Utility of Polymer Blends

There are many factors that affect the drug release from inert matrices such as concentration and solubihty of the drug, type of polymer, utilization of polymer blends, particle size of the drug and polymer and hydrophobia of the other excipients that can be employed (fillers, lubricants, binders, etc.). 

Influence of the Utilization of Polymer Blends on Critical Points... 

Solubility differences among components of polymer blends can be utilized in different ways to identify the polymer blends. 

Note 1 The Flory-Huggins theory has often been found to have utility for polymer blends, however, there are many equation-of-state theories that provide more accurate descriptions of polymer-polymer interactions. 

Although the concept of polymer blends is sometimes a route for avoiding the development of new polymers, it often has been an integral part of the utilization of new polymer chemistry, eg, the commercial success of PPO hinged on the advantages of its blends with PS. 

Of course, nanocomposites are not the only area where mesoscale theories are being used to predict nanostructure and morphology. Other applications include—but are not limited to—block copolymer-based materials, surfactant and lipid liquid crystalline phases, micro-encapsulation of drugs and other actives, and phase behavior of polymer blends and solutions. In all these areas, mesoscale models are utilized to describe—qualitatively and often semi-quantitatively—how the structure of each component and the overall formulation influence the formation of the nanoscale morphology. 

Hame resistance has become a legal requirement for commercial utilization of polymers and their blends in many apphcations. Innumerable test methods for flammabUity have been developed in different countries and several books and handbooks are exclusively dealing with this subject. Discussion of the test methods that are en vogue in various countries is beyond the scope of this chapter, thus only the most popular test methods are discussed. The fire retardant chemicals and their suppliers are tabulated in Appendix 1. 

Poly(aryl ketones) (PEEK, PEK, and PEKK) are commercial high temperature polymers offering an excellent combination of properties combined with thermoplastic behavior. Poly(aryl ether ketone) PAEK blends have been reviewed by Harris and Robeson [1989]. Miscibility with PEI (Ultem 1000 GE) and other PI containing isopropylidene bridging units was noted. Arzak et al. [1997] reviewed the performance ofPEEK/PEI blends and noted a synergistic behavior in ductility and impact strength as reported earlier. Utility of these blends as a thermoplastic matrix candidate for advanced composites has been proposed [Harris and Robeson, 1989 Davis et al., 1992]. 

For those cases with weak to moderate specific interactions, a guide for assessing the miscibility and phase behavior of polymer blends is also presented based on classical thermodynamics utilizing a method of balancing the specific interactions and the negative dispersive forces [Coleman et al., 1990, 1991]. This approach successfully predicts the window of miscibility of copolymers with... 

T uminescence emission from irradiated materials has been known for many years. The phenomenon has been studied primarily on inorganic systems but also with polymers. A review of this work has been published by Partridge (i). A clearer understanding of the processes involved has led in more recent years to the use of this technique as a tool to probe the structure of heterogeneous polymer systems (2,3). This chapter describes the technique and shows its utility for the analysis of polymer blends and block copolymers. 

Though miscibility is by no means a prerequisite to commercial utility, homogeneous polymer blends are more convenient from the standpoint of being able to predict properties or processing characteristics. 

A powerful method of examining the morphology of many multicomponent polymer materials utilizes transmission electron microscopy (Woodward 1989). If the two phases are nearly equal in electron density, staining with osmium tetroxide or other agents can be used. For more detailed discussion on the methods of morphology characterization, see Chap. 8, Morphology of Polymer Blends. ... 

This chapter presents an overview of properties and performance of polymer blends. It is structured into nine sections dealing with aspects required for assessing the performance of a polymer blend. These are mechanical properties comprising of both low-speed and high-speed popularly studied properties chemical and solvent effects thermal and thermodynamic properties flammability electrical, optical, and sound transmission properties and some special test methods which assumed prominence recently because of their utility. 

Besides mechanical performance, the introduction of nanoclay to the proper location and with the proper phase morphology can also be utilized to enhance the permeation properties of polymer blends in barrier film applications. The high aspect ratio and platelike shape of impermeable montmorillonite inclusions allow them to disrupt the diffusion of permeants through a polymer, thereby increasing the tortuosity of the path through the film and reducing its permeability. The component polymers comprising blends are often selected for reasons other than... 

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