Water Absorption of Elastomers

Abstract

This study considers high temperature (160° C) water absorption in the absence of oxygen. Examination of the freezing behavior of water-swollen butyl gum vulcanizates shows the water to be disposed as discrete droplets of the order of 3µ diameter, corresponding in this case with soluble residues based on zinc. Data are shown for peroxide gum vulcanizates of natural rubber, SBR, NBR, ethylene-propylene rubber, and cis-1,4 poly butadiene. Equilibrium absorption occurs, the degree being dependent on polymer impurities and state of cure. Model systems based on cis-polybutadiene show the effects of typical emulsion polymerization residues and the nature of the equilibrium balance between osmotic pressure and the retractive pressure exerted by the rubber. Classes of absorption behavior, whether low equilibrium, moderate to high equilibrium, or nonequilibrium, are discussed in terms of osmotic and rubber pressures. The temperature dependence of absorption rate is shown for the various polymers for the range 25° to 92° C. Five decades are required to accomodate the data, ranging from low rates for butyl rubber to high rates for NBR and natural rubber. Curing systems are compared, with cis-polybutadiene and butyl rubber as base polymers. Common classes of fillers and reinforcing agents are compared, particular consideration being given to the hydrophylic calcium silicate and silica fillers, which appear to facilitate leaching of electrolytes when present in sufficient loading. From the combined experience, illustrative water-resistant formulations are derived.

Physico‐mechanical, dynamic mechanical, and swelling properties of sodium chloride filled chlorobutyl vulcanizates

“…The values of CLD thus obtained will give different results partly because of the time scale of the measurements 6. Because of the equilibrium nature of swelling measurements, the value of CLD will have lower contributions from the entanglements, as the time scale of the experiment permits disentanglement of temporary entanglements.…”

“…Bahar et al5 gave a detailed study of the swelling of butadiene elastomers of different crosslink densities with finely divided sodium chloride (NaCl) particles in water, water/acetone, and water/THF mixtures. Briggs et al6 and Edwards7 reported absorption of water by butyl elastomers. They observed that crosslinked butyl elastomers absorbed significant amount of water when small amount of salts were added to the samples during crosslinking.…”

Transport of Water through Polyamide-Nitrile Rubber Blends and its Influence on Mechanical Properties

“…The phenomena of sorption and diffusion in aliphatic polyamides have received considerable attention [1][2][3][4] . Numerous studies have been done on diffusion of water in polymers 5 and the basic mechanism of water absorption in rubber vulcanizates containing hydrophilic impurities is known 6,7 . Studies on moisture sorption and diffusion in crystalline materials, such as aromatic polyamide fibres with rigid and extended chain conformation, are available [8][9][10] .…”

The effects of ionizing radiation on the thermal properties of linear high polymers. Part 5. Ethylene/isotactic propylene block copolymer

“…He reports G values of 2.2 and 4.8 fbr the chain scission and crosslinking processes, respectively. BRIGGS et al 7) have studied the deformation under applied pressure of a number of ethylene/propylene elastomers after irradiation in vacuo. KARPOV and coworkers@ reported an increased crosslinking efficiency when irradiation of ethylene/propylene copolymer is carried out in the presence of nitrous oxide.…”