Structure-property relationship of castor oil based diol chain extended polyurethanes (PUs)

A series of 1,4-butane diol and 1,6-hexane diol based chain extended polyurethanes (PUs) have been prepared using castor oil with different diisocyanates such as methylene bis (phenyl isocyanate) (MDI), toluene-2,4-diisocyanate (TDI) and hexa methylene diisocyanate (HMDI) as crosslinkers. The prepared aliphatic diol based chain extended PU's have been characterised for physico-mechanical properties such as density, tensile strength, percentage elongation at break, tensile modulus and surface hardness; and optical properties like total transmittance and haze. The properties imparted by the chain extenders and diisocyanates on PUs have been explained on the basis of chemical structure. Effect of heat aging on mechanical properties of PUs have also studied. These changes have been interpreted quantitatively in terms of microcrystalline parameters computed using wide-angle X-ray scattering (WAXS) data.     

Sorption and diffusion of arenes through poly (ethylene-co-vinyl acetate) membranes

The sorption and diffusion of aromatic hydrocarbons through poly (ethylene-co-vinyl acetate) membranes has been investigated in the temperature interval of 25–70 °C using the sorption gravimetric analysis. The carbon–carbon crosslinks are introduced by using benzoyl peroxide (BP). Diffusion through membranes containing different loading of BP was carried out. For all liquids, the equilibrium solvent uptake was influenced by the penetrant size, temperature and crosslinking density. Thermodynamic constants are estimated from the sorption measurements. The values of polymer–solvent interaction parameters obtained from the diffusion experiments have been used to calculate the molecular mass between crosslinks of the network polymer. The transport mechanism was found to follow close Fickian behavior at 28 °C, but at high temperature, mechanism deviates to anomalous mode of transport.     

聚氨酯脲和聚氨酯酰亚胺膜的制备与渗透汽化芳烃/烷烃分离性能研究

通过两步聚合的方法,成功制备了以聚己二酸乙二醇酯(PEA)为软段的聚氨酯脲(PUU)和聚氨酯酰亚胺(PUI)膜材料,用FT-IR,NMR和DSC等方法对两种膜材料的分子结构及性质等进行了表征,并考察了两种膜对芳烃/烷烃混合物的渗透汽化分离性能.结果表明,两种膜都对芳烃表现出良好的选择渗透性,在相同的条件下,PUU膜的渗透通量比PUI膜更大而分离因子更小.对于苯的浓度为50%的苯/环己烷混合物分离体系,45℃时PUI膜的渗透通量为18.6 kg·μm/(m2·h),分离因子为7.3;而对于苯/正己烷混合物分离体系,渗透通量则为22.4 kg·μm/(m2·h),分离因子为15.2.     

聚四氢呋喃醚二醇脂肪族超支化聚氨酯的合成及表征

利用聚四氢呋喃醚二醇(PTMG,Mn=2000)和异佛尔酮二异氰酸酯(IPDI)为原料,以二月桂酸二丁基锡(DBTDL)为催化剂,通过逐步聚合反应合成了—NCO封端的聚氨酯预聚体(PPU),通过单因素实验,根据反应过程中异氰酸酯基团和羟值含量的变化规律,优化出了PPU的合成条件:反应温度75℃,反应时间为1.5h,m(DBTDL)=0.007%(以IPDI和PT-MG2000的总质量计)。再通过接枝使PPU与端羟基超支化聚合物(HPAE)共聚反应制备得到一种新型超支化聚氨酯(HBPU)。经过单因素实验分析方法优化出了HBPU的合成条件为反应温度75℃,反应时间4h。分别利用FT-IR和综合热分析对PPU和HBPU的结构以及热稳定性进行了表征。     

Sorption and diffusion of aromatic solvents through linear low density polyethylene–ethylene vinyl acetate blend membranes

An investigation has been made for understanding the transport behaviour of organic solvents through linear low-density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blend membranes with special reference to the effects of blend ratio, concentration of cross-linking agent, penetrant size and temperature. Attempts have been made to relate the transport parameter with the morphology of the blend. The various transport parameters such as diffusion coefficient (D), permeation coefficient (P) and sorption coefficients (S) were evaluated at different diffusion conditions. The results were compared with theoretical predictions and found that the diffusion process follows anomolous type behaviour. The blends show dispersed/matrix and co-continuous phase morphologies depending on the composition. Dynamic vulcanization leads to fine and uniform distribution of the dispersed domains with a stable morphology. Among the blends E₇₀ sample shows the maximum solvent uptake and E₃₀ the minimum. The solvent uptake of blend varies with concentration of cross-linking agent. Molecular size of the solvent is a decisive factor in the solvent uptake. The rate of sorption and maximum solvent uptake increase with increase of temperature. Irrespective of the solvents used, the maximum solvent uptake increases with increase of temperature. The observed sorptivity, diffusivity and permeability are associated with cross-link densities of different samples. The D, S and P values increase with increase of EVA content in the blend.     

赖氨酸二乙酯扩链聚氨酯的制备与降解研究

以1,6-六亚甲基二异氰酸酯(HDI)为硬段,聚碳酸酯二元醇(PCDL)为软段,赖氨酸二乙酯盐酸盐(Lys-OEt)为扩链剂合成了一种新型聚氨酯弹性体,并研究了聚氨酯膜在磷酸盐缓冲溶液和木瓜蛋白酶溶液中的降解情况.结果表明:聚氨酯在磷酸盐缓冲溶液(PBS)中的降解很慢,木瓜蛋白酶对聚氨酯的降解主要是作用于软硬段之间形成的酰胺和脲键上,降解方式以表面降解为主.     

Sorption, diffusion, and pervaporation characteristics of dimethylformamide/water mixtures using sodium alginate/polyvinyl pyrrolidone blend membranes

Separation of aqueous dimethylformamide (DMF) solutions in the concentration range of 0-100 wt% were studied using sodium alginate (NaAlg)/polyvinyl pyrrolidone (PVP) blend membranes. The NaAlg was blended in different ratios with PVP. Prepared membranes were crosslinked with CaCl₂ for testing in pervaporation (PV) separation of DMF/water mixtures. Effects of feed composition (0-100 wt%), operating temperature (30-50 °C), and membrane thickness were investigated. Best results were obtained at the conditions of 75/25 NaAlg/PVP blend ratio (w/w), 40 °C temperature, 20 wt% DMF concentration, and 70 μm membrane thickness. Blending of PVP with NaAlg increased permeation flux whereas it decreased the separation factor. NaAlg/PVP membranes gave separation factors of 5.5-27 for permeation flux of 0.96-1.81 kg/m²h depending on the operating temperature and the feed mixture composition. Arrhenius plot of permeation flux data versus reciprocal of temperature exhibited linear trends. Permeation activation energy of DMF and water in the PV was calculated as 6.76 and 1.88 kcal/mol, respectively, using an Arrhenius type relationship. Sorption-diffusion properties of the NaAlg/PVP membranes were also investigated at the operating temperature and the feed composition.     

脂肪族聚氨酯/磷灰石复合材料的原位制备及性能

为避免芳香族聚氨酯在体内降解时产生有毒物质,选用生物相容性良好的脂肪族聚氨酯(PU)与生物活性的羟基磷灰石(HA)为原料,通过原位聚合法制备了脂肪族PU/HA组织工程用多孔支架,并采用SEM、IR和力学试验等方法对多孔支架的形貌和性能进行了表征,进一步研究了发泡剂(水)用量和HA含量对支架泡孔结构和力学强度的影响。结果表明,当发泡剂用量为1%～1.5%(质量分数)时制得的多孔PU/HA复合支架材料孔隙之间相互贯通,孔径范围分布在300～800μm,大孔壁上分布着孔径为50～200μm的小孔,孔隙率达80%以上。随HA含量增加,支架抗压强度和弹性模量显著上升。综合考虑HA的增强效果和组织工程支架的孔隙结构,本体系中HA的最佳添加量为40%(质量分数),发泡剂的最佳用量为1%(质量分数)。     

Reconstitution of membrane proteins into polymer-supported membranes for probing diffusion and interactions by single molecule techniques

We have established a robust and versatile analytical platform for probing membrane protein function in a defined lipid environment on solid supports. This approach is based on vesicle capturing onto an ultrathin poly(ethylene glycol) (PEG) polymer brush functionalized with fatty acid moieties and subsequent vesicle fusion into a contiguous membrane. In order to ensure efficient formation of these tethered polymer-supported membranes (PSM), very small unilamellar vesicles (VSUV) containing fluorescent lipids or model transmembrane proteins were generated by detergent depletion with cyclodextrin. Thus, very rapid reconstitution of membrane proteins into PSM was possible in a format compatible with microfluidics. Moreover, surfaces could be regenerated with detergent solution and reused multiple times. Lipid and protein diffusion in these membranes was investigated by fluorescence recovery after photobleaching, single molecule tracking, and fluorescence correlation spectroscopy. Full mobility of lipids and a high degree of protein mobility as well as homogeneous diffusion of both were observed. Quantitative ligand binding studies by solid phase detection techniques confirmed functional integrity of a transmembrane receptor reconstituted into these PSM. Colocomotion of individual ligand-receptor complexes was detected, demonstrating the applicability for single molecule fluorescence techniques.     

芳香/脂肪族共聚脲多孔膜的微观形态及其性能的初步研究

在相同制膜条件下,采用扩散致相转化法制备了芳香/脂肪族共聚脲多孔膜.通过对孔隙率、力学性能的测试及扫描电镜的微观分析,讨论了凝胶浴体系中溶剂的体积百分数及同类制膜大分子的不同链段结构对膜微观结构和机械性能的影响.实验结果表明:随着凝固浴中溶剂体积百分含量的增加,多孔膜表面的微孔直径逐渐增大;而相应截面的指状孔有缩小的趋势,直到最终消失而形成完全海绵状孔的截面形态;制膜大分子本身的结构对膜形态结构及性能有重大影响:三种共聚脲多孔膜都具有非对称结构,不同结构的共聚脲制备出的多孔膜各自的表面、截面形态都不相同;多孔膜的机械性能也都各不相同,其中芳香族共聚脲多孔膜具有最好的机械性能.     

Design and fabrication of imidazolium ion-immobilized electrospun polyurethane membranes with antibacterial activity

By covalently immobilizing imidazolium ion onto molecular chain, functional polyurethane (PU) is fabricated and thus an effective way is initiated to prepare electrospun membranes with antibacterial activity. In the experiment, PUs containing imidazolium ion side group (Bmim-PUs) are synthesized through a two-step polymerization process. It includes prepolymerization of isophorone diisocyanate (IPDI) with polyester glycol and chain extension polymerization using imidazolium-based ionic diol (Bmim-OH). Then, the obtained Bmim-PUs are electrospun into fibrous membranes with a diameter of ~640 nm. After a careful assessment, antibacterial activities of electrospun membranes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are clearly exhibited. The antibacterial efficiency of Bmim-PUs on both bacteria species improves by 60% in comparison with PU without imidazolium ion. This research suggests a simple but effective methodology to design and fabricate ultrafine fibrous membrane with significant antibacterial activity. Moreover, the obtained fibrous membranes have widely potential applications in protective textiles, filtration, and biomedical engineering.     

Viscosity of defined and undefined hydrocarbon liquids calculated using an extended corresponding-states model

We predict the viscosity of petroleum fractions using extended corresponding states. Our model builds upon the TRAPP procedure, which is the most advanced approach to predict transport properties of straight-chain nonpolar hydrocarbons and their mixtures. We perform comparisons with experimental viscosity data for pure hydrocarbons, treating them as nonstandard components; we find deviations of 10–15%. We also extend the model to predict the transport properties of petroleum fractions and compare with an experimental database of more than 80 crude oils, including highly aromatic petroleum fractions. The model predicts the viscosity of the crude oil fractions within experimental uncertainty.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Synthesis and evaluation of novel absorptive and antibacterial polyurethane membranes as wound dressing

Preparation and evaluation of new polyurethane membranes for wound dressing application was considered in this work. The membranes were prepared through amine curing reaction of epoxy-terminated polyurethane prepolymers and an antibacterial epoxy-functional quaternary ammonium compound (glycidyltriehtylammonium chloride, GTEACl. To render the prepared membranes to be highly absorptive of wound exudates, poly (ethylene glycol) polyols were introduced into the polyurethane networks. Evaluation of biocompatibity via both MTT assay and direct contact with two different cell lines (fibroblast and epidermal keratinocytes) reveled that membranes with appropriate loading of GTEACl showed proper biocompatibility. Promising antibacterial activity of the prepared membranes against Staphylococcus aureus and Escherichia coli bacteria was confirmed by both agar diffusion and shaking flask methods. The membranes with balanced crosslink density and ionic groups' concentration possessed appropriate hydrophilicity and water vapor transmission rate; therefore, they could prevent the accumulation of exudates and decrease the surface inflammation in the wounded area.     

A two-color three-photon ionization scheme for the efficient and selective ionization of a chlorinated aromatic hydrocarbon

A two-color three-photon ionization scheme, for the efficient and selective ionization of a chlorinated aromatic hydrocarbon that has an ionization potential higher than the two-photon energy of the laser used for excitation, is described. In this technique, an ultraviolet (UV) laser, i.e., the second harmonic emission of a fundamental (VIS) laser, is used for excitation and a UV and VIS laser for the subsequent two-photon ionization from the electronic excited state. A sample of o-chlorophenol was used as a model compound to demonstrate the advantage of this technique. The signal in supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry was increased approximately 4 times by the introduction of the VIS beam, when the polarization was adjusted to be parallel to the UV beam. Thus, the two-color three-photon (2UV+VIS) ionization scheme is more sensitive than one-color three-photon (3UV) ionization. The merits of this method over other ionization schemes such as two-color two-photon (UV(1)+UV(2)) ionization are discussed in terms of sensitivity and selectivity in spectrometric analysis.     

聚碳酸亚乙酯多元醇制备湿固化聚氨酯热熔胶及其性能研究

以聚碳酸亚乙酯多元醇(PEC)、二苯基甲烷4,4'-二异氰酸酯(MDI)和1,4-丁二醇(BDO)为主要原料,采用预聚物法合成了一种新型的湿固化聚氨酯热熔胶,并用聚四氢呋喃二醇(PTMG)型和聚己内酯二醇(PCL)型湿固化聚氨酯热熔胶进行性能比较.结果表明,热熔胶中多元醇种类、催化剂及异氰酸根(-NCO)含量对热熔胶的性能有较大的影响.用预聚物法合成的PEC型聚氨酯热熔胶具有较好的拉伸强度、粘接强度、耐水性能和可生物降解性,是一种新型环保粘接材料.     

Absorbing TiOx thin film enabling laser welding of polyurethane membranes and polyamide fibers

Abstract

We report on the optical properties of thin titanium suboxide (TiO_x) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiO_x coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiO_x coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiO_x films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.     

Absorbing TiOx thin film enabling laser welding of polyurethane membranes and polyamide fibers

We report on the optical properties of thin titanium suboxide (TiO_x) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiO_x coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiO_x coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiO_x films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.     

Sorption of polycyclic aromatic hydrocarbons on electrospun nanofibrous membranes: sorption kinetics and mechanism

Five types of nanofibrous membranes were prepared by electrospinning poly(?-caprolactone) (PCL), poly(d,l-lactide) (PDLLA), poly(lactide-co-caprolactone) (P(LA/CL)), poly(d,l-lactide-co-glycolide) (PDLGA) and methoxy polyethylene glycol-poly(lactide-co-glycolide) (MPEG-PLGA), respectively. These electrospun nanofibrous membranes (ENFMs) were used to adsorb anthracene (ANT), benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) from aqueous solution, and the sorption kinetics and isotherms of these PAHs on the five ENFMs were investigated. The pseudo-second-order model (PSOM) can well describe the sorption kinetics of the three PAHs on five ENFMs, and the partition-adsorption model (PAM) can interpret the sorption processes of PAHs on the ENFMs. PCL ENFMs, which had the largest surface areas (8.57 m² g⁻¹), exhibited excellent sorption capacity for ANT at over 4112.3 ± 35.5 μg g⁻¹. Moreover, the hydrophobicity and pore volume of ENFMs significantly affected the sorption kinetics and sorption capacity of the PAHs. The main sorption mechanisms of three PAHs on the PDLLA ENFMs included hydrophobic interactions and pore-filling, while those of PCL, P(LA/CL) and PDLGA ENFMs were dominated by the hydrophobic interactions. The sorption mechanisms of MPEG-PLGA ENFMs primarily included pore-filling, hydrogen bonding interactions and hydrophobic interactions. Additionally, π-π bonding interaction was also deduced to be involved in all of ENFMs sorption systems.     

环氧改性醇溶性聚氨酯分散液的制备及成膜性能?

以二月桂酸二丁基锡(T-12)为催化剂,通过异佛尔酮二异氰酸酯(IPDI ),聚四氢呋喃二醇(PTMG1000),二羟甲基丁酸(DMBA)、γ-氨丙基三乙氧基硅烷(γ-APTES)和环氧树脂(E-44)的反应制备了醇溶性羟基封端聚氨酯(EPPU).采用傅立叶变换红外光谱(FT-IR )、X 射线衍射(XRD )、透射电镜(TEM)和扫描电镜(SEM)对聚氨酯的结构进行了表征,并测试了环氧树脂含量w(E-44)对胶膜的耐热性、力学性能和耐水性的影响.FT-IR测试结果表明环氧树脂与聚氨酯发生了反应,实现了化学改性.环氧改性使聚氨酯的结晶度下降,同时热稳定性和机械性能得到改善.当w(E-44)从0％(质量分数)提高到10％(质量分数),改性使聚氨酯的拉伸强度从5．19~6．99 MPa,吸水率从19．81％降低至4．865％.