Innovative Application of Biopolymer Keratin as a Filler of Synthetic Acrylonitrile-Butadiene Rubber NBR

Table 2

Cross-linking density determined by measurement of equilibrium module and equilibrium swelling.

Symbol	Parameters
	𝜈𝑇/𝜈𝑇/NH3 [mol/dm^3]∗10^4	Δ𝜈NH3 [mol/dm^3]∗10^4	𝐴1 [%]	𝑄𝑤 for water [mg/mg]	Content of bonds [%]:
					C–C, C–S–C, C–S2–C	C–S𝑥–C
Standard	0,70/0,45	0,26	37,14	0,055	9,30	90,70
Sample I	1,00/0,82	0,18	18,00	0,089	15,24	84,76
Sample II	1,08/0,44	0,64	59,26	0,092	2,98	97,02

𝜈_𝑇—cross-linking density of vulcanizate calculated from the measurement of equilibrium swelling in toluene [mol/dm³] 
𝜈_𝑇/NH3—cross-linking density of vulcanizate calculated from the measurement of equilibrium swelling in toluene and ammonia vapour [mol/dm³] 
Δ𝜈_NH3—concentration of the ion lattice points decomposing under the influence of ammonia [mol/dm³]:
Δ𝜈_NH3=𝜈_𝑇−𝜈_𝑇/NH3 
𝐴₁—percentage content of the ion lattice points decomposing under the influence of ammonia [%]:
𝐴₁=(Δ𝜈_NH3/𝜈_𝑇)∗100%
The parameters of rubber-elastomer interactions:
𝜇—Huggins’ parameter (parameter of polymer-solvent interaction):
𝜇=𝜇₀+𝛽𝑉_𝑟
where
𝑉_𝑟—volumetric content of elastomer in the sample under test
𝜇—the parameter of polymer-solvent interaction when 𝑉_𝑟=0 
𝜇₀—slope of the straight line describing the relationship: 𝜇=𝑓(𝑉_𝑟)
For NBR (Nipol N41) rubber: in toluene 𝜇₀=0.479; 𝛽=0.164; in toluene and ammonia vapour
𝜇₀=0.502; 𝛽=0.282 
𝑄_𝑤—equilibrium swelling in water [mg/mg] 
C–C, C–S–C, C–S₂–C; carbon, monosulfide and disulphide bonds [%] 
C–S_𝑥–C; polysulphide bonds [%].