanism of PA‐MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPR) are composed of prepolymers and styrene diluents, while the former are produced by co-polycondensation between diol, unsaturated diacid and saturated diacid. In this work, bio-based UPR prepolymers were synthesized from bio-based oxalic acid, itaconic acid, and ethylene glycol, which were then diluted with bio-based isosorbide methacrylate (MI). Meanwhile, the phenylphosphonate were introduced into the molecular chains of prepolymers to achieve intrinsic flame retardancy of bio-based UPR. The potential of the reactive MI diluents as substitutes of volatile styrene, was also assessed through the volatility test, curing kinetics and gel contents analysis. For UPR materials with styrene diluents, the UPR materials can achieve UL-94 V0 level and the 28% of limiting oxygen index (LOI) with 2.63 wt% of phosphorus contents. By contrast, the UPR materials with MI diluents can reach UL-94 V0 level with only 2.14 wt% of phosphorus contents. As the phosphorus contents were further increased to 2.63 wt%, UPR materials can achieve highest 29%, while the peak of heat release rate (PHRR) and total heat release (THR) were decreased by 68.01% and 48.62%, respectively. The Flame Retardancy Index (FRI) was also used to comprehensively evaluate the flame retardant performance of UPR composites. Compared with neat UPR, the composites with MI diluents and phosphorus containing structures increased from 1.00 to 6.46. The mechanism for improved flame retardancy was analyzed from gaseous and condensed phase. Additionally, the tensile strengths of bio-based UPR materials with styrene and MI diluents were studied. This work provides an effective method to prepared high-performance and fully bio-based UPR materials with improved flame retardant properties and safety application of reactive diluents. [Display omitted] • Fully bio-based and intrinsically flame retardant UPR was synthesized. • Bio-based MI diluents can effectively replace toxic and volatile styrene VOC. • Fully bio-based UPR achieved UL-94 V0 with only 2.14 wt% of phosphorus. • Fully bio-based UPR exhibits promising comprehensive application prospects. [ABSTRACT FROM AUTHOR]

Despite extensive applications in modern industry, unsaturated polyester resin (UPR) suffers intrinsic flammability, presenting fire threats to both environment and properties. Existing environmentally benign flame retardants, in particular ammonium polyphosphate (APP), often show a limited efficiency in UPR. Herein, a Schiff base-coated ammonium polyphosphate (MAPP) was synthesized using APP, 1,2-bis(2-aminoethoxy)ethane, and terephthalaldehyde (TPA). The results show that MAPP retards the initial decomposition of UPR and promotes its carbonization under heating, imparting enhanced thermal stability. Notably, 17 wt% of MAPP endows UPR with a UL-94 V-0 rating and a limiting oxygen index (LOI) of 28.6 %. MAPP is also effective in inhibiting heat and smoke release during combustion, and 17 wt% of it brings about 39.5 % and 18.0 % reductions in total heat release and total smoke production. Because of improved interfacial compatibility, the final UPR/MAPP displays significantly improved mechanical properties relative to UPR/APP. This work proposes a new functionalization surface modification strategy for creating efficient APP-based flame retardant for UPR, which is expected to be more widely applied in industries. [Display omitted] • A Schiff base-modified APP, MAPP, was prepared by one-step surface encapsulation. • MAPP shows a better fire-retardant efficiency than APP in UPR. • 17 wt% of MAPP enables UPR to achieve a UL-94 V-0 rating and a LOI of 28.6 %. • The surface Schiff base layer improves the compatibility between MAPP and UPR. [ABSTRACT FROM AUTHOR]

In this work, five additives were used, namely: (5,6-diphenyl-6H-1,3,4-thiadiazin-2-amine)(Additive I). (5,6-diphenyl-2-[(Z)-(2,4,6-trimethyl-2H-1,3-thiazin-5-yl)diazenyl]-6H-1,3,4-thiadiazine)(Additive II). (5-(1,4-phenylene)bis (1,3,4-thiadiazinol-2-amine)(Additive III). (2,2-(1,4-phenylene)bis(4,5-dihydro-1, thiazole-4-carboxylicacid)(Additive IV). (5,5'-[1,4-phenylene bis(4,5-dihydro-1.3-thiazole-2,4-diyl) bis (1,3,4-thiadiazol-2-amine))(Additive V). The effects of these additives on flammability of some of the thermosetting polymers (unsaturated polyester and epoxy resins), have been studied. Sheets of the specimens (resins with different weight percentages of additives), in dimensions (150X150X3) mm were prepared. Two standard test methods used to measured the flame retardation which are: (ASTM: D-2863) and (ASTM: D-635). Results are obtained from these tests indicated that, additive IV has high efficiency as flame retardant, self-extinguishing (S.E.) at the percentage (0.2 %) for unsaturated polyester resin and the percentage (0.4 %) for epoxy resin. Also self-extinguishing (S.E.) at the percentage (0.4%) for additives II in unsaturated polyester resin and the (0.6%) for additives II in epoxy resin; Additive V show low effect on flammability in both resins. [ABSTRACT FROM AUTHOR]

A novel flame‐retardant unsaturated polyester (UP) was obtained by introducing ammonium polyphosphate (APP) and aluminum hypophosphite (AHP) into UP matrix. The UP/APP/AHP composites obtained were characterized by Fourier Transform Infrared Spectra (FTIR). From limiting oxygen index (LOI), microscale combustion calorimetry (MCC), and UL‐94 tests, the UP/APP/AHP composites present significantly enhanced flame retardancy when compared to pure UP, such as passed UL‐94 V‐0 classification, decreased peak heat release rate (PHRR) maximally by 50.0% and total heat release (THR) maximally by 22.0%, and increased LOI by 34.8%. Thermal degradation behaviors of composites studied by thermogravimetric analysis (TGA) suggest that APP/AHP hybrids have a higher catalytic charring efficiency than APP alone. Char morphology investigated by scanning electron microscopy (SEM) indicates that the UP/APP/AHP composites form a compact and intumescent char on the sample surface during combustion, which could retard the transfer of heat and oxygen. Thermogravimetric analysis/infrared spectrometry (TGIR) results reveal that the APP/AHP hybrids reduce the release amount of combustible gas from polymer matrix during combustion. The UP/APP/AHP system acts in gas phase through flame inhibition and in condensed phase through charring, resulting in significantly enhanced flame retardancy. This work combining condensed‐phase mechanisms with gas‐phase mechanisms in flame retardance of UP would stimulate more efforts to explore highly effective flame‐retardant system of polymers. POLYM. COMPOS., 39:1763–1770, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Developing a strategy to improve the flame retardancy and water resistance of waterborne bio-based coatings on wood is an effective route to enhance safety and applicability of timbers. In this work, the waterborne itaconate-based unsaturated polyester (IAF) were synthesized from biomass-derived itaconic acid (IA) and flame retardants FRC-6 by melt polycondensation in one pot, which was investigated as an ideal waterborne resin for UV-curable coating applications. A series of UV-cured hybrid coatings on wood were prepared consisting of IAF, N-(Hydroxymethyl) acrylamide (NMA), and γ-methacryloxypropyltrimethoxysilane (MPS) in various proportions via UV-curing and sol-gel process. The incorporation of MPS enhanced the rigidity, cross-linkage, and water resistance of UV-cured hybrid coatings, but the excessive silicone gel limited the further improvement of coating performances due to the phase separation and reduced film-forming property. Moreover, the UV-cured hybrid coatings appeared exceptional charring properties and endowed wood with superior flame retardancy. It was noticed that P/N/Si synergistically promoted the formation of remarkable, dense, and stable char layer on wood as a barrier, retarding the spread of heat, oxygen, or flammable volatile and the further combustion of substrates. Besides, the free radical capture of phosphorus and the dilution effect of inert gas played an essential role in gas-phase flame retardancy. [Display omitted] • The waterborne itaconate-based unsaturated polyester was synthesized in one-pot. • The hybrid coatings were efficiently prepared by UV-curing and sol-gel process. • The silicone improved cross-linkage and water resistance of hybrid network. • The UV-cured hybrid coatings enhanced char formation and flame retardancy of wood. • P/N/Si played a synergistic role in the condensed and gas-phase flame retardancy. [ABSTRACT FROM AUTHOR]

Different characterization techniques were used to study the hydrolysis and condensation reaction kinetics of 3-methacryloxypropyltrimethoxysilane (MAPTMS) to obtain open cage silsesquioxane oligomers. The formation of hydrogen bonds, which condition the chemical structures of the resulting products, was identified. Improved thermal and fire resistant behavior of unsaturated polyester (UP) composites prepared with aluminium trihydroxide (ATH) and the synthesized oligomer were registered. Opened silsesquioxane structures also showed an improvement in the mechanical properties of the char formed after firing. [ABSTRACT FROM AUTHOR]

A novel reactive phosphorus-containing flame retardant 1,4-phenylene-bis((6-oxido-6H-dibenz[c,e][1,2]-oxaphosphorinyl) methylene) diacrylate (TDCAA-DOPO), with two symmetrical 9,10-dihydro-9-oxa-10-phosphaphena-nthrene-10-oxide structure (bi-DOPO), was synthesized and combined with unsaturated polyester resin (UPR) via cross-linking to prepare flame-retardant UPR (FR-UPR). To make clear both the effects of the bi-DOPO structure and the cross-linking reaction on the thermal stability and flame retardancy of UPR, an additive flame retardant that also owned bi-DOPO structure but without a vinyl bond, 1,4-phenylene-bis((6-oxido-6H-dibenz[c,e][1,2]-oxaphosphorinyl) carbinol) (TDCA-DOPO), was used as a contrast. The results showed that the incorporation of TDCAA-DOPO or TDCA-DOPO into UPR can reduce its peak heat release rate (PHRR) and total heat release (THR), as well as improve the limiting oxygen index (LOI) value. As compared to TDCA-DOPO, the reactive TDCAA-DOPO endowed FR-UPR with enhanced thermal stability, residual char, and glass transition temperature (T g), which were even higher than those of pure UPR. Besides, their flame-retardant mechanism for UPR had been well investigated. [ABSTRACT FROM AUTHOR]

Although possessing polymer with excellent flame retardant and low heat release have emerged in previous work, synchronously suppressing smoke (fatal hazards in fire disasters) is still a dilemma. Adjusting the key intermediate-polycyclic aromatic hydrocarbons (PAHs) during the burning processes is a promising path to achieve low smoke release. In this work, we constructed the benzimidazole structure, as an aromatization precursor to chemically modify ammonium polyphosphate (APP) to obtain a trinity flame retardant (APP-BIM). Unsaturated polyester resin (UP), as a typical polymer with high flammability and smoke hazards being the research model, exhibit excellent thermal stability and fire safety compared with previous work. Meanwhile, a homemade smoke sampling module (SSM) coupling with a cone calorimeter (Cone-SSM) is also constructed for online acquiring the soot particles during burning for in-depth investigation of smoke suppression mechanism. This strategy provides a promising new approach to effectively reduce the fire hazard of polymers. [Display omitted] • Adjusting the structure of key intermediate-polycyclic aromatic hydrocarbons (PAHs) formed at the initial stage of burning to directly suppress the soot formation process. • Benzimidazole, as an aromatization precursor, is used to chemically modify ammonium polyphosphate to obtain a trinity flame retardant. • A homemade smoke sampling module (SSM) coupling with a cone calorimeter (Cone-SSM) is constructed for in-depth investigation of smoke suppression mechanisms. [ABSTRACT FROM AUTHOR]

It is urgent to develop the highly efficient flame-retarding UPR composites to decrease the risk of conflagration. In the present work, an ionic liquid containing phosphorus and nitrogen was designed by the coulomb force between adenosine triphosphate (ATP) and 2-Methylimidazole (MI), and it was stored in pre-expanded EG (pEG) to enhance the fire safety of the UPR. For the UPR/pEGAM 9 composites, its thermal conductivity was 0.331 W m−1 K−1, which was 36.9% higher than that of neat UPR, and the tensile strength were was 24.6 MPa. Meanwhile, it passed the UL-94 V-0 rating with a LOI of 36.5%. The PHRR, THR, TSP, SPR, PCOP and PCO 2 P of UPR/pEGAM 9 composites decreased by 71.6%, 17.7%, 42.3%, 75.2%, 72.7% and 73.3% comparing to that of neat UPR, showing a large reduction in the heat hazard and smoke toxicity. Moreover, it was concluded that the condensed phase attributing to the excellent synergistic effect between the pre-expanded EG and [ATP][MI] dominated in the flame-retarding mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

The synergistic flame retardant effects of AlPi and ATH in UPR were investigated. The flammability and thermal stability of UPR composites were evaluated with LOI, UL-94 vertical burning, MCC and TG. The structure and morphology of filler and char residues were examined with SEM and FTIR. The interaction between AlPi and ATH was observed when the mass ratio of AlPi and ATH was 3:2 and LOI value of flame-retarded UPR increased to 30 and UL-94 rating passed V-0; however, the SEM showed that AlPi and ATH have a good dispersion in UPR. The pHRR of UPR-15AlPi/10ATH was 241.6 Wg, decreasing by 30.4 % compared with pure UPR. The experimental TG curve of AlPi/ATH in N was lower than calculated one at the second stage and had lower char residue at 700 °C, demonstrating interaction of AlPi and ATH during thermal degradation. The char residue of UPR-15AlPi/10ATH at 700° suggested that the interaction between AlPi and ATH strengthened the char -formation ability and thermal stability of UPR, so the SEM showed a strong and dense char surface. The FTIR of char residues at different temperatures showed that AlPi and ATH interactions changed the type of aluminum phosphates, making char residue of UPR/AlPi/ATH system increased eventually. [ABSTRACT FROM AUTHOR]

A phenolic novolac resin has been chemically reacted with 4-vinylbenzyl chloride to introduce polymerizable vinyl benzyl groups. The modified novolac spontaneously polymerizes like styrene, is physically and chemically compatible with a typical unsaturated polyester (UP) resin, and can be free-radically cured (crosslinked) alone and in mixtures with UP using styrene as a reactive diluent. The cured vinylbenzylated novolac and co-cured blends of it with UP show superior flame retardance to cured UP alone and have potential applications as matrix resins in glass-reinforced composite laminates especially for marine structures. [ABSTRACT FROM AUTHOR]

• Highly efficient flame retardant (MA-DOPO) was prepared by nucleophilic substitution reaction. • The mechanical properties of UPR composites can be increased while the flame retardant properties are improved. • The enhancement mechanism is the formation of an interpenetrating network structure of hydrogen bond cross-links between the flame retardant MA-DOPO and UPR. Unsaturated polyester resin (UPR) composites with excellent flame retardancy and high mechanical property is a great challenge to its widely application. In present work, a highly efficient flame retardant (MA-DOPO) containing nitrogen, sulfur and phosphorus elements was designed via a nucleophilic substitution reaction of amino and aldehyde groups. For the UPR/MA-DOPO 15 composites, its tensile strength was 28.3 MPa, which was 19.9 % higher than that of neat UPR attributing to the formation of hydrogen bonds with UPR. It should be noted that tensile strength of UPR/MA-DOPO 20 composites reached the highest 39.6 MPa, showing a growth trend with the enhancement of incorporation amount of MA-DOPO. Meanwhile, the UPR/MA-DOPO 15 composites passed the UL-94 V-0 rating with a LOI of 27.0%, and the peak heat release rate (PHRR) and total heat release rate (THR) were reduced by 35.1% and 41.6% in cone calorimeter (CC) test comparing to that of neat UPR respectively. Moreover, the detailed flame-retarding mechanism of MA-DOPO was investigated by the thermogravimetric infrared spectroscopy (TG-IR), Raman spectrum, X-ray photoelectron spectroscopy (XPS) and pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS), in which the releasement of inert gas in gas-phase and the catalytic carbonation in condensed phase jointly taking effect. [ABSTRACT FROM AUTHOR]

ABSTRACT Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (1HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn-Wall-Ozawa methods. Cone calorimeter, UL-94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42068. [ABSTRACT FROM AUTHOR]

Novel blends of two furan resins with an unsaturated polyester have been prepared and cured by parallel free radical (for the unsaturated polyester) and acid-catalysed crosslinking (for the furan resin) to give co-cured composite materials. Although these materials have inferior physical properties, such as low Tg and low storage modulus compared with those of unsaturated polyester and furan resins alone, they show markedly improved flame retardance compared with that of the normally highly flammable unsaturated polyester. This increased flame retardance arises from a condensed phase mechanism in which the furanic component forms a semi-protective char, reducing rates of thermal degradation and total heat release and heat of combustion. The blends also burn with reduced smoke output compared with that from unsaturated polyester alone. [ABSTRACT FROM AUTHOR]

• The effect of phosphorus valence states on combustion behaviors of UPR was analyzed. • Flame retardant UPR achieved UL-94 V0 with only 15 wt% of PBPG. • +3 phosphorus valance of PBEG was more helpful to improve flame retardancy of UPR. • The preparation of flame retardant UPR was mainly based on gaseous phase mechanism. This work analyzes the effect of different valence states in phosphorus structures on thermal stability, pyrolysis kinetics and flame retardancy of unsaturated polyester resin (UPR). Then, the corresponding mechanisms are systematically analyzed. The poly(ethylene phenylphosphonate) (PBEG) and poly(ethylene phenoxyphosphate) (POEG) were synthesized, and the combustion behaviors of UPR, such as pyrolysis, ignition, heat suppression and charring capacity were studied. The phosphorus structures with +5 valence states in POEG was more conducive to formation of carbon layers than that of +3 valence states in PBEG. The better charring capacity made pyrolysis activation energy (E k) of UPR/POEG different from UPR/PBEG in F-W-O and DAEM fitting methods. The E k of UPR/POEG was larger than pure UPR at high mass conversions, but E k of UPR/PBEG was less than pure UPR during entire pyrolysis process, due to different phosphorus-containing pyrolysis products. For PBEG, more phosphorus-containing species existed in gaseous phase to capture H· radicals; By contrast, POEG left more products in condensed phase, promoting the formation of thermally stable carbon layers. Different phosphorus-containing products also affected flame retardancy of UPR. UPR reached UL-94 V0 with only 15 wt% of PBEG, where peak heat release rate (PHRR), total heat release (THR), fire growth index (FGI) were obviously reduced. However, flame retardant efficiency of POEG were lower than PBEG. This indicates that +3 phosphorus valance of PBEG is more helpful to improve flame retardancy of UPR, and the essential reasons have been systematically analyzed. Meanwhile, the selection of high-efficiency flame retardant systems for UPR materials can be based on gaseous-phase mechanism and supplemented by condensed-phase mechanism. [ABSTRACT FROM AUTHOR]