FIBERS (TEXTILE) 



fiber is now measured, while the rotator is 

 turned 90± to measure the fiber thickness. 



Special measuring methods. Special meth- 

 ods that may be ment ioned are the microme- 

 ter plates for determining denier and fullness 

 and the measurements for determining 

 lumen percentage. 



Various methods have been suggested in 

 the course of the years but few have become 

 widely used (e.g., the "Universalokular nach 

 A. Herzog" marketed by VEB Optik, Jena). 

 In this ocular, a reticulated micrometer 

 makes it possible to determine the titre of 

 viscose fibers direct from the cross section. 

 Calibration of the micrometer also makes it 

 suitable for all other fiber sections. 



The fullness of fibers of irregular section 

 can be calculated by determining the true 

 surface with a planimeter and calculating 

 the area of a circle described from the sec- 

 tion. The fullness V, as a percentage, is then 

 V = (400 F/ttB-') = 127.32 {F/B'-), in which 

 F is the fiber-section and B the greatest di- 

 mension of the section. If a projection micro- 

 scope is not available the true area can easily 

 be determined with a reticulated micrometer. 



The lumen percentage can be determined 

 most easily using a fixed magnification pro- 

 jection microscope. The fibers are compared 

 wdth a number of round "ideal" sections, in 

 which both lumen and sections are circular. 



Preparation ^lethods for Electron 

 Microscopic Examination. Duglosz' semi- 

 embedding method jor making replicas. As 

 fibers are usually bigger than lOju in diame- 

 ter, it is difficult to make replicas that have 

 retained their original form after the neces- 

 sary manipulation. With the semi-embedding 

 method, fibers are dropped on to a photo- 

 graphic plate, the gelatine layer of which has 

 been swollen. After the gelatine layer has 

 dried, a microscope sUde covered with a 

 marco-resin film with catalyst and acceler- 

 ator is placed on the gelatin layer. When the 

 plastic has hardened, the photographic plate 

 is pressed off. The sHde with the resin and 



the fibers fixed in it are now used to make a 

 replica by the silver-carbon method. 



Pagers replica method for extensive surfaces. 

 Fibers out of a suspension are put to dr}^ on a 

 clean slide. A film of meth}^ met hacry late 

 swollen at the surface in plasticizer is pressed 

 on the slide. After hardening, the film is re- 

 moved together with the fibers. With the 

 aid of a film of polyvinyl alcohol, allowed to 

 form from a 10% solution, the fibers are 

 pulled from the methacrylate. Lastly, a posi- 

 tive replica is formed, again with 10 % poly- 

 vinyl alcohol. 



Other replica methods. (1) Impressions in 

 polyisobutyl methacrylate which softens at 

 the surface at 100°C. (2) Semi-embedding in 

 polystyrene. The upper surface is then used 

 for making a replica. (3) Bradley's two-stage 

 replica technique is also widely used for 

 fibers. 



Fiber embedding for idtra-microtomy. Cut- 

 ting ultra-thin sections of fibers necessitates 

 embedding them in a synthetic resin. This 

 raises the following problems: 



(1) The embedding medium must in- 

 filtrate properly into the fiber and must not 

 change its structure. 



(2) During hardening the plastic must not 

 loosen from the fiber. 



(3) It must be possible to orient the fiber 

 properly in the sj^nthetic resin. 



Embedding media that are used are 50/50 

 mixtures of butyl and methyl methacr\'late 

 or epoxy resins. The latter are more suitable 

 because they do not loosen from the fibers 

 so readily. The fact that the epoxy resins 

 have a rather distinct structure under the 

 electron microscope is a drawback however. 



Electron staining reactions, ^"arious stain- 

 ing reactions are recommended for electron 

 microscopic examination of fibers. Good re- 

 sults are obtained with osmium tetroxide, 

 ferrialum and ZnCU . For cellulose fibers, 

 20 % AgNOs for several hours also gives good 

 results. 



Hess successfully used KI3 (Iodine 5%, 

 KI 10%, pH 5). He got very good results 



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