溶剂对聚氨酯纳米纤维膜的影响

选用不同体积比的N,N-二甲基甲酰胺(DMF)和丙酮混合溶剂配制聚氨酯(PU)溶液,运用"Nanospider"纺丝技术制备聚氨酯纳米纤维膜。研究不同溶剂配比条件下PU溶液的电导率、粘度、高分子—溶剂相互作用参数和表面张力,从热力学、高分子溶液理论及高分子表面性质等方面对溶液进行分析。采用扫描电镜观察纳米纤维膜的表面形貌并对纳米纤维膜进行疏水性能和力学性能测试。结果表明:丙酮的加入显著改变混合溶液的溶解度参数、高分子与溶剂间相互作用参数、电导率、粘度等溶液性质。当DMF/丙酮体积比为33/67时获得的纳米纤维膜表面形貌较好;纳米纤维的直径随DMF体积减少而增大,DMF/丙酮体积比为67/33时纤维直径为(300±60)nm;纤维膜的水接触角随丙酮体积比的增加而逐渐增大,最大水接触角为112.52°;DMF/丙酮体积比为33/67时,力学性能最佳,应力和应变分别为8.6 MPa和309%。     

高强度纤维及分子混合物的最新进展(二) 四.用湿纺及拉伸制备超高模量,超高强度纤维

<正> 1.前言对分解温度低于熔融温度的刚性,棒状高分子物的制备,只能从溶液加工,虽然刚性,棒状高分子物一般很难溶解,系统的溶剂研究已经导致发现了几种适合于制备纤维的聚合物溶剂。在顺利的情况下,棒状聚合物表现出Flory统计理论所预言的自发的各     

棉麻纤维素聚合度测定方法探讨

一、测定纤维素聚合度意义棉、麻纤维素的铜氨溶液聚合度(比粘度)是表示纤维素损伤程度的物理化学指标,能较客观地定量反映纺、织、染加工过程中纤维素损伤程度的数值大小,对科学合理优化制订亚麻加工工艺技术参数具有重要指导意义,现作介绍。比粘度是指溶剂与纤维素纤维高分子之间、纤维素纤维高分子之间的内摩擦效应。它与纤维素纤维的分子量、纤维溶液的浓度、温度及溶剂性质有关。纤维素铜氨溶液比粘度可由施塔亭格公式求得:     

玉米黄素在不同溶剂中的可见吸收光谱研究

研究了玉米黄素在不同溶剂中的可见吸收光谱,探讨了环己烷、石油醚、丙酮、乙醇和乙酸乙酯对玉米黄素的紫外-可见光谱的影响。结果表明,在一定的浓度范围内,玉米黄素稀溶液的吸收规律符合朗伯-比尔定律。玉米黄素在环己烷、石油醚、丙酮和乙酸乙酯溶液中特征吸收峰的波长位置与以乙醇作为溶剂时相比有1 3nm的移动。产生这一现象的原因可能是玉米黄素溶于不同溶剂时,溶剂分子与玉米黄素分子间相互作用不同所致。     

经N-三氟乙酰化测定聚酰胺的分子量

由于受溶解度的限制,致使测定聚酰胺(PA)在溶液中的性质复杂化。聚酰胺的常用溶剂有浓酸类、酚类、脂肪族的氟代醇以及醇的盐助溶浓溶液等。PA在这些溶剂中由于有可能产生水解、高分子电解质效应以及可能对机体和仪器产生腐蚀等问题,而使分子量测定造成困难,甚至无法进行分子量测定。     

水性聚氨酯高分子染料的制备及酸致变色性能

利用醇羟基与异氰酸酯基反应,将偶氮苯低分子染料引入聚氨酯分子链中,制成水性聚氨酯高分子染料,再用于棉织物涂层,以制备柔性pH值传感器。探讨该高分子染料的颜色性能及其涂层织物的酸致变色性能。结果表明,偶氮苯低分子染料引入水性聚氨酯分子链前后的紫外可见光谱基本一致,无色变现象。当pH值从6降至3时,高分子染料溶液颜色由大红色变成紫红色;待涂层织物放置一段时间后,其颜色恢复为原来的大红色,显示出良好的可逆性和耐疲劳度。     

溶质在多苯基溶剂中的溶解热力学性质测量

用改装了层析室的国产１０２Ｇ型气相色谱仪，在全部实验范围内水浴控温精度为士０．０１℃，用气液色谱法测量了环烷烃、环烯烃及芳烃分别在二苯甲烷、二苄醚、对苄基联苯、二苯亚矾四个溶剂构成的二十九个二元液系不同温度下的比保留体积值，计算了溶质溶解溶剂的溶解焓△Ｈ°ｓ，溶解吉布斯自由能△Ｇ°ｓ，溶解熵△Ｓ°ｓ的值，并用△Ｈ°ｓ的测量值与文献值［１］［２］对分子间的相互作用作了讨论。     

酚醛-乙醇体系在铜粉表面吸附及其对复合材料力学性能影响

采用电导率、黏度和表面自由能测量研究了酚醛-乙醇体系在电解铜粉表面的吸附行为,结果表明：作为溶剂的乙醇与酚醛树脂在铜粉表面形成竞争性吸附,而且乙醇被优先吸附。为了进一步了解吸附对复合材料性能的影响,采用热压成型方法制备了以质量百分比为35%和60%酚醛树脂体系为基体的高分子复合材料,其力学性能测试表明,高浓度酚醛树脂溶液,有利于树脂分子在铜粉表面吸附,成型后树脂与铜粉界面结合好,制品机械强度高。     

玻璃纤维分散性能的研究

主要介绍了玻璃纤维的表面性能,比较经二氯甲烷、三氯甲烷、四氯乙烷、硅烷偶联剂醇溶液、苯酚-四氯乙烷等溶剂或溶液处理后玻璃纤维的分散效果.结果表明,苯酚-四氯乙烷溶液处理的玻璃纤维分散效果最好.经不同溶剂或溶液处理后,玻璃纤维表面较处理前未发生变化,只是破坏了纤维间分子作用力.     

用光散射法和粘度法研究纤维素在DMSO/PF溶剂系统中溶液的性质

本文研究纤维素在二甲基亚砜/多聚甲醛(DMSO/PF)溶剂系统中溶液的性质和影响溶解过程的若干因素,发现光散射法测得的分子量总是大大高于粘度法测定的分子量,羟甲基纤维素在DMsO中的溶液得到相似的结果,由此推设,纤维素在这种溶剂系统中以若个干分子链彼此交联在一起。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the