244 TABLE 235.— PHYSICAL PROPERTIES OF MISCELLANEOUS FIBERS 



Acetate * 

 (cellulose) 



Density (g/cm 8 ) 1.30-1.35 



Refractive index: epsilon .... 1.476-1.478 

 omega 1.470-1.473 



Tensile strength (1000 lb/in. 2 ). 20-30 



Tenacity: dry (g/denier +) ... 1.2-1.5 

 wet (% of dry) .... 60-65 



Elongation to break (%) 23-50 



Recovery from strain 



Elongation (%) 2 



Recovery " 94 



Elongation " 20 



Recovery " 23 



Average stiffness § 3-7 



Toughnens index H 16-32 



Moisture regain at 65% R. H. 

 and 70° F (% of bone-dry 

 weight) 6.0-6.5 



Swelling in water, cross-section 



swelling (%) 7.9 



Heat stability ; temperature °C 

 at or above which fiber 



contracts 



loses strength 90-107 



softens 177-208 



melts 



decomposes 



* Acetate rayon or estron. t Including regular 



in grams of 9000 meters of the fiber. § The value 



substance to resist deformation. II The toughness 



to absorb work. 



12-15 



14 



100-171 

 232-246 



2.0-3.7 



3 

 100 



290 

 6 



10.0-15.5 .0 



5.0-10.0 .0 



316 

 816 



14-25 



2 



100 

 20 

 75 



22-41 



45 



3.5^1.5 



3.2 



Does not 

 contract 

 140 

 220 



74 

 i04 



and high-tenacity varieties. t "Denier" is the weight 



given for stiffness is a measure of the ability of the fiber 

 index is a measure of the ability of the fiber substance 



SMITHSONIAN PHYSICAL TABLES 



