Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as an impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss on ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33 wt.%, which decreased to as low as 20 wt.% after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young’s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40 wt.% blend, which resulted in a super toughened material (impact strength exceeding 500 J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2 μm (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure.     

Polymer coated sensor array based on quartz crystal microbalance for chemical agent analysis

Quartz crystal microbalance (QCM) gas sensors based on polymeric material were fabricated and their gas response characteristics were examined for four simulant gases of chemical agents, which were dimethyl methyl phosphonate (DMMP), N,N-dimethylacetamide (DMA), 1,5-dichloropentane (DCP) and dichloroethane (DCE). For the selection of appropriate coating materials, both principal component analysis (PCA) and hierarchical cluster methods were applied to a data set collected from 15 QCM sensors for 12 analytes. Four appropriate coating materials were selected after optimizing the correlation between the 15 coating materials and the first four principal component (PC) factors. The four chosen polymers were used as sensitive component for a sensor array, and then PCA is adapted to classify four simulant gases. The results show that the QCM sensor array has high sensitivity and selectivity to four chemical agents.     

环境友好型消毒抗菌剂——二溴海因

二溴海因是一种高效、广谱、低残留的新型环境友好型消毒抗菌剂.介绍了二溴海因的结构、性质、抗菌机理、生产工艺与应用等.     

Dynamic mechanical and dielectric relaxation characteristics of microcellular rubber composites

An in‐depth study of the surface characteristics of novel conductive carbon black Ensaco 350G has been carried out using XPS and high‐resolution vacuum FTIR. Both methods showed the existence of oxygen containing surface groups like carboxyls, carbonyls, etc. Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black (Ensaco 350G) reinforced microcellular EPDM composites were used to study the relaxation behavior as a function of temperature (?90 to +100°C) and frequency (100–10⁶ Hz). The effect of filler and blowing agent loadings on dynamic mechanical and dielectric relaxation characteristics has been investigated. The effect of filler and blowing agent loadings on glass transition temperature was marginal for all the composites (T_g value was in the range of ?37 to ?32°C), which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The variation in the real and imaginary parts of the complex impedance with frequency has been studied as a function of filler and blowing agent loading. Additionally, an in‐depth study of the surface characteristics of the filler using XPS, high‐resolution vacuum FTIR and Raman spectra is also reported. Copyright © 2008 John Wiley & Sons, Ltd.     

Determination of cyclosporin A in blood and plasma by column switching-HPLC after rapid sample preparation

A method for the determination of cyclosporin A in human whole blood and plasma is described which uses liquid chromatography with step gradient elution and a column switching technique. The chromatographic conditions chosen allow simple and rapid sample preparation, so that a result can be obtained within one hour. Blood and plasma are deproteinized with diluted methanol and an aliquot of the clear supernatant is directly injected. The detection limit for cyclosporin A is about 20 ng/ml starting from a 0.5 ml sample. The method is sensitive enough for monitoring the drug in the therapeutic range.     

Determination of 3‐chloro‐1,2‐propanediol in polyamideamine epichlorohydrin resin solution by reaction‐based headspace gas chromatography

We report on a headspace gas chromatographic method for determining the content of 3‐chloro‐1,2‐propanediol in polyamideamine epichlorohydrin resin solution. It was based on quantitatively converting 3‐chloro‐1,2‐propanediol to formaldehyde by periodate oxidation in a closed headspace sample vial at a room temperature for 10 min, and then to methanol by borohydride reduction at 90°C for 40 min followed by the headspace gas chromatographic measurement. The results showed that the present method has an excellent measurement precision (relative standard deviation < 2.60%) and accuracy (recoveries from 96.4–102%) in 3‐chloro‐1,2‐propanediol analysis. The limit of quantitation was 0.031 mg/mL. It is simple and suitable for determining the 3‐chloro‐1,2‐propanediol content in polyamideamine epichlorohydrin resin solution.     

Poly(vinylidene fluoride) (PVDF)/potassium sodium niobate (KNN)–based nanofibrous web: A unique nanogenerator for renewable energy harvesting and investigating the role of KNN nanostructures

In the recent era, finding renewable energy sources that are environmentally benign the main focus of scientific community around the globe. There is a plenty of renewable energy sources that are currently being researched such as solar power, thermal energy, wind energy, salinity gradients, and kinetic energy. Polymer‐ceramic–based nanocomposite piezoelectric material is known for quite some time for energy harvesting, but the real challenge lies as it requires very high loading of the ceramic part to obtain the required property and thus almost makes the system nonflexible. Developed material needs to be poled later on to use it as an electric energy generator from ambient mechanical movement. This current study is the first time attempt to produce a simple yet unique lightweight energy harvester using polyvinylidene fluoride (PVDF)/potassium sodium niobate (KNN) nanostructures–based nanocomposite flexible fibrous web where the material is in situ poled during its production using an electrospinning setup. At the beginning, various parameters were identified to synthesize and modulate KNN as nanostructural materials having higher aspect ratio, which is intended to provide a unique connection between KNN once these are embedded within the fibrous matrix. The incorporated KNN nanostructure having higher aspect ratio was also found to act as a beta nucleating agent in PVDF matrix and enhances the β‐phase crystal into the resultant fibrous web, which in turn increases the piezoelectric energy‐harvesting capacity manifold as compared with bare PVDF fibrous web. The in situ alignment of the nanostructured KNN (with a minimum loading, 5% only) into the fibrous nanocomposite is another achievement to obtain higher output. X‐ray diffraction and Fourier transform infrared analysis confirmed the mixture of α‐ and β‐crystalline phase of pure PVDF, which gets converted into β phase once KNN nanostructures are incorporated inside the nanofibrous web. An output voltage of 1.9 V was obtained from PVDF/KNN nanocomposite–based web, which is significantly higher (38 times) than generated voltage (50 mV) from the pure PVDF nanoweb without any subsequent poling operation.     

Preparation of phosphorus‐containing phenolic resin and its application in epoxy resin as a curing agent and flame retardant

For the sake of improving the flame retardancy of epoxy resin (EP), a novel phosphorus‐containing phenolic resin (PPR) synthesized in our group instead of conventional phenolic resin (PR) was used to cure EP in the present research. The curing processes and the corresponding crosslinking structure and mechanical performance were investigated by differential scanning calorimeter and dynamic mechanical thermal analysis. Because of the introduction of flame‐retarding elements including P and Si, PPR exhibited higher charring capacity in the condensed phase, which is helpful to construct a char layer of higher quality. Correspondingly, PPR‐cured EP displayed remarkably improved flame retardance as compared to conventional PR‐cured EP through the related evaluations including limiting oxygen index, vertical burning test, and microscale combustion colorimeter. As a multifunction agent, it is believable that PPR possesses potential commercial value to prepare flame‐retardant EP with high performance.     

不同调节剂制备MOF-Fe的性质及对Se(Ⅳ)的吸附性能

以HF、HCl、H_2O和Na Ac溶液为调节剂合成了4种MOF-Fe样品,用X射线衍射(XRD)、透射电镜(TEM)、N_2等温吸附-脱附、综合热分析(TG/DTG和DTA)和质子电位滴定研究了4种样品的结构与表面性质,以及对亚硒酸根(Se(Ⅳ))等温吸附特性。MOF-Fe(HF)、MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(Na Ac)四种样品均具有八面体MIL-100(Fe)的晶体结构,但它们的结晶度和晶面取向略有差异。4种样品的比表面积分别为1 683、1 517、1 641和1 734 m~2·g~(-1),其总孔体积依次降低,微孔孔径分别为1.27、1.22、1.22和1.17 nm。MOF-Fe(HF)样品的脱羧基失重峰温度最高(415℃),苯环碳化失重峰温度最低(462℃);MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(Na Ac)样品出现了因氧化铁被碳还原所致的失重平台(566~716℃)。样品悬浮液从p H=6.0降到3.0时,消耗H~+的量表现为MOF-Fe(H_2O)MOF-Fe(HCl)MOF-Fe(HF)=MOF-Fe(Na Ac),它们的电荷零点(p H_(ZPC))依次为3.1、3.5、3.6和3.5。MOF-Fe(Na Ac)、MOF-Fe(HCl)、MOF-Fe(H_2O)和MOF-Fe(HF)对Se(Ⅳ)的吸附亲和力依次减小,它们对Se(Ⅳ)的吸附容量(Q_m)分别为77.69、107.07、117.40和87.15 mg·g~(-1)。显著性分析显示,MOF-Fe的羟基密度与样品吸附Se(Ⅳ)的Q_m显著正相关。研究结果表明,MOF-Fe样品的结构热稳定性和羟基/配位水分子等活性位点密度受合成样品时加入的调节剂影响,用HF作为调节剂合成MOF-Fe样品有利于提高样品中羧基与苯环之间的C-C键合强度和热分解产物的稳定性,降低苯环碳化温度;HCl和H_2O作为调节剂有利于提高样品的活性位点密度,可提高MOF-Fe样品对Se(Ⅳ)吸附容量。     

Structure-activity relationship study of leucinostatin A,a modulator of tumor−stroma interaction

Structure-activity relationship study of leucinostatin A, a natural nonapeptide, was performed to gain insight into the structural requirements for leucinostatin A to exhibit antiproliferative activity against DU-145 prostate cancer cells under cocultured conditions with the corresponding stromal cells. Twenty truncated peptide analogs of leucinostatin A revealed that the nonapeptide structure as a whole is essential for the biological activity. Alanine scanning demonstrated the importance of some of the amino acid components, including hydroxyleucine and the second leucine from the N-terminus. Two of the three aminoisobutyric acids could be substituted with one of the enantiomers of alanine, clearly demonstrating that each methyl group in these portions has a distinct influence on the growth-inhibitory activity.