Fibres, identification

Preparation of Sections of the Fibres.—Identification of animal or vegetable fibres is based mainly on the physical characters, the fibres being mostly so transparent that their form and structure, and particularly the thickness of the walls and the form of the internal canal or lumen, are easily observed. In some cases, however, owing to the close resemblance between certain fibres, recognition is doubtful. This is the case, for instance, with the poorer qualities of flax and hemp, and with certain types of artificial silk. In these instances the transverse sections of the fibres are studied, these permitting of observation of the thickness of the walls, the strata... 

Cut or ground cross-sections of fibres, yams and fabrics are of interest for fibre identification, in fault analysis in primary and secondary spinning and in checking the penetration of dyes into fibres, filaments, yams and fabrics. These methods are also used to investigate hollow and multicomponent fibres, the build-up, adhesion and evenness of coating layers and the analysis of other textile composites. AU of this can be useful for damage analysis. Grieve has written a review on cross-section preparation methods for fibres. 

The determination of melting point as used for fibre identification can itself be included under TA, because here the phase change is determined as a function of temperature. It can be carried out very easily using a Kofler hot bench. This has a temperature range from about 50-260 °C. Fibre snippets are moved with tweezers from the colder to the warmer end until they begin to melt. The relevant... 

A special case of fibre identification involves vehicle accidents with fatal injuries to the occupants. The high pressure of impact causes such a high frictional heat that fibres are embedded in plastic surfaces which are momentarily softened and the fibres are retained there after the plastic cools down. With these traces, known as fusion marks, it is possible to reconstruct where the passengers were... 

There is no easy traceability for fibre deployment, fibre identification and tracking. 

AA.TCC Technical Manual, Vol. 59, American Association of Textile Chemists and Colorists, Research Triangle Park, N.C., 1984. D. M. Colling and J. E. Grayson, Identification ofi Vegetable Fibres, Chapman and Hall Ltd., London, 1982. 

E. Clayton, Identification of Dyes on Textile Fibres, 2nd ed.. Society of Dyers and Colorists, Bradford, UK, 1963. 

DSM and Allied Signal have developed carpet identification equipment that can identify specific plastics. Particularly carpet made of nylon 6 (or nylon 66) fibres are separated, cut into pieces, isolated, and converted by polycondensation into their monomeric components. The monomers can then be reused in the production of nylon. DSM and Allied Signal opened the world s first large scale carpet recycling plant in Augusta, Georgia, US in November 1999. This plant has a capacity of 90,000 tpa nylon 6 carpet waste (109). 

The main features of PC are low cost, need for small sample amount, high level of resolution, ease of detection and quantitation, simplicity of apparatus and use, difficult reproducibility (because of variation in fibres) and susceptibility to chemical attack. Identification of the separated components is facilitated by the reproducible Rj values. Detection methods in PC have been reviewed [368]. Fluorescence has been used for many years as a means of locating the components of a mixture separated by PC or TLC. However, also ATR-IR and SERS are useful. Preparative PC is unsuitable for trace analysis because filter paper inevitably contains contaminants (e.g. phthalate esters, plasticisers) [369]. For that purpose an acceptable substitute is glass-fibre paper [28]. 

Identification of dyes on dyed textiles is traditionally carried out by destructive techniques [493], TLC is an outstanding technique for identification of extracted dyestuffs and examination of inks. Figure 4.9 shows HPTLC/SERRS analysis of acridine orange [492], Wright et al. [494] have described a simple and rapid TLC-videodensitometric method for in situ quantification of lower halogenated subsidiary colours (LHSC) in multiple dye samples. The results obtained by this method were compared with those obtained by an indirect TLC-spectrophotometric method and those from HPLC. The total time for the TLC-videodensitometric assay of five standards and four samples applied to each plate was less than 45 min. The method is applicable for use in routine batch-certification analysis. Loger et al. [495,496] have chromatographed 19 basic dyes for PAN fibres on alumina on thin-layer with ethanol-water (5 2) and another 11 dyes on silica gel G with pyridine-water... 

Most dyes, including sulfonated azo dyes, are nonvolatile or thermally unstable, and therefore are not amenable to GC or gas-phase ionisation processes. Therefore, GC-MS techniques cannot be used. GC-MS and TGA were applied for the identification of acrylated polyurethanes in coatings on optical fibres [295]. Although GC-MS is not suited for the analysis of polymers, the technique can be used for the study of the products of pyrolysis in air, e.g. related to smoke behaviour of CPVC/ABS and PVC/ABS blends [263],... 

SPME/GC/MS is an efficient technique to reveal the presence of resinic substances in archaeological samples. Indeed, volatile terpenes are still present in very old archaeological samples (4000 years old), particularly in the case of compact matrixes, and can be trapped by the SPME fibre. In comparison with methylene chloride extraction, SPME is very specific and allows the direct analysis of the volatile terpenes content in complex mixtures including oils, fats or waxes. For this reason, headspace SPME is the first method to use when analysing an archaeological sample it will either allow the identification of the resin or indicate further sample treatment in order to detect characteristic triterpenes. The method is not really nondestructive because it uses a little of the sample but the same sample can be used for several SPME extractions and then for other chemical treatments. 

Elaboration of the method for the identification of colour compounds by RPLC MS should comprise four steps (1) spectral characterization of reference materials (standards) and subsequent optimization of detection parameters, as well as those of their chromatographic separation (2) analysis of natural dyestuffs used as colouring materials in historical objects (3) analysis of model samples (dyed fibres, paintings) prepared according to old recipes (4) application of the acquired knowledge to identification of colourants present in historical objects. 

Analysis of dyed fibres allows identification of real colouring components of natural dyestuffs taking part in the dyeing process. Wool threads dyed with madder (Rubia tinc-torum) as well as Our Lady s bedstraw (Galium verum), were studied by HPLC DAD ESI MS" (SIM mode).[8] Chromatograms of the extracts from wool dyed with madder... 

Flavonoids bonded to fibres undergo photodegradation over the course of time their identification in historic textiles is thus often difficult. The analysis of a wool orange fibre (from a nineteenth century Aubusson tapestry) dyed with alum mordant and quercetin enabled the presence of quercetin (at m/z 301) and its decomposition products, 3,4-dihydroxybenzoic acid (at m/z 153) and methyl 3,4-dihydroxybenzoate (at m/z 167), to be confirmed. [30] The samples were hydrolysed with hydrochloric acid and analysed with RPLC MS. 

Mild extraction was also found to be effective in the analysis of extracts of Flaveria haumanii, l in which quercetin, kaempferol, isorhamnetin as well as their glycosides and sulfate esters were identified. The obtained results were useful in the identification of the colourants from fibres from pre-Columbian Andean textiles extracted with the use of water-methanol solution with formic or hydrochloric acid. The components of each extract were separated on a reversed phase HPLC column and the eluates were monitored at... 

The optimized RPLC UV-Vis ESI MS method for all typical blue colourants (indi-goids, hematein, tannins, anthocyanins and selected flavonoids) was used for the identification of dyes extracted from a thread taken from an Italian tapestry of unknown origin from the collection of the National Museum in Warsaw (Poland). It was found that to obtain the red-blue colour of the fibre a mixture of dyestuffs was probably used. The presence of indigotin, tannic and ellagic acid (at m/z 301, NI), as well as carminic acid, suggested the use of indigo and cochineal. Reseda luteola could also have been used due to the presence of luteolin and apigenin. 

In environmental analytical applications where analyte concentrations, e.g. surfactants or their metabolites, are quite low, extraction and concentration steps become essential. Solid phase extraction (SPE) with cartridges, disks or SPME fibres (solid phase micro extraction) because of its good variety of SP materials available has become the method of choice for the analysis of surfactants in water samples in combination with FIA as well as LC—MS analysis. SPE followed by sequential selective elution provides far-reaching pre-separations if eluents with different polarities and their mixtures are applied. The compounds under these conditions are separated in the MS spectrometer by their m/z ratios providing an overview of the ionisable compounds contained in a sample. Identification in the sense it has been mentioned before, however, requires the generation of fragments. 

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