Stability of polymers

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. 

The thermal stability of polymers of types (1) and (2) is also dependent on the nature of the substituents on phosphoms. Polymers with methoxy and ethoxy substituents undergo skeletal changes and degradation above about 100°C, but aryloxy and fluoroalkoxy substituents provide higher thermal stability (4). Most of the P—N- and P—O-substituted polymers either depolymerize via ring-chain equilibration or undergo cross-linking reactions at temperatures much above 150—175°C. 

Although the primary bonds are important when considering the chemical reactivity and thermal stability of polymers, it is the secondary bonds which are... 

The effect of substitution of labile chlorines by acetoxy groups on the thermal stability of polymer taken in isolation appears to correspond to the thermal degradation behavior of VCA Ac copolymers over the whole composition range [136,137]. 

K. S. Minsker, S. V. Kolesov, and G. E. Zaikov, Degradation and Stabilization of Polymers on the Base of Vinyl-chloride, Pergamon Press, Oxford, p. 526 (1988). 

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... 

UV absorbers have been found to be quite effective for stabilization of polymers and are very much in demand. They function by the absorption and harmless dissipation of the sunlight or UV-rich artificial radiation, which would have otherwise initiated degradation of a polymer material. Meyer and Geurhart reported, for the first time in 1945 [10], the use of UV absorber in a polymer. They found that the outdoor life of cellulose acetate film was greatly prolonged by adding phenyl salicylate (salol) [10]. After that, resorcinol monobenzoate, a much more effective absorber, was introduced in 1951 [11] for stabilization of PP, but salol continued to be the only important commercial stabilizer for several years. The 2,4-dihydroxybenzophenone was marketed in 1953, followed shortly by 2-hydroxy-4-methoxybenzophenone and other derivatives. Of the more commonly known UV absorbers, the 2-hydroxybenzophenones, 2-hy-droxy-phenyl-triazines, derivatives of phenol salicylates, its metal chelates, and hindered amine light stabilizers (HALS) are widely used in the polymer industry. 

Another concern, is the potential reactivity of 10 as a transfer agent under polymerization conditions (see 3.3.1.1.4).103 Tetramethylsuccinonitrile (9) appears to be essentially inert under polymerization conditions. However, the compound is reported to be toxic and may be a problem in polymers used in food contact applications.1" 30 Methacrylonitrile (MAN) formed by disproportionation readily copolymerizes.7"34 The copolymerized MAN may affect the thermal stability of polymers. A suggestion103 that copolymerized MAN may be a "weak link" in PS initiated with AIBN has been disputed.14... 

Such functionality can also be of great practical importance since functional initiators, transfer agents, etc. are applied to prepare end-functional polymers (see Section 7.5) or block or graft copolymers (Section 7.6). In these cases the need to maximize the fraction of chains that contain the reactive or other desired functionality is obvious. However, there are also well-documented cases where weak links formed by initiation, termination, or abnormal propagation processes impair the thermal or photochemical stability of polymers. 

R. T. Conley, Thermal Stability of Polymers, Marcel Dekker, New York, 1970, pp. 459-496. 

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. 

Ranby, B. and Rabek, J., Photo Degradation, Photo Oxidation and Photo Stabilization of Polymers, Wiley, New York, 1975, 75. 

The stability of polymers is advantageous while they are being used, but it becomes a liability when these materials need to be discarded. Up to 15% of the volume of municipal waste dumps is polymeric material. Unlike... 

A. G. Sommese and R. Nagarajan. Settling stabilization of polymer containing particle dispersions in oil. Patent US 5438088, 1995. 

Prediction of Viscoelastic Properties and Shear Stability of Polymers in Solution 17... 

Grest, G.S. Normal and Shear Forces Between Polymer Brushes. Vol. 138, pp. 149-184 Grigorescu, G, Kulicke, W.-M.t Prediction of Viscoelastic Properties and Shear Stability of Polymers in Solution. Vol. 152, p, 1-40. 

Measuring the relative oxidative stability of polymers is important. Measurements can be used to determine dependencies on structural and molecular weight/weight distribution or the effectiveness of an antioxidant, or to perhaps assess the amount present in a polymer sample, etc. The preferred and commonest method consists in raising the sample temperature to a predetermined level, while in an inert atmosphere, then switching the atmosphere to air or oxygen. The time to the onset of exothermic reaction is measured. 

The polymer degradation scheme discussed above and shown in Figure 1 is valid in polymers without any additives. However, most commercially available materials are doped with UV absorbers and with light and thermal stabilizers in order to extend their lifetime. The HAS rank among the most important additives used for light and heat stabilization of polymers [9,15,16]. Most commercially available HAS stabilizers are 4-substituted 2,2,6,6-tetramethylpiperidines, as shown below [17],... 

N.M. Emanuel and A.L. Buchachenko, Chemical Physics of Molecular Destruction and Stabilization of Polymer, VNU Science Press, Utrecht, Netherlands, 1987. 

Preparation and Stability of Polymer-Grafted Silica Dispersions... 

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