Characterisation of Polyurethane Coatings Using Thermoanalytical Techniques

A two-pack polyurethane coating was analyzed using thermoanalytical techniques. The curing reaction, monitored using pressure differential calorimetry (PDSC), rheometry and dynamic mechanical analysis (DMA) shows the temperature dependency of activation energy and hence rate of curing. In-situ ATR-FTIR shows the formation of urethane linkage over time. The decomposition behavior carried out under non-isothermal mode using thermogravimetric analysis (TGA) shows bimodal behavior. The activation energies of the initial step (10% decomposition) from both iso and non-isothermal experiments are in very good agreement with each other. The use of dynamic mechanical analysis (DMA) shows the difference in glass transition behavior (T_g) and elastic modulus (E') due to the different state of cure. Also the coating exhibits a very broad loss modulus peak (E') indicating higher energy dissipation with deformation.This revised version was published online in November 2005 with corrections to the Cover Date.     

丁苯、丁腈基聚氨酯的形态与性能

用示差扫描量热法 (DSC)、红外分光光度计 (FTIR)和原子力显微镜 (AFM)研究了端羟基聚丁二烯 苯乙烯共聚物 (HTBS)、端羟基聚丁二烯 丙烯腈共聚物 (HTBN)和端羟基聚丁二烯 (HTPB)与甲苯二异氰酸酯、1 ,4 丁二醇构成的溶液法聚二烯烃基聚氨酯 (PU)的形态结构 .结果表明HTPB和HTBS基PU的相分离程度很大 ,而HTBN基PU的相分离程度小 .这可能归因于HTBS软段的极性低 ,不能与硬段形成氢键 ,而HTBN软段中的腈基具有很强的极性 ,且可以与硬段形成氢键作用 ,增加了软硬段间的相容性 ,相分离程度明显降低 .AFM表明HTBN PU随着硬段含量提高 ,表面粗糙度增大 ,由软段为连续相逐渐过渡到双连续结构 .在硬段含量 6 3%时 ,HTBN和HTPB基PU均呈双连续结构 ,而HTBS PU中硬段为连续相 .HTBN PU软段的相区尺寸在1 2nm左右 ,表面粗糙度较大 ,HPBS PU软段的相区尺寸在 1 1nm左右 ,表面粗糙度最小 ,HTPB PU存在 1 4nm和 5 0nm大小不等的软段相区尺寸 .力学性能表明 ,在软段中引入苯乙烯和丙烯腈结构 ,可使聚氨酯抗张强度分别提高 1 5和 2倍 ,模量和断裂伸长率也明显提高     

HTPB‐based polyurethanes. II. SINs with PMMA

Simultaneous interpenetrating networks from poly(methyl methacrylate‐co‐ethyleneglycol dimethacrylate) (PA) and a hydroxyl‐terminated polybutadiene‐based polyurethane (PU) were prepared with various hard‐segment contents (X) in the PU and different ratios (PU/PA) between the components. The level of the reinforcement, the mechanism of molecular failure, and the phase inversion depended strongly on X. Dynamic mechanical results indicated that the interpenetration occurred in the rigid blocks of the PU. The improved thermal and mechanical properties observed with higher values of X were interpreted in terms of the molecular weight and polydispersity of the hard blocks in the PU. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2861–2872, 2000     

Preconcentration Systems Using Polyurethane Foam/Me-BDBD for Determination of Copper in Food Samples

A new reagent, 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD), was synthesised and used in on-line and off-line systems for copper preconcentration by solid-phase extraction. Spectrophotometry and Flame Atomic Absorption Spectrometry (FAAS) were the detection techniques. Polyurethane foam loaded with Me-BDBD packed in a minicolumn was used as sorbent in both systems. The spectral characteristics of Me-BDBD were investigated. The optimum pH values for maximum sorption of the metal are between 7.0 and 8.5. Copper was desorbed with 0.05 and 0.50 mol L⁻¹ hydrochloric acid solutions, for on-line and off-line systems, respectively. The effects of several foreign substances on the adsorption of copper are reported. The enrichment factors obtained were 7 (on-line) and 26 (off-line) for the systems. The proposed procedures allowed the determination of copper with detection limits of 3.4 and 1.4 μg L⁻¹ (0.85 and 0.35 μg per gram of sample) for on-line and off-line systems, respectively. The precision of the procedures was also calculated: 3.2 (on-line) and 1.9% (off-line). The validation of the procedures was carried out by analysis of certified reference material. The copper contents in corn and rice flour and black tea samples were determined by applying the proposed procedures.     

Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples

The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption (t_1/2) of 3.32 min. The variation of the sorption of Pd(II) with temperature gives average values of ΔH, ΔS, ΔG and ΔE to be −38.3 kJ mol⁻¹, −100.7 J K⁻¹ mol⁻¹, −8.3 and 11.8 kJ mol⁻¹, respectively. The sorption capacity of PUFIX was 1.69 mmol g⁻¹ for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D. ≈ 1.24%). The lower detection limit, 1.28 ng mL⁻¹ was evaluated using spectrophotometric method (R.S.D. ≈ 2.46%).     

An investigation of the accelerated thermal degradation of different epoxy resin composites using X-ray microcomputed tomography and optical coherence tomography

Epoxy resin composites reinforced with hollow glass microspheres, microlight microspheres, 3D parabeam glass, and E-Glass individually were subjected to accelerated thermal degradation conditions. X-ray microcomputed tomography (XμCT) was used to evaluate density changes, reinforcement filler damage, homogeneity, cracks and microcracks in the bulk of the different epoxy resin composites. XμCT 3D images, 2D reconstructed images and voids calculations revealed microspheres damage, filler distributions and showed cracks in all composites with different shapes and volume in response to the thermal degradation conditions. In addition, expansion of air bubbles/voids was observed and recorded in the microsphere and microlight epoxy composite samples. In a complementary way, optical coherence tomography (OCT) was used as a novel optical characterisation technique to study structural changes of the surface and near-surface regions of the composites, uncovering signs of surface shrinkage caused by the thermal treatment. Thus, combining XμCT and OCT proved useful in examining epoxy resin composites' structure, filler-resin interface and surface characteristics.     

Synthesis of ZnTiO3/tourmaline/Ni foam catalyst and enhanced photocatalytic performance

ZnTiO₃/tourmaline loaded on the nickel foam (ZnTiO₃/tourmaline/Ni-foam) is prepared by a facile coating method. Morphology and structure of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electrons microscopy (SEM), raman spectroscopy, UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic properties of the materials were tested by using the Rhodamine B (RhB) solution as the target pollutant. The results indicates that the ZnTiO₃/tourmaline/Ni foam exhibited higher photocatalytic activity than that of ZnTiO₃ and ZnTiO₃/Ni foam under ultraviolet (UV) light irradiation, and its degradation rate was up to 99.2%. Moreover, the degradation rate remained at 91.3% after eight consecutive photocatalytic reaction cycles. The outstanding photocatalytic performances of ZnTiO₃/tourmaline/Ni foam was mainly attributed to the existence of tourmaline, which can help to inhibit the recombination of electron-hole paris, and the proper pore structure of the carrier. Meanwhile, the trapping experiments indicated that ·O₂^– was the main active species in the photocatalytic degradation of RhB.     

Ni(OH)2修饰的三聚氰胺泡沫用于可压缩超级电容器电极

通过化学镀和电化学镀的方法制备了一种Ni(OH)₂电化学活性材料修饰三聚氰胺泡沫(MF)可压缩骨架的超级电容器电极材料MF/Ni(OH)₂。MF/Ni(OH)₂可压缩电极材料表现出最佳的电容性能,例如循环稳定性(即使在40 mA/cm^-3的电流密度下经过2000次充放电循环后,可压缩电极仍能保持90.63%的初始电容)和可压缩稳定性(即使在压缩率为50%时,仍具有97.88%的电容保持率)。层状可压缩超级电容器由MF/Ni(OH)₂弹性材料作为阳极,镍/碳(Ni/C)为阴极以及实验室中常用的滤纸作隔膜材料组成。这种超级电容器装置在不同的压缩下表现出良好的电化学性能和优异的压缩稳定性。最后,使用可压缩的超级电容器来点亮LED灯,以展示其在柔性电子设备中的应用。这些优化的电化学和机械性能表明MF/Ni(OH)₂可作为可压缩超级电容器的应用中的候选电极。     

TPU增韧MABS的研究

利用双螺杆挤出机制备聚氨酯和甲基丙烯酸甲酯—丙烯腈-丁二烯-苯乙烯树脂熔融共混物(合金).研究TPU的类型以及含量对TPU/MABS合金的透光率、力学性能和缺口冲击强度影响.结果表明:TPU/MABS合金可以保持较好透明性,随TPU含量的增加,合金材料的拉伸强度和弯曲模量逐渐降低,但是合金材料的冲击强度得到明显提高.扫...     

Studying the Suitability of Nineteen Lignins as Partial Polyol Replacement in Rigid Polyurethane/Polyisocyanurate Foam

In this study, nineteen unmodified lignins from various sources (hardwood, softwood, wheat straw, and corn stover) and isolation processes (kraft, soda, organosolv, sulfite, and enzymatic hydrolysis) were used to replace 30 wt.% of petroleum-based polyol in rigid polyurethane/polyisocyanurate (PUR/PIR) foam formulations. Lignin samples were characterized by measuring their ash content, hydroxyl content (Phosphorus Nuclear Magnetic Resonance Spectroscopy), impurities (Inductively Coupled Plasma), and pH. After foam formulation, properties of lignin-based foams were evaluated and compared with a control foam (with no lignin) via cell morphology, closed-cell content, compression strength, apparent density, thermal conductivity, and color analysis. Lignin-based foams passed all measured standard specifications required by ASTM International C1029-15 for type 1 rigid insulation foams, except for three foams. These three foams had poor compressive strengths, significantly larger cell sizes, darker color, lower closed-cell contents, and slower foaming times. The foam made with corn stover enzymatic hydrolysis lignin showed no significant difference from the control foam in terms of compressive strength and outperformed all other lignin-based foams due to its higher aliphatic and p-hydroxyphenyl hydroxyl contents. Lignin-based foams that passed all required performance testing were made with lignins having higher pH, potassium, sodium, calcium, magnesium, and aliphatic/p-hydroxyphenyl hydroxyl group contents than those that failed.