236 



TABLE 225.— PROPERTIES OF GR-S (HYDROCARBON OF ABOUT 23.5 PERCENT 



BOUND STYRENE CONTENT) 



Vulcanizate 

 containing 



Unit 



Density g cm" 3 



Expansivity (l/V)(dV/dT) (degC)" 1 



Thermal 



Specific heat cal g" 1 (deg C)" 



Second-order transition temperature., deg C 



Optical 



Refractive index, nD 



dn D /dT (degC)- 1 



Electrical 



Dielectric constant (1000 cps) 



Loss factor, tan (90°— e) (1000 cps).. 



Mechanical 



Shear modulus dynes cm' 2 



Initial slope of stress-strain curve.... dynes cm" 2 



Ultimate elongation percent 



Tensile strength kg cm" 2 



Complex dynamic shear modulus 



<(.c\ \ ff '+i ff " 



(60 cps), 



f 



Real part G', — dynes cm -2 



ff" 

 Imaginary part G", — dynes cm" 2 



Resilience (ball rebound) percent 



5X10 9 



1-2X10" 

 65 



55X10" 



9X10" 



40-50 



TABLE 226.— PROPERTIES OF NEOPRENE (CHLOROBUTADIENE POLYMER) 



Unit Unvulcanized 



Density g cm" 3 1.23 



Expansivity (l/V)(dV/dT) (degC)" 1 



Thermal 



Second-order transition temperature deg C — 38 to — 41 



Optical 



Refractive Index nD 1.558 



dn D /dT (degC)- 1 -36X10" 5 



Mechanical 



Shear modulus dynes cm" 2 



Initial slope of stress-strain curve dynes cm" 2 



Ultimate elongation percent 



Tensile strength kg cm" 2 



Complex dynamic shear modulus (60 cps), 

 g'-f-jq" 



e 

 Real part G', — dynes cm" 2 



a" 

 Imaginary part G", — dynes cm" 2 



Resilience (ball rebound) percent 



Pure-gum 

 vulcanizate 



1.30 

 61X10" 8 



Vulcanizate 

 containing 

 about 33% 



carbon black 



15-30X10" 



800-1000 



250-375 



6X10" 



1X10" 

 65 



14X10" 



30-36X10" 



6X10" 

 40-50 



SMITHSONIAN PHYSICAL TABLES 



