Determination of effective crosslink density in silicone rubber

1965 ◽  
Vol 9 (1) ◽  
pp. 151-168 ◽  
Author(s):  
Robert D. Seeley ◽  
George W. Dyckes
Keyword(s):  
Silicone Rubber ◽  
Crosslink Density

Determination of Effective Crosslink Density in Silicone Rubber

1965 ◽  
Vol 38 (4) ◽  
pp. 924-939
Author(s):  
Robert D. Seeley ◽  
George W. Dyckes
Keyword(s):  
Silicone Rubber ◽  
Crosslink Density ◽  
Theoretical Calculations ◽  
Empirical Relationships ◽  
Physical Test ◽  
Swelling Agent ◽  
Rubber Compounds ◽  
Resultant Data ◽  
Volume Swelling

Abstract As a result of the investigations reported here, a simple and precise method was evised to measure the compression-deflection of solvent-swollen silicone rubber. The method was found to be reliable, and the resultant data were used to calculate effective crosslink densities of solid and cellular silicone rubber compounds. Empirical equations were derived relating compression and deflection to effective crosslinking of solid and cellular silicone rubber swollen in toluene. The weak swelling action of MEK precludes the derivation of empirical relationships between compression, deflection, and effective cross-linking of the rubber. The investigation further showed that toluene is a better and more useful swelling agent than methyl ethyl ketone (MEK). The volume swelling ratios for toluene and MEK were determined. Toluene was found to be about 1.4 times more effective as a swelling agent than MEK. Limited laboratory physical test data show a reasonable correlation to νe/Vr data. (More testing will be required to establish definite relationships.) This investigation also showed that the method employed here for crosslinking determinations is suitable for cellular rubber, since the data obtained from toluene-swollen specimens agrees quite well with theoretical calculations. Finally, the Flory-Huggins interaction parameters for toluene and MEK were determined.

Effect and Detection of Loose Chain Ends in Crosslinked Polyurethane Elastomers

1971 ◽  
Vol 44 (1) ◽  
pp. 152-165 ◽  
Author(s):  
A. E. Oberth
Keyword(s):  
Crosslink Density ◽  
Volume Fraction ◽  
Present Theory ◽  
Swelling Ratio ◽  
Polyurethane Elastomers ◽  
Equilibrium Volume ◽  
Equilibrium Swelling ◽  
Volume Swelling

Abstract The effect of loose chain ends on tensile properties and equilibrium swelling of crosslinked polyurethane rubbers is studied. As in plasticized elastomers, tensile strength and elastic modulus are reduced approximately by a factor (1−νE,P)2, where νE,P is the volume fraction of loose chain ends, plasticizer, or both. This effect is much larger than predicted by present theory. Also the equilibrium volume swelling ratio, V0/V, of rubbers having terminal chains or an equal volume of plasticizer is the same, provided they do not differ in crosslink density. However, the volume fraction of “network rubber” in the equilibrium swollen specimen, ν2, differs owing to the non-extractability of terminal chains. On this basis a method is proposed which allows experimental determination of the volume fraction of loose ends. Elastomers abounding in loose chain ends show markedly less long term stress relaxation. This effect is not clearly understood but is useful to detect the presence of non load-bearing network.

Sign in / Sign up

Export Citation Format

Share Document