The dissolution speed of powders is affected by ionicity, particle size, concentration, water temperature. Polymers mechanical properties pdf 1 approximate range of mechanical properties for various engineering. Created by o kotchawan srimala o supa sunthornvatin o kanokwun meesuntud o varinya panusuvat oxidative degradation occurs when polymer is attacked by atmospheric oxygen. These metrics are regularly updated to reflect usage leading up to the last few days. Polymer degradation is usually evidenced by molecular weight variations as consequence of exposure to high processing temperature and to relevant mechanical stresses. The thermooxidative stability of polymers depends on the cc and ch bond energies. Polymer degradation is a change in the propertiestensile strength, color, shape, etc. Biological degradation of polymers in the environment. Mechanical degradation of filter polymer materials. Mechanical degradation hampers the practical usage of polymers for turbulent. Introduction to materials science, chapter 15, polymer structures university tennessee, dept. High moisture accelerated mechanical behavior degradation of. The breakage of polymer chain induces a significant loss on polymer viscosity. Mechanical degradation of drag reducing polymers in.
Impact of mechanical degradation on polymer injectivity in. Intensity of mechanical action and mechanical degradation. Polymers respond to the energy of motion in two ways. Degradation of drag reducing polymers in suspensions of 25 s. Mechanical degradation of polymer can be described as an irreversible process that leads to the breakage of polymer molecules due to high mechanical stresses induced by high flow velocities or elongational deformations 16,26,27,28. Mechanical degradation of high polymers bueche 1960. A sample of polyisoprene having a narrow molecular weight distribution has been degraded. It assumes the molecules to exist in the rubbery or liquid state and does not include.
Pdf in this work, we present an experimental study of flowinduced degradation of hydrolyzed polyacrylamide in aqueous solutions flowing through. Mechanical properties of polymersstress strain behaviours. Booth a sample of polyisoprene having a narrow molecular weight distribution has been degraded mechanically in several ways and the molecular weight distribu tions of the degradation products have been determined. Effect of combined polymers on the loss of efficiency caused.
In a highpower white light emitting diode led package, the phosphorsilicone composite is typically used for photometric and colorimetric conversions, ultimately producing the white light. Furthermore, mechanical degradation and serial filtration can be used in combination to produce polymer solutions that can be filtered at extremely small pore sizes, down to one tenth of a micrometer in diameter, with surprising retention of viscosity that makes them suitable for chemical eor core floods. Poly ethylene oxide peo, polyacrylamide pam, and xanthan gum xg. White paper characterization of polymers using dynamic. Photodegradation is usually oxidation and hydrolysis. Polymer degradation and stability deals with the degradation reactions and their control which are a major preoccupation of practitioners of the many and diverse aspects of modern polymer technology deteriorative reactions occur during processing, when polymers are subjected to heat, oxygen and mechanical stress, and during the useful life of the materials when oxygen and sunlight are the. Bueche 1961 mechanical degradation of high polymers. Mechanical degradation of drag reducing polymers in suspensions. Mechanical properties of polymers encyclopedia of life. In laminar flow, degradation is independent of tube length, indicating that entrance effects are dominant.
The free radical can, in turn, react and result in. Mechanical degradation of polymers rubber division, acs. In a fuel cell, the mechanical assembly state directly affects the performance of polymer electrolyte membrane fuel cells. Mechanical degradation of high polymers bueche 1960 journal. Degradation of drag reducing polymers in suspensions 601 ethanol and then reconstituted in saline. Polymers present to modern society remarkable performance characteristics desired by a wide range of consumers but the fate of polymers in the environment has become a massive management problem. For such applications a dynamic elastic modulus is more useful to characterizethe performance of the polymerunder an oscillating mechanical load. Autoxidation is initiated by heat, light high energy radiation, mechanical stress, catalyst residues, or reaction with impurities to form alkyl radicals. Mechanical degradation of high polymers wiley online library. A theory for the shear degradation of high polymers is presented.
Mechanicalpropertiesof polymers harvard university. In these circumstances it is difficult to interpret the differences between the original molecular weight distribution and the narrower, but still wide, molecular weight distributions of the products of mechanical degradation. Diffusion, swelling and mechanical properties of polymers janis e. Polymer degradation and stability deals with the degradation reactions and their control which are a major preoccupation of practitioners of the many and diverse aspects of modern polymer technology. The authors have investigated the relation between the degradation of rigid carbonchain polystyrene, polyvinyl acetate, and polymethyl methacrylate polymers with the kinetics of mechanical degradation during vibromilling. While some of the stressstrain curves for polymers might look similar to ones for metals, polymers are mechanically different than metals or ceramics. The polymers in extruder are faced with thermomechanical degradation while with appropriate stability against thermomechanical degradation, the shelf time of the final products increases, and. In this work polymers of very narrow molecular weight distribution, produced via anionic polymerization, have been used and the changes in molecular weight after mechanical degradation have been studied in some detail. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Polymer applications offer molecular structures attractive to product engineers desirous of prolonged lifetime properties. Nov 22, 2016 created by o kotchawan srimala o supa sunthornvatin o kanokwun meesuntud o varinya panusuvat mechanical degradation polymers can be crack in small pieces by external load.
Mar 18, 2016 the mechanical molecular degradation in drag reducing flows is a huge problem in the effort to improve the efficiency of drag reducers, which is clearly increased when a combination of materials is used. It is known that the ethanol insoluble portion of the aloe gel is a polysaccharide consisting of mannans of varying molecular weights, degrees of acetylation and mannoseglucose ratios 8,10,33,43. Other polymers processed by zeus such as peek and ultem also have excellent resistance to thermal degradation because of the strong bonds in their long chain backbone that restrict movement. Polymers free fulltext effects of freezethaw thermal. The mechanical degradation of polymers is typically limited to a single chain scission per triggering chain stretching event, and the loss of stress transfer that results from the scission limits the extent of degradation that can be achieved. The mechanical molecular degradation in drag reducing flows is a huge problem in the effort to improve the efficiency of drag reducers, which is clearly increased when a combination of materials is used.
Abstract a theory for the shear degradation of high polymers is presented. Some of these are discussedherewithinthefollowingsections. Heat thermal degradation oxygen oxidative and thermaloxidative degradation light photodegradation weathering generally uvozone degradation the deterioation due to oxidation and heat is greatly accelerated by stress, and exposure to other reactive compounds like ozone. Dynamic mechanical analysis dma is used to study these responses, called viscoelastic properties, under conditions of low. The main carbonaceous polymers with no heteroatoms are polyolefins, polydienes, and aromatic hydrocarbon polymers typically. In more specialised applications, degradation may be induced by high energy radiation, ozone, atmospheric pollutants, mechanical stress, biological action, hydrolysis and many other influences. It assumes the molecules to exist in the rubbery or liquid state and does not include the effects of chemical reactions which might occur subsequent to chain rupture. Polymer processing often activates material degradation, which affects to some extent the performance or the life cycle of the obtained products. Mechanical degradation describes the breakdown of molecules in the high flow rate region close to a well as a result of high mechanical stresses on the macromolecules.
Internal mechanical stress stress as sources of later mechanical deterioration inititation of or assistants to various chemical attacks contaminants ingredients forms radical which may then attack the polymer additives some undergo radical formation which may then attack polymer. Here, we analyze mixtures of three kinds of watersoluble polymers. Pdf on nov 1, 2011, izzat n slaiman and others published. Thermaloxidative degradation leads to chain scission or cross linking resulting in the loss of mechanical properties. Exposure to ultraviolet uv radiation may cause the significant degradation of many materials. Institute of rubber research, university of akron, akron, ohio. Intensity of mechanical action and mechanical degradation of. They determine the critical value of the intensity necessary for the onset of the degradation process. Mechanical degradation of high polymers rubber division, acs. Mechanisms of environmental degradation in polymers 2. The chemical processes are responsible for the generation of.
Current interpretations for this unexpected phenomenon are based either on geomechanical considerations for unconsolidated sand formations or on polymer mechanical degradation, potentially occurring in the injection facilities and the near wellbore area. Created by o kotchawan srimala o supa sunthornvatin o kanokwun meesuntud o varinya panusuvat mechanical degradation polymers can be crack in small pieces by external load. Mechanical degradation and cross linking of polymers by plastic deformation at high pressure. Pdf mechanical degradation of dilute solutions of high. Photodegradation and photostabilization of polymers. Mastication of natural rubber but if it occurs in service the polymer properties will be adversely affected. Purchase degradation of polymers, volume 14 1st edition. One can infer that moleculars entanglement played the major role in the much. Pdf mechanical degradation of filter polymer materials. Mechanical properties, dynamic mechanical properties, stress, strain, polymer, plastics, elastomers, rubber contents 1. Yielding or excessive plastic deformation failure of polymers in certain applications to carry design loads or occasional accidental overloads may be due to excessive plastic deformation resulting from the inadequate strength properties of the polymer. Apr 22, 2020 the mechanical degradation of polymers is typically limited to a single chain scission per triggering chain stretching event, and the loss of stress transfer that results from the scission limits the extent of degradation that can be achieved. In the same solutions, the viscosities were much closer at high shear rates 10.
Mechanical degradation and cross linking of polymers by plastic deformation at high pressure h. Particularly, the gas diffusion layer repeatedly withstands the complex heat and humidity environmental conditions in which the. Field data from polymer flooding operations sometimes indicate a betterthanexpected polymer injectivity below fracturing pressure. Thermoplastic polymers consist of linear or branched chains and can be amorphous or semicrystalline. The polymers in extruder are faced with thermo mechanical degradation while with appropriate stability against thermo mechanical degradation, the shelf time of the final products increases, and. The stronger the bonds, the slower the oxidation bond cleavage and hydrogen abstraction. Antioxidants to prevent polymer oxidation polymer additives. The mechanical degradation of polymers sciencedirect. Hourston department of materials, loughborough university, uk this article is a revision of the third edition article 18. Study of the behaviour of certain organic polymers under conditions of high pressure and shear stress. Unesco eolss sample chapters materials science and engineering vol.
The mechanical response of thermoplastic polymers is highly. They reduce the intermolecular cohesive forces between the polymer chains, which in turn decreaset g. The effect is to reduce the polymer molecular mass. Introduction to materials science, chapter 15, polymers. Thermal and mechanical degradation during polymer extrusion.
In this paper, the mechanical degradation of a commercial gas diffusion layer subjected to repeated freezethaw thermal cycles is studied. Mechanical degradation an overview sciencedirect topics. The best example for mechanical degradation is during the. Impact of polymer mechanical degradation on shear and. Mechanical degradation the polymer chain is ruptured by mechanical means. Mechanical degradation mechanical degradation describes the breakdown of molecules in the high flow rate region close to a well as a result of high mechanical stresses on the macromolecules. However, the phosphorsilicone composite is always exposed under harsh environments with high temperature, high blue light irradiation and high moisture when the led operates. The grains tend to agglomerate if they are not correctly dispersed. Polyphenylene sulfide article pdf available in polymer degradation and stability 9111. Mechanicalpropertiesof polymers kamyardavoudi october,20 materialsscienceseminar. Technical whitepaper thermal degradation of plastics.
Experimental results on mechanical degradation in capillary tubes of polyisobutylene polymers in dilute solution are described. Some polymers, especially the elastomers, are used in structures for the purpose of isolation and absorption of shock and vibration. Polymer degradation and stability journal elsevier. Often photodegradation is avoided, since it destroys paintings and other artifacts. Polymers can also be classified in terms of their chemical composition. Organic materials react with molecular oxygen in a process called autoxidation.
Deteriorative reactions occur during processing, when polymers are subjected to heat, oxygen and. Polymers usually contain many more than five monomers, and some may contain. This shortterm effect is important only in the reservoir near the wellbore and also in some of the polymer handling equipment, in chokes, and so on. For such failure, the controlling material mechanical property is the elastic modulus. Polymers are sensitive to mechanical degradation agitation. These products spread over damp surface are extremely slippery. Bhowmick encyclopedia of life support systems eolss 9 k g e 3k g. Photodegradation is the alteration of materials by light. Effect of combined polymers on the loss of efficiency. Mechanical degradation involves the degradation of polymers under mechanical stresses. Citations are the number of other articles citing this article, calculated by crossref and updated daily. Tailoring polymer molecular weight distribution to pore.
Four major routes determine the mechanical degradation. Mechanical degradation and cross linking of polymers by. Uv radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. The best example for mechanical degradation is during the processing of polymers. These changes are usually undesirable, such as cracking and chemical disintegration of products or, more rarely, desirable, as in. Impact of mechanical degradation on polymer injectivity. Typically, the term refers to the combined action of sunlight and air. Pdf mechanical degradation of polymers in flows through. These characteristics also figure prominently in the environmental lifetimes. Mechanicallyinduced chemical changes in polymeric materials.
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