Preparation and properties of polyurethane nanocomposites of novel architecture as advanced barrier materials

The helium gas permeation through polyurethanes (PU) having novel microstructures derived from different polyols (varying from linear to hyperbranched) in the presence and absence of modified and unmodified nanoclays has been studied thoroughly in this paper. The permeation rate of helium gas decreases from linear to fourth generation polyols (PU₄₀) by about 80% due to increase in the crosslinking density. Similarly, the permeation rate of 8 wt% clay filled third generation hyperbranched PU dramatically decreases by about 76% in comparison to the unfilled PU. Gas-impermeable clay platelets in the PU matrix form tortuous pathways that further retard the progress of gas molecules. In addition, the well dispersed modified nanoclays contribute to improvement of the permeability properties to a great extent when compared with the aggregated unmodified ones. Further, interaction between the clays and the PU matrix plays a great role. Good correlation between dispersion of nanoclays in the PU matrix, as characterized by high resolution transmission electron microscopy and atomic force microscopy, and barrier resistance has been established. The permeation results have been compared with the different contemporary permeability models. The results are in line with the prediction by the Gusev-Lusti, the Nielsen and the Cussler (regular array) models at lower concentration of clay.     

Effect of crosslinking density on the physical properties of interpenetrating polymer networks of polyurethane and 2-hydroxyethyl methacrylate-teminated polyurethane

Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate-terminated polyurethane (HPU) and polyurethane (PU) with different crosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the PU network. Physical properties such as density and water absorption rely on the subtle balance between the degree of phase separation and the crosslinking density of the PU network. In spite of the occurrence of phase separation, the tensile moduli and tensile strength of the IPNs increase with the crosslinking density of the PU network. Morphological observation by scanning electron microscopy revealed different fracture surfaces between the compatible and incompatible IPNs. Surface characteristics of the IPNs, indicated as hydrogen bonding index and hard-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.     

Modification of aqueous polyurethanes via latex AB crosslinked polymers

A series of Latex AB crosslinked polymers have been synthesized from polyurethane (PU) (polymer A) and polystyrene (PS) (polymer B). The effect of PU/PS composition, crosslinking density in the PS domain, as well as in PU has been studied in terms of dispersion size, TEM morphology, mechanical, dynamic mechanical properties, in addition to swellability in water and toluene of the dispersion cast film. An inverted core (PS)‐shell (PU) morphology with very fine (tens of nanometers) dispersion was obtained, and the film properties were well controlled by the Latex composition and crosslinking density of both phases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1315–1322, 2001     

交联对CO2共聚物为基聚氨酯降解性能的影响

讨论ＣＯ２ 共聚物为基聚氨酯聚碳酸亚乙酯聚氨酯（ＰＥＣＰＵ） 交联方式、交联程度对其生物降解性能的影响。实验结果显示,交联程度越大,降解速度有所降低,但一定交联程度的交联型ＰＥＣＰＵ仍然具有良好的生物降解性能。     

Permeation-fließanalyse an polymernetzwerken

To detect the permeation flow through a swollen polymer network an apparatus for the flow analysis on polymer membranes was developed and used for the determination of the permeation coefficient P and the diffusion coefficient D. Polymer membranes were prepared from 1,4-cis-polybutadiene (Buna cis 132) and addition crosslinking silicon rubber (Wacker SilGel 600) by means of β-ray- and thermal treatment, respectively. These crosslinked products were characterized by solgel analysis and measurements of the uniaxial bulk modulus. The uncrosslinked original materials were characterized by means of size exclusion chromatography (SEC). The permeation and diffusion coefficients of the specimens were calculated from the stationary permeation progress. They correlated as a linear and an exponential function, respectively, with regard to the crosslink density and the equilibrium swelling degree of each sample.     

TIPA/BDO扩链的聚氨酯弹性体力学性能的研究

以聚酯(PEA、PEPA)或聚醚(PTMG)和TDI为原料合成聚氨酯(PU)预聚体,用三异丙醇胺(TIPA)和1,4-丁二醇(BDO)的混合物作扩链剂制备PU弹性体。讨论了软段相对分子质量、弹性体交联点相对分子质量和扩链剂的种类对PU弹性体性能的影响。结果表明,PU弹性体的硬度、拉伸强度、300%模量和撕裂强度随软段相对分子质量的增加而下降,而伸长率和冲击弹性随软段相对分子质量的增加而增加;交联点相对分子质量为6600时,PTMG2000为软段的PU弹性体的拉伸强度最高,达到28.44MPa;与TMP/BDO扩链的聚酯型PU弹性体相比,TIPA/BDO扩链的弹性体的拉伸强度、伸长率和撕裂强度均较高,而硬度、300%模量和冲击弹性差异不大。     

Flexible cross‐linking by both pentaerythritol and polyethyleneglycol spacer and its impact on the mechanical properties and the shape memory effects of polyurethane

A series of polyurethane (PU) polymers cross‐linked laterally by pentaerythritol and polyethyleneglycol (PEG) spacers were compared with linear PU. The PU was composed of 4,4′‐methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol), 1,4‐butanediol (BD), pentaerythritol, and PEG‐200 as a spacer. PEG‐200 connected the pentaerythritol hydroxyl groups of two PU chains with MDI as a connecting agent. The phase separation between hard and soft segments was disrupted by the PEG crosslinking, and T_m did not change with an increase in cross‐linking content. Instead, the cross‐link density increased with an increase of pentaerythritol content. A significant increase in maximum stress compared with linear PU was attained, together with an increase in strain. The combination of both pentaerythritol and PEG‐200 in the PU resulted in the improvement of both stress and strain, unlike in the conventional cross‐linking method. The shape recovery increased to 90% and did not decrease after three test cycles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis, characterization, and analyses of mechanical, adhesion, and thermal properties of polysiloxane resin modified with segmented polyurethane

Novel heat-resistant coating materials with excellent adhesion properties were prepared by modification of polysiloxane resin (PSil) with a pre-synthesized tailored polyurethane/polyurea copolymer end-capped with siloxane (PU). The modification was achieved by crosslinking the hydroxyl group of PSil and ethoxy group of PU in the presence of di-n-butyltin dilaurate. The chemical structure of PU was analyzed by Fourier Transform Infrared and Hydrogen-1 Nuclear Magnetic Resonance spectroscopic methods. A series of modified silicone resins (MSRs) have been synthesized and investigated. The molecular weights of the resins were determined by means of gel permeation chromatography. The morphology of the MSR studied by scanning electron microscopy has shown that the resin containing 30% of PU has a small particle size and a good particle size distribution. The adhesion and the mechanical properties of the resins containing 20, 30, and 40% of PU have shown a good performance. Using thermogravimetric analysis, the thermal properties and the thermal degradation of the MSR were investigated.     

Polyurethane-crosslinked epoxy resins. I. Mechanical behavior

Polyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU-crosslinked DGEBA. The tensile strength of both the PU(PBA)-crosslinked DGEBA and PU(PTMO)-crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content. Izod impact property of these PU-crosslinked DGEBA indicated that the PU(PBA)-crosslinked DGEBA had much more significant improvement than the PU(PTMO)-crosslinked DGEBA. On the contrary, the fracture energy (G_{1 C} value) of the resultant PU-crosslinked DGEBA showed that the PU(PTMO)-crosslinked DGEBA had much higher G_{1 C} values than the PU(PBA)-crosslinked DGEBA.     

Preparation of water‐compatible antifungal polyurethane with grafted benzimidazole as the antifungal agent

We compared two series of benzimidazole (BI)‐grafted polyurethane (PU), one of which was water‐compatible, to compare their antifungal activities. The water‐compatible PU series had an additional 2,2‐bis(hydroxymethyl)propanoic acid group in the PU backbone. The water‐compatible PU series had a lower crosslinking density and tensile strength compared to the other PU series with increasing BI content. Although ordinary PU did not suppress fungal growth (Chaetomium globosum), the water‐compatible PU completely suppressed the growth even though it contained half as many BI groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41676.     

The temperature-sensitive water vapor permeation control of polyurethane membrane using the graft-polymerized poly(N-isopropylacrylamide) and the impact on the tensile strength and shape recovery effect

Poly(N-isopropylacrylamide) (poly(NIPAM)) was grafted onto polyurethane (PU) using a graft-polymerization method to develop a thermo-responsive PU and to investigate the impact on cross-link density, solution viscosity, soft segment thermal transitions, tensile properties, shape memory effect, and water vapor permeation through PU membrane. The soft segment crystallization peak sharply decreased with the increase in NIPAM content, whereas the glass transition temperature (T_g) slightly increased with the increase of NIPAM content. The breaking tensile stress rapidly increased with the increase in NIPAM content due to the cross-linking effect between the grafted poly(NIPAM) chains, whereas the strain at break did not significantly decreased as the NIPAM content increased. The shape recovery at 10°C rapidly increased from 46.9% for plain PU to above 90% after the grafting of poly(NIPAM) onto PU, and the shape retention at ?25°C slightly decreased with the increase in NIPAM content. Finally, the grafting of poly(NIPAM) onto PU demonstrated the temperature-responsive control of water vapor permeation through PU film due to the conformational change of the grafted poly(NIPAM) with the increase of temperature and the potential applications of the resulting PUs are discussed.     

High‐molecular‐weight polyurethanes prepared by one‐step miniemulsion polymerization

Through one‐step miniemulsion polymerization, hydrophobic polyurethane (PU) dispersions were prepared, with hexadecane (HD) as costabilizer in the oil phase and sodium dodecyl sulfate (SDS) as surfactant in the water phase. The oil phase, including isophorone diisocyanate, poly(oxytetramethylene) glycol, a costabilizer HD, a chain extender 1,4‐butanediol, a crosslinking agent trimethylol propane, and a catalyst dibutyltin dilaurate (SnDBL), was dispersed in the water phase containing SDS. The influences of experimental parameters, such as SnDBL, NCO/OH equivalents, and concentrations of surfactant, were discussed. The particle size and the molecular weight of PU polymer were measured by light scattering and gel permeation chromatography, respectively. With the addition of SnDBL and higher NCO/OH ratio, PU films with higher molecular weights were produced. The chemical structure of the PU polymer was identified by Fourier transform infrared spectrometer, and the adsorption of urethane group was observed. Thermal gravimetric analysis was used to characterize the thermal stability of PU. Furthermore, mechanical property was also investigated and characterized by tensile strength and elongation at break. With a higher NCO/OH ratio and the existence of SnDBL, the tensile strength of PU films was significantly increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Rigid polyurethane foams from a soybean oil-based Polyol

Polyurethane (PU) rigid foams were synthesized by substituting a polypropylene-based polyol with soybean oil-based polyol (SBOP). All the soy-based foams maintained a regular cell structure and had even smaller average cell size than the control foams. The density of soy-based foams was within 5% of the controls, except that the density of foams from 100% SBOP was 17% higher. Soy-based foams also had comparable initial thermal conductivity (k value) and closed cell content, higher T_g and compressive strength. However, while foams from 50% SBOP showed similar increase in k value to the 0% SBOP foams, under accelerated aging conditions, the 100% SBOP foams aged faster. Gas permeation tests performed on PU thin films showed higher N₂ permeation for PU thin films made from SBOP which is believed to be the cause of accelerated thermal aging.     

交联剂对聚氨酯乳液性能的影响

合成了以水合联氨、乙二胺、二乙烯三胺、三乙烯四胺为交联剂的聚氨酯水乳液。探讨了不同交联剂及同种交联剂不同用量对聚氨酯水乳液粘度、储存稳定性、胶膜力学性能的影响及相应乳液在纸涂层中的作用。结果表明:交联剂过量不利于乳液的储存稳定性;胶膜的扯断强度按水合联氨、乙二胺、二乙烯三胺、三乙烯四胺的顺序依次增强:以二乙烯三胺为交联剂的乳液用于纸涂层中显示的综合性能最好。     

Castor oil‐based polyurethane–polyester nonwoven fabric composites: Mechanical properties,chemical resistance,and water sorption behavior at different temperatures

Castor oil‐based polyurethane (PU)–polyester nonwoven fabric composites were fabricated by impregnating the polyester nonwoven fabric in a composition containing castor oil and diisocyanate. The effects of different diisocyanates such as toluene‐2,4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) on the mechanical properties have been studied for neat PU sheets and their composites with polyester nonwoven fabric. Chemical resistance of the PU composites has been assessed by exposing the specimens to different chemical environments. Percentage water absorption of composites and neat PU sheets has been determined both at room temperature and in boiling water. Both TDI‐ and HMDI‐based PU composites showed a marginal improvement in tensile strength retention at 100°C heat ageing. Water sorption studies were carried out at different temperatures, viz, 30, 50, and 70°C, based on immersion weight gain method. From the sorption results, the diffusion (D) and permeation (P) coefficients of water penetrant have been calculated. Attempts were made to estimate the empirical parameters such as n, which suggests the mode of transport (non‐Fickian), and K, a constant which depends on the structural characteristics of the polymer in addition to its interaction in boiling water. The temperature dependence of the transport coefficients has been used to estimate the activation energy parameters for diffusion (E_D) and permeation (E_p) processes from Arrhenius plots. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

新型紫外线固化环氧树脂/丙烯酸酯改性水性聚氨酯的合成与性能

合成了一种新型的具有高交联密度和优异涂膜性能的环氧树脂和丙烯酸酯同时改性的紫外线（UV）固化水性聚氨酯（UV-EP-AC-WPUD）。通过环氧基团与以异氰酸酯基团（-N=C=O）封端的聚氨酯预聚体之间的反应引入质量分数为4%的环氧树脂E-20。同时,通过聚氨酯链的-N=C=O与二元丙烯酸酯（PEDA）以及季戊四醇三丙烯酸酯（PETA）的羟基之间的反应引入碳碳双键（C=C）,C=C的含量达到4.65 meq·g-1。 质量分数为3%的光引发剂Irgacure 2959被用于引发涂膜中C=C的聚合,涂膜的凝胶含量在12 s UV辐射之后达到91%,意味着C=C的聚合和交联速度快,同时所得到的涂膜的交联度非常高,不溶于溶剂丙酮,测试表明环氧树脂和两种丙烯酸酯单体已经成功嵌入聚氨酯链中,涂膜具有优异的力学性能和化学性能。     

Role of strain induced crystallization and oxidative crosslinking in fracture properties of rubbers

Tensile properties and crack propagation properties, especially critical strain energy release rate in mode I, G_IC, have been used to investigate fracture properties of elastomers and their relationships with microstructure. These investigations were mainly based on a series of comparisons: first, the behaviour of polychloroprene rubber (CR), undergoing stress hardening due to strain induced crystallization (SIC) and oxidative crosslinking (OCL) was compared with that of chlorinated polyethylene (CPE), which undergoes SIC but not OCL, and with a polyurethane based on hydroxyl terminated polybutadiene (PU) which undergoes OCL but not SIC. Comparisons were also made on CR between fracture behaviour at ambient temperature, where SIC occurs and at 100 °C where there is no SIC. Finally, oxidative crosslinking was used to vary in a continuous way the crosslink density in CR and PU, in order to evaluate the role of crosslinking in fracture behaviour.     

A study on permeation behavior of a liquid mixture through PVA membranes having a crosslinking gradient structure in pervaporation

Two types of dense poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde were prepared by a new solution technique: membranes with uniform crosslinking structure and with crosslinking gradient structure. From the permeation of pure water through a membrane having a uniform crosslinking structure, the effect of crosslinking density in the membrane on the permeation activation energy, plasticizing coefficient, and diffusivity of the permeant was investigated. The concentration and activity profiles of the permeant in the membrane in the pervaporation process were determined using the diffusion equation and Flory–Huggins thermodynamics. PVA membranes having a crosslinking gradient structure were fabricated by exposing one side of the membrane to the reaction solution while the other side was blocked by a polyester film to prevent the reaction solution from contacting it. The extent of the gradient was controlled by the exposing time. The pervaporation separation of the water–acetic acid mixture was carried out on the membrane having a crosslinking gradient structure, and the pervaporation performance with different membrane loading in the membrane cell was discussed using a schematic concentration and activity profiles of the permeant which was made based on the results from the permeation of a pure component through the membrane with a uniform crosslinking structure. © 1996 John Wiley & Sons, Inc.     

IPN中聚氨酯固化反应动力学的FTIR研究

用傅立叶变换红外光谱(FTIR)研究纯聚氨酯弹性体和聚氨酯/聚二甲基硅氧烷IPN中聚氨酯的固化反应动力学。结果表明,在PU/PDMS IPN体系中聚氩酯的交联反应仍为二级反应,聚二甲基硅氧烷的存在大大降低了PU/PDMS IPN的交联速率,并提高了反应活化能。     

Preparation and properties of reactive polyurethane polyacrylate blends based on carbonyl‐hydrazide reaction

A new reactive polyurethane/polyacrylate (PU/PA) blend was developed by mixing a core–shell polyacrylate latex containing keto groups in shell layer and a polyurethane dispersion incorporating multiple hydrazide groups which was synthesized by introducing the poly‐hydrazide groups into the end of the vinyl‐terminated polyurethane chains. Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) results indicated that poly‐hydrazide groups had been incorporated in the polyurethane chains. Transmission electron microscopy (TEM) micrograph revealed that polyacrylate particles had a clear core–shell structure. The results of FTIR, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) indicated that the crosslinking reaction between two polymer systems had happened and crosslinking structure could effectively improve the compatibility between PA and PU. Thermogravimetric analysis (TGA) and mechanical tests results suggested that crosslinking structure could enhance the thermal stability and mechanical properties of blends. The influence of the PA content and the n(? CO? )/n(? NHNH₂) ratio on the hardness, water resistance, solvent resistance, and gel fraction of the blend films were comprehensively studied. The optimal PA content and n(? CO? )/n(? NHNH₂) ratio was 30% and 1.5:1 in this experiment, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44443.