Thermal degradation and flame retardancy of rigid polyurethane foams containing a novel intumescent flame retardant

A novel cheap macromolecular intumescent flame retardants (MIFR) was synthesized, and its structure was a macromolecule containing phosphorus characterized by IR. Rigid polyurethane foam (PUF) filled with MIFR as fire retardant additive was prepared. The effects of MIFR on properties such as density, compressive strength, flame-retardant behavior, thermal stability, and morphology of char were studied. The compressive strength of the MIFR-filled PUF increased initially and then decreased with further increase of MIFR content while its density straightly increased. Its flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). Twenty five percent of MIFR was doped into PUF to get 24.5 of LOI and UL 94 V-0. Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for PUF containing MIFR, compared with PUF, the mass loss, thermal stability, and the decomposition activation energy decreased, the char yield increased, which shows that MIFR can catalyze decomposition and carbonization of PUF to form an effective charring layer to protect the underlying substrate.     

软质聚氨酯泡沫塑料用无卤阻燃剂的研究

本文以羟基苯氧膦丙烯酸(CEPP)和三聚氰胺(MA)为原料合成了一种含磷、氮无卤阻燃剂(CMA),采用FT-IR表征了阻燃剂的化学结构,并将该阻燃剂用于软质聚氨酯泡沫(FPUF)的阻燃。用扫描电镜(SEM)研究了阻燃剂的加入对FPUF的形态的影响,通过LO I和垂直燃烧(Cal.117A)测试研究了该阻燃剂对FPUF的阻燃效果。结果表明,CMA可以有效提高FPUF的阻燃性:当CMA的添加量为10%时,FPUF即可通过Cal.117A测试,其LO I值也从17.3提高到23.0;随阻燃剂添加量的增加,FPUF的阻燃性能也逐渐提高。TG测试结果表明CMA的加入对FPUF的热稳定性没有多大影响。     

Synergistic effects between iron–graphene and melamine salt of pentaerythritol phosphate on flame retardant thermoplastic polyurethane

A comparison of melamine salt of pentaerythritol phosphate (MPP), and a synergistic agents, iron–graphene (IG) was performed in thermoplastic polyurethane (TPU) by masterbatch‐melt blending on thermal and flame retardant properties. The flame retardant properties of TPU composites were characterized by limiting oxygen index (LOI), UL 94 and cone calorimeter test (CCT). The CCT results revealed that IG can significantly enhance flame retardant properties of MPP in TPU. The peak heat release rate of neat TPU and flame retardant TPU/MPP composites decreased from 2192.6 and 226.7 to 187.2 kW/m² compared with that of TPU containing 0.25 wt% IG. The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis (TGA) and thermogravimetric/Fourier infrared spectrum analysis (TG‐IR). The results indicated IG and MPP can improve the thermal stability of TPU. The formation of thermal conductive network by IG can promote the decomposition of MPP into nonflammable melt, which can play the role of heat barrier and restrict the diffusion of fuels into combustion zone and access of oxygen to the unburned fuels. Copyright © 2016 John Wiley & Sons, Ltd.     

Aluminum phosphate modified brucite and its flame retardant and smoke suppression performance on ethylene‐vinyl acetate resin

A novel halogen‐free flame retardant (FR) consisting of brucite, aluminum phosphate (AlP), and silane coupling agent (B/AlP/A) was prepared via co‐precipitation assembly technique. The morphology, chemical compositions, size distribution, and thermal stability of B/AlP/A were investigated. When used in ethylene‐vinyl acetate (EVA) resin, the B/AlP/A could significantly enhance the flame retardant and smoke suppression performance of the EVA composites, which is mainly attributed to the AIP. With 50 wt% FR loading, the peak heat release rate (PHRR) of EVA‐B/AlP/A (299.2 kW · m^?2) is much lower than that of EVA‐B/A (387.4 kW · m^?2). Moreover, B/AlP/A shows an excellent smoke suppression performance. For example, the smoke production rate is 0.017 m² · g^?1 that has been decreased by 72.1%, compared with B/A. The improvement arises from the amorphous AlP layer on brucite, which helps to create a firm and porous protective char layers on the burning EVA composites. Meanwhile, better mechanical property could be simultaneously obtained with the large FR amount. The fluffy surface of B/AlP/A has good compatibility with EVA and tangle more polymer chains, enhancing the mechanical properties. In a word, this simple and convenient method could pave the way for developing a more efficient and cost‐effective brucite‐based FR.     

Studies of degradation enhancement of polystyrene by flame retardant additives

Experimental methods as well as thermodynamic modeling techniques were utilized to explore potential gas and condensed-phase contributions of various flame retardant (FR) additives with polystyrene polymer. FR additives investigated include hexabromocyclododecane (HBCD), triphenyl phosphine oxide (TPPO), triphenyl phosphate (TPP), triphenyl phosphine sulfide (TPPS), and sulfur. Flame studies of fundamental FR activity were also employed using molecular beam mass spectrometry analysis of FR active species directly in a flame system. The flame studies show direct evidence for active bromine (HBr, Br) species for HBCD and active phosphorous species (HPO₂, PO, PO₂ HPO₃) species for TPPO and TPP which provide high potential for gas-phase activity for these FR additives. Various experimental measurements were also done to assess the degradation species and the degree of degradation of polystyrene by the FR additives. These studies support enhanced degradation of the base polystyrene polymer by the FR additive as a major pathway for condensed FR activity for HBCD and sulfur FR additives. Phosphorous based structures appear to show little enhancement of polystyrene degradation.     

Investigation of melamine and DOPO-derived flame retardants for the bioplastic cellulose acetate

In order to identify suitable flame retardant additives for the eco-friendly polymer cellulose acetate (CA), high-melting derivatives of the known flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were combined with the thermoplastic CA and the combustion properties were tested. CA mixtures with bis-phosphonamidates (EDA-DOPO and PIP-DOPO) showed distinct flame retardation effects and a reduction of peak heat release rates (PHRR) by up to 18%. CA mixtures with MDOP, a melamine salt of DOPA (an oxidation product of DOPO), also showed considerable effects and a reduction of PHRR by up to 27%. While producing more smoke than pure CA and CA plus melamine, owing to its aromatic component, MDOP was superior to the CA mixtures with DOPO, EDA-DOPO and PIP-DOPO in this regard. The mixture of CA with melamine gave rise to a distinctly reduced formation of toxic CO and smoke when compared with pure CA. Thus, these additives can be considered for future applications of CA-based polymers with enhanced flame protection.     

Influence of maleic anhydride-grafted EPDM and flame retardant on interfacial interaction of glass fiber reinforced PA-66

In this paper, the effects of melamine polyphosphate flame retardant (MPP-FR) and maleic anhydride-grafted EPDM (MA-EPDM) on the interfacial interaction of PA66/GF were investigated by means of scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), rheological behavior and mechanical properties. The experimental results demonstrate that MPP-FR and MA-EPDM could effectively improve interfacial interactions between the PA66 and GF. Based on SEM, good interfacial adhesion between PA66 and GF in PA66/GF/FR and PA66/GF/FR/MA-EPDM composites was observed, however, MPP-FR destroyed the PA66 matrix. DMA results show that MPP-FR increased glass transition temperature (T_g) and storage modulus, and lower tan δ, while MA-EPDM showed a little effect on them in PA66/GF/FR/MA-EPDM composite compared with PA66/GF/FR. MPP-FR made PA66 crystallization temperature and the activation energy of the macromolecular segments transport increase clearly, and enhanced crystallization degree of PA66 according to DSC results. These results demonstrate MPP-FR presented the nucleate effect for the crystallization of PA66. At the low shear rate, MPP-FR and MA-EPDM obviously enhanced apparent viscosities of the composites. This is attributed that MPP-FR improved the interfacial interaction of the composites, and MA-EPDM promoted the formation of high molecular weight structures by the reactions between MA and amine groups. All results in this paper were consistent, and showed the good interaction among PA66, GF, MPP and MA-EPDM, which were proved by the mechanical properties of the composites.     

Flame‐retardant poly (ethylene terephthalate) enabled by a novel melamine polyphosphate nanowire

A novel strategy was developed for the preparation of melamine polyphosphate (MPP) nanowires to achieve a superior flame‐retardant poly (ethylene terephthalate) (PET). Thanks to the well‐designed nanostructure, the prepared MPP nanowires exhibited great thermal stability and flame retardance. Herein with incorporation of only 1‐wt% MPP nanowires (PET/FR1.0 nanocomposite), the limiting oxygen index (LOI) value was dramatically increased to 29.4% from 20.5%, showing self‐extinguishing behavior. Moreover, PET/FR1.0 nanocomposite passed V‐0 UL‐94 rating in the vertical combustion test. However, PET containing 5‐wt% commercial MPP powder (PET/FR_C5.0) only showed a LOI of 27.9% and ignited the absorbent cotton with flammable melt‐droplets. Cone results also presented that introducing 1‐wt% MPP nanowires brought about a crucial decrease in fire hazard of PET, for instance, 11.1% and 7.7% maximum reduction in heat release rate and total heat release, respectively. Thermogravimetric analysis/infrared spectrometry (TG‐FTIR) result indicated that the main pyrolysis volatiles generated from PET degradation including benzoic acid, aromatic compounds, and carbon dioxide were apparently suppressed after introducing MPP nanowires into PET matrixes, suggesting the outstanding obstructing effect of graphited char residue formed in the combustion. This enhanced flame retardancy rooting in addition of MPP nanowires can be attributed to the combined dilution effect in gaseous phase and catalytic carbonization effect in condensed phase.     

Preparation and characterization of phenolic foams with eco-friendly halogen-free flame retardant

The high solid resol phenolic resin was prepared via step polymerization of formaldehyde, paraformaldehyde, and phenol using sodium hydroxide and calcium oxide as catalysts, and employed to prepare the phenolic foams (PFs) by the introduction of retardant additives including eco-friendly halogen-free flame retardants (ammonium polyphosphate), char-forming agents (pentaerythritol), and synergists (zinc oxide, molybdenum trioxide, cuprous chloride, and stannous chloride). The effects of these additives on flame retardancy, heat resistance, and fire properties of flame-retardant composite phenolic foams (FRCPFs) were evaluated by limiting oxygen index (LOI) tests, thermogravimetric analyzer, and cone calorimeter tests. It was found that the flame retardan significantly increased the LOIs of FRCPFs. Compared with PF, heat release rate, total heat release, effective heat of combustion, production or yield of carbon monoxide (COP or COY), and Oxygen consumption (O₂C) of FRCPFs all remarkably decreased. However specific extinction area and total smoke release significantly increased, which agreed with the gas-phase mechanism of the flame-retardant system. The results indicate that FRCPFs have excellent fire-retardant performance and less smoke release. APP/PER/ZnO is shown to be better flame-retardant system for PFs.     

Effect of a Nanoclay on the Mechanical,Thermal and Flame Retardant Properties of Rigid Polyurethane Foam

Water blown rigid polyurethane foams (PUF) with organoclay/organically modified nanoclay (ONC) were prepared and their properties such as density, mechanical, morphological, insulation, thermal and flame retardant properties were studied. In this investigation, the ONC content was varied from 1 to 10 parts per hundred of polyol (php) by weight. It was observed that the compressive strength of ONC filled PUF increased up to 3 php of ONC loading and then it decreased. Wide angle X-ray diffraction and transmission electron microscopy studies indicated the exfoliated dispersion of ONC in PUF. The thermal conductivity of ONC filled PUF decreases up to 5 php and then increases. The glass transition temperature (Tg) of PUF decreases on loading of ONC. The TGA analysis shows that there is slight increase in degradation temperature with increase in ONC loading. The flame retardant properties (LOI and flame spread rate) are improved slightly on addition (3 php) of ONC filled PUF.     

The effect of hBN on the flame retardancy and thermal stability of P-N flame retardant PA6

A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char.     

反应性挤出加工制备无卤阻燃高分子材料

聚合物反应性加工集聚合物加工与化学反应为一体,以聚合物加工装置为反应器,通过聚合物加工过程中的化学反应形成新物质和新结构,实现高分子材料的高性能化和功能化,是高分子材料科学的研究前沿之一.本文简要介绍了我们研究小组近年来采用反应性挤出加工制备高性能无卤阻燃高分子材料方面的研究进展.利用反应性挤出加工剪切力强、温度可控以及易于传质传热的特点实现了常规方法难以合成的高黏阻燃剂三聚氰胺磷酸盐季戊四醇酯（MPP）和三聚氰胺氰尿酸（MCA）的高效合成,制备了综合性能优良的聚丙烯/MPP、尼龙6/MCA等无卤阻燃高分子材料.研究所涉及的化学和物理方法,为聚合物无卤阻燃提供了高效、经济、环保和易于工业化的新技术,并拓宽了聚合物反应性加工的应用领域.     

Effect of nitrogen additives on flame retardant action of tributyl phosphate: Phosphorus-nitrogen synergism

The effects of three nitrogen additives (urea, guanidine carbonate, and melamine formaldehyde) on the flame retardant action of cotton cellulose treated with tributyl phosphate (TBP) were investigated in this research. The limiting oxygen index (LOI) of treated cotton cellulose clearly revealed the synergistic interactions of TBP and nitrogen compounds. The Kissinger method was used to evaluate the kinetics of thermal decomposition on treated cellulose. The results show that adding nitrogen additives increases the activation energy at a higher degree of degradation, thus indicating better thermal stability at higher temperatures. Scanning electron microscope pictures of chars formed after a LOI test show the formation of protective polymeric coatings on char surfaces. Evaluating char surfaces using attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggests that these coatings are composed of species containing phosphorus-nitrogen-oxygen. Possible chemical interactions of phosphorus and nitrogen compounds during the burning process and the formation of a protective coating could be the reason for the observed synergism. Potential reaction pathways contributing to the formation of this protective polymeric coating have also been proposed.     

Effect of zinc oxide on flame retardant finishing of plasma pre-treated cotton fabric

An organic phosphorus compound (flame retardant agent, FR) in combination with a melamine resin (crosslinking agent, CL), phosphoric acid (catalyst, PA) and zinc oxide (co-catalyst, ZnO/nano-ZnO) imparted effective and durable flame retardant properties. Also, atmospheric pressure plasma jet was applied as pre-treatment to improve post-finishing (flame retardant finishing) on cotton fabrics. In the present paper, surface morphology, chemical structure analysis, combustibility and mechanical properties of plasma pre-treated cotton fabrics subjected to flame-retardant treatment were investigated. Surface morphology of treated cotton specimens showed roughened and wrinkled fabric surface with high deposition of the flame retardant finishing agent, which was caused by the plasma etching effect and attack of acidic FR. The FTIR-ATR spectra for the treated cotton specimens showed some new characteristic peaks in chemical structure, interpreted as carbonyl bands, OH stretching vibration, COO⁻ stretching vibration, CH₂ rocking band and CH₃ asymmetric and CH₂ symmetric stretching. Moreover, FR-CL-PA-treated specimens showed remarkable flame-retardant property, which was further improved by the plasma pre-treatment and ZnO/nano-ZnO co-catalyst. However, flame-retardant-treated cotton specimens had poor mechanical strength when compared with control sample, resulting from side effects of the crosslinking agent used, while plasma pre-treatment and ZnO/nano-ZnO co-catalyst may compensate for the reduction in tensile and tearing strength caused by flame-retardant agents.     

Reaction of melamine phosphate with pentaerythritol and its products for flame retardation of polypropylene

Due to being halogen‐free, non‐toxic, non‐erosive and environmentally friendly, melamine‐based flame retardants are attracting more and more attention. As a melamine‐based intumescent flame retardant, in this study the melamine salt of pentaerythritol phosphate (MPP) was prepared from melamine phosphate (MP) and pentaerythritol (PER). The reaction of MP with PER was then systematically investigated. The reaction product MPP was utilized to flame‐retard polypropylene (PP). FT‐IR, TGA and DSC were used to characterize MPP and also to investigate the reaction of MP and PER in depth. The experimental results show that MPP has good thermal stability and matched decomposition temperature with that of PP, making it suitable for flame retarding of PP. Also, MPP is melting‐blendable due to its softening during the heating process. The structure of MPP at a MP:PER molar ratio of 2.0 was confirmed as the same to that of the product synthesized from phosphorus oxychloride, pentaerythritol and melamine. The reaction of MP with PER was greatly influenced by the MP:PER proportion, reaction temperature and reaction time, rather than the physical state of PER, and the reaction mechanism of MP with PER was proposed. The prepared flame‐retarded polypropylene composite with 35 wt% intumescent flame‐retardant MPP has a flame retarding level of 3.2 mm UL 94 V‐0, tensile strength 27.0 MPa, Young's modulus 2442 MPa and Izod notched impact strength 3.8 kJ/m². Copyright © 2007 John Wiley & Sons, Ltd.     

Red phosphorus as a flame retardant for a thermoplastic nitrogen-containing polymer

Studies were made of the flame-retardant and smoke-suppressant activity of red phosphorus, in the presence of a brominated (decabromobiphenyl) and/or a nitrogenated (melamine) compound, on acrylonitrile-butadiene-styrene terpolymer. These studies were complemented by simultaneous thermal analyses of the polymeric systems. Red phosphorus is oxidised on heating and the thermal decomposition of any system containing this additive includes a substantial weight gain stage at ca 700 K. Melamine is volatilised very early on and thereafter acts only as a smoke suppressant in the gas phase. Decabromobiphenyl and red phosphorus interact positively in decreasing the flammability of the substrate, particularly at atomic ratios not lower than stoichiometric. The acrylonitrile content in ABS is very important, suggesting that the additives act mainly in the gas phase but that they also form some sort of charry layer on the polymer surface.     

Melamine cyanurate-microencapsulated red phosphorus flame retardant unreinforced and glass fiber reinforced polyamide 66

A novel microencapsulated red phosphorus (RP) was prepared through the molecular self-assembly of melamine cyanurate (MCA). Compared with the conventional encapsulated RP, MCA-encapsulated RP (MERP) shows simpler and more environment-friendly preparation process higher thermal stability and lower moisture absorption. With MERP filled in unreinforced polyamide 66 (PA66) and glass fiber (GF) reinforced PA66, flame retardant materials with satisfactory flame retardancy and mechanical performance can be obtained. The influence of the MCA/RP ratio on the flame retardancy as well as the condensed phase of MERP flame retardant PA66 was investigated to reveal the nitrogen-phosphorus (N-P) synergistic flame retarding effects between MCA and RP.     

Fire retardancy of melamine and zinc aluminum layered double hydroxide in poly(methyl methacrylate)

The thermal and fire properties of PMMA modified with various loadings of melamine or zinc aluminum undecenoate LDH were evaluated using TGA, DTA and cone calorimetry. The additives were characterized by X-ray diffraction, TGA, FT-IR and elemental analysis. While the two additives are very effective with this polymer, a higher loading of melamine (30%) is required to reach a good reduction in PHRR (47%) relative to the pure polymer, while with the LDH, 10% loading is enough to obtain a similar reduction. The combinations of these additives in PMMA reveal that the time to PHRR and the amount of smoke produced are the key differences, with melamine increasing the first parameter and leading to less smoke production relative to LDH-rich PMMA systems at similar total additive loadings. Analysis of the residue shows that melamine is completely lost during combustion while the LDH forms ZnO and ZnAl₂O₄.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene material

The flame retardancy and thermal degradation properties of polypropylene (PP) containing intumescent flame retardant additives, i.e. melamine pyrophosphate (MPyP) and charring‐foaming agent (CFA) were characterized by limiting oxygen index (LOI), UL 94, cone calorimeter, microscale combustion calorimetry, and thermogravimetric analysis (TGA). It has been found that the PP material containing only MPyP does not show good flame retardancy even at 30% additive level. Compared with the PP/MPyP binary system, the LOI values of the PP/MPyP/CFA ternary materials at the same additive loading are all increased, and UL 94 rating is raised to V‐0 from no rating (PP/MPyP). The cone calorimeter results show that the heat release rate and mass loss rate of some ternary materials decrease in comparison with the binary material. The microscale combustion calorimetry results indicate that the sample containing 22.5 wt% MPyP and 7.5 wt% CFA has the lowest heat release rate among all samples. The TGA results show that the thermal stability of the materials increases with the addition of MPyP, while decreases with the addition of CFA. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication of diatomite‐based microencapsulated flame retardant and its improved fire safety of unsaturated polyester resin

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.