Mechanical stability of polymers

The most detailed studies of mechanical degradation in rock materials are those of Seright (1980) and Seright et al (1981), which are again further 

Much work has been reported in the polymer science literature on 

For a given fluid shear stress there is a critical molecular weight. Me, below which no mechanical degradation will occur (Harrington and Zimm, 1965 Ram and Kadim, 1970 Abdel-Alim and Hamielec, 1973 Basedow et al, 1979 Agarwal and Porter, 1980). Using a high-shear couette viscometer and a polyacrylamide sample, Abdel-Alim and Hamielec (1973) showed that this Mq is related to shear stress, T, by a relationship of form  

The initial MWD of the polymer is altered to a final MWD showing a higher peak at lower molecular weights (see below) for example see Basedow et al (1979). 

Flow-induced mechanical stress along the polymer molecule is the primary cause of scission (Harrington and Zimm, 1965 Ram and Kadim, 1970 Abdel-Alim and Hamielec, 1973 Basedow et al, 1979). 

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These monomers provide a means for introducing carboxyl groups into copolymers. In copolymers these acids can improve adhesion properties, improve freeze-thaw and mechanical stability of polymer dispersions, provide stability in alkalies (including ammonia), increase resistance to attack by oils, and provide reactive centers for cross-linking by divalent metal ions, diamines, or epoxides. 

Needham D, McIntosh TJ, Lasic DD (1992) Repulsive interactions and mechanical stability of polymer-grafted lipid membranes. Biochim Biophys Acta 1108 40-48... 

The mechanical stability of polymers was related to the polymer s conformation in some of the earlier drag-reduction studies. Above a critical stress, degradation was faster the more contracted and entangled the polymer s conformation (5-7). In petroleum applications the mechanical instability of synthetic relative to carbohydrate polymers was well-recognized. The relative stability problems (possibly related to DUEVs (8)) encountered in the use of high molecular weight hydrolyzed poly(acrylamide) (HPAM) led to the development of an inverse-emulsion polymerization technique (9). (Current research directions using this technique are discussed in Chapter 9.)... 

Imaging plates are exposed similar to radiographic films. They are read out by a LASER-scanner to a digital image without any developing process. After optical erasing of the virtual picture the same IP can be used cyclic up to more than 1000 times. The life time is limited by the mechanical stability of the IP s. An IP consists of a flexible polymer carrier which is coated with the sensitive layer. This layer is covered with a thin transparent protective foil. 

The degradation and stabilization of polymers are very important problems from the scientific and industrial points of view. A better understanding of their mechanism is necessary to achieve better stabilization. A small amount of compounds, called stabilizers, are added into the polymer matrix to retard degradation and to impart... 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

Suspension Model of Interaction of Asphaltene and Oil This model is based upon the concept that asphaltenes exist as particles suspended in oil. Their suspension is assisted by resins (heavy and mostly aromatic molecules) adsorbed to the surface of asphaltenes and keeping them afloat because of the repulsive forces between resin molecules in the solution and the adsorbed resins on the asphaltene surface (see Figure 4). Stability of such a suspension is considered to be a function of the concentration of resins in solution, the fraction of asphaltene surface sites occupied by resin molecules, and the equilibrium conditions between the resins in solution and on the asphaltene surface. Utilization of this model requires the following (12) 1. Resin chemical potential calculation based on the statistical mechanical theory of polymer solutions. 2. Studies regarding resin adsorption on asphaltene particle surface and... 

As a rule, however, most of the ESIPT dyes exhibit weak to very weak fluorescence quantum yields, i.e., the quantum yield of the nonradiative processes is near unity. Such dyes, if they show little permanent photodestruction, can be used as ultraviolet (UV)-stabilizers of polymers, such as Tinuvin (a hydroxy-benzotria-zole),(45) because they efficiently convert UV radiation, harmful for the polymer, into harmless heat. The mechanisms of these nonradiative decay paths are often linked to... 

Lee, L-H. "Mechanism of Thermal Degradation of Phenolic Condensation Polymers" in Proceedings of Battelle Sym., on Thermal Stability of Polymers" Dec. 5,6, 1963. 

The quality of the water used in emulsion polymerization affects the manufacture of ESBR. Water hardness and other ionic content can directly affect the chemical and mechanical stability of the polymer emulsion (latex). Solution polymerization can use various solvents, primarily aliphatic and aromatic hydrocarbons, SSBR polymerization depends on recovery and reuse of the solvent for economical operation as well as operation under the air-quality permitting of the local, state, and federal mandates involved,... 

Molecularly imprinted composite membranes have been developed based on the functionalisation of a commercial membrane with an MIP in order to improve the mechanical stability of the imprinted polymer phase, similarly to the preparation of MIP composite beads, discussed in Sect. 2.2.2. 

Natural polymers like cellulose and amylose comprise the Type IIIA CSPs, but the mechanical stability of these packings is not sufficiently adequate to be used as a chromatographic sorbent. More satisfactory sorbents have been obtained by chemically modifying them as ester or carbamate derivatives and then coating them onto large-pore silica (300 A) [276]. These CSPs are marketed under the trade names ChiralCel (cellulose) and ChiralPak (amylose). These packings have a wide scope of applications, good stability, and use on a preparative scale. 

FIGURE 11.36 (See color insert following page 530.) Mechanism of how crack-free and networked char barrier affects the thermal stability of polymer matrix. (From Gilman, J.F., Flame retardant polymer nanocomposite, http //www.epa.gov/oppt/nano/p2docs/casestudy2 gilman.pdf)... 

Yang, F., Bogdanova, I., and Nelson, G. L. Mechanism study on the flammability and thermal stability of polymer/alumina nanocomposites via extrusion, PMSE Preprints (2008), 98, 319-320. 

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