Flame-retardant Unsaturated Polyester Resin Research Articles

Novel coating flame retardant APP@UiO for preparation of flame retardant unsaturated polyester resin composites

A novel coating flame retardant named APP@UiO was successfully synthesized by in-situ synthesis of UiO-66-NH2 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.

State-of-the-Art Research in Flame-Retardant Unsaturated Polyester Resins: Progress, Challenges and Prospects

State-of-the-Art Research in Flame-Retardant Unsaturated Polyester Resins: Progress, Challenges and Prospects

Preparation, Characterization and Properties of Flame Retardant Unsaturated Polyester Resin Based on r-PET

Preparation, Characterization and Properties of Flame Retardant Unsaturated Polyester Resin Based on r-PET

Exploration on structural rules of highly efficient flame retardant unsaturated polyester resins

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 PCH3-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 SO2 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.

Surface-modified ammonium polyphosphate with (3-aminopropyl) triethoxysilane, pentaerythritol and melamine dramatically improve flame retardancy and thermal stability of unsaturated polyester resin

Ammonium polyphosphate surface-modified by silane coupling agent (3-aminopropyl) triethoxysilane (KH-550), named STAPP, incorporated with pentaerythritol and melamine to prepare intumescent flame retardant unsaturated polyester resin (UPR/IFRs). Surface groups, surface elements, thermal stability and surface morphology of STAPP were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The flame retardancy of the UPR composites was studied by limit oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test, and its thermal stability was evaluated by TG. The results showed that IFRs greatly improves flame retardancy, thermal stability and carbon formation ability of UPR. Compared with pure UPR, when the loading of IFRs was 25 mass%, the LOI was increased from 19.8 to 41.5%, the UL-94 test reached the V-0 rating from NR, peak heat release rate and total smoke production was decreased by 54.1 and 38.7%. Furthermore, the addition of IFRs delayed the product of smoke and release heat. TG results showed that 27.6 mass% chars remained in UPR/IFRs at 1073 K, showing a good char forming ability. Besides, honeycomb-type carbon layer with few cracks and holes was observed by SEM. Finally, the flame retardancy mechanism of IFRs was elaborated in detail, which was attributed to the siloxy groups and expanded carbon layer.

Effects of a Reactive Phosphorus-Sulfur Containing Flame-Retardant Monomer on the Flame Retardancy and Thermal and Mechanical Properties of Unsaturated Polyester Resin.

A novel reactive phosphorus and sulfur-containing monomer (bis(acryloxyethyldiphenylphosphate)sulfone, BADPS) was synthesized to enhance the comprehensive performance of unsaturated polyester resin (UPR), and corresponding flame-retardant unsaturated polyester resins (FR-UPRs) with various amounts of BADPS were prepared by radical bulk polymerization. The flame retardancy and thermal and mechanical properties of the UPR samples were investigated by limiting oxygen index (LOI) measurements, cone calorimetry, differential scanning calorimetry (DSC), a thermogravimetric analysis (TGA), and a tension test. The results showed that the introduction of BADPS remarkably enhanced the flame resistance and high-temperature stability, as well as the tensile performance of UPR. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and Raman spectroscopy studies revealed that BADPS can efficaciously promote the formation of UPR char residue with an improved microstructure and increased graphitization degree, which enhancedthe high-temperature stability and char yield of UPR. Additionally, a thermogravimetry-Fourier transform infrared (TG-FTIR) analysis corroborated that the evolution of combustible volatiles from UPR decomposition was substantially restrained by the incorporation of BADPS, which is beneficial for the suppression of fire hazards in UPR.

An efficient synergistic system for simultaneously enhancing the fire retardancy, moisture resistance and electrical insulation performance of unsaturated polyester resins

Unsaturated polyester resins (UPR) are usually used in the field of electronic appliances, but their inherent flammability and hygroscopicity severely limit their wide application. In this research, dimelamine pyrophosphate (DMPY) was synthesized and constituted a synergistic flame retardant system (FRs) with aluminum diethylphosphinate (ADP). The FRs was applied to flame retarded UPR thermosets and the fire retardancy, moisture resistance, mechanical properties and flame retarded mechanisms of UPR/FRs were comprehensively investigated. When as low as 15 wt% FRs was incorporated, UPR/FRs achieved UL-94 V-0 rating during vertical burning tests and the limiting oxygen index value reached 27.9%. FRs stimulated UPR matrix to form uniform, stiff and dense char layer on materials surface during combustion process. Besides, the phosphine and phosphine oxygen radicals and inert gases generated from FRs exerted the inhibition and dilution effect in gas phase. Thus, the heat release and effective heat combustion of UPR/FRs were conspicuously suppressed. Moreover, UPR/FRs retained satisfactory flame retardancy and mechanical performance after water resistance tests. The moisture resistance of UPR/FRs was evidently enhanced compared with UPR and it led to the maintenance of electrical insulation properties of water treated UPR/FRs. Overall, the superior fire safety, moisture resistance and electrical insulation performance promised the flame retardant UPR thermosets crucial application values in the key areas.

Influence of expandable graphite on flame retardancy and thermal stability property of unsaturated polyester resins/organic magnesium hydroxide composites

ABSTRACTAn eco‐friendly flame retardant unsaturated polyester resin (UPR) material was prepared by combination organic magnesium hydroxide (OMH) and expandable graphite (EG). Different from direct addition of magnesium hydroxide (MH) in UPR matrix‐like traditional method, OMH as a reactive monomer participates in the polycondensation reaction of UPR was more effective in improving the compatibility of flame retardant with matrix. Interestingly, the flame retardant UPR composites exhibited a more satisfactory flame retardant effect when a certain amount of 8 wt % EG was added into UPR/OMH matrix because of the synergistic effect between OMH and EG, resulted in the limited oxygen index from 21.7 to 28.5% and UL‐94 test passed V‐0 rating. Moreover, the peak heat release rate, total heat release, and smoke production rate of flame retardant UPR composites significantly reduced. The excellent flame retardancy was due to the formation of a dense and continuous carbon layer in the later stages of combustion. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47881.

Preparation of highly efficient flame retardant unsaturated polyester resin by exerting the fire resistant effect in gaseous and condensed phase simultaneously

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.

Effects of Dimethyl Methylphosphonate, Aluminum Hydroxide and Ammonium Polyphosphate on the Flame Retardancy and Thermal Properties of Unsaturated Polyester Resin

The flame-retardant unsaturated polyester resin with dimethyl methylphosphonate (DMMP), aluminum hydroxide (ATH) and ammonium polyphosphate (APP) were prepared and found to exhibit a high flame-retardant efficiency and low cost. The different dosages of flame retardant effect on the flame retardant were evaluated based on limiting oxygen index (LOI) measurements, vertical burning test (UL94), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). A LOI value of 29.8% and a UL-94 vertical burning V-0 rating was achieved for UPR with 10phr DMMP, 15phr ATH and 9phr APP. In the presence of DMMP, ATH and APP, the dense char structure were produced in the combustion process of UPR.

Establishment of highly effective flame‐retardant unsaturated polyester resin system based on multiple strategies

AbstractConsidered that unsaturated polyester resin (UPR) as one of the most commonly used thermoset materials often exhibit severe fire hazards, graphene can be used to act as barriers to enhance the flame retardancy of UPR. However, graphene easily shows irreversible aggregation when being introduced into polymer matrix, which limits its further application in industry. In this work, we synthesized a novel organophosphorus oligomer (DHP), which contained double bond and multivalent phosphorus (−1 and +5) with highly effective flame retardancy, onto graphene oxide via in situ atom‐transfer radical polymerization (ATRP). Then, the obtained graphene‐DHP was incorporated into UPR matrix by curing. The homogeneous dispersion of graphene‐DHP in UPR matrix was confirmed by transmission electron microscopy (TEM). The addition of 2.0 wt% graphene‐DHP significantly improved the flame retardancy of UPR/graphene‐DHP nanocomposites, which was demonstrated by the peak of heat release rate (PHRR) decreased by 41.79%. Moreover, it is found that graphene‐DHP in nanocomposites cannot only act as barriers, but also catalyze the char formation in condensed phase as well as capture free radicals in gaseous phase. This work provides a feasible approach to combine graphene and phosphorus‐containing flame retardant and would also trigger more scientific interest in exploiting new type nanocomposites for flame retardants.

Synergistic effect of combined dimethyl methylphosphonate with aluminum hydroxide or ammonium polyphosphate retardant systems on the flame retardancy and thermal properties of unsaturated polyester resin

ABSTRACTA series of flame-retardant unsaturated polyester resin (UPR) were prepared by the addition of dimethyl methylphosphonate (DMMP) with various amounts of aluminum hydroxide (ATH) or ammonium polyphosphate (APP) as the flame retardants. The combustion resistance effects of ATH/DMMP and APP/DMMP systems were evaluated by limiting oxygen index test and vertical burning test (UL-94). The thermal properties of UPR were investigated by thermogravimetric analysis. The structure of char was observed by scanning electron microscopy. DMMP incorporated with ATH or APP improved the flame retardancy and thermal properties of UPR. However, the fire-retardant mechanism of these two systems were different: The ATH/DMMP system provided synergistic effect in charring property of the UPR, produced great amount of residual char, and thus revealed the excellent flame retardancy. The APP/DMMP system further improved the flame retardancy of the UPR due to the change in the residual char structure rather than the increase in the production of char.

Bi-DOPO Structure Flame Retardants with or without Reactive Group: Their Effects on Thermal Stability and Flammability of Unsaturated Polyester

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 stabil...

In situ loading ultra-small Cu2O nanoparticles on 2D hierarchical TiO2-graphene oxide dual-nanosheets: Towards reducing fire hazards of unsaturated polyester resin

Fire hazards have seriously hindered the commercial application of unsaturated polyester resin (UPR), and polymer inorganic nanosheet nanocomposites hold great promise in improving their flame-retardant properties. Herein, the hierarchical structured Cu2OTiO2GO nanosheets were synthesized and characterized by XRD, Raman, TEM and XPS. Then Cu2OTiO2GO nanosheets were incorporated into UPR matrix to obtain flame-retardant UPR nanocomposite. Incorporation of 2wt% Cu2OTiO2GO nanosheets into UPR matrix resulted in an obvious reduction in PHRR and THR by 29.7 and 19.1%. TG-IR-MS results revealed that toxic pyrolysis gas such as benzene, CO and aromatic compounds greatly were decreased. In addition, RIIR spectra demonstrated the limited influence of Cu2OTiO2GO nanosheets on thermal degradation of UPR matrix, and SEM images of char residues showed that Cu2OTiO2GO nanosheets could improve their compactness. Based on the analysis of gaseous and condensed phase, a plausible flame-retardant mechanism was hypothesized to elaborate how Cu2OTiO2GO nanosheets work inside the flaming UPR nanocomposite. This innovative idea may be expanded to other polymer system and open a new door to develop polymeric nanocomposites with high performance.

Study on thermal degradation and combustion behavior of flame retardant unsaturated polyester resin modified with a reactive phosphorus containing monomer

A halogen-free phosphorus-containing monomer (TAOPO) was successfully synthesized and used as a co-curing agent to prepare intrinsic flame-retardant unsaturated polyester resin (FR-UPR) by radical bulk polymerization with different TAOPO content.

The Thermal Properties of Unsaturated Polyester Resin Treated with Intumescent Flame Retardants

A novel cheap macromolecular intumescent flame retardant (IFR), was synthesized. Unsaturated polyester resin (UPR) was modified with IFR to get the flame retardant UPR, whose flammability and burning behavior were characterized by limiting oxygen index (LOI). 22.7% of weight of IFR was doped into UPR to get 28.5 of LOI. The thermal properties of epoxy resins containing IFR were investigated with thermogravimetry (TG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for UPR containing IFR, compared with UPR, IFR decreased weight loss, thermal stability, increased the char yield, which shows that IFR can catalyze decomposition and carbonization of UPR.

Investigation on flame retardancy, combustion and pyrolysis behavior of flame retarded unsaturated polyester resin with a star-shaped phosphorus-containing compound

The phosphorus-containing star-shaped flame retardant (TRIPOD-DOPO) was synthesized, while the flame retardant unsaturated polyester resins (FR-UPRs) composites with various amounts of TRIPOD-DOPO were prepared. The thermogravimetric analysis (TGA) and oxygen index (OI) results showed that the incorporation of TRIPOD-DOPO improves the thermal stability and flame retardancy of UPR. The combustion properties of composites were evaluated by microscale combustion calorimeter (MCC), and the results indicated that TRIPOD-DOPO decreased the peak heat release rate (pHRR) and total heat release (THR) of UPR. Fourier transform infrared coupled with the thermogravimetric analyzer (TG–IR) revealed that UPR and TRIPOD-DOPO decomposed independently of each other. Flame inhibition was expected to occur in the gas phase. Under the air condition, TRIPOD-DOPO showed a more obviously condensed phase interaction increasing charring from the TG results. The SEM results showed that the residual char of composites were more compact and continuous, which could prevent mass and thermal transfer.

Preparation, Flame Retardancy, and Thermal Degradation of Unsaturated Polyester Resin Modified with a Novel Phosphorus Containing Acrylate

A novel reactive phosphorus-containing acrylate (ODOPB-AC) was successfully synthesized and characterized, and the flame retardant unsaturated polyester resins (FR-UPR) with various amounts of ODOPB-AC were prepared. The thermal decomposition and flame retardant properties of samples were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and microscale combustion calorimetry (MCC). As the ODOPB-AC content increased, the LOI value of FR-UPR was increased, while the value of peak heat release rate (PHRR) and total heat release (THR) were reduced. The evolved gas analysis and condensed thermo-oxidative degradation process of UPR and FR-UPR were monitored by thermogravimetric analysis/infrared spectrometry (TG-IR) and real-time infrared spectrometry (RT-IR), providing insight into the thermal degradation mechanism. ODOPB-AC acted in the gas phase through flame inhibition and in the condensed phase through charring. Moreover, scanning electron microscopy (SEM) and X-ray photoelectr...

Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.

Study of the flame retardancy and thermal properties of unsaturated polyester resin via incorporation of a reactive cyclic phosphorus-containing monomer

A reactive cyclic phosphorus-containing monomer (ethyl acrylate cyclic glycol phosphate; EACGP) was synthesized in a facile way and various amounts of EACGP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (UPR) samples were investigated using thermogravimetric analysis, limiting oxygen index (LOI), and microscale combustion calorimetry tests. Due to the high phosphorus content of EACGP, incorporation of this monomer led to a marked decrease in the peak heat release rate and the total heat release, an increase in the LOI and the combustion char formation. Furthermore, real-time Fourier transform infrared spectroscopy was employed to investigate the thermooxidative degradation behavior of UPRs and the charring effect of EACGP as well as the UPR char morphology was studied, illustrating the flame retardancy mechanism in UPR.