Application of Ultra-Microtomy to the 

 Fine Structure Study of Rayon Viscose Fibre' 



P. Kassenbeck 



Iiistitut Textile de Fiance, Paris 



Several papers have already been delivered on the 

 subject of electron microscopy studies of the fine 

 structure of regenerated cellulose fibres (15, 17, 18). 



All these papers were on the interpretation of 

 E.M. obtained by replica methods. May we recall 

 briefly that we have been able to show with this 

 method, modifications of the surface of fibres accord- 

 ing to the treatment they were subjected to and also 

 the presence on the surface of rayon viscose fibres 

 of an extremely thin layer. Thestructurecharacteristics 

 of this layer differ greatly from the remaining mass 

 of the fibre. 



The application of ultra-microtomy to the study 

 of the sub-microscopic architecture of these fibres 

 confirms the results obtained by previous studies. 

 Furthermore it shows details of internal structure 

 which could not be seen by replica methods. 



The problem of embedding textile fibres for ultra- 

 microtomy applications can be summarized as follows: 



1. It is necessary to obtain penetration and fixation 

 of the embedding medium into the fibre without any 

 change of micro-structure. 



2. The cutting angle must be perfectly known if sche- 

 matic reconstitution of the fibre structure is required. For 

 this reason fibres must be oriented in the embedding 

 medium. 



Experience shows that simple immersion of dehydrated 

 rayon viscose fibres in methacrylate monomer is not 

 sufficient to obtain a proper embedding. 



We overcame this difficulty by the use of an embedding 

 method which we call "double cut technic". 



Our starting material is about 0.5 cm^ of fibre sections 

 which are cut on an ordinary microtome. The thickness of 



Fig. 2. Thermal advance microtome. 



the cross-sections varies from 30 to 60 /< for fibres 20 /< 

 in diameter. These cross-sections are swollen in water 

 and swelling is fixed by the zinc chloroiodine reagent. 

 They are dehydrated in alcohol and immersed two days 

 in a first mixture of destabilized methyl methacrylate 

 and butyl methacrylate 50/50. Polymerization is carried 

 out in a second mixture of the same composition in a 

 special cell which allows the orientation of the cross- 

 sections (3, 10, II 12). 



A perspex tube, 10 mm long, containing the monomer 

 and the cross-sections is mounted between the two 

 electrodes of the cell (fig. 1 ). A 50 cycles alternative current 

 of 3 to 4 KV is applied between the electrodes. The whole 

 cell is rocked one cycle per second with an 180 angle. 

 There cannot be any decantation of the cross-sections 

 towards the bottom of the perspex tube. Rocking insures 

 good dispersion of these cross-sections into the embedding 

 medium. Under the elTect of the electric field, the fibre 

 sections are oriented while the polymerization takes 

 place at 40"C for 6 hours. 



Cross sectioning on a thermal advance microtome. — 

 After polymerization is completed, we have at our dispo- 

 sal a cylindrical perspex block in which all cross-sections 

 are oriented parallel to the cylinder axis. This block is 

 cut with a thermal advance microtome (fig. 2) (2, 5). 



The cross-sections are cut again in a much thinner 

 section (100 to 300 A thick). A small brass container 

 (7, 8) is fixed with the help of paraffin to a glass knife 

 (13). The brass container is connected to a glass tube 

 by rubber tubing. By these means the level of the liquid 

 (water-acetone mixture) is ajusted correctly. The ribbon 

 of sections is picked up on formvar film coated grids. 



Fig. 3 shows a result obtained when the embedding 

 medium has not been removed. Contrast in this micro- 



Fig. 1. Perspex cell for the embedding of sections of fibres 

 under tension (scale 1:1). 



^ A more detailed report lias appeared in Bulletin Institiit 

 Textile de France 61, 7-15 (1956). 



