Polymer blend definition

A polymer blend is a physical or mechanical blend (alloy) of two or more homopolymers or copolymers. Although a polymer blend is not a copolymer according to the above definition, it is mentioned here because of its commercial importance and the frequency with which blends are compared with chemically bonded copolymers. Another technologically significant material relative to the copolymer is the composite, a physical or mechanical combination of a polymer with some unlike material, eg, reinforcing materials such as carbon black, graphite fiber, and glass (see Composite materials). 

Definitions of terms related to polymer blends, composites, and multiphase polymeric materials (lUPAC Recommendations 2004), Pure Appl. Chem. 76, 1985-2007 (2004). Reprinted as Chapter 9, this edition. 

Definitions of terms related to polymer blends, composites, and multiphase polymeric materials... 

Note 5 The use of the term "polymer alloy for polymer blend is discouraged, as the former term includes multiphase copolymers but excludes incompatible polymer blends (see Definition 1.3). 

Note 1 The definition and the name of the term have been modified from that which appears in ref. [5] to reflect its broader use in the context of polymer blends. In its simplest form, the %. parameter is defined according to the Flory-Huggins equation for binary mixtures... 

Definitions of Terms Related to Polymer Blends, Composites, and Multiphase Polymeric Materials (2004), 186... 

This article reviews the phase behavior of polymer blends with special emphasis on blends of random copolymers. Thermodynamic issues are considered and then experimental results on miscibility and phase separation are summarized. Section 3 deals with characteristic features of both the liquid-liquid phase separation process and the reverse phenomenon of phase dissolution in blends. This also involves morphology control by definite phase decomposition. In Sect. 4 attention will be focused on flow-induced phase changes in polymer blends. Experimental results and theoretical approaches are outlined. 

There is some confusion in the literature regarding polymer blend nomenclature. Here the following definitions are assigned to the commonly used terms ... 

As defined in Appendix 5 compatibilization means A process of modification of interfacial properties of an immiscible polymer blend, leading to creation of polymer alloy . A polymer alloy in turn is defined as An immiscible polymer blend having a modified interface and/or morphology , whereas a polymer blend is simply A mixture of at least two polymers or copolymers . In other words, all polymer alloys are blends, but not all polymer blends are alloys. A somewhat more elaborate definition of a polymer alloy would describe a blend of at least two immiscible polymers stabilized either by covalent bond or ionic bond formation between phases, or by attractive intermolecular interaction, e.g., dipole-dipole, ion-dipole, charge-transfer, H-bonding, van der Waals forces, etc. 

By definition, miscible polymer blends are singlephase mixtures. Miscibility depends on the molecular weight, concentration, temperature, pressure, deformation rate, etc. Flow of these systems can be compared to that of solutions of low molecular weight, miscible components, or to flow of mixtures of polymeric fractions. Both models are far from perfect, but they serve to illustrate the basic behavior of miscible systems. 

As discussed in Chapter 2 of this Handbook, by definition, the miscible polymer blend is characterized by negative value of the free energy of mixing, AG = < 0, and positive value of... 

By definition, polymer blends are mixtures of at least two macromolecular species, polymers and/or copolymers. For this reason any mixture of polymers should be treated as a blend. Most blends of chemically different polymers are immiscible. However, it has been documented that blends of chemically identical polymers (viz. LLDPE s) can also be immiscible when their macromolecules sufficiently differ in chain configuration. The polymer/polymer miscibility is limited to mixtures of homologous fractions, rare cases of polymeric pairs with strong specific interactions, or systems with the so-called miscibility... 

The concept of physically blending two or more existing polymers or copolymers to obtain new products or for problem solving is now attracting widespread interest and commercial utilization [61-65]. By definition, any physical mixture of two or more different polymers or copolymers that are not linked by covalent bonds is a polymer blend or polyblend. 

To make an analogy with metals polymer blends are sometimes referred to as polymer alloys. Thus the term alloy has been used to describe miscible or immiscible mixtures of polymers that are usually blended as melts. Another definition often used for a polymer alloy is that it is an immiscible PB having a modified interface and/or morphology. The general relationship between blends and alloys is shown in Figure 4.39. The term compatibilization in the figure refers to a process of modification of interfadal properties (discussed later) of an immiscible PB, leading to the creation of a polymer alloy. 

During the last years, a number of products consisting of a mixture of different plastics have made their appearance they are usually called polymer blends or polymer alloys. Their identification using simple methods presents considerable difficulties because flame tests and pyrolysis tests are usually not unambiguous. Also a separation into different groups according to the pH-value of the pyrolysates does not permit a definite conclusion. In some cases, however, it is possible to separate polymer mixtures into their components if these have different solubility characteristics and then to identify the components (see Section 6.3). 

The industrial practice of introducing new polymer compositions, which is dictated by market requirements, initially overtook the state of knowledge concerning multicomponent polymer blends, but the intensive investigations carried out during the past twenty years led to the formulation of some definitions and scientific... 

From this preliminary definition, we can conclude that, by taking advantage of this spontaneous phenomenon and considering the aspects that rule the migration of a particular component in a polymer blend we will be able to vary the surface behavior. In the next paragraphs of this chapter we illustrate how this phenomenon has been employed both to modify the chemical composition of the polymer surface and to produce nanostructured interfaces. Moreover, the adaptive/responsive behavior of the polymer blend surfaces as a function among others of the environment, temperature or pH will be also described. But first of aU we have to review the various parameters that require a consideration in order to obtain functional surfaces by segregation. 

Compatibility in the polymer blends is defined by either miscibility on the molecular scale or absence of gross symptoms of phase separation. This definition is phenomenological and empirical but no unanimous theoretical scheme for predicting compatibility has been established. Thermodynamics predicts that exothermic mixtures satisfying Equation 5 would spontaneously mix,... 

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