Polymeric materials, influence

Owing to their versatility and wide range of applications, polymeric materials are of great commercial importance. The physical and chemical properties of polymeric materials influence their processing and use, so familiarity with the properties and behavior is not only interesting but also crucial to ensure proper utilization of such polymers. 

In the last three chapters we have examined the mechanical properties of bulk polymers. Although the structure of individual molecules has not been our primary concern, we have sought to understand the influence of molecular properties on the mechanical behavior of polymeric materials. We have seen, for example, how the viscosity of a liquid polymer depends on the substituents along the chain backbone, how the elasticity depends on crosslinking, and how the crystallinity depends on the stereoregularity of the polymer. In the preceding chapters we took the existence of these polymers for granted and focused attention on their bulk behavior. In the next three chapters these priorities are reversed Our main concern is some of the reactions which produce polymers and the structures of the products formed. 

After a temptative structure-based classification of different kinds of polymorphism, a description of possible crystallization and interconversion conditions is presented. The influence on the polymorphic behavior of comonomeric units and of a second polymeric component in miscible blends is described for some polymer systems. It is also shown that other characterization techniques, besides diffraction techniques, can be useful in the study of polymorphism in polymers. Finally, some effects of polymorphism on the properties of polymeric materials are discussed. 

In this article some literature studies together with studies conducted recently in our laboratories on the crystalline and molecular structure of polymorphic polymers are reviewed, also with the aim of showing possible influences of the polymorphism on the properties and, as a consequence, on the applications of polymeric materials. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

These three factors influence the ability of the polymer to crystallise, the melting point of any resulting crystalline regions, and also the glass transition temperature. It is the last of these features of polymeric materials which we will concentrate on for the rest of this chapter. 

The influence of metal species like copper has been investigated on the product pattern and yield of PBDD/F (Fig. 7) (ref. 11). This study is relevant to accidental fires of polymeric materials of electronic devices which are associated with various metals like copper. As a result of the presence of the metal species substantial amounts of both PBDF and PBDD are formed. 

Cross-linking of polymers is done routinely by radiation technology. The factors influencing the cross-linking or the efficiency of cross-linking of polymeric materials are ... 

It was discovered that viscosifying the acid showed a remarkable improvement in acid fluid loss control. The enhancement was most pronounced in very-low-permeability limestone cores. The nature of the viscosifying agent also influenced the success. Polymeric materials were more effective than surfactant-type viscosifiers [682]. 

It is of course important to note that the overall rate of crystallization is not only determined by the growth rate of the spherulites, but also by the amount of nuclei being present in the system. This possibility is used as an effective method to influence the total crystallization rate of commercial polymeric materials in a controlled manner and to influence the size of spherulites and thus the physical properties of finished articles made from semicrystalline polymers. 

Polymeric materials are widely used to control the corrosion of metals, both to maintain appearance and to prevent loss of structural integrity. In this chapter, the fundamentals of metallic corrosion are briefly reviewed. Methods of studying corrosion, and of evaluating the performance of polymeric materials used in corrosion protection, are outlined. Factors that influence the corrosion protective perfoi iance of polymeric materials are discussed, and some of the research needs and important unsolved problems are highlighted. 

FIGURE 18.1 Relationships, which influence the important interrelationships that exist for polymeric materials with respect to processing and end-product properties. 

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