Degradation foams

Operating problems Solution degradation, foaming, corrosion Column instability, erosion, corrosion Absorption of heavy hydrocarbons... 

Operating problems Solution degradation foaming Column instability erosion Absorption of heavy... 

Biby G, Hanna M A, Fang Q (2001), Water-resistant degradable foam and method of making the same , US Patent 6 184 261. 

Finishes Thermal insulations require an external covering (finish) to provide protection against entry of water or process fluids, mechanical damage, and ultraviolet degradation of foamed materials. In some cases the finish can reduce the flame-spread rating and/or provide fire protection. 

Foam Breaking It is usually desirable to collapse the overflowing foam. This can be accomphshed by chemical means (Bikerman, op. cit.) if external reflux is not employed or by thermal means [Kishi-moto, Kolloid Z., 192, 66 (1963)] if degradation of the overhead product is not a fac tor. 

FRISCH, K. c., and saunders, j. h. (Eds.), Plastic Foams Part I, Dekker, New York (1972) GEUSKENS, G. (Ed.), Degradation and Stabilisation of Polymers, Applied Science, London (1975) HAWKINS, E. L. (Ed.), Polymer Stabilisation, Wiley-Interscience, New York (1972)... 

The most common catalyst used in urethane adhesives is a tin(lV) salt, dibutyltin dilaurate. Tin(IV) salts are known to catalyze degradation reactions at high temperatures [30J. Tin(II) salts, such as stannous octoate, are excellent urethane catalysts but can hydrolyze easily in the presence of water and deactivate. More recently, bismuth carboxylates, such as bismuth neodecanoate, have been found to be active urethane catalysts with good selectivity toward the hydroxyl/isocyanate reaction, as opposed to catalyzing the water/isocyanate reaction, which, in turn, could cause foaming in an adhesive bond line [31]. 

MEA systems foam rather easily resulting in excessive amine can y over from the absorber. Foaming can be caused by a number of foreign materials such as condensed hydrocarbons, degradation products, solids such as carbon or iron sulfide, excess corrosion inhibitor, valve grease, etc. Solids can be removed with cartridge filters. Hydrocarbon liquids aie usually removed in the flash tank. Degradation products are removed in a reclaimer as previously described. 

Polyurethane materials are extremely versatile in that it is possible to produce a large variety of structures which range in properties from linear and flexible to crosslinked and rigid. The crosslinked PURs are thermosets, which are insoluble and infusible and therefore cannot be reprocessed by extrusion without suffering extensive thermal degradation. At present, the main sources of recyclable waste are flexible PUR foams and automobile waste. Waste and scraps of these materials may consist of 15-25% by weight of total PUR foam production. 

Good thermal stability is a requirement for surfactants used in processes to enhance oil recovery. This applies most particularly to steam foam applications where surfactants such as AOS may be exposed to temperatures far above 100°C albeit for short times. Many authors have approached the problem of the thermal stability of a surfactant through a determination of the activation energy of the thermal degradation process. Once the activation energy is known, it can be used to estimate the rate of thermal degradation under various conditions. 

The effect of oxidative irradiation on mechanical properties on the foams of E-plastomers has been investigated. In this study, stress relaxation and dynamic rheological experiments are used to probe the effects of oxidative irradiation on the stmcture and final properties of these polymeric foams. Experiments conducted on irradiated E-plastomer (octene comonomer) foams of two different densities reveal significantly different behavior. Gamma irradiation of the lighter foam causes stmctural degradation due to chain scission reactions. This is manifested in faster stress-relaxation rates and lower values of elastic modulus and gel fraction in the irradiated samples. The incorporation of O2 into the polymer backbone, verified by IR analysis, conftrms the hypothesis of... 

Saad B, CiardeUi G, Matter S, Welti M, Uhlschmid GK, Neuenschwander P, and Suter UW. Degradable and highly porous polyestherurethane foam as biomaterial Effects and phagocytosis of degradation products in osteoblasts. J Biomed Mater Res, 1998, 39, 594—602. 

Over the last few decades, the use of radiation sources for industrial applications has been widespread. The areas of radiation applications are as follows (i) Wires and cables (ii) heat shrinkable tubes and films (iii) polymeric foam (iv) coating on wooden panels (v) coating on thin film-video/audio tapes (vi) printing and lithography (vii) degradation of polymers (viii) irradiation of diamonds (ix) vulcanization of mbber and rubber latex (x) grain irradiation. 

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