D.s.c. investigation of the states of water in poly(vinyl alcohol-co-itaconic acid) membranes

The state of water in water-swollen poly(vinyl alcohol-co-itaconic acid) membranes, having various water contents from 0.31 to 0.83, was investigated by d.s.c. measurements and compared with those in water-swollen poly(vinyl alcohol) membranes. The amount of freezing water in the membranes was estimated by use of a relationship between the phase transition temperature and the enthalpy of the crystallization of supercooled water. The melting temperature of the water in the membranes immersed in urea and NaCl 0–2 mol l^?1 aqueous solutions was also determined by d.s.c. analysis. The present study proposes a method for estimating the solubilities of urea and NaCl in both of the freezing and the non-freezing water using the melting point depression of the freezing water in the membranes immersed in the solute solution.     

Preparation of silk fibroin and polyallylamine composites

Composite films made of silk fibroin (SF) and polyallylamine (PAA) are prepared that contain various compositional ratios. These materials are analyzed to elucidate the resulting physical properties and to assess their potential toward advanced applications as industrial materials. The composite films are obtained from a SF and PAA binary system by dry casting from aqueous solution. These composite films exhibit excellent processability such as film forming capabilities, and the elongation at break is increased in the wet state. The differential scanning calorimetry (DSC) curves of the composites suggest that a mutual interaction takes place between the SF and PAA. This interaction is believed to occur because the endothermic peak, corresponding to the individual polymer, shifts with increasing SF content. The random coil conformation of the SF is present, regardless of the PAA blending, as confirmed by FTIR and DSC measurements. Additionally, living cells from Antheraea pernyi and Bombyx mori insect tissues are shown to grow effectively on the composite films. Maximum growth levels occur when the cultivation flask is coated with the material in SF/PAA ratios of 75:25 to 25:75. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1963–1970, 2002; DOI 10.1002/app.10491     

Photopolymerization of HEMA/DEGDMA hydrogels in solution

Photopolymerization is a widely used technique to synthesize polymers and hydrogels. The commonly used ultraviolet (UV)-curable mono-, di- or multifunctional vinylated monomers are often volatile, causing difficulty in kinetics analysis such as photo-differential scanning calorimetry (PhotoDSC). In this work, the DSC sample pan is chemically and physically modified such that the resin can be placed uniformly in the sample pan with minimum sample weight loss during measurement. This approach substantially improved experimental accuracy, which in turn provides a better understanding of the reaction kinetics of UV-curable polymers. Kinetic experiments were carried out for poly(2-hydroxyethyl methacrylate) (HEMA)-based hydrogels. The effects of light intensity and water concentration on the reaction kinetics and rheological change was investigated. It was found that increasing the light intensity enhances the polymerization, but too high an intensity slows down the reaction at the later stage. The addition of solvent and high light intensity facilitates the cyclization, delaying macrogelation. The viscosity rise of the resin system and the formed polymer size were also measured using a photorheometer and a particle size analyzer, respectively. The measured gel time, gel conversion and polymer size distribution agree with the kinetic analysis.     

Epoxy‐montmorillonite clay nanocomposites: Synthesis and characterization

Nanocomposites of epoxy resin with montmorillonite clay were synthesized by swelling of different proportions of the clay in a diglycidyl ether of bisphenol‐A followed by in situ polymerization with aromatic diamine as a curing agent. The montmorillonite was modified with octadecylamine and made organophilic. The organoclay was found to be intercalated easily by incorporation of the epoxy precursor and the clay galleries were simultaneously expanded. However, Na‐montmorillonite clay could not be intercalated during the mixing or through the curing process. Curing temperature was found to provide a balance between the reaction rate of the epoxy precursor and the diffusion rate of the curing agent into the clay galleries. The cure kinetics were studied by differential scanning calorimetry. The exfoliation behavior of the organoclay system was investigated by X‐ray diffraction. Thermogravimetric analysis was used to determine the thermal stability, which was correlated with the ionic exchange between the organic species and the silicate layers. The morphology of the nanocomposites was evaluated by scanning electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2201–2210, 2004     

Polymorphic behavior of gondoic acid and phase behavior of its binary mixtures with asclepic acid and oleic acid

Molecular properties of polymorphic forms of gondoic acid [cis-C_20:1Δ11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C_18:1Δ9ω9 (OA)], erucic acid [cis-C_22:1Δ13ω9 (ERA)], petroselinic acid [cis-C_18:1Δ6ω12 (PSA)], asclepic acid [cis-C_18:1Δ11ω7 (APA)], palmitoleic acid [cis-C_16:1Δ9ω7 (POA)], and elaidic acid [trans-C_18:1Δ9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double bond and CH₃ group, as a transition from all-trans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the Δ-chain, the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form the miscible mixing phase.     

扫描隧道显微镜技术在腐蚀防护研究中的应用

简述了扫描隧道显微镜技术的发展概况，着重介绍了扫描隧道显微镜在局部腐蚀、点蚀、钝化膜形成等方面的应用。     

注射成型薄壁制品的结晶度

简要概述了注射成型过程中的非等温结晶和2种计算结晶度的方法。结果表明，在注射模CAE开发中，用DSC测量是一种比较实用简便的计算结晶度的方法。     

Nucleating activity of the quinacridone and phthalocyanine pigments in polypropylene crystallization

The nucleating ability of two organic pigments, quinacridone and phthalocyanine, in nonisothermal polypropylene (PP) crystallization was investigated. The investigations were carried out using DSC and polarizing microscopy. The efficiency of pigments in the nucleation process was determined in a simple test comparing the crystallization temperature of the PP‐containing pigments with respect to the pure polymer. Both pigments revealed good nucleating activity. In the presence of pigments the increment of the crystallization temperature and the increase of nucleation rate were observed. The nucleating efficiency of pigments was confirmed in investigations of the obtained structure. The nucleating activity of pigments was explained by their features fulfilling several requirements for good nucleating agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3957–3964, 2003     

三维激光扫描技术在引水隧洞检修中的应用

三维激光扫描技术是国际上近年发展的一项集光、电和计算机技术于一体的新技术,利用该技术可以快速、精确地获取空间数据。锦屏二级水电站引水隧洞放空检修时发现少数洞内存在混凝土破损情况,但受时间与费用等因素限制,难于以采用常规手段详细检查混凝土表面缺陷与变形等问题。通过采用三维激光扫描技术对隧洞进行全断面扫描,及时探查了混凝土表面的缺陷并进行了处理,确保了工程安全运行;同时,还得到混凝土表面的三维坐标信息,建立了混凝土表面缺陷基准数据库,可为后续进一步分析混凝土表面缺陷的变化情况提供参考。     

Influence of the synthesis conditions on the curing behavior of phenol–urea–formaldehyde resol resins

The curing behavior of synthesized phenol–urea–formaldehyde (PUF) resol resins with various formaldehyde/urea/phenol ratios was studied with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicated that the synthesis parameters, including the urea content, formaldehyde/phenol ratio, and pH value, had a combined effect on the curing behavior. The pH value played an important role in affecting the shape of the DSC curing curves, the activation energy, and the reaction rate constant. Depending on the pH value, one or two peaks could appear in the DSC curve. The activation energy was lower when pH was below 11. The reaction rate constant increased with an increase in the pH value at both low and high temperatures. The urea content and formaldehyde/phenol ratio had no significant influence on the activation energy and rate constant. DMA showed that both the gel point and tan δ peak temperature (T_tanδ) had the lowest values in the mid‐pH range for the PUF resins. A different trend was observed for the phenol–formaldehyde resin without the urea component. Instead, the gel point and T_tanδ decreased monotonically with an increase in the pH value. For the PUF resins, a high urea content or a low formaldehyde/phenol ratio resulted in a high gel point. The effect of the urea content on T_tanδ was bigger than that on the gel point because of the reversible reaction associated with the urea component. Too much formaldehyde could lead to more reversible reactions and a higher T_tanδ value. The effects of the synthesis conditions on the rigidity of the cured network were complex for the PUF resins. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1368–1375, 2005