纸浆纤维在NaOH/硫脲/尿素水溶液中的溶解性能

通过正交实验设计,探讨NaOH/硫脲/尿素溶剂体系中不同组分含量对针叶木纸浆纤维溶解性能的影响,分析经不同温度处理后未溶解纤维的形态变化,并对原料纤维和再生纤维素的结构和性能进行表征。结果表明:当溶解温度-10℃,混合溶剂中NaOH、硫脲、尿素、水的质量比为7:7:7:79时,纸浆纤维的溶解效果最好,且溶解过程属于非衍生化性溶解;经碱脲溶剂润胀和溶解处理后,未溶解纤维的平均纤维长度值变小和平均宽度值变大,纤维表面出现一定程度的破坏,且纤维素晶型由纤维素I型向纤维素II型转变;与原料纤维相比较,溶解后再生纤维素的结晶度由66.77%降低到28.70%,并且转化成为纤维素II晶型。     

NaOH-尿素体系对棉纤维润胀性能的影响

利用NaOH-尿素体系对棉纤维进行了润胀处理,初步探讨了NaOH-尿素体系的反应温度、体系浓度、体系量等对棉纤维润胀性能的影响,并通过红外光谱分析、光学显微镜观察等方式分别对处理前后棉纤维进行结构表征和形态分析。实验结果表明,NaOH-尿素体系可明显提高棉纤维的润胀性能,处理后棉纤维的最大保水值比未处理棉纤维提高了186.91%;处理后棉纤维分子结构没有明显变化;但纤维表面发生局部溶解,其细纤维化程度和表面粗糙程度均有所提高。     

纤维素的活化对其溶解性能的影响

采用了3种方法活化纤维素,将活化后的纤维素溶解在NaOH-尿素-硫脲体系里.利用傅立叶红外光谱仪(FT-IR)及扫描电镜(SEM),分析了活化后纤维素的溶解度、氢键、分子量及表面形态的变化.研究发现,各种活化方法均能提高纤维素的溶解性能,其中以超声波活化处理纤维素的综合效果较好.     

不同针叶木化学浆在碱尿素水溶液体系中溶解行为的研究

以用于生产黏胶纤维的漂白针叶木硫酸盐浆(BSK)和硫酸盐法针叶木溶解浆为原料,通过测定纸浆纤维-纤维素-溶剂(7%NaOH/12%尿素水溶液)溶解体系的透光率及溶解生成的纤维素溶液的黏度、观察纸浆纤维冷冻过程的微观形态、分析溶解前后纸浆纤维长度和宽度的变化、检测未溶部分的X射线衍射谱图,研究对比了这两种浆在7%NaOH/12%尿素水溶液体系中溶解行为的差异。结果表明,相同浆浓下,聚合度高的漂白针叶木硫酸盐浆在7%NaOH/12%尿素水溶液中溶解后体系的透明度比聚合度低的针叶木溶解浆体系的高,前者溶解生成的纤维素溶液的黏度大于后者溶解生成的纤维素溶液的黏度,即纤维素含量高、聚合度低的溶解浆反而较难溶解在7%NaOH/12%尿素水溶液中。针叶木硫酸盐浆溶解后纤维变短且变粗,而针叶木溶解浆因大部分短小纤维被溶解导致溶解后纤维的平均长度变长,且宽度变化较小。针叶木硫酸盐浆保留了完整的纹孔结构,溶剂渗透性较好,其溶解效果优于在制浆过程中细胞壁经受严重破坏的针叶木溶解浆的溶解效果。     

大麻纤维在氯化锂/N,N-二甲基乙酰胺溶解体系中的溶解特性

为提高大麻纤维溶解性能,对大麻纤维进行氢氧化钠预处理和氯化锂/N,N-二甲基乙酰胺（LiCl/DMAc）溶解处理。用质量分数为18%的氢氧化钠在60℃处理大麻纤维1～4h,然后将预处理后的大麻纤维在不同温度（70、80、95℃）下溶解于质量分数为10％的LiCl/DMAc溶解体系。用扫描电镜、红外光谱仪 和 X 射线衍射仪对溶解前后的大麻纤维进行表征,测试溶解后溶液黏度值。结果表明：氢氧化钠预处理后纤维素的晶型由纤维素Ⅰ转变为纤维素Ⅱ;溶解温度升高,大麻纤维溶解性增强,95℃条件下,预处理2h和3h的大麻纤维在10%LiCl/DMAc溶解体系中能够完全溶解,溶解质量分别为1.0～1.2g和1.2～1.5g;预处理3h的大麻纤维/LiCl/DMAc溶液黏度值更大,溶液稳定。     

LiOH复合溶剂体系直接溶解法制备新型再生纤维素纤维

首次发现纤维素可快速溶解于LiOH/硫脲/尿素水溶液中。通过偏光显微镜进行了观察,纤维素在新溶剂体系中的溶解过程,并通过湿法纺丝技术在10%(质量分数)H2SO4/12.5%(质量分数)Na2SO4的凝固浴中凝固再生纤维素,成功制备了新型纤维素纤维。再生纤维的结构通过扫描电镜和广角X射线衍射进行了表征,研究发现,这种再生纤维分子量较高,形态上具有圆形的截面和光滑的表面,结构上属于典型的纤维素Ⅱ,并具有较高的结晶度。这些形态结构特性保证了新纤维具有较好的力学性能。     

纤维素/NaOH-尿素-硫脲溶液体系流变性能的研究

借助Rt2000型高效毛细管流变仪及DV-Ⅱ型旋转粘度计对纤维素/NaOH-尿素-硫脲溶液体系的流变性能进行了研究.考察了剪切力、温度、纤维素原料质量分数对溶液表观粘度的影响.结果表明:纤维素/NaOH-尿素-硫脲溶液体系属于假塑性流体,该体系的流动活化能较低,其表观粘度随温度升高而降低;纤维素质量分数增加使溶液表观粘度增加.     

非衍生化溶剂体系制备再生纤维素膜及其性能研究

以NaOH/尿素/硫脲、［Amim］Cl、［Amim］Cl/DMF和氯化胆碱/尿素低共熔溶剂4种溶剂作为纤维素浆粕的溶剂体系并制备再生纤维素膜。采用红外光谱、X射线衍射、热重分析、扫描电镜和万能材料试验机对再生纤维素及再生纤维素膜进行结构表征。结果表明,将纤维素溶解在不同溶剂体系中,再生纤维素晶型均由纤维素Ⅰ型转变为纤维素Ⅱ型,再生纤维素的结晶度、热稳定性及再生纤维素膜的力学性能均有不同程度的降低。从再生纤维素膜性能及成本核算方面考虑,［Amim］Cl /DMF溶剂体系制备再生纤维素膜效果最佳。     

氢氧化钠活化前后纤维素在离子液体/DMSO溶剂体系中溶解性能的变化

研究了棉短绒纤维和针叶木纤维经氢氧化钠活化后对其在离子液体1-丁基-3-甲基咪唑氯代盐([BMIN]Cl)与二甲基亚砜(DMSO)共容积体系中溶解度的影响。研究结果表明棉短绒纤维和针叶木纤维活化后在该溶解体系的溶解度分别从3.9%、2.8%提高到7.1%、5.0%,比未活化前增大了近1倍,说明这两种纤维素用氢氧化钠活化后在离子液体中更易溶解。活化的棉短绒纤维和未活化的棉短绒纤维在溶解再生后聚合度分别从612、578下降至423、350,分别降低了30.8%、39.4%;活化的针叶木纤维和未活化的针叶木纤维在溶解再生后聚合度则分别从736、704下降至607、502,降低了17.5%、28.7%.红外光谱证实离子液体[BMIN]Cl/DMSO溶解体系为纤维素的非衍生化溶剂。X-射线衍射(XRD)实验证实经过氢氧化钠活化处理的纤维素相比未经过活化处理的纤维素衍射峰强度降低得更厉害,说明在氢氧化钠活化过程中也能降低纤维素的结晶度,有助于纤维素在离子液体中的溶解。     

微溶解处理对大麻/棉混纺织物拉伸性能的影响

为探讨预处理和微溶解工艺对汉麻/棉混纺织物拉伸性能的影响,对织物和原汉麻纤维进行预处理和LiCl/DMAc微溶解。其中,LiCl/DMAc是一种具有良好稳定性的新型绿色纤维素溶剂体系,微溶解的具体工艺是10%的LiCl/DMAC溶剂,温度65℃。用红外光谱分析(FT-IR)和X-射线衍射(XRD)对纤维进行表征,并用万能强力机测试织物的拉伸性能。结果表明：汉麻纤维经过预处理和微溶解溶解体系后,主要基团没有发生明显的变化,且纤维素在微溶解过程中未发生衍生化反应。经过不同工艺处理体系后,织物的断裂伸长率和断裂强力均得到不同程度的增加。其中,经碱活化和LiCl/DMAc微溶解后,织物拉伸性能性能得到提高,断裂强力提高44.5%。     

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.     

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.     

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.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.