Polymer alloys, definition

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). 

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. 

Polymer alloys and blends constitute over 30 wt% of polymer consumption, and with an annual growth rate of about 9.3% that has remained constant for the last ten years (i.e., four times the growth rate of the plastics industry as a whole), their role can only increase. In the text, the following standard definitions will be used [Utracki, 1989 1991 see also Nomenclature in Chapter 1 of this Handbook],... 

Polymer HDT decreases with apphed stress. The major cause of this effect is the decrease of modulus with temperature with the consequent greater deformation at the higher temperature for a given load. HDT occurs, by definition, at a constant deformation. The deformation is proportional to the load and inversely proportional to the modulus. HDT values of some commercial polymer alloys are given in Table 12.30. 

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). 

Several interesting observations relate to such thermodynamic measurements. For example, the exothermic effects, associated with phase separation in LCST-type polymer blends, showed a correlation between the exothermic enthalpy and the interactions between the components (Natansohn 1985) however, the specific interaction parameter xn was not calculated. In another example, there are definitive correlations between the thermodynamic and the transport properties (see Chap. 7, Rheology of Polymer Alloys and Blends ). Thermodynamic properties of multiphase polymeric systems affect the flow, and vice versa. As discussed in Chap. 7, Rheology of Polymer Alloys and Blends , the effects of stress can engender significant shift of the spinodal temperature, AT = 16 °C. While at low stresses the effects can vary, i.e., the miscibility can either increase or decrease. 

Sometimes, in analogous to metal alloys, the term polymer alloy is used. According to the lUPAC recommendation, the term polymer alloy for a polymer blend is discouraged. The term polymer alloy should be used for polymeric materials with macroscopically uniform physical properties in their whole volume. This definition includes compatible polymer blends, miscible polymer blends, or multiphase copolymers. 

From all that was said above, it follows that the polymer alloy is a comph-cated midtiphase system with properties which are determined by the properties of constituent phases. It is very important to note that if, on the macrolevel, the thickness of the interphase regions is low, as compared with the size of the polymer species, for small sizes of the microregions of phase separation such approximation is not vahd. In comparison with the size of the microphase regions, the thickness of the interphase may be of the same order of magnitude. Therefore, they should be taken into accoiuit as an independent quasi-phase in calculation of properties of polymer alloys. We say quasi-phase because these region are not at equilibrium and are formed as a result of the non-equilibrium, incomplete phase separation. The interphase region may be considered as a dissipative structure, formed in the coiu-se of the phase separation. Although it is impossible to locate its position in the space (the result of arbitrary choice of the manner of its definition), its representation as an independent phase is convenient for model calculations (compare the situation with calculations of the properties of filled polymer systems, which takes into account the existence of the surface layer). 

There are few data on rheological properties of melts of filled alloys. It was shown that the main features of the rheological behavior of filled alloy PVA-EVC can be related to the formation of the structural network formed by filler particles. For the production of fdled polymer alloy, it is important to use the effect of substantial decrease of melt viscosity by addition of a small amormt of one component to another. Due to a sharp decrease of viscosity in a definite concentration region, it becomes possible to introduce larger amounts of filler, compared with pure components. 

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). 

Whether there is currently a nanotechnology is a question of definition. If one asks whether there are (or are soon likely to be) commercial electronic fluidic, photonic, or mechanical devices with critical lateral dimensions less than 20 nm, the answer is no, although there may be in 10 to 20 years. There is, however, a range of important technologies—especially involving colloids, emulsions, polymers, ceramic and semiconductor particles, and metallic alloys—that currently exist. But there is no question that the field of nanoscience already exists. 

Corrosion is the deterioration of a material by reaction with its enviromnent. Although the term is used primarily in conjunction with the deterioration of metals, the broader definition allows it to be used in conjunction with all types of materials. We will limit the description to corrosion of metals and alloys for the moment and will save the degradation of other types of materials, such as polymers, for a later section. In this section, we will see how corrosion is perhaps the clearest example of the battle between thermodynamics and kinetics for determining the likelihood of a given reaction occurring within a specified time period. We will also see how important this process is from an industrial standpoint. For example, a 1995 study showed that metallic corrosion costs the U.S. economy about 300 billion each year and that 30% of this cost could be prevented by using modem corrosion control techniques [9], It is important to understand the mechanisms of corrosion before we can attempt to control it. 

Such transformations have been extensively studied in quenched steels, but they can also be found in nonferrous alloys, ceramics, minerals, and polymers. They have been studied mainly for technical reasons, since the transformed material often has useful mechanical properties (hard, stiff, high damping (internal friction), shape memory). Martensitic transformations can occur at rather low temperature ( 100 K) where diffusional jumps of atoms are definitely frozen, but also at much higher temperature. Since they occur without transport of matter, they are not of central interest to solid state kinetics. However, in view of the crystallographic as well as the elastic and even plastic implications, diffusionless transformations may inform us about the principles involved in the structural part of heterogeneous solid state reactions, and for this reason we will discuss them. 

In further quest for development of more efficient materials, clue had been provided by ongoing mixed (interdisciplinary) research. Intelligently the immediate inspiration was drawn from mixed systems (i.e., blends, alloys or composites) based on conventional polymers, metals, and ceramics. Soon it was realized that the already established wide applicability of CPs/ICPs can be further expended by formation of multiscale/multiphase systems, e.g., a wide variety of electronically, electrochemically, and/or optoelec-tronically active blends (BLNs), conjugated copolymers (CCPs) and composites (CMPs) [both bulk or nanocomposites (NCs)] or hybrids (HYBs) [11,14-16,52,109,113,120,128,131,132,191-205]. The next section of the chapter covers the fundamental aspects of CP-based BLNs, CCPs, and NCs/ HYBs. In particular, their definitions (including etymology), types, properties, synthetic routes, and practical applications have been discussed with the help of suitable examples from the open literature. 

The often used FPL etdi of an aluminum-lithium alloy bonded with polysulfone leads to interfacial (at the metal oxide/polymer interface) failure (38) which is a surprisingly uncommon type of failure. The results leading to this assignment are shown as XPS C Is and O Is narrow scan spectra in Figure 15. This definitive assignment of failure mode is based on the fact that one failure surfece has an oi gen photopeak similar to the pretreated adherend before bonding and the other failure surfece has an 0 gen photopeak similar to the adhesive. 

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