Effect of monomer temperature on foaming and properties of flexible polyurethane foams

Polyurethane foam formation involves simultaneous polymerization and expansion. In an open cell foam, foam lamellae rupture at some stage of foam formation, resulting in a foam with continuous air channels. Experiments are carried out to study the effect of initial temperature of monomers on the open cell content of water‐blown flexible polyurethane foams. The change in kinetics of the polymerization and blowing with initial monomer temperature is noted by measuring the gel and rise times during foaming. Both polymerization and blowing reactions are found to be faster with increasing monomer temperature. The cell size is found to increase with initial monomer temperature, and the height of the cured free rise foam is found to decrease. The open cell content of the foam increased considerably with initial monomer temperature, leading finally to the collapse of the foam at the highest temperatures studied. The mechanical properties of the foam at different monomer temperatures are determined by making molded foams. The indentation load deflection decreased with increasing monomer temperature indicating the formation of softer foams, but showed a slight increase near the temperature of collapse. Other mechanical properties showed a small degradation with increase in initial monomer temperatures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

用于网化的柔性开孔聚氨酯泡沫的制备

以三乙烯二胺和辛酸亚锡为催化剂、L580作泡沫稳定剂，对两种聚醚多元醇(TMN3050和TMN450)进行复配，制得了具有网络骨架的软质开孔聚氨酯泡沫，讨论了原料用量对泡沫性能的影响，用扫描电镜和差热热重分析对泡沫进行了观察。结果表明，优化配方为：TMN305050份，TMN45050份，水22份，L580 1．5份，异氰酸酯指数1．15。     

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...     

Curing of silylated polyurethane with BF3‐monoethylamine complex as moisture‐curable adhesives and their properties

Boron trifluoride monoethylamine complex (BF₃‐MEA) was evaluated as one of the curing catalyst, for the moisture‐curable adhesive based on the polyurethane end‐capped with trimethoxysilane (silylated polyurethane). BF₃‐MEA worked as the catalyst of condensation reaction of trimethoxysilyl groups in silylated polyurethane to give the corresponding networked polymer. The curing speed, the bond strength, and the heat resistance of the crosslinked adhesives with BF₃‐MEA were compared with dibutyltin dimethoxide. It was found that BF₃‐MEA was a good curing catalyst, which showed the same performance in the bond strength and remarkable advantages in the curing speed and the heat resistance, compared with organotin compound. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine and its application as latent curing agents

A kind of new compound of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was successfully synthesized by addition–condensation reaction of phenyl aldehyde and β‐hydroxylethanolamine and purified by vacuum distillation. Its purity was examined by gas chromatographic analysis. Its structure was confirmed by ¹³C NMR and FTIR. When this compound was added as a latent curing agent in single‐component moisture‐curable polyurethane system (SPU), bubbles of SPU formed during curing was obviously restrained, and the elongation at break of the cured SPU contained a certain content of 2‐phenyl‐3‐hydroxyethanyl‐1,3‐oxazolidine was increased to 16 times when compared with that uncontained this oxazolidine derivative. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrically conductive foamed polyurethane/silicone rubber/graphite nanocomposites as radio frequency wave absorbing material: The role of foam structure

Radio frequency wave absorber nanocomposites based on a flexible polyurethane (PU) foam has been manufactured by impregnation of the foam in n‐hexane solution of room temperature vulcanizing silicone rubber (SR), hybridized with graphite nanosheets (GNs) called doping solution. After impregnation, dried samples were kept at ambient temperature for the curing of the soaked graphitized SR. To evaluate the influences of the PU foam structural parameters on electrical conductivity, permittivity, and reflection loss characteristics, various foams with different structures were impregnated in the crosslinkable doping solution. Electrical conductivity, real, and imaginary parts of permittivity were measured within the frequency range of 4–6 GHz via performing waveguide measurements. The coarse thick wall PU foam sample exhibited higher conductivity and permittivity than the fine wire mesh sample having similar amounts of conductive SR/GN doping agent. Moreover, nanocomposites based on coarse foam samples showed higher potential for the wave absorption at lower absorber thickness than the fine wire mesh PU foam. The higher conductivity and hence imaginary permittivity of the coarse structure is attributed to the better coincidence of conductive paths in the PU/SR/GN nanocomposite foam with lines of electric field of the incident wave. The higher real permittivity of the coarse nanocomposite is suggested to be related to the more mutual interactions between graphite nanolayers and aggregates which form a network of minicapacitors in the structure of nanocomposites, leading to a higher capacitance and hence more real permittivity. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

单组分湿固化聚氨酯热熔胶黏剂的研制

以多元醇和异氰酸酯为主要原料合成不同-NCO含量的单组分湿固化聚氨酯热熔胶黏剂。阐述了固化机理,讨论了软段结构、-NCO含量、固化时间和其它填料对其性能的影响。结果表明,以自制的多元醇,设定-NCO质量分数为3．0％左右时,添加适量的EVA和萜烯树脂改性,其性能较好,固化时间为24h,拉伸强度达到9．5MPa,初黏强度达到0．38MPa,剪切强度达到8．4MPa。     

Thermally initiated oxidation and ignition of flexible polyurethane foams

Oxidation and ignition of flexible polyurethane foams have been investigated by observing the effects of internal and external heating. External temperatures of some 190°C are required to induce combustion. Internal temperatures of 250 ?350°C initiate a self-propagating internal reaction which results in foam ignition when the reaction reaches the foam surface. The stability of a polyurethane foam to such heating increases with the age of the foam.     

聚氨酯软质泡沫的制备及其泡孔结构和吸油性能的研究

采用全水发泡工艺,通过对配方的调节,研制了一种具有一定耐压强度和较好吸油性能的聚氨酯软质泡沫塑料。研究了催化剂配比及用量、泡沫稳定剂用量、粗MDI指数对聚氨酯软质泡沫吸油性能的影响。采用聚醚(N-220),当催化剂辛酸亚锡的质量份为0.20、催化剂A33的质量份为0.55、泡沫稳定剂有机硅油的质量份为1.0、粗MDI指数0.85左右、发泡剂去离子水的质量份为4～8时,所制备的聚氨酯泡沫泡孔结构和吸油效果较好。     

Ink and moisture sorption study in UV‐curable polyurethane acrylate

A study of the interaction of commercial black ink with a UV‐curable polyurethane acrylate (PUA) is presented. Diffusivity and solubility in PUA cured using different UV dosages, and subjected to different post‐UV curing conditions, were studied, as was the swelling produced by such sorption. Experiments were also conducted using water, to serve as a benchmark and compare with the effect of ink. The percentage ink absorption was found to decrease with higher degree of cure. In addition, through desorption measurements, ink induced swelling of PUA processed under different conditions was determined. The degree of swelling per unit solvent uptake was observed to increase with the degree of cure. PUA was determined to be more prone to moisture rather than solvent uptake. However, the coefficient of moisture expansion (CME) was found to be ～ 35% lower than the coefficient of ink expansion (CIE) for a fully cured PUA. © 2006 Wiley Periodicals, Inc. JAppl PolymSci 103: 1985–1991, 2007     

Studies of acoustical absorption of flexible polyurethane foam

It was confirmed that one of the principal factors which influences the acoustical absorption of flexible polyurethane foam is flow resistance of foam. Normal polyester-based flexible polyurethane foam itself has an adequate value of flow resistance and shows fairly good sound absorption. Acoustical absorption of normal polyether-based flexible polyurethane foam, which generally has lower flow resistance, can be improved by using some expedients such as setting up a certain skin layer on the foam surface so that the flow resistance of the foam can be increased. Surface treatment of foam such as gluing film, heat melting, spraying, or heat adhesion with film can not only improve sound absorption and mechanical properties of polyether-based flexible polyurethane foam, but also improve the hydrolysis resistance of polyester-based flexible polyurethane foam. Inserting some metal foil or plastic film between flexible polyurethane foams can change the sound absorption behavior according to the position of the foil or the film in the foam. The effects of foam thickness, existence of air layer behind foam, and foam profiling on acoustic absorption were also investigated.     

网化聚氨酯泡沫塑料的研制

以聚酯多元醇、甲苯二异氰酸酯、特种催化剂及表面活性剂等为原料,采用水发泡,制备了大孔径块状软质聚氨酯泡沫,泡沫经网化液化学法处理,制得性能较好的网化聚氨酯泡沫塑料。介绍了块泡生产的基本配方,对影响泡沫孔径的因素进行了探讨,并对几种网化液的处理效果进行了研究。网化后泡沫的拉伸强度及伸长率增加,硬度降低;泡孔增大,则拉伸强度和伸长率降低。     

湿固化作用对NCO／OH型双组分聚氨酯涂料漆膜性能的贡献

NCO/OH型聚氨酯漆的固化机制是—NCO与—OH反应交联和—NCO与空气中水分反应交联的叠加。通过同一种NCO/OH聚氨酯漆的漆膜在相同温度而湿度悬殊的环境中固化过程中漆膜性能增长情况的对比,证实了湿固化对漆膜的充分固化与漆膜性能的增长有明显的贡献。     

The mechano-sorptive behavior of flexible water-blown polyurethane foams

Samples of flexible water-blown slabstock polyurethane foams were compressed under constant load to study the effects of cycling moisture content on creep behavior and compare this behavior with the creep response where either a constant high or low moisture environment existed at the same temperature. Three sets of foams were tested: (1) 4 pph water content slabstock foam; (2) 5 pph water content slabstock foam; and (3) 2 pph water content molded foam. As the moisture conditions were cycled from low to high humidity while maintaining constant temperature in an environmental chamber, the compressive strain increased in subsequent steps with larger increases observed during the desorption portion of the humidity cycling. All three sets of foams showed similar behavior at a given temperature. At a temperature of 40°C, the strain levels under cyclic moisture conditions surpassed those levels observed at the highest constant relative humidity. During the first absorption step, the creep level increased. During any subsequent absorption step, the creep level either increased very little or none at all. Finally, during any desorption step, the creep level increased. This overall phenomenon of enhanced creep under cyclic moisture levels is attributed to water interacting with the hydrogen bonded structure within the foam. These hydrophillic interactions, principally promoted within the hard segment regions due to high hydrogen bonding, are disrupted causing slippage and increased in strain. As the foam is rapidly dired, regions of free volume are induced by the loss of water thus causing further increases in strain Prior to the reestablishment of well ordered hydrogen bonding. Further support to this proposition was given by the results obtained at a temperature of 90° C where it is well known that hydrogen bonds are much more mobile. Here, the strain levels under cyclic moisture conditions were nearly the same as those under constant high relative humidity. Weakening of the hydrogen bonds by means such as increased temperature resulted in similar strain levels to those under cyclic moisture levels. © 1993 John Wiley & Sons, Inc.     

湿固化型聚氨酯胶粘剂

研制了单组分无溶剂型湿固化聚氨酯胶粘剂。通过配方设计,原料选择和制备工艺的控制,得到一些相关数据并获得最佳配比。     

含液晶基元聚氨酯对普通聚氨酯性能的影响

合成了一类既含有刚性液晶基元又含有柔性链段的主链型含液晶基元聚氨酯(LCPU)，以端羟基四氢呋喃-环氧乙烷共聚醚为基体材料，多异氰酸酯N-100为固化剂，探讨这类含液晶基元聚氨酯对聚氨酯弹性体力学性能的影响。结果表明，5种含液晶基元聚氨酯随着柔性链段长度的变化和在聚氨酯弹性体中加入比例的变化。表现出对聚氨酯弹性体力学性能的影响有较大的差异。与未改性聚氨酯弹性体相比，改性后聚氨酯弹性体共混物垃伸强座量大提高71％倍．断裂伸长率最大提高8．7倍．     

Effect of solvent exposure on the properties of hydroxy‐terminated polybutadiene‐based polyurethanes

Hydroxy‐terminated polybutadiene‐based prepolyurethanes and diamine chain extended polyurethane‐ureas were prepared and treated with various organic solvents in the moisture‐cured state in order to modify their ultimate strength. FTIR studies with solvent‐treated polyurethanes and polyurethane‐ureas confirmed that organic solvents penetrated inside the polyurethane hard segments and affected hydrogen bonding. The polar and non‐polar solvents showed different abilities to penetrate into polyurethane hard segments. Solvent treatment after moisture curing increased the tensile strength of these polyurethanes and polyurethane‐ureas with respect to control samples. The stress–strain behaviour of solvent‐treated polyurethane follows the constrained junction model. The change in hard segment crystallinity on solvent treatment has been explained by wide‐angle X‐ray diffraction study. The better orientation in polybutadiene soft segments evidenced from SEM (scanning electron microscopy) pictures is believed to be the main reason behind the improved tensile properties of solvent‐treated polyurethane samples. The effect of solvent treatment, as well as stretching, on the diffusion coefficient of hexane in polyurethanes was investigated. Copyright © 2003 Society of Chemical Industry     

聚氨酯泡沫塑料在低密度炸药制备中的应用

以软质聚氨酯泡沫塑料为载体，制备低密度炸药。探讨了聚氨酯泡沫塑料在低密度炸药中的应用。简单介绍了采用炸药溶液浸渍法、水分散液浸泡法和原料混合发泡法这三种方法的工艺过程以及产品的爆炸性能。     

Structure–property relationships in one‐component polyurethane adhesives for wood: Sensitivity to low moisture content

The causes of strength loss of wood joints and their consequent delamination from one‐component polyurethane adhesives used for bonding structural wood when used at a low moisture content was investigated by testing wood joint strength and elongation at rupture at different wood moisture contents and by ¹³C‐NMR spectroscopy and scanning electron microscopy of the hardened bond line. The combination of the relative proportion of the still‐reactive free ? NCO groups on the polyurethane, of the wise choice of degree of polymerization of the resin, and of a slower rate of reaction were the three parameters found to be important in overcoming the problem of poor or no bonding of wood at low to very low moisture contents from one‐component polyurethane adhesives. The results obtained indicated that one‐component polyurethane adhesives that had a combination of a higher proportion of still‐unreacted ? NCO groups, a lower degree of polymerization, and a slower reaction rate were capable of overcoming the problem of the high sensitivity of polyurethane gluing at low to very low wood moisture contents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4181–4192, 2006     

聚氨酯预聚体增韧改性酚醛泡沫塑料

采用异氰酸酯封端且不含游离异氰酸酯单体的聚氨酯预聚体作为酚醛泡沫的增韧改性剂,并在后期混合发泡工艺中减少酸性固化剂的用量,制备了不粉化、韧性高的改性酚醛泡沫体,并考察了异氰酸酯基含量对酚醛泡沫体的表观密度、压缩强度、吸水率、阻燃性和导热性能等的影响.结果表明:随着聚氨酯预聚体用量以及异氰酸酯基含量的增加,改性酚醛泡沫体的表观密度、压缩强度增大;当异氰酸酯基含量为8.6%时,抗粉化程度最好;随着聚氨酯预聚体用量的增加,吸水率和热导率变化不大,当聚氨酯用量不超过6%时,临界氧指数仍大于40.