Effect of high temperature alkali cooking on the constituents,structure and thermal degradation of hemp fiber

Degumming of hemp fiber by high temperature alkali cooking was investigated, and the effect of temperature and dosage of alkali on the constituents, structure, and thermal degradation of hemp fiber was also discussed in this work. The morphology, structure, and thermal degradation of hemp fiber after high temperature cooking were investigated through SEM, FTIR, WAXD, and TG analysis. The results indicated that the high temperature cooking process was effective for removing hemicelluloses and lignin and could also improve the thermal stability of cellulose. Crystallinity index of the treated hemp fiber was increased, which was related to the cooking temperature and NaOH dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and structural characterization of methacrylic acid/octadecyl acrylate‐graft‐poly(methylhydrosiloxane) by hydrosilylation

Methylmethacrylate (MMA) and octadecyl acrylate (OA) were grafted to poly(methylhydrosiloxane) (PMHS) by hydrosilylation, respectively, with hexachloroplatinic acid as catalyst, and the former was further hydrolyzed to prepare methacrylic acid (MAA)‐graft‐PMHS under the alkaline condition. Through orthogonal experiment, main factors affecting the graft reaction between OA and PMHS were discussed and arranged in a decreasing order according to their abilities of the effect on the hydrosilylation of OA with PMHS: catalyst dosage, reaction temperature, reaction time, material ratio, and solvent dosage. It was found that the hydrosilylation of OA with PMHS was easier to that of MMA with PMHS. Under optimal conditions, the grafting ratios of MMA with PMHS and OA with PMHS reached about 90 and 95%, respectively. FTIR and ¹H NMR spectra indicated that the hydrosilylation reactions followed the Markovnikov's rule and played a strong preference toward β‐1,2‐addition. The test of contact angle indicated that surface energy of a system was mainly dependent on the polar groups. The surface energy of OA‐graft‐PMHS (35.07 mN/m) was similar to those of PMHS (35.62 mN/m) and polyoctadecyl acrylate (36.57 mN/m), and lower than that of MAA‐graft‐PMHS (43.50 mN/m). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Shear-induced crystallization of poly(phenylene sulfide)

The crystalline morphology of poly(phenylene sulfide) (PPS) isothermally crystallized from the melt under shear has been observed by polarized optical microscope (POM) equipped with a CSS450 hot-stage. The shish–kebab-like fibrillar crystal structure is formed at a higher shear rate or for a longer shear time, which is ascribed to the tight aggregation of numerous oriented nuclei in the direction of shear. The crystallization induction time of PPS decreases with the shear time, indicating that the shear accelerates the formation of stable crystal nuclei. Under shear, the increase of spherulite growth rate results from highly oriented chains. The melting behavior of shear-induced crystallized PPS performed by differential scanning calorimetry (DSC) shows multiple melting peaks. The lower melting peak corresponds to melting of imperfect crystal, and the degree of crystal perfection decreases as the shear rate increases. The higher melting peak is related to the orientation of molecular chains. These oriented molecular chains form the orientation nuclei which have higher thermal stability than the kebab-like lamellae that are developed later. A new model based on the above observation has been proposed to explain the mechanism of shish–kebab-like fibrillar crystal formation under shear flow.     

Viscoelastic properties of polyarylene ether nitriles/thermotropic liquid crystalline polymer blend

Polyarylene ether nitriles (PEN)/thermotropic liquid crystalline polymer (TLCP) blend was prepared via melt mixing. The immiscible phase morphologies, linear and nonlinear, as well as transient viscoelastic properties of the blend were studied using SEM, rheometer, and DMA. The linear dynamic viscoelastic behavior of the blend shows temperature dependence due to further evolution of the immiscible morphology and, as a result, the principle of time‐temperature superposition (TTS) is invalid. In the steady shear flow, the discrete TLCP phase is difficult to be broken up because of the high viscosity ratio of the blend systems, while is easy to be coarsened and followed by elongation, and finally, to form fibrous morphology at high TLCP content and high shear level. During this morphological evolution process, the transient stress response presents step increase and nonzero residual relaxation behavior, leading to increase of the dynamic viscoelastic responses after steady preshear. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymer transcrystallinity induced by carbon nanotubes

In this work, we provide the evidence of polymer transcrystallinity in the presence of carbon nanotubes (CNTs). The interfacial morphology of carbon nanotube fiber-polypropylene matrix is investigated by means of polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The supramolecular microstructures of polypropylene transcrystals induced by the nanotube fiber are observed in the range of isothermal crystallization temperatures from 118 °C to 132 °C. The dynamic process of transcrystallization is analyzed by using the theory of heterogeneous nucleation. Microstructure analysis shows that the nanotubes can nucleate the growth of both α- and γ-transcrystal, and α-transcrystals dominate the overall interfacial morphology. Close to the nanotube fiber surface, a cross-hatched lamellar microstructure composed of mother lamellae and daughter lamellae is observed.     

吹风气余热锅炉系统的优化设计与应用

针对吹风气余热锅炉设计和运行中存在的问题进行了优化设计;以新型吹风气余热锅炉Q145/805-50-4.0/450型为例,论述了余热资源的特点和设计原则,从方案的选取、流程的设置、受热面的合理布置等方面进行了设计方案的优化论证;简要介绍了锅炉本体、锅炉水冷段、蒸汽过热器、软水加热器、空气预热器等设备的设计计算和设计特点;生产运行测试数据表明,锅炉余热利用率达86.84%,仅吹风气余热回收1项,每年创收达几千万元,投资回收期仅6个月.     

外墙渗水防治措施探讨

针对建筑物外墙渗水的原因,结合施工实践对防治措施的可行性进行探讨。     

Modelling asymmetry in the peripheral auditory system of the lizard

The ears of lizards are highly directional. The directionality is generated by strong acoustical coupling of the eardrums. A simple lumped-parameter model of the ear followed by binaural comparisons has been shown to perform successful phonotaxis in robot implementations. However, such a model will produce localization errors in the form of response bias if the ears are asymmetrical. We have evaluated how large errors are generated by asymmetry using simulations of the ear model in Mathematica 5.2. The study shows that the effect of asymmetry is minimal around the most directional frequency of the ear, but that biases reduce the useful bandwidth of localization. This work was presented in part at the First European Workshop on Artificial Life and Robotics, Vienna, Austria, July 12–13, 2007     

Preparation and Characterization of Carboxymethyl Chitosan and β-Cyclodextrin Microspheres by Spray Drying

Three kinds of carboxymethyl chitosan/β-cyclodextrin microspheres loaded with theophylline were prepared by spray drying intended for pulmonary delivery. Mucociliotoxicity, permeation rate, and drug release characteristics of the product were investigated. The microspheres obtained by spray drying were found to be spherical with smooth or wrinkled surfaces. The mean particle size was between 3.39 and 6.06 µm. The microspheres demonstrated high product yield (43.7-50.2%), high drug loading (13.7-38.1%), and high encapsulation efficiency (86.9-92.8%). FT-IR indicated that there were interactions of theophylline with carboxymethyl chitosan matrix. Further studies on mucociliotoxicity and permeation confirmed that microspheres had better adaptability and high permeation rate. In vitro drug release from the microspheres was not related to the drug/polymer ratios.