Novel flame‐retardant epoxy composites containing aluminium β‐carboxylethylmethylphosphinate

A novel flame‐retardant aluminum β‐carboxylethylmethylphosphinate [Al(CEP)] was synthesizedby a simple process. The effect of Al(CEP) on the curing of epoxy resin (EP) was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The flame retardancy and thermal properties of Al(CEP)/EP were analyzed by a limiting oxygen index (LOI), vertical burning test (UL‐94), scanning electron microscopy (SEM) with energy‐dispersive X‐ray (EDX), gravimetric analyses, and DSC. Results disclosed that curing of EP is delayed by incorporating Al(CEP). The flexural strength of EP is reduced but the flexural modulus is increased by adding Al(CEP). Adding Al(CEP) depresses the decomposition of EP while leads to a increase in the glass transition temperature (T_g), in char formation and in flame retardancy of EP. EP containing 25 phr Al(CEP) provides LOI of 28.3% and passes UL‐94 V‐0 rating. SEM results show that the sample passing V‐0 rating can form the condensed char whereas porous char is observed from the sample failing in V‐0 rating after combustion. EDX analysis shows that the condensed char presents higher weight ratio of carbon to phosphorus than the porous char, indicating appropriate amount of Al(CEP) is necessary for formation of the stable char. POLYM. ENG. SCI., 55:657–663, 2015. © 2014 Society of Plastics Engineers     

Development of a DOPO‐containing melamine epoxy hardeners and its thermal and flame‐retardant properties of cured products

In this study, a novel Schiff base of melamine used as flame‐retardant curing agent for epoxy resins, was synthesized via condensation reaction of 4‐hydroxybenzaldehyde with melamine, followed by the addition of 9,10‐dihydro‐9‐oxa‐10‐phosphaphen‐anthrene 10‐oxide (DOPO) to the resulting imine linkage. The structure of DOPO‐containing melamine Schiff base (P‐MSB) was characterized by Fourier transformed infrared spectroscopy, ¹H‐nuclear magnetic resonance (¹H‐NMR) and ³¹P‐NMR. The compound (P‐MSB) was used as a reactive flame retardant in o‐cresol formaldehyde novolac epoxy resin (CNE) to prepare flame‐retardant epoxy resins for electronic application. The thermal and flame‐retardant properties of the epoxy resins cured by various equivalent ratios phenol formaldehyde novolac (PN) and P‐MSB were investigated by the nonisothermal differential scanning calorimetry, the thermogravimetric analysis, and limiting oxygen index test. The obtained results showed that the cured epoxy resins possessed high T_g (165°C) and good thermal stability (T_5%, 321°C). Moreover, the P‐MSB/CNE systems exhibited higher limiting oxygen index (35) and more char was maintained in P‐MSB/CNE systems than that in PN/CNE system and the effective synergism of phosphorus–nitrogen indicated their excellent flame retardancy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flame retarding mechanism of Polyamide 6 with phosphorus‐nitrogen flame retardant and DOPO derivatives

A novel flame‐retardant composite was prepared by introducing a phosphorus‐nitrogen flame retardant and DOPO‐SiO₂ into PA6. DOPO‐SiO₂ was synthesized successfully in a one‐step process. PA6/OP1314/DOPO‐SiO₂ achieved a UL 94 V‐0 rating with an LOI value of 31%. The maximum mass loss rate of decomposition decreased significantly and char residue increased to 11.6 wt % compared with that of pure PA6. The compacted and dense char was formed due to the combination of the P‐N flame retardant and DOPO‐SiO₂. The complex viscosity of PA6/OP1314/DOPO‐SiO₂ increased considerably which tend to prevent the dripping phenomenon. The flame‐retardant mechanism of PA6/OP1314/DOPO‐SiO₂ was also investigated by Fourier transform infrared spectroscopy FTIR at different temperatures and the pyrolysis products were investigated by pyrolysis gas chromatography/ mass spectrum (Py‐GC/MS). It was assumed that DOPO‐SiO₂ and the hypophosphite of OP1314 possess excellent flame retardancy during the gaseous phase. Meanwhile, melamine and phosphate reacted with the pyrolytic products of PA6 to protect the matrix during the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42932.     

Thermodynamic insight into the evolution of medieval glassworking properties

We present differential scanning calorimetry (DSC) analyses of seven French stained glasses from the 13th to 16th centuries. These glasses illustrate the dramatic compositional change from the antique soda‐rich glasses to potash‐ and lime‐rich compositions, resulting in drastic temperature and viscosity increases. We investigate the influence of chemical composition on glass thermal properties: glass‐transition (T_g), crystallization, and melting temperatures. We find that T_g varies from 533°C (soda type) to 638°C±17°C (potash type) to 685°C±5°C (lime type). The viscous slowdown of the melt as a function of the temperature, close to T_g, was modeled using the Vogel‐Tammann‐Fulcher equation. This enables temperature‐viscosity profile calculations, and suggests that recipes have been empirically optimized to reach similar thermoelastic properties suitable for glassmaking despite changing the nature of raw materials.     

Fireproofing of polyurethane elastomers by reactive organophosphonates

Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4′‐diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol–ene addition of allyl or vinyl dialkyl phosphonate to 3‐mercapto‐1,2‐propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250 °C. The percentage of residual char at 600 °C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (T_g) is observed as the percentage of P increases, whereas the T_g of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry     

Novel flame‐retardant epoxy based on zinc methylethyl phosphinate

A novel flame retardant zinc methylethylphosphinate (Zn(MEP)) was used to fill epoxy resins (EPs). The structure of Zn(MEP) was conformed with Fourier transform infrared, hydrogen nuclear magnetic resonance and phosphorus nuclear magnetic resonance, and X‐ray fluorescent and X‐ray diffraction. The flammability, decomposition behavior, and glass transition temperature (T_g) of cured EP/Zn(MEP) were investigated. Zn(MEP) is stable below 406°C. EP containing 20 phr of Zn(MEP) achieves 27.5% of limiting oxygen index and UL‐94 V0 rating. Scanning electron microscopy‐energy‐dispersive X‐ray and Fourier transform infrared spectroscopy investigations show that a condensed char layer with carbon‐rich and phosphorus‐rich components was formed during heating Zn(MEP)/EP, the atomic ratio of P to Zn on the surface of the char is reduced compared with the initial sample. The P‐rich components and lower atomic ratio of P/Zn on the char surface implies that the Zn(MEP) acts in both condensed phase and gas phase. TGA investigation shows that there are interactions between Zn(MEP) and EP when they are copyrolyzed. The interactions lead to a modification in degradation process and promote the char forming. Compared with aluminum diethylphosphinate Zn(MEP) filled EP shows lower limiting oxygen index but higher T_g. In addition, the interactions between polymer and additive are different when aluminum diethylphosphinate instead of Zn(MEP) is added into EP. Copyright © 2013 John Wiley & Sons, Ltd.     

DOPO‐Based Phosphorus‐Containing Methacrylic (Co)Polymers: Glass Transition Temperature Investigation

A two‐step synthetic procedure is designed for preparing new flame‐retardant methacrylic monomers containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as a substituent side group. DOPO and methacrylate moieties are linked by linear aliphatic hydrocarbon spacers (3 to 11 carbon atoms). Copolymerization with methyl methacrylate is carried out leading to copolymers containing between 2 and 10 wt% phosphorus. All homo‐ and copolymers exhibit a unique glass transition temperature (T_g ). A new group contribution for DOPO‐based substituent is extracted that leads to reasonable estimations of T_g s of other published polymers. The Fox equation provides a good estimation of T_g s for most copolymers and for physical blends of poly(methyl methacrylate) (PMMA) and DOPO. When using monomers having three and four carbon atoms in the hydrocarbon spacer, the T_g of copolymers remains close to that of PMMA over a wide range of composition.     

New Types of Ecologically Safe Flame Retardant Polymer Systems

Abstract

New types of ecologically safe flame retardant composition based on poly(vinyl)alcohol and poly(vinyl)alcohol oxidized by KMnO₄ (polymer-organic char formers) were proposed for nylon 6,6. These systems can promote the formation of char by intermolecular crosslinking (“synergetic carbonization”). The Cone Calorimeter tests indicated the improvement of fire retardant properties for the compositions of nylon 6,6 with poly(vinyl)alcohol and poly(vinyl)alcohol oxidized by KMnO₄ in comparison with pure nylon 6,6.     

Thermal stability,flame retardance,and mechanical properties of polyamide 66 modified by a nitrogen–phosphorous reacting flame retardant

Flame‐retardant polyamide 66 (PA66) was prepared by the polymerization between PA66 prepolymer and N‐benzoic acid (ethyl‐N‐benzoic acid formamide) phosphamide (NENP). Compared with the pure PA66, the flame‐retardant PA66 exhibited better thermal stability, as indicated by thermogravimetric analysis results. The limiting oxygen index was 28% and the UL‐94 test results of the flame‐retardant PA66 indicated a V‐0 rating when the content of the NENP prepolymer was 5 wt %. The flammability and flame‐retardant mechanism of PA66 were also studied with cone calorimetry and scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, respectively. The mechanical properties results show that the flame‐retardant PA66 resin had favorable mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43538.     

Research on properties of rigid polyurethane foam with heteroaromatic and brominated benzyl polyols

Rigid polyurethane foams (RPUFs) were prepared with specific heteroaromatic and brominated benzyl polyols. The mechanical properties and thermal stability were studied using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TG). The limiting oxygen index (LOI) was used to investigate the flame retardancy of the RPUFs. The results showed that the glass transition temperature (T_g) of the RPUF prepared by heteroaromatic polyol was 182°C, demonstrating an improved thermal stability for this specific heteroaromatic polyol. Brominated benzyl polyol exhibited less negative influence on mechanical properties of the RPUFs at the same time of improving the flame retardancy. The LOI values increased with an increase in the brominated polyol content to 27.5%, and the char‐forming ability of the RPUF improved; the char residue rate reached 12.6% at 700°C, but it was only 6.2% without the flame retardant. Scanning electron microscope (SEM) and energy‐dispersive spectrometry (EDS) verified that the mechanism of flame retardancy was due to a synergistic effect of the gas phase and the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42349.     

Thermal and flame resistance properties of natural rubber‐g‐poly‐(dimethyl(methacryloyloxymethyl)phosphonate)

Natural rubber grafted with poly(dimethyl(methacryloyloxymethyl)phosphonate) (i.e., NR‐g‐PDMMMP) was prepared in latex medium via photopolymerization. Thermal and flame resistance properties of the NR‐g‐PDMMMP prepared with various levels of grafted PDMMMP or grafting rate (GR) were investigated. Thermal behaviors were investigated by thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). It was found that the graft copolymer exhibited phase separation with double T_g values. A shift of T_gs toward each other was observed with increasing GR, which indicated tendency to become a single phase material. Increasing GRs also caused increasing heat and flame resistance with increasing degradation temperature and level of char residue. Furthermore, increasing level of limited oxygen index (LOI) and decreasing burning rate were observed with increasing the GR. This is attributed to increasing content of char residue of the phosphorus compound, which acted as the thermal insulation and a barrier of oxygen to transfer to the burning materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

High Glass Transition Temperature Barium Silicophosphate Glasses Designed with Topological Constraint Theory

Alkali‐free glasses have attracted tremendous attentions for their high glass transition temperature (T_g). Such a feature broadens their potential applications, especially in the area of high‐density and high‐power laser glasses. BaO–P₂O₅ glasses, as one of the major matrix materials due to its high‐T_g, can be applied in high‐power laser glasses. Introducing SiO₂ is an effective method to improve the thermal, refractive index, and mechanical properties of phosphate glasses. Herein, we studied the barium silicophosphate glasses with MAS NMR and the T_g was successfully calculated by the topological constraint theory. The designed glass (20BaO–26.7SiO₂–53.3P₂O₅, mol%) with a high T_g (789K) was prepared and it also exhibited high refractive index and high Vickers hardness, suggesting the barium silicophosphate glasses have widespread applications in high‐power laser glasses and optical fibers.     

In situ polymerization of flame retardant modification polyamide 6,6 with 2-carboxy ethyl (phenyl) phosphinic acid

A novel halogen-free flame retardant copolyamide 6,6 (FR-PA66) was prepared successfully by in situ polymerizing with adipic acid hexamethylene salt and 2-carboxy ethyl (phenyl) phosphinic acid (CEPPA). The elemental composition and chemical structure of FR-PA66 were characterized by energy dispersive X-ray spectroscopy, Fourier transform infrared spectrometer and ¹³C Nuclear magnetic resonance spectrometer. The flame retardancy, thermal stability, and morphology of char residues were also investigated by the limiting oxygen index (LOI), UL 94 test, thermogravimetric analysis, and scanning electron microscopy. The results showed that FR-PA66 samples had much better flame retardancy and char formation ability than pure PA66 after the flame retardant modification. The LOI values were increased from 24.0 to 28.0% by adding 6 wt % of CEPPA and all FR-PA66 samples were rated as V-0 rating in UL-94 test. Furthermore, the thermal stability analysis indicated that in situ polymerization with CEPPA effectively decreased the initial decomposition temperature and increased the amount of char residue. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48687.     

Polypropylene/clay nanocomposites prepared by in situ grafting‐melt intercalation with a novel cointercalating monomer

Polypropylene (PP)/clay nanocomposites were prepared by melt‐compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP‐g‐MA) as the primary compatibilizer and N‐imidazol‐O‐(bicyclo pentaerythritol phosphate)‐O‐(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X‐ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d‐spacing further increased with the addition of PP‐g‐MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI‐containing PP nanocomposites exhibited better thermal stability than PEBI‐free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (T_g) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI‐containing PP/OMT composites gave a lower T_g value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame‐retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of ammonium polyphosphate and triphenyl phosphate on the flame retardancy,thermal, and mechanical properties of glass fiber–reinforced PLA/PC composites

The purpose of this study is to increase of the flammability properties of the glass fiber (GF)–reinforced poly (lactic acid)/polycarbonate (PLA/PC) composites. Ammonium polyphosphate (APP) and triphenyl phosphate (TPP) were used as flame retardants that are including the organic phosphor to increase flame retardancy of GF‐reinforced composites. APP, TPP, and APP‐TPP mixture flame retardant including composites were prepared by using extrusion and injection molding methods. The properties of the composites were determined by the tensile test, limiting oxygen index (LOI), differential scanning calorimetry (DSC), and heat release rate (HRR) test. The minimum T_g value was observed for the TPP including PLA/PC composites in DSC analysis. The highest tensile strength was observed in GF‐reinforced PLA/PC composites. In the LOI test, GF including composite was burned with the lowest concentration of oxygen, and burning time was the longest of this composite. However, the shortest burning time was obtained by using the mixture flame retardant system. The flame retardancy properties of GF‐reinforced PLA/PC composite was improved by using mixture flame retardant. When analyzed the results of HRR, time to ignition (TTI), and mass loss rate together, the best value was obtained for the composite including APP.     

Flame retardancy and thermal and mechanical performance of intercalated,layered double hydroxide composites of polyamide 11, aluminum phosphinate,and sulfamic acid

Sulfamic acid‐intercalated MgAl‐layered double hydroxide (SA‐LDH) was prepared and added with aluminum phosphinate (AlPi) into polyamide 11 (PA11). The results showed that AlPi/SA‐LDH made a positive contribution to both flame retardancy and thermostability, and the effect was demonstrated with the limiting oxygen index (LOI), vertical burning tests (UL‐94), cone calorimetry (CONE), and thermogravimetric analysis (TGA). The char morphologies were observed by SEM, and its chemical composition was investigated by Fourier transform infrared spectroscopy (FTIR). The decomposition mechanism was examined by TGA‐FTIR. The results showed that the LOI of PA11 was only 23.0 and cannot pass any UL‐94 rating. The addition of 20% AlPi increased the LOI to 31.5 and passed the UL‐94 V‐1 rating, and AlPi/SA‐LDH 15%/5% increased the LOI to 32.4 and also passed the UL‐94 V‐1 rating. The CONE results revealed that 20% of either AlPi or AlPi/SA‐LDH brought about a 30% decrease in the peak heat release rate (pHRR). The contribution of SA‐LDH to flame behavior was especially reflected in the postponement of pHRR. SEM showed that the char morphologies became denser after SA‐LDH incorporation. The improvement in thermal stability of the AlPi/SA‐LDH combination was documented by TGA in both N₂ and air atmospheres. The mechanical performance deterioration caused by AlPi was partly improved by SA‐LDH. The storage modulus (E′) below the T_g of AlPi/SA‐LDH 15%/5% was about 300 MPa higher than with 20% AlPi. This was attributed to a compatibility improvement. The interaction forces among PA11, AlPi, and SA‐LDH were probed by X‐ray photoelectron spectrometry. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43370.     

Fire retardant mechanism of PA66 modified by a “trinity” reactive flame retardant

A “trinity” reactive flame retardant (TRFR) was successfully synthesized from pentaerythritol, phosphorus oxychloride (POC), and p-aminobenzoic acid in two steps. The flame retardant polyamide 66 (PA66) was prepared by polymerizing TRFR with PA66 salt; the structural changes during the heating process, the morphology, and composition after combustion of flame retardant PA66 were analyzed. Fourier transform infrared, scanning electron microscopy, and Raman analysis results showed that the TRFR structure on flame retardant PA66 decomposed at the temperature of 25–550 °C, forming compounds containing phosphorus, carbon, and nitrogen, respectively. These compounds promoted the dehydration of the combustion surface to form char, increased the char formation rate, and produced nonflammable gases, resulting in a dense, porous, noncombustible carbon layer. The carbon layer may isolate oxygen and heat, thereby preventing the polymer from sustainability of combustion. When the TRFR salt content was 3%, TRFR flame retardant PA66 has excellent flame retardancy with limited oxygen index value of 29 and UL94 of V-0 rating. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47488.     

Preparation of alginate flame retardant containing P and Si and its flame retardancy in epoxy resin

In the present paper, a novel biomass flame retardant based on alginic acid was synthesized through chemical combination with a reactive P–Si compound. Compared with alginates, the modified alginate showed obviously increased thermal stability and water resisting property, as well as better compatibility with epoxy resin, which can satisfy the requirements of a flame‐retardant additive in the polymer. The flame‐retardant properties were evaluated by vertical burning tests, limiting oxygen index, and microscale combustion calorimetry. Due to the self‐charring capacity of alginate combined with the charring catalyst from P and the charring reinforcer from Si, the modified alginate exhibited much better flame retardancy, taking advantage of the formation of a more continuous, denser, and strengthened char layer than either individual alginate or P–Si flame retardant. The corresponding flame‐retardant mechanisms were investigated and discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45552.     

Synthesis of polyundecamethylene 2,6‐naphthalamide as semiaromatic polyamide‐containing naphthalene ring

A novel engineering plastic polyundecamethylene 2,6‐naphthalamide (PA11N) was prepared via a reaction of 2,6‐naphthalene dicarboxylic acid and 1,11‐undecanediamine through a three‐step procedure. The structure of synthesized PA11N was characterized by elemental analysis, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance (¹H‐NMR). The thermal behaviors were determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The solubility, water‐absorbing capacity, and mechanical properties of PA11N have also been investigated. Melting temperature (T_m), glass transition temperature (T_g), and decomposition temperature (T_d) of PA11N are 294, 139, and 493°C, respectively. The results show that the heat resistance and mechanical properties of PA11N are near to those of polynonamethylene terephthalamide, and PA11N is a promising heat‐resistant and processable engineering plastic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A high-efficiency DOPO-based reactive flame retardant with bi-hydroxyl for low-flammability epoxy resin

A high-efficiency DOPO-based reactive flame retardant (DPE) with bi-hydroxyl was successfully synthesized via reacting DOPO with imine obtained from the condensation of ethanolamine and 1,4-phthalaldehyde, and used as co-curing agent to improve the fire safety of epoxy resin (EP). Its chemical structure was characterized by Fourier transform infrared (FTIR) spectra, ¹H, ³¹P nuclear magnetic resonance (NMR) spectra and elemental analysis. The curing behavior, thermal properties, flame-retardant properties of EP/DPE systems were investigated. The results revealed that DPE slightly decreased the glass transition temperature (T_g), but accelerated the curing cross-linking reaction of EP. Furthermore, DPE decreased thermal degradation rate of epoxy matrix and promoted the formation of residual char at high temperature. After adding DPE, the flame retardant of epoxy thermosets was greatly improved. Especially, the thermoset modified with 5 wt% DPE achieved limiting oxygen index (LOI) value of 33.6% and V-0 rating in UL-94 test, demonstrating the highly efficient flame retardancy. While its peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) were respectively decreased by 32.6%, 17.8%, and 13.9% compared with neat EP. Moreover, the research on flame retardant mechanism disclosed that DPE played dual flame-retardant effect in the gaseous and condensed phases.