Explosive decompression effect

Table 5.2 [5] shows the effects of four important filler variables on the physical properties of a sealing compound, those being quantity, surface area, structure and surface reactivity. The resistance to blistering, or explosive decompression, is found to increase with an increase of all the four variables. Table 5.2 shows how these properties change as each of these variables increases. It should be studied in conjunction with Figure 5.1, from which the specific properties can be optimized. Since each of these variables can affect properties differently, and cross-link density of the compound will have yet another effect, (shown Figure 5.1), the choice of properties to be optimized should be selected very carefully, and should be limited. 

Explosive decompression High-pressure extrusion Effect of corrosion inhibitors Effect of hydrogen sulphide Steam/add resistance Methanol resistance... 

The effects of stresses and associated strains on O-rings used in sealing pressurised fluids are discussed. Results are presented of studies of ageing and property changes of stressed and unstressed elastomers exposed to a hot aqueous solution of ethylene diamine, transient effects of temperature on sealing force, and the influence of memory effects on gas induced fracture by explosive decompression. Materials examined included fluoroelastomers, nitrile mbber and hydrogenated nitrile rubber. 7 refs. 

Hydrogenated nitrile mbbers were evaluated for use in seals and hoses for automotive air conditioning systems. Studies were made of the resistance of these materials to hydrofluorocarbon refrigerants and polyalkylene glycol and mineral oil based lubricants, and permeation resistance, explosive decompression and low temperature performance characteristics were investigated. Designed experiments were undertaken to study the effect of compounding techniques on permeation and explosive decompression. 4 refs. 

Two demanding environments are considered explosive decompression and hydrogen sulphide exposure. A brief review of previous data is given for the former, comparing different polymer types. An attempt is also made to establish a compounding baseline to optimise HNBR performance by examining formulation variables and their effects. For the latter, a comparison of HNBR with NBR, FKM fluoroelastomer and TFE/P is made, as well as a brief look at the effect of ACN (acrylonitrile) content on performance. 4 refs. CANADA... 

Experimentation at temps, up to 130C and pressures up to 700 atmospheres was carried out to assess the explosive decompression performance of a number of elastomeric compounds. Permeation measurements showed that permeation rate decreased from proportionality against pressure at high pressures, and at 700 atm. and 27C for carbon dioxide (now a liquid) permeation apparently was effectively halted reasons suggested include the forced close packing of molecular chains and the dependency of D on concentration. These observations are discussed together with aspects of nucleation, bubble growth and elastomer fracture an optimised balance of properties related to these factors is presumably necessary for an elastomer to withstand explosive decompression. 10 refs. UK... 

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