History of Polymer Blends

The first polymer blend patent appeared in 1846 in Birmingham, Alabama. A. Parkes blended gutta percha with natural rubber. Soon after the invention of nitrocellulose, blends of nitrocellulose with natural rubber were obtained. The first blend of two synthetic polymers came about in 1928 when polyvinyl chloride was mixed with polyvinyl acetate. By 1993, the polymer blend patent literature reached about 3000 patents a year [1]. 

Blending and mixing are important unit operations in the polymer blend industry. Hancock patented the first internal mixer in 1923. Freyburger in 1876 improved the device to a more efficient counter-rotating twin-shaft machine. The Banbury mixer is a modification of this patent. The Parrel Co. introduced two-roll mills, then the Ram extruder surfaced in 1797. Screw machines that were capable of manufacturing 

Baker [2] patented a twin-sCTew co-rotating device now used for extrusion and other polymer processing operations. Counter-rotating machines came about in 1895 [3]. 

Polymer blends as products have been the result of billions of dollars of research and technology development expenditures. By 1982, the per annum worldwide sales of polyphenylene/polystyrene exceeded US 1 billion. Polyvinyl chloride/ acrylonitrile butadiene styrene (ABS) blends have captured the markets worldwide. Compatibilized nylon/ABS blends appeared on the market and were sold under the name Triax 1000 by Monsanto with step-change improvement in product performance properties. 

Blends often offer better processability by reduction in viscosity. Polymer blends are also inherently recyclable. 

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Some of the important events in the history of polymer blend technology development are in Table 1.1. 

It seems that mixing has been a natural tendency for the human beings from the dawn of civilization. No sooner do two materials become available than someone starts experimenting with them. Blending is a natural way to widen the range of properties. This has been well illustrated by the history of polymer blends. When in 1846 only natural rubber, NR, and gutta percha, GP, were available, these were blended. Once nitrocellulose, NC, was invented, its blend with NR was patented in 1865 — three years before commercialization of NC. Then cellulose acetate, CA, was invented — blends of CA with NC were... 

The history of polymer blend discoveries and developments has been well documented very recently by Utracki [1]. 

Throughout the history of polymer science there have been efforts to improve (increase) the Tg to increase the useful operating temperature range of polymers. The preponderance of the literature has concentrated on mechanically blended polymeric systems with little component interaction on the molecular level. Where epoxy systems are concerned, the incorporation of additives into the systems results in many changes to the morphology and physical behavior of the material formed. 

Mechanical Interlocking of Components. In some instances the polymers in a blend may be prevented from demixing because of numerous mutual entanglements produced by mechanical processing or the polymerization history of the blend. 

The structure and morphology of immiscible blends depends on many factors among which the flow history and the interfacial properties are the most important. At high dilution, and at low flow rates the morphology of polymer blends is controlled by three dimensionless microrheologi-cal parameters (i) the viscosity ratio, where r j is the viscosity of the dispersed liquid and r 2 that of the matrix (ii) the capillarity number, k = d / Vj2, where d... 

The majority of polymer blends containing elastomeric, thermoplastic, and/or liquid crystalline polymers are processed by melt extrusion at some point in their history. After melt extrusion with intensive mixing, the morphology of an immiscible polymer blend on a microscopic scale will often consist of a dispersed phase of the more viscous polymer in a continuous matrix of the less viscous polymer (depending upon the relative amounts and viscosities of the two polymers in the blend). A good analogy from every-day experience is a dispersed mixture of viscous oil in an immiscible water matrix. 

Improving the recyclability and reprocessability aspects of polymer blends, particularly with respect to the retention of properties after multiple processing histories, to increase the efficiency of regrind use. 

It is noted that the specific phase morphology of the injected molded tensile specimens used in the present study may differ from the compression molded film morphology. In the case of extruded samples of polymer blends displaying macrophase separation. Van Oene (25) indicates that the dispersed phase may appear as either ribbons (stratification) or droplets independent of shear strain rate but dependent of the post-extrusion thermal history. A study of the effect of morphology and phase inversion on the mechanical properties of the incompatible PPO blends is presently in progress. 

The thermal history has a profound influence on the DSC curves of polymer blends containing at least one crystalline component. In order to obtain by DSC experiments, the samples are usually first heated to a temperature between the phase separation temperature and the melting point of the crystalline component and held for several minutes to remove the thermal history. 

Even at the end of mixing, the system is not uniform and consists of parts having different viscoelastic history. The model described here represents only macroscopic changes. Microscopic change such as growth of bound rubber must be accommodated later. This type of phase-modelling is in progress in the field of polymer blends and a similar approach may be adopted here. 

For shape memory applications, crystals formed upon cooling of the semicrystalline polymer act as physical crosslinks by which a permanent or equilibrium shape can be set. In a complementary fashion, the miscible amorphous phase governs temporary shape fixing. In turn, crystallization kinetics, crystallite size, and degree of crystallinity collectively determine kinetics of permanent shape setting and shape memory performance characteristics. Thus, it is possible to tailor the shape memory properties of a system by varying the composition and the thermal history of such blends[9], leading us to the present study focused on crystallization kinetics from melt-miscible crystalline-amorphous blends. 

Lipson (1943, 1944), who had examined a copper-nickeMron ternary alloy. A few years ago, on an occasion in honour of Mats Hillert, Cahn (1991) mapped out in masterly fashion the history of the spinodal concept and its establishment as a widespread alternative mechanism to classical nucleation in phase transformations, specially of the solid-solid variety. An excellent, up-to-date account of the present status of the theory of spinodal decomposition and its relation to experiment and to other branches of physics is by Binder (1991). The Hillert/Cahn/Hilliard theory has also proved particularly useful to modern polymer physicists concerned with structure control in polymer blends, since that theory was first applied to these materials in 1979 (see outline by Kyu 1993). 

Electron microscopy, 16 464, 487-495 history of, 16 487-488 in polymer blend morphology determination, 20 339-340 of PVC particles, 25 658-659 of silica, 22 371-372 in surface and interface imaging, 24 75-80... 

A second approach to biodegradable packaging is to blend polyethylene with a second synthetic polymer with polar repeating units that are capable of degradation, such as ester linkages (chapter 12). Poly(caprolactone) represents such a class of polymer, which has a long history of compatibility ( with a variety of polymers and degradability (5) recently, improved miscibility and Glm properties have been reported when poly(caprolactone) is blended with commodity plastics... 

L.A. Utracki, History of commercial polymer alloys and blends (from a perspective of the patent literature), Polymer Engineering Science, 35(1) 2-17, January 1995. 

Polymer Age, 46 Polymer blends, 71, 98 Polymer Chemistry Innovations, Inc., 189 Polymer cycle, 178-179, 179 Polymer science future of, 203-219 history of, 45-79 relationships of, xxiv... 

Similar heat treatment of the blends also yielded multiple melting peaks (Table II). Because the specific heats of blends are influenced by the thermal histories of the samples, only two mixtures containing 40 and 60% terpolymer, respectively, were selected for quantitative Cp measurements. Each sample experienced the same thermal history as the two component polymers, namely, cooling at 40°C/min from 140° to — 90°C. The Cp curves of the two mixtures are also shown in Figure 9. In the liquid state, the Cp of the blend was found to be the weight average of... 

The direct measurement of the heats of mixing of two polymers is not possible. Several authors have attempted to measure the heats of mixing in the presence of a solvent, using Hess s law to extract the heat of mixing of the polymers In order to do this one needs to measure the heats of dissolution of the base polymers and of the blend in a common solvent. Some workers have said that this technique should be confined to rubber samples since glasses are not at equilibrium and results depend on the history of the glassy samples In principle this is a very attractive... 

In the following sections, the ceramization process of polymethylsilane (PMS) and polyvinylsilane (PVS) is described from the viewpoint of the thermal history of the starting polymers and spectroscopic analysis. After these descriptions, simple applications of these polymers for SiC ceramic hbers via the polymer blend technique are discussed. The major modihcation of PCS with PMS or PVS is carried out not in an atomic scale, but sufficiently homogeneous in a polymer chain scale. 

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