两种超细纤维复合空气过滤纸的结构与性能研究

由于超细纤维可以显著提高过滤效率,在过滤材料中的应用得到越来越多的重视,但不同方法制备的超细纤维复合空气过滤材料在性能上存在着较大差异。本文主要对静电纺复合和造纸湿法复合这两种不同方法制备的超细纤维复合空气过滤纸进行结构与性能的研究。结果表明,两种不同方法制备的超细纤维复合空气过滤纸的初始过滤效率非常接近,静电纺复合滤纸的透气度为243mm/s,比造纸湿法复合滤纸的高近1倍;静电纺复合滤纸的容尘量为82g/m~2,造纸湿法复合滤纸的容尘量比其高14g/m~2;经过10次反吹清灰循环,静电纺复合滤纸的粉尘剥离率由91.6%降低为71.9%,造纸湿法复合滤纸的由67.4%降为38.8%,静电纺复合滤纸的反吹清灰性能比造纸湿法复合滤纸的更优异。     

串珠纤维对静电纺纤维复合滤纸结构和性能的影响

本研究制备了静电纺串珠纤维复合滤纸和静电纺纳米纤维复合滤纸,对其微观形貌和孔径等结构特性以及过滤阻力、过滤效率和容尘量等过滤性能进行了分析。结果表明,静电纺串珠纤维复合滤纸和静电纺纳米纤维复合滤纸的纺丝层纤维平均直径接近,分别为225、250 nm。通过控制纺丝时间使二者的初始过滤阻力相近时,静电纺串珠纤维复合滤纸过滤效率为73.1%,静电纺纳米纤维复合滤纸过滤效率为38.2%。相同测试条件下,静电纺串珠纤维复合滤纸阻力上升速度比静电纺纳米纤维复合滤纸慢,达到相同终止阻力时,静电纺串珠纤维复合滤纸的作用时间更长、容尘量更大,二者的容尘量分别为119.29、96.23 g/m~2;并采用仿真模拟软件GeoDict建立模型,探究了两者阻力变化情况和容尘量的差异。     

具有梯度结构的超细纤维复合空气过滤材料对油-灰混合颗粒的容尘性能研究

通过湿法成形制备了超细纤维在厚度方向呈梯度分布的复合空气过滤材料,并分析了滤材对不同粒径的NaCl颗粒的过滤效率及对纯A2灰、纯癸二酸二异辛(DEHS)和不同DEHS含量的DEHS-A2灰混合尘的容尘量。结果表明,滤材最易穿透粒径为100 nm,对纯A2灰及纯DEHS的容尘量分别为92.0 g/m²和182.5 g/m²。对DEHS含量为20%的混合尘的容尘量最大,为414.7 g/m²,对DEHS含量为60%的混合尘的容尘量最低,为84.1 g/m²,远高于商业化产品熔喷纤维复合滤材的容尘量(26.5 g/m²)。对DEHS含量为20%的混合尘滤材压差增加速率最小,混合尘在滤材表面形成疏松的滤饼;对DEHS含量为80%的混合尘滤材压差增加速率最大,A2灰颗粒浸没在DEHS中,灰尘颗粒间的孔隙被完全堵塞,混合尘形成“海岛”结构的滤饼。     

微纳米纤维复合滤纸的过滤性能研究

为了探究复合滤纸不同复合方式的性能差异,本研究对两种初始过滤效率接近的复合滤纸进行了效率特征曲线、容尘量和反吹性能的研究.结果表明,静电纺丝复合滤纸最易穿透粒径为150 nm,熔喷复合滤纸最易穿透粒径为200 nm.相同条件下加载A2细灰时,熔喷复合滤纸的阻力增加速率小于静电纺丝复合滤纸;加载油灰混合颗粒时,熔喷复合滤...     

静电纺PBS/熔喷复合滤材的制备及性能表征

通过正交试验得到PBS静电纺丝最优工艺,以熔喷非织造布为接收基材,在PBS静电纺丝最优工艺下制备静电纺PBS/熔喷复合滤材。并对复合前后材料的性能进行表征,结果表明:静电纺PBS纤维比熔喷非织造布纤维直径更小,且分布更均匀;熔喷非织造布与静电纺PBS纤维复合后平均孔径从10μm降低到3μm,且孔径分布很均匀,孔隙率基本无变化,材料表面的润湿性稍微有所改善。     

聚丙烯腈静电纺/聚丙烯熔喷复合材料的制备及过滤性能研究

以聚丙烯腈(PAN)为原料,N,N-二甲基甲酰胺为溶剂制备纺丝液并进行静电纺丝,用熔喷聚丙烯(PP)非织造材料为基材接收静电纺PAN纳米纤维膜,制备PAN静电纺/PP熔喷复合材料。研究了静电纺丝工艺参数对纤维直径及均匀度的影响,优化了静电纺丝工艺,在此基础上改变纺丝时间控制熔喷非织造材料表面复合的静电纺纳米纤维含量,通过AFC-131滤料性能测试系统测试了PAN静电纺/PP熔喷复合材料的空气过滤性能。结果表明,在熔喷非织造材料喷覆静电纺PAN纳米纤维膜后,过滤效率明显提高,颗粒越小,过滤效率提高越多,且随喷覆时间的增加,过滤效率提高,滤阻增加,但滤阻增加值小于过滤效率增加值,综合考虑在纺丝时间为10min时,可以制备高效低阻的PAN静电纺/PP熔喷复合非织造过滤材料。     

过滤时间对空气过滤材料过滤性能的影响

通过设定不同的过滤时间,测试静电纺纳米纤维膜和熔喷非织造材料的过滤性能,研究其过滤效率和过滤阻力随过滤时间的变化规律。结果发现:过滤时间的增加使得过滤效率和过滤阻力呈现不同程度的增长。过滤时间的增加对静电纺纳米纤维膜过滤性能的影响较显著,设计面密度为10.00 g/m~2的静电纺纳米纤维膜的过滤效率和过滤阻力明显上升,而设计面密度为20.00和40.00 g/m~2的静电纺纳米纤维膜因孔径过小导致其过滤阻力在短时间内超过1 000 Pa,故面密度较大的静电纺纳米纤维膜不适合用于普通的空气过滤。熔喷非织造材料结构较蓬松,孔径较大,孔隙不易被堵塞,当过滤时间为12 h时,除设计面密度为40.00 g/m~2的熔喷非织造材料过滤阻力增加较明显外,其他熔喷非织造材料的过滤效率和过滤阻力增幅均不大。     

空气过滤用高容尘膨体聚四氟乙烯复合材料的制备及其性能

为提高膨体聚四氟乙烯 (ePTFE)膜的容尘性能,拓展ePTFE膜复合材料在净化领域的应用,通过将不同厚度、不同纤维直径以及驻极处理后的聚丙烯熔喷过滤材料作为容尘层与ePTFE膜复合制备ePTFE复合材料,并对复合材料的容尘性能以及微观结构进行分析。结果表明:复合材料的容尘量随容尘层厚度增加呈线性增加趋势,容尘层厚度为0.45 mm时,复合材料的容尘量达到6.37 g/m²,较ePTFE膜提高了266%;复合材料的容尘量随容尘层纤维直径的减小呈增加趋势,容尘层纤维直径为1.462 μm时,复合材料的容尘量达7.96 g/m²,较ePTFE膜提高了357%;驻极处理后,容尘层纤维直径为3.611 μm时,复合材料的容尘量较驻极处理前提高了136%。     

静电纺高效防尘复合滤料的制备及其性能

为获得无毒无害高效防尘口罩的过滤材料,采用静电纺丝技术制备直径为（0.088±0.01）μm的锦纶6∕ 壳聚糖（PA6/CS）共混纳米纤维,与丙纶熔喷非织造布复合形成高效防尘复合滤料,研究了静电纺丝时间对复合滤料表面形貌、孔径及其分布、过滤性能和透气透湿性能的影响。结果表明,静电纺（PA6/CS）纳米纤维层可显著提高丙纶熔喷非织造布的过滤效率,静电纺丝 90 min 后复合滤料对 NaCl 气溶胶的过滤效率达到99%以上,明显高于丙纶熔喷非织造布的过滤效率（29%）,但是随着静电纺丝时间的延长,复合滤料的孔径、过滤阻力和透气性能明显下降,而透湿性能变化不明显。     

静电纺PA6/CS复合纤维膜的过滤性能研究

采用自制单喷头静电纺丝设备,以聚丙烯熔喷非织造布为基布,制备静电纺聚酰胺6/壳聚糖(PA 6/CS)复合纤维膜,研究了静电纺丝时间对复合膜表面形貌、孔径和过滤性能的影响。结果表明:随着静电纺丝时间增加,复合纤维膜对Na Cl气溶胶的过滤效率显著增加,过滤阻力明显增加,品质因子先增加后减小;连续纺丝90 min后,复合纤维膜的过滤效率达到99%以上。     

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.     

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.     

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.     

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.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.