Effect of the Additive Fire Retardants on the Properties of Rigid Polyurethane Foams,Obtained Using Hydroxyethyl Derivatives of Oxamide and Polymeric 4,4′-diphenylmethane Diisocyanate

The present work investigates the effect of polyol structure and physical addition of boric acid and N,N′-bis(2-hydroxyethyl)oxamide on the properties of rigid polyurethane foams. The product of hydroxyalkylation of oxamide by ethylene carbonate has been used as a polyol component. The new polyol has been foamed using polymeric 4,4′-diphenylmethane diisocyanate, water, and triethylamine. To decrease the flammability of the foams, boric acid, and N,N′-bis(2-hydroxyethyl)oxamide were used as the additive flame retardants. It has been found, that chemical modification of the foam structure by means of oxamide groups decreases their flammability only to a small extent, whereas physical addition of N,N′-bis(2-hydroxyethyl)oxamide does not influence the flammability. However, the addition of boric acid to the foam composition resulted in a distinct decrease of foam flammability, according to the amount of boric acid added. All the foams, modified and nonmodified by boron, have been categorized into flammability class HF-1, according to the applicable standard. The introduction of flame retardants had its impact on the properties of polyurethane foams obtained, as described in this work.     

Thermal Insulating Rigid Polyurethane Foams with Bio-Polyol from Rapeseed Oil Modified by Phosphorus Additive and Reactive Flame Retardants

In this article, rigid polyurethane foams obtained with the addition of a bio-polyol from rapeseed oil, were modified with the dimethyl propane phosphonate as additive flame retardant and two reactive flame retardants diethyl (hydroxymethyl)phosphonate and diethyl bis-(2-hydroxyethyl)-aminomethylphosphonate. The influence of used flame retardants on the foaming process and characteristic processing times of tested polyurethane systems were determined. The obtained foams were tested in terms of cell structure, physical and mechanical properties, as well as flammability. Modified foams had worse mechanical and thermal insulation properties, caused by lower cellular density and higher anisotropy coefficient in the cross-section parallel to the foam rise direction, compared to unmodified foam. However, the thermal conductivity of all tested foam materials was lower than 25.82 mW/m∙K. The applied modifiers effectively reduced the flammability of rigid polyurethane foams, among others, increasing the oxygen index above 21.4 vol.%, reducing the total heat released by about 41–51% and the rate of heat release by about 2–52%. A correlation between the limiting oxygen index values and both total heat released parameters from the pyrolysis combustion flow calorimetry and cone calorimetry was observed. The correlation was also visible between the value of the heat release capacity (HRC) parameter obtained from the pyrolysis combustion flow calorimetry and the maximum average rate of heat emission (MARHE) from the cone calorimeter test.     

New polyol for production of rigid polyurethane‐polyisocyanurate foams,Part 2: Preparation of rigid polyurethane‐polyisocyanurate foams with the new polyol

The method of preparation, determination of foaming parameters, and methods for the determination of physicochemical properties of polyurethane‐polyisocyanurate (PUR‐PIR) foams prepared with the use of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid derivatives are presented in this paper. It was found that application of the borate as a polyol component and simultaneously as a flame retardant in the recipe for production of PUR‐PIR foams was very favorable. The foams prepared were characterized by reduced brittleness, higher compressive strength and content of closed cells, as well as considerably lower flammability in comparison with standard foam. The results show that the new polyol prepared on the basis of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid can be applied for production of rigid PUR‐PIR foams, and it improves their physicochemical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Some Polyamides,Polyesters, and Polyurethanes Containing AZO Groups

The paper discusses the synthesis of the N,N,′-azobis(formamidopropionic) acid (AFP), along with some characteristics determined from NMR spectrum, differential thermal analysis, and DSC. The behavior of AFP acid—as well as of its analogue, N,N′-azobis(formamidoacetic) acid (AFA)—has been studied in the reaction with aromatic diamine and with bis(glycol)terephthalate, leading to azopolymers of the azopolyamide, or azopolyester, type. On employing N,N′-bis(β-hydroxyethyl) azobis-formamide (HEAF) as the azo bifunctional compound in the reaction with diphenylmethane diisocyanate, a polyurethane possessing azo groups was obtained. The structure of the azopolymers has been spectroscopically confirmed.     

Mechanical Properties and Flame Retardancy of Rigid Polyurethane Foams Containing SiO2 Nanospheres/Graphene Oxide Hybrid and Dimethyl Methylphosphonate

Halogen-free flame-retardant rigid polyurethane foams were prepared using the combination of SiO₂ nanospheres/graphene oxide hybrid and a phosphorus-containing flame retardant, dimethyl methylphosphonate. The flame retardancy, mechanical, and thermal properties of flame-retardant rigid polyurethane foams containing dimethyl methylphosphonate and SiO₂ nanospheres/graphene oxide were investigated. The results demonstrated that the combination of dimethyl methylphosphonate and SiO₂ nanospheres/graphene oxide enhanced flame retardant and mechanical properties of rigid polyurethane foam greatly compared with pure rigid polyurethane foam and dimethyl methylphosphonate-modified foam. Morphological study indicated that the partial substitution of dimethyl methylphosphonate with SiO₂ nanospheres/graphene oxide led to smaller cell sizes and more uniform cell sizes of dimethyl methylphosphonate-modified rigid polyurethane foams.     

Flame retardation and thermal stability of novel phosphoramide/expandable graphite in rigid polyurethane foam

A novel flame retardant named diethylene N,N',N''‐tri (diethoxy)phosphoramide (DTP) was synthesized using diethyl phosphate and diethylenetriamine via Atherton–Todd reaction. Then, series of flame‐retardant water‐blown rigid polyurethane foams (RPUFs) with expandable graphite (EG) and DTP were prepared through box‐foaming. The results of thermogravimetric analysis showed that DTP/EG changed thermal degradation process of RPUF and promoted enhancing char residues. The complex flame‐retardant system (EG/DTP) endowed RPUF higher limiting oxygen index (LOI) values (29.1%–30.2%) and lower heat release rate peak (PHRR) values according to LOI and microscale combustion calorimeter tests. More importantly, the synergistic flame‐retardant effect between EG and DTP in RPUF was proved by the analysis of synergistic effectivity values. Based on the analysis of cone calorimetric tests, EG/DTP revealed remarkable effects to inhibit the fire intensity and smoke release of RPUF with decreased PHRR and total smoke production due to good char‐forming action. To further investigate the char‐residues of the foams after combustion, scanning electron microscope and energy dispersive X‐ray spectroscopy analyses were conducted. The results suggested that EG/DTP flame‐retardant system promoted RPUF forming a compact, continuous and phosphorus‐rich char layer as a good fire barrier in combustion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46434.     

反应型磷氮阻燃剂/可膨胀石墨复配阻燃聚氨酯泡沫

将反应型阻燃剂六(4-磷酸二乙酯羟甲基苯氧基)环三磷腈(HPHPCP)和可膨胀石墨(EG)复配,制备了阻燃聚氨酯泡沫,详细研究了复配阻燃剂对聚氨酯泡沫的物理力学性能、热稳定性以及阻燃性能的影响。结果表明,阻燃聚氨酯泡沫的密度和热导率随着复配阻燃剂中EG含量的增加而升高;压缩强度随着EG含量的增加呈现先增加后降低的趋势。热失重表明复配阻燃剂大大提高了聚氨酯泡沫的热稳定性。聚氨酯泡沫的初始分解温度(T_10%)从212.9℃,分别提高到222.0、231.2和243.2℃;700℃残炭量从7.6%分别提高到26.3%、31.6%和37.9%。聚氨酯泡沫的阻燃性能随着复配阻燃剂中EG含量的增加而提高。阻燃聚氨酯泡沫的极限氧指数从19%提高到29%,均能通过UL-94水平燃烧HF-1等级和垂直燃烧V-0等级。     

Novel polyurethane–silicone hydrogels

Polyurethane hydrogels derived from polysiloxane-based ultraviolet-curable polyurethane prepolymers and hydrophilic monomers were prepared and their properties were evaluated. The polyurethane prepolymers used in this study contained different arrangements of hard and soft segments and were derived from isophorone diisocyanate, neopentyl glycol, diethylene glycol, 1,4-butanediol, hydroxy-terminated polydimethylsiloxane, and 2-hydroxyethyl methacrylates. The hydrophilic monomers used were 2-hydroxyethyl methacrylate and N,N-dimethyl acrylamide. All compositions can be cured under ultraviolet (UV) and form hydrogels after hydration. The oxygen permeabilities of the hydrogels are much higher than those of nonsilicone hydrogels and decreased as the water contents increased. The tear strengths and moduli decreased as the water contents of the hydrogels increased. All hydrogels prepared showed good hydrolytic stability and did not absorb lysozyme. © 1995 John Wiley & Sons, Inc.     

制备工艺对聚氨酯酰亚胺泡沫性能的影响

以均苯四甲酸二酐(PMDA)、多苯基多亚甲基多异氰酸酯(PAPI)、聚醚多元醇为主要原料,分别采用聚酰亚胺(PI)预聚法、聚氨酯(PU)预聚法和一步法制备聚氨酯酰亚胺泡沫,从微观形貌、力学性能、热稳定性能以及阻燃性能方面对上述3种制备工艺进行对比和评估。实验结果表明,采用一步法制备PUI泡沫时,PU链段和PI链段同时增长,容易造成泡孔缺陷,导致泡沫的力学性能较差;在采用PU预聚法制备的PUI泡沫中,PU链段含量较高,因此,泡孔孔径分布较宽且平均泡孔直径较大,对应的热稳定性和阻燃性能较差;采用PI预聚法制备的PUI泡沫的泡孔孔径分布窄且平均泡孔直径较小,对应的压缩性能、热稳定性以及阻燃性能均达到最佳。     

Synthesis and Characterization of Ricinoleamide-Based Polyurethane

Ricinus communis (RC) oil-based materials are currently receiving increasing attention because of economic and environmental concerns. In the present work, RC oil—a natural triol has been utilized for the development of an advanced polymeric material—poly(urethane-ricinoleamide) (PUR) through very simple synthesis and curing strategy, omitting derivatization steps or side reactions, chain extenders and crosslinkers. The synthesis of PUR was carried out in two steps. The first step is the introduction of an amide group in the RC oil (89.5% ricinoleic acid) via base catalyzed amidation, which results in N, N-bis (2-hydroxyethyl) ricinoleamide (HERA). The second step is urethanation of HERA by the reaction of toluene-2,4-diisocyanate (TDI) in minimal possible organic solvent by one-shot technique, which results in the formation of polyurethane along with amide linkages. The physico-chemical and spectral studies (FT-IR, ¹H-NMR and ¹³C-NMR techniques) confirm these two reactions and the structure of PUR. The resin was cured at ambient temperature without any cross linker. Solubility of the resin was investigated in different polar and non-polar solvents. Thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and Differential Scanning Calorimetry (DSC) were used to determine the thermal stability and curing behavior of PUR. An ambient cured ricinoleamide modified polyurethane resin exhibited thermal resistance up to 200–220 °C.     

Poly(urea-urethane) polymers with multi-functional properties

Polyurea-urethanes with multifunctional properties were synthesized by reacting 4,4′-diphenylmethane disocyanate (MDI) with a two diol mixture of polytetramethylene glycol (PTMG (1000, 2000) and biocidal quaternary ammonium monomer ((N-benzyl-N-dodecyl-N-bis2-hydroxyethyl) ammonium chloride (BDAC)), and extended with N-(2-hydroxyethyl) ethylene diamine (HEDA) to form PU polymers. The PU polymer was then grafted with a disperse dye via a coupling agent of epichlorohydrin to form a dye grafted polyurethane with biocidal and covalent bond dyeing properties. In consideration of the mechanical properties, it is found that both the modulus and the strength of the dye grafted PU polymer films are lower than those of pure PU polymers due to the bulkiness of their dye molecules. For thermal properties, the dye grafted PU polymers exhibit higher T_gh than those without dye molecules. However,neither the T_gs nor the T_ms vary in the presence of BDAC or dye molecules, but they are changed with various chain lengths of the soft segment. For dyeing properties, the effective dyeing efficiency of dye grafted PU is over 85%. Moreover, the dye grafted PU polymers exhibit lower dye migration (M_p%) than those of simple mixtures of PU and dyestuff, and they show a higher grade of color fastness when exposed to light. In the shake method of antibacterial testing, the modified PU polymers exhibit a long lasting biocidal activity.     

Flame retardant polyurethane foam prepared from compatible blends of soybean oil‐based polyol and phosphorus containing polyol

A phosphorus containing polyether polyol (THPO‐PO) was synthesized by polymerization between tris(hydroxymethyl) phosphine oxide (THPO) and propylene oxide (PO). A soybean oil‐based polyol(SBP) was synthesized from epoxidized soybean oil by ring‐opening reaction with lactic acid. The corresponding polyurethane foams (PUFs) were prepared by mixing SBP with THPO‐PO. The density of these foams decreased as the content of THPO‐PO increased. The yield strength of PUFs was observed to be decreased firstly and then increased with the addition of THPO‐PO. Microphotographs of PUFs were examined by scanning electron microscope which displayed the cells as spherical or polyhedral. The thermal degradation and fire behavior of PUFs were investigated by thermogravimetric analysis, limiting oxygen index (LOI), and UL‐94 test. Although the thermal stability of PUFs were decreased with increasing THPO‐PO percentage, the flame retardancy of PUFs were improved. The LOI value increased to 27.5 with 40% THPO‐PO. THPO‐PO in sequence worked in inhibiting flame and forming phosphorus‐rich char layer, thus endowing PUFs with the increased flame‐retardant performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45779.     

Preparation and characterization of microencapsulated ammonium polyphosphate and its synergistic flame‐retarded polyurethane rigid foams with expandable graphite

A facile and effective method for the preparation of microencapsulated ammonium polyphosphate (MAPP) by in situ surface polymerization was introduced. The ‘polyurethane‐like’ shell structure on the surface of MAPP was characterized by using Fourier transform infrared spectroscopy. The hydrophobicity and thermal behavior of MAPP were studied by using water contact angle tests and thermogravimetric analysis. The foam density and mechanical properties of polyurethane (PU) rigid foams were investigated. The flame retardancy of PU rigid foams formulated with MAPP was evaluated by using limiting oxygen index and cone calorimetry. The results show that MAPP can greatly increase the flame retardancy of PU materials. Also, there is a synergistic effect between MAPP and expandable graphite in flame retarding PU rigid foams. Moreover, the water resistance property of PU/MAPP composites is better than that of PU/ammonium polyphosphate. The morphology and chemical structure of PU/MAPP rigid foams after burning were systematically investigated. © 2013 Society of Chemical Industry     

Synergistic effects of hydroxides and dimethyl methylphosphonate on rigid halogen‐free and flame‐retarding polyurethane foams

Rigid halogen‐free and flame‐retarding polyurethane foams are prepared with aluminum hydroxide, brucite, and DMMP. The effects of the hydroxides and DMMP on the foaming process and flame retarding properties of the foams are investigated by thermo gravimetric analysis, limiting oxygen index, and X‐ray powder diffraction. The thermal stability of the rigid polyurethane foams is close to that of the hydroxide fillers, with aluminum hydroxide providing better flammability performance than brucite. The hydroxide fillers and DMMP play a synergistic role in the rigid polyurethane foams and the limiting oxygen indices are up to 28.4% and 32.4%, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Melamine amino trimethylene phosphate as a novel flame retardant for rigid polyurethane foams with improved flame retardant,mechanical and thermal properties

Melamine amino trimethylene phosphate (MATMP) as a novel nitrogen‐phosphorus flame retardant, was synthesized by the reaction of melamine with amino trimethylene phosphonic acid (ATMP) in aqueous solution. The structure of MATMP was characterized by Fourier transform infrared spectroscopy, solid state 31 P nuclear magnetic resonance, and thermogravimetric analysis. Rigid polyurethane (RPU) foams were prepared by one‐shot and free‐rise method, using MATMP as a flame retardant. The flame retardant, mechanical and thermal properties of MATMP in RPU foams were studied. It is found that the RPU foam containing 15 wt % MATMP (sample RPUMA‐15) can pass the UL‐94 V0 test with a limiting oxygen index of 25.5%. The cone calorimeter test results show that the peak heat release rate of RPUMA‐15 is reduced about 34% compared with that of untreated RPU foam. SEM results indicate that the RPU foams with MATMP can form the good and compact char during burning which provides better flame retardancy. The compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content comparing with that of untreated RPU foam. Moreover, thermal conductivities of the MATMP filled RPU foams are about 0.03 W/m K. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45234.     

Investigation on flammability of rigid polyurethane foam‐mineral fillers composite

This study investigates the incorporation of castor oil–based rigid polyurethane foam with mineral fillers feldspar or kaolinite clay in order to enhance the mechanical, thermal, and flame retardant properties. Influence of mineral fillers on the mechanical strength was characterized by compressive strength and flexural strength measurement. Thermogravimetric analysis (TGA) was performed to diagnose the changes in thermal properties, while cone calorimeter test was performed to ascertain the flame retardancy of the mineral filler–incorporated rigid polyurethane foam composites. Results showed that the foams incorporated with mineral filler demonstrated up to 182% increase in compressive strength and 351% increase in flexural strength. Thermal stability of these composite foams was also found to be enhanced on the incorporation of kaolinite clay filler with an increase in 5% weight loss temperature (T_5%) from 192°C to 260°C. Furthermore, peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decreased on the incorporation of mineral filler in the rigid polyurethane foam. So mineral fillers are ascertained as a potential filler to enhance the mechanical, thermal, and flame retardant behaviors of bio‐based rigid polyurethane foam composites.     

Preparation and properties of a novel flame retardant polyurethane quasi‐prepolymer for toughening phenolic foam

A novel phosphorus‐ and nitrogen‐containing polyurethane quasi‐prepolymer (PNPUQP) was synthesized and incorporated into phenolic foam (PF) in different ratios in order to improve the toughness. The structure of PNPUQP was confirmed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The effects of PNPUQP on the flame retardant properties, thermal stability and mechanical properties of modified PF were investigated. The results suggested that the addition of 3 wt % PNPUQP increased the toughness of PF and improved the flame retardancy. The investigation on the morphology of PF and modified PF by scanning electron microscope (SEM) certified the good toughness of the PNPUQP on PF. Additionally, the thermal properties of the foams were investigated by thermogravimetric analysis (TGA) under N₂ atmosphere. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42424.     

Polyurethane foams with the contribution of products of hydroxyalkylation of N,N′‐bis(2‐hydroxyalkyl)oxamides with alkylene carbonates—obtaining and properties

In the reactions of N,N′‐bis(2‐hydroxyethyl)oxamide (BHEOD) with an excess of ethylene carbonate (EC) and N,N′‐bis(2‐hydroxypropyl)oxamide (BHPOD) with an excess of propylene carbonate (PC), the hydroxyethoxy and hydroxypropoxy derivatives of oxamide (OD) were obtained, respectively, distinguished by an increased thermal stability. First time, these derivatives were used as polyol components to obtain foamed polyurethane plastics with the contribution of 4,4′‐diisocyanate diphenylmethane (MDI). The rigid polyurethane foams of a slight water uptake, good stability of dimensions, enhanced thermal stability, and compression strength were obtained. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

Rigid polyurethane foams with halogen-free flame retardants: Thermal insulation,mechanical, and flame retardant properties

Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one-shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04–21.58 mW m⁻¹ K⁻¹. The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self-extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47611.