Letter

¹⁵N variable contact time (VCT) cross polarization magic angle spinning (CPMAS) NMR experiments were employed to investigate the reaction products formed in wood composites bonded with ¹⁵N-enriched polymeric diphenylmethane diisocyanate (PMDI)-based adhesives. Two wood species were studied. Aspen (Populus tremuloides) and Southern Pine (Pinus sylvestris). The influence of temperature and wood moisture content on the distribution of PMDI-derived species are presented and discussed.     

双环戊二烯-马来酸酐共聚物的合成、表征及其与聚氨酯反应性共混研究

合成了双环戊二烯-马来酸酐交替共聚物(DCPD-co-MA),产率约25%。采用红外、核磁共振氢谱和碳谱对共聚物进行了表征,差热分析和热重分析表明该共聚物具有较好的热性能,其T_g为210℃,起始热失重温度为310℃。采用反应性共混方法合成了DCPD-co-MA与聚氨酯(PU)的共混物(PU/DCPD-co MA),反应温度为80℃。该共混物具有较好的综合性能,其起始热失重温度较纯PU提高了约41℃,共混后,其耐热性能有较大改善。     

Structural performance of lightweight steel-foamed concrete–steel composite walling system under compression

This paper presents the results of an experimental and analytical investigation on the structural behaviour of a composite panel system consisting of two outer skins of profiled thin-walled steel plates with lightweight foamed concrete (LFC) core under axial compression. The gross dimensions of the test specimens were 400 mm×400 mm×100 mm. A total of 12 tests were carried out, composed of two duplicates of 6 variants which were distinguished by two steel sheeting thicknesses (0.4 mm and 0.8 mm) and three edge conditions of the sheeting. The density of LFC was 1000 kg/m³. Experimental results include failure modes, maximum loads and load-vertical strain responses. In analysis, full bond between the steel sheets and the concrete core was assumed and the LFC was considered effective in restraining inward buckling of the steel sheets. Using the effective width method for the steel sheets, the load carrying capacities of the test specimens were calculated and compared with the experimental results. It was found that a combination of the Uy and Bradford plate local buckling coefficients with the Liang and Uy effective width formulation produced calculation results in good agreement with the experimental results. Finally, a feasibility study was undertaken to demonstrate the applicability and limit of this new composite walling system in low rise construction.     

Synthesis and characterization of polyurethane cationomer/MMT hybrid composite

BACKGROUND: The development of polymeric nanocomposites incorporating intercalated or exfoliated layered silicate clays into the organic matrix has been substantially motivated by the significant improvements induced by the presence of the inorganic component. Moreover, understanding and controlling the dispersion of inorganic layers into segmented polyurethane matrices by means of ionic interactions, and exploiting these interactions to enhance physicomechanical behaviour, could be of great interest in the field of polymer nanocomposites. RESULTS: New cationic polyurethane elastomers were prepared starting from poly(butylene adipate)diol (M_n = 1000 g mol^?1), 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol and N‐methyldiethanolamine or N,N′‐β‐hydroxyethylpiperazine, used as potential quaternizable moieties. The characterization of the polymers was achieved using specific analyses employed for the macromolecular samples (Fourier transform infrared and ¹H NMR spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography). An extension of our research on polymers reinforced with organically modified montmorillonite (OM‐MMT) in order to prepare hybrid composites with improved properties was performed and the resulting materials were characterized using TGA, X‐ray diffraction, atomic force microscopy and scanning electron microscopy. Also, the mechanical properties of the cationic polyurethane/OM‐MMT composites were investigated in comparison with the pristine ionic/non‐ionic polymers and their composites containing non‐ionic polymer blended with OM‐MMT or ionic polymer and unmodified MMT. CONCLUSION: The insertion of the organically modified clay into the polymeric matrix gave an improvement of the mechanical properties of the polyurethane composites, especially the tensile strength and stiffness of the hybrid materials. Copyright © 2009 Society of Chemical Industry     

水性聚氨酯涂料的制备与应用

水性聚氨酯涂料主要有单组分水必聚氨酯涂料，双组分水性聚氨酯涂料及改性水性聚氨酯涂料，介绍了这三种涂料的制备方法及其在建筑，汽车，木器家具，皮革涂饰方向的应用。     

环氧树脂改性PUA乳液的合成及性能研究

以异佛尔酮二异氰酸酯（IPDI）、聚醚二元醇（N220）、二羟甲基丙酸（DMPA）、1，4-丁二醇（BDO）和甲基丙烯酸甲酯（MMA）为主要原料合成了脂肪族聚氨酯-丙烯酸酯复合乳液（PUA），并用环氧树脂对其进行了改性。研究了nNCO／nOH比、DMPA添加量、环氧添加方式及添加量对其性能的影响，结果表明，当nNCO／nOH为1．35-1．4、DMPA为6％～7％时，以环氧和BDO一起加入，环氧添加量在2％～3％时能获得综合性能较好且贮存稳定的聚氨酯丙烯酸酯复合乳液。     

TDI-TMP聚氨酯固化剂合成的影响因素

以TDI和TMP为原料合成了低游离TDI、浅色的TDI-TMP型固化剂,讨论了TDI与TMP投料比、反应温度、催化剂用量等工艺条件对低游离浅色TDI-TMP型固化剂产品的TDI游离含量、粘度、色度、稳定性等指标的影响。结果表明,制备TDI-TMP型固化剂的最佳工艺条件:当nTDI/nTMP为3.0～3.2时,选用多次加料法,温度选择在50～60℃之间使NCO基和OH基反应,并在70℃保温使反应趋于完全;催化剂质量分数为0.4‰左右(按固体质量分数为50%计);阻聚剂质量分数为1.5‰～3.0‰;抗氧剂质量分数一般在4‰左右时,游离TDI符合TDI-TMP型固化剂行业技术指标。     

Boundary element analysis of flat cracked panels with adhesively bonded patches

Adhesively bonded patch repairs for cracked finite sheets are analysed by the boundary element method. The interaction between the plate and the patch on a repaired sheet is modelled as a distribution of forces which include in-plane, out-of-plane and two moment body forces. The coupled boundary integral formulations of shear deformable plate (Mindlin theory) and two-dimensional plane stress elasticity are presented. Stress intensity factors, three for the bending problem and two for the membrane problem, are evaluated from crack opening displacements. Several examples are presented to demonstrate the accuracy and efficiency of the proposed method. Comparison with two-dimensional solutions demonstrate the significance of the bending loads on the stress intensity factors.     

给水管网模拟显示屏及水闸微机管理系统研究

对给水管网模拟显示屏和水闸微机管理系统进行了研究，根据ＦＯＸＰＲＯ系统建立了管网图形与数据库，编制了数据库管理与管网分析程序，实践证明，该系统功能安全，实用性强，是给水管网管理的有力工具。