Influences of copolymer polyol on structural and viscoelastic properties in molded flexible polyurethane foams

In this study, the viscoelastic and morphological properties of molded foams were investigated to determine the influence of the presence or absence of reinforcing particulate copolymer polyols (CPP). The molded foams were based on toluene diisocyanate (TDI) and glycerol‐initiated ethylene‐oxide endcapped polypropylene oxide and, in most samples, some amount of copolymer polyol. Two series of foams were studied. In Series 1, as CPP is added to the formulation, the amount of TDI fed is kept constant. This results in a constant amount of hard‐segment content as the filler in the system displaces, by weight, the polyether polyol in the foam, and it increases the hard segment to soft segment ratio (HS/SS). In Series 2, the amount of hard‐segment material is proportionally decreased as CPP is added, resulting in a constant HS/SS ratio. Structural investigations of the foams displayed rather similar textures. The cellular structures of a CPP‐containing foam was very similar to a foam lacking the copolymer polyols. Transmission electron microscopy revealed that the CPP particles were well dispersed and that they possessed significant rigidity even at high temperature and under high compression. Although all of the foams were microphase‐separated, they varied slightly in that the copolymer polyol containing foams exhibited higher weight fractions of extractables in both Series 1 and Series 2. This suggests that not all of the CPP material is covalently bonded into the polyol matrix. It was found that temperatures above ambient as well as humidity plasticized the viscoelastic behavior of all the molded foams evaluated. It was also found that the copolymer polyol particles, as added to the molded foams of Series 1, increased load‐bearing capabilities but had a negative effect on the stress relaxation, creep, and compression set properties. In particular, the viscoelastic properties of the CPP‐containing foam were distinctly more time‐dependent than those of the foam lacking these particles. However, the Series 2 foams show that most of these effects are a result of the increased HS/SS ratio and not a result of the CPP particulate. It was shown that adding CPP while maintaining a constant HS/SS ratio improves percent load loss and load bearing under high‐humidity conditions, two important properties in flexible polyurethane foams. Finally, it was shown that at high temperatures (ca. 100°C), an additional relaxation mechanism occurs which cannot be attributed to changes in the HS/SS ratio, but must be a result of the CPP components themselves. This additional mechanism results in higher rates of load relaxation and creep in foams containing CPP at high temperatures for foams of both series. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 766–786, 2000     

环氧树脂加成多元醇增强聚氨酯软质泡沫塑料

用双酚 A型环氧树脂与乙酸反应,合成了具有刚性骨架的环氧树脂加成多元醇 (EAP),并用 FTIR与 1H－ NMR对其进行了表征。研究结果表明,工业聚醚多元醇中添加 EAP后制备的全水发泡软质聚氨酯（ PU）泡沫塑料的压入硬度显著提高,但回弹性不变。进一步研究了不同水用量对所制备 PU软质泡沫塑料力学性能的影响,并用 FTIR和光学显微镜考察了 PU软质泡沫塑料中脲基的氢键行为和泡孔结构。结果表明,在 PU软质泡沫塑料中引入 EAP刚性链对 PU泡沫塑料的结构及性能有很大影响。     

Substituting soybean oil-based polyol into polyurethane flexible foams

Polyurethane (PU) flexible foams were synthesized by substituting a portion of base polyether polyol with soybean oil-derived polyol (SBOP) as well as well-known substituent: crosslinker polyol and styrene acrylonitrile (SAN) copolymer-filled polyol. Increases in compression modulus were observed in all substituted foams and the most substantial increase was found in the 30% SBOP-substituted sample. Scanning electron microscopy (SEM) was used to examine cellular structure, in particular cell size. Polymer phase morphology, i.e., interdomain spacing and microphase separation, was studied using small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). Hydrogen bonding was investigated via Fourier transform infrared (FTIR) spectroscopy. Thermal and mechanical behaviors of foams were examined using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Compression properties were tested and compared via a 65% indentation force deflection (IFD) test. It was found that substituting SAN-filled polyol slightly reduced foam cell size and had no effect on polymer phase morphology. Crosslinker and SBOP polyols, on the other hand, had appreciable influence on polymer phase morphology. Crosslinker polyol disrupted hydrogen bonding between hard segments and was mixed with hard domains. SBOP polyol reduced hard domain size and soft domain fraction, and showed a broad distribution of interdomain spacings. Compression modulus increases in foams correlated well with shear modulus by DMA and could be associated with the polymer phase morphology changes.     

软质聚氨酯泡沫塑料无卤阻燃技术研究进展

软质聚氨酯泡沫(FPUF)是聚氨酯材料的主要产品之一,由于其较低的密度和热传导率而易燃,在燃烧过程中会放出大量烟雾和有毒气体,对FPUF进行阻燃处理尤为重要。卤系阻燃剂由于存在潜在的毒性和环境问题而受到限制,因此FPUF的无卤阻燃技术是今后主要的研究方向。本文综述了近年有关软质聚氨酯泡沫无卤阻燃技术的研究进展,包括添加型无卤阻燃剂法、反应型无卤阻燃剂法、层层组装涂层法。指出开发高相对分子质量、含多种阻燃元素的有机添加型阻燃剂和膨胀型阻燃剂以及复配型阻燃剂,解决层层组装涂层法的组装慢等问题将是FPUF无卤阻燃技术的发展趋势。     

Expandable graphite in polyurethane foams: The effect of expansion volume and intercalants on flame retardancy

Several expandable graphites (EGs), differing in expansion volume but with the same mean size, are compared as flame retardants in polyurethane (PUR) foams. Not only common sulfur‐intercalated graphites are investigated but also a new one intercalated with phosphorus. The main aim of this article is to understand which properties of EG are important for its flame retardancy effectiveness in PUR foams. Thermal stability, flammability, and fire behavior are analyzed through limiting oxygen index and cone calorimeter tests. Detailed characterization of the phosphorus‐intercalated graphite is also provided as well as physical–mechanical characterization. The results show that the well‐known sulfur‐intercalated graphites and the one with phosphorus both enhance the residue yield, induce a protective layer, and thus efficiently flame‐retard PUR foams. While the expansion volume of the EGs had a surprisingly limited influence on the performance of the foams, at least in the range tested, the most important feature controlling the effectiveness of EG in terms of flame retardant PUR foams was the type of intercalant. The presence of EG affected the physical–mechanical properties of the foams; however, no significant effect of the expansion volume or intercalant type has been revealed on the physical–mechanical properties of the foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45173.     

Synergistic effect of carbon and phosphorus flame retardants in rigid polyurethane foams

Two kinds of carbon and phosphorus synergistic system used to improve the flame retardancy of rigid polyurethane foams (RPUF) were studied. One is the synergistic effect of expandable graphite and guanidinium phosphate; the other is red phosphorus and guanidinium phosphate. The flame retardant properties and mechanical properties of these composites were investigated by limiting oxygen index, cone calorimeter test, as well as tension and compression test. These 2 groups of mixed inorganic flame retardants can greatly improve the flame retardancy of RPUF composites, as the limiting oxygen index increases from 20.1% to about 33% and the HRR reduces from 395 kW/m² to below 200 kW/m². It provides a convenient and inexpensive way to obtain RPUF with demanding properties.     

Intrinsic flame resistance of polyurethane flexible foams: Unexpectedly low flammability without any flame retardant

Virgin polyurethane flexible foams are widely assumed to be highly flammable materials. The flammability of three model polyurethane flexible foams suggests that this may not be universally true. Two of them show unexpectedly low flammability in the limiting oxygen index test and pass flammability tests such as FMVSS 302 and FAR 25.853. Cone calorimetric measurements at 25 kW/m² and 50 kW/m² furthermore show a high resistance against ignition and demonstrate the self‐extinguishing properties of these two virgin, flame‐retardant‐free, polyurethane flexible foams.     

Influence of diethanolamine on hard segment ordering in flexible polyurethane foams

In this study the microphase separation and structural organization of the hard segment domains were studied as a function of diethanolamine (DEOA) content for two series of model foams based on toluene diisocyanate (TDI) and glycerol initiated ethylene-oxide-capped propylene-oxide or glycerol initiated propylene-oxide. It was found that as the DEOA content was increased, the more disordered the hard segment domains became. Extractions in dimethyl formamide (DMF) showed that increasing the DEOA content increased the gel fraction, confirming that DEOA further crosslinked the system. More importantly, it was also found that the hard segment domains were also influenced by the DEOA content where the foams lacking DEOA had a much higher level of short range ordering. This was first confirmed by wide-angle x-ray scattering (WAXS) patterns where the amorphous character was much more pronounced as the DEOA content was increased. In addition, Fourier transform infrared (FTIR) data from the carbonyl region showed that the level of bidentate urea or strong hydrogen bonding also decreased as the DEOA content was increased, confirming that the short range ordering does decrease with increased DEOA content. This observation is believed to help explain the greater ease of “plasticization” by temperature and moisture observed of foams that included DEOA in their formulation. This was exemplified by comparing the load relaxation behavior at a low temperature (35°C) and a high temperature (100°C) between two foams varying in DEOA content. At ambient conditions (40°C, 35%RH), the foam with DEOA exhibited slightly higher loads at any given loading time, while at elevated conditions (100°C, 98%RH), there was very little difference between the two foams. Although the observed load relaxation behavior was mostly a result of the increased crosslinking, the increased closed cell content induced by the greater crosslinking also contributed to the load values. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:525–537, 1997     

Synergistic effect of aluminum hydroxide and expandable graphite on the flame retardancy of polyisocyanurate–polyurethane foams

For the first time, expandable graphite (EG) and aluminum hydroxide (ATH) was combined to improve the flame retardancy of polyisocyanurate–polyurethane (PIR–PUR) foam. The limited oxygen index increased from 26.5 for the PIR–PUR matrix to an incredible value of 92.8 when 24 phr (parts per 100 of matrix) EG and 60 phr ATH were incorporated into the matrix. Based on morphology observation and thermogravimetric analysis, it was speculated that two factors contributed to the improvement of flame retardancy primarily. First, ATH could effectively induce “villi” like particles, which was useful to form a dense char. The compact char layer could effectively impede the transport of bubbles and heat. Second, ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface of the composites. Thus, the degradation of the composite was slowed down and the diffusion of volatile combustible fragments to flame zone was delayed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39936.     

Intumescent foams—A novel flame retardant system for flexible polyurethane foams

A combination of intumescent components was evaluated as a novel flame retardant system in a flexible polyurethane foam, and the incorporation of these components gave rise to a significant enhancement of the flame retardant properties of the foam. The heat release rate was lowered at an early stage as well as throughout the fire, the total heat production was decreased and the time to ignition was prolonged. Mechanical measurements of the foam revealed enhanced properties in terms of stiffness accompanied by a large decrease in elongation at break as compared with a reference foam. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology of water-blown flexible polyurethane foams

A series of four TDI–polypropylene oxide (PO) water-blown flexible polyurethane foams was produced in which the water content was varied from 2 to 5 pph at a constant isocyanate index of 110. A portion of each foam was thermally compression molded into a plaque. The morphology of both the foams and plaques was investigated using dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), swelling, wide angle X-ray scattering (WAXS), and small angle X-ray scattering (SAXS). A high degree of microphase separation occurs in these foams, and its degree is nearly independent of water (hard segment) content. In the foam with the lowest water content the morphology possesses many similarities to that of typical linear segmented urethane elastomers. Small hard segment domains are present with a correlation distance of about 7.0 nm. When the water content is increased a binodal distribution of hard segment material appears. There are the small hard segment domains typical of segmented urethane elastomers as well as larger “hard aggregates” greater than 100 nm in size. The larger domains are thought to be aggregates of rich polyurea that develop by precipitation during the foaming reaction. WAXS patterns of the foams suggest urea and possibly hard segment ordering that may be of a paracrystalline nature but certainly lacking in true 3-dimensional crystallinity.     

Cushioning performance of flexible polyurethane foams

Impact cushioning and deformation of flexible open-cell polyester polyurethane (PU) foams were studied as a function of specimen geometry, including the incorporation of controlled voids. It was shown that cushioning behavior is dependent on sample geometry, which was in trun due to a complex balance of air compression and air flow, which changes with surface area-to-volume ratio of the impact specimen. Deformation studies show that impact compression proceeded initially by crushing the surface layers with little or no deformation of the center layers. As bulk compression was increased, deformation progressively propagated for the collapsed layers tending to a more uniform strain distribution at high bulk compression strains. Local asymmetric strain patterns were exaggerated using square cushions, because of cornr effects which complicated air flow paths. It was concluded that cushion curve determination of open-cell foams would be more accurately performed using circular samples and deflecting air pressure form the top surface of the cushion to more closely simulate practical conditions. When designing at or near the margin, the number of cushions should be kept to a minimum and open surface area to volume ratios minimized by adopting square rather than strip cushions.     

Synthesis and flame retardancy of phosphorus containing polycarbonate

Novel P-containing copolycarbonate was prepared via melt polycondensation of diphenyl carbonate (DPC), bisphenol-A (BPA) and 2-(6-oxid-6H-dibenz〈;c,e〉〈1,2〉oxa-phosphorin-6-yl)-1,4-benzenediol (ODOPB). The copolycarbonates were characterized by infra-red spectra, reduced viscosity, and differential scanning calorimetry. The copolycarbonates with reduced viscosities of 0.21∼0.25 dL/g were obtained in quantitative yields. These phosphorus containing copolycarbonates have excellent thermal and flame retardant properties. Owing to the incorporation of the rigid structure of ODOPB and the pendant P group, the resulting phosphorus containing copolycarbonates exhibited better flame retardancy, higher char yield, higher degradation temperature and thermal stability than homopolymers of polycarbonate (PC). High LOI value and UL 94-VO rating could be achieved with a phosphorus content of as low as 0.75% for PC, and no fumes or toxic gas emissions were observed.     

New developments in flame retardancy of styrene thermoplastics and foams

This review provides an insight into new developments in flame retardancy of the broad class of styrenic polymers but mostly focuses on commercially important styrene thermoplastics, on some blends based on polystyrene as well as on polystyrene foams. Although halogen‐based systems continue to dominate in flame retardancy of styrenic polymers, various alternative systems are being developed. Especially, activity is observed with phosphorus‐based flame retardants, where some systems are already commercially available. There is also significant activity with nanocomposites, where good results in retarding flame spread have been achieved, but the problem of ignition resistance has not been solved yet. Critical discussion of various flame‐retardant systems developed for styrenics is given. Copyright © 2007 Society of Chemical Industry     

Enhanced flame retardancy and mechanical properties of waterborne polyurethane based on the phosphorus and nitrogen containing polybutadiene acrylonitrile

To further improve fire resistance of waterborne polyurethane, the macromolecular intumescent flame retardant (APBDH) was designed and prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 4-aminothiophenol, benzaldehyde, and hydroxyl-terminated polybutadiene acrylonitrile (HTBN). Then, it was incorporated into waterborne polyurethane (WPU) to preparing flame retarded WPU (FR-WPU). TGA results suggested that the incorporation of APBDH into WPU increased thermal stability of FR-WPU. The fire resistance of FR-WPU were investigated by limiting oxygen index (LOI) test, the vertical burning test (UL-94), SEM-EDS analysis, the Laser Raman test, and cone calorimeter test. An LOI value of 28.82% and a UL-94 V-0 rating can be achieved when the WPU sample conjugated with 7.5 wt% APBDH. It indicated that the fire resistance of FR-WPU remarkably improved and displayed both gas and condensed phase mechanism. As the content of APBDH increased, the tensile strength and the elongation at break of FR-WPU increased firstly and then decreased. The thermo-mechanical behaviors indicated that the storage modulus increase at first and then descend with the addition of APBDH, while the T_gs firstly decreased and then increased. Additionally, the T_gh increased with the addition of APBDH.     

高回弹聚氨酯软泡的无卤阻燃研究

随着人们环保意识的不断提高,卤系阻燃剂的毒性问题受到越来越多的关注,阻燃剂无卤化已经成为必然趋势。间苯二酚双(二苯基磷酸酯)齐聚物(RDP)阻燃剂是一种无卤添加型阻燃剂,因具有优异的热稳定性和低挥发性而得到广泛应用。实验中分别用它与膨胀石墨来阻燃高回弹聚氨酯软泡并进行了二者协同阻燃聚氨酯软泡的研究。用氧指数仪和民航飞机用垂直燃烧方法测试表征了制备的泡沫样品,并对其阻燃性能进行了研究。     

Effects of the functionality of polyol in rigid polyurethane foams

Rigid polyurethane foams (RPUFs) have been fabricated from crude MDI (CMDI) and polypropylene glycols (PPGs) of various functionalities (f) with HFC 365mfc as a blowing agent. Foam density increased, cell size and density distribution decreased with increasing f while the closed cell content was kept constant over 92%. The gel time, tack‐free time, volume change, and the thermal conductivity of the foam showed a minimum with f = 5, and the existence of minimum has been explained in terms of a large mixture viscosity and cell wall resistance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microstructure,mechanical properties,and flame retardancy of nanoclay‐incorporated polyurethane flexible foam composites

The present work seeks to investigate microstructure, mechanical properties, and flame retardancy of polyurethane/nanoclay flexible foam composites. In this regard, we prepared various nanocomposites with and without nanoclay and observed the resulting morphologies to correlate them with the other corresponding characteristics. The results provided support for the fact that tensile strength and compression set will increase with nanoclay content, while elongation at break and tear strength decrease to some extent. Flame‐retardancy test results showed that the introduction of nanoclay into the polyurethane flexible foam causes an almost optimal trend in the flame retardancy over clay content. The microcellular‐properties correlations were established on account of changes in microcell architecture. J. VINYL ADDIT. TECHNOL., 22:415–422, 2016. © 2015 Society of Plastics Engineers     

Improvement in flame retardancy of polyurethane dispersions by newer reactive flame retardant

A novel phosphorus containing reactive flame retardant was synthesized and incorporated successfully in polyurethane backbone to obtain flame retardant aqueous polyurethane dispersions (FRPUDs). The reactive flame retardant compound was synthesized by using phosphorus oxychloride (1 mole) and N-methylaminoethanol (3 mole). The structure of synthesized phosphorus containing triol was confirmed by FTIR, ¹H NMR and ³¹P NMR spectrometry. Further, polyurethane prepolymer was modified with phosphorus containing triol compound in various amounts (30, 40 and 50% on equivalent basis) and FRPUDs were prepared. PUD films were applied on wood and mild steel panels and air dried. It was then characterized for mechanical, chemical, thermal and flame retardant properties. It was observed that all FRPUDs exhibited good mechanical properties and improved flame retardancy as compared to the conventional one. The maximum limiting oxygen index (LOI) value of 37 was obtained for FRPUD containing 0.8 mass% of phosphorus and 1 mass% of nitrogen. The flame retardancy was greatly depending on the phosphorus content and increased with increase in phosphorus content.     

不同含量配比制备聚氨酯泡沫及其性能研究

采用一步法以异佛尔酮二异氰酸酯和聚醚多元醇为原料,选用A～D4种配比制备了聚氨酯泡沫材料,通过红外光谱仪、扫描电子显微镜、差示扫描量热仪、热重分析仪和噪声振动测试系统等对聚氨酯泡沫的泡孔结构、热稳定性及吸音隔音性能进行了测试.结果表明,聚醚多元醇的用量对聚氨酯泡沫成分未造成差异,聚氨酯泡沫中出现闭孔、半闭孔、开孔并存现...