Polymeric materials/polymers glassy

The potential application of organic and polymeric materials, especially glassy polymers, is promising as evidenced by the pertinent material properties. A model nonlinear optical glassy polymer system, combining the large nonlinear susceptibilities of the dopant and favorable optical properties of the host polymer glass, was fabricated and evaluated. The nonlinear optical... 

Fig. 19. Generalized modulus—temperature curves for polymeric materials showing the high modulus glassy state, glass-transition regions for cured and uncured polymers, plateau regions for cross-linked polymers, and the dropoff in modulus for a linear polymer.

Thus, the possibility to regulate effectively the orientation of polymer side groups by varying the parameters of the electric field, together with the possibility to fix the oriented structure in a glassy state enables the use of such LC systems for making polymeric materials with required optical properties. 

The density or its reciprocal, the specific volume, is a commonly used property for polymeric materials. The specific volume is often plotted as a function of pressure and temperature in what is known as a pvT diagram. A typical pvT diagram for an unfilled and filled amorphous polymer is shown, using polycarbonate as an example, in Figs. 2.10 and 2.11 The two slopes in the curves represent the specific volume of the melt and of the glassy amorphous polycarbonate, separated by the glass transition temperature. 

Haward RN, "The Nature of the Glassy State in Polymers", in Ledwith A and North AN (Eds), "Molecular behaviour and development of polymeric materials, pp 404—459, Chapman and Hill, London, 1975. 

Einhorn IN, "Fire Retardance of Polymeric Materials", J Macromol Sd, Revs Polymer Technol D1 (2) (1971) 113-184. Haward RN (Ed), "The Physics of Glassy Polymers", Applied Science Publishers, London 1973. 

Thermosets are polymeric materials which when heated form permanent network structures via the formation of intermolecular crosslinks. Whether the final product has a glass transition temperature, Tg, above or below room temperature, and therefore normally exists as an elastomer or a glass, it is, strictly speaking, a thermo-set. In practice, however, thermosets are identified as highly crosslinked polymers that are glassy and brittle at room temperature. These materials typically exhibit high moduli, near linear elastic stress-strain behavior, and poor resistance to fracture. 

Among the various applications of SFM in polymer science, the imaging of heterogeneous synthetic polymeric materials (blends, copolymers, hybrid materials, etc.) is probably most widespread and can be considered the easiest task, in particular when the materials are (at least partly) glassy at the imaging... 

While restricted here to glassy polymers, such configuration test may be extended to other polymeric materials such as polymer blends and could help in determining the mechanism involved before unstable crack propagation. 

The successful co-polymerization of ethylene with styrene is another polymeric material conquest of homogeneous catalysis. At low styrene incorporation, the co-polymer is substantially a functionalized crystalline polyethylene. Increasing the styrene content results in a decrease of crystallinity while elastomeric properties arise, 3 up to about 80 mol% styrene for higher styrene contents, the co-polymer becomes a glassy amorphous material. A comprehensive review on the properties of ethylene/styrene co-polymers is available.624... 

Plasticization of glassy polymers induced by CO2 plays an important role in the process of foaming of glassy polymers. The preparation of polymeric foams is aimed at the production of microcellular polymers that have closed cells about 10 pm or less in diameter and cell density of about 10 cells/cm. Such foamed polymeric materials have applications in many areas including biomedical devices. Pioneering work by Skripov and coworkers (54,55) stimulated the original interest in this field. 

For example, Song et al [209] described three methods for predicting the long-term mechanical behavior and lifetime of polymeric materials based on the detailed analysis and interpretation of experimental data. They used semicrystalline, glassy amorphous and rubbery polymers as examples in validating these methods. The three methods are the following ... 

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