The Incompatibility Problem

It should be pointed out that in order to develop superior mechanical properties in a two-component polymer system, the components should not be so incompatible that they do not wet, nor so mutually soluble that they form one homogeneous phase (Tobolsky, 1960, pp. 81-82). Most of the presently important systems are compatible to the extent that a slight (but usually unknown ) degree of mixing takes place, or interfacial bonding is developed directly, as in grafts or blocks. 

The experimental evidence for phase separation in polymer mixtures was briefly developed in the previous section. In the present section a thermodynamic explanation for mutual insolubility, or incompatibility, of polymer pairs will be outlined. 

Dobry and Boyer-Kawenoki (1947) investigated the phase relationships existing in ternary systems polymer (l)-polymer (2)-mutual solvent (3). They prepared dilute solutions of polymers in common solvents, and then mixed the two solutions of interest. All of the polymer pairs studied were found to undergo phase separation at only 5-10% polymer concentration. For instance, cellulose acetate and polystyrene were immiscible at 5% concentration in toluene. These investigators concluded that incompatibility of two polymers even highly diluted is the normal situation. 

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One of the principal factors to be considered is the concentration of pigment m the dispersion concentrate. Compatibility of the carrier (solvent additives, etc) used in the preparation of concentrated dispersion and that used in the finished color product also plays an important role. In some cases this can be difficult because the earners having the best performance, from the standpoint of processing, could be poor in the application systems. However, in the majority of the applications, particularly in coatings and colored plastics, the concentration of the pigment in the finished product is quite low. and the incompatibility problem is easily overcome. 

Demulsifiers and corrosion inhibitors are often the cause of poor dehydration performance. Corrosion inhibitors are surfactant chemicals that often act as emulsifying agents, thus making the demulsifier work harder. In cases of conflict, it is usually easier to blend a new demulsifier or change the injection points of the chemicals than it is to replace the corrosion inhibitor. However, in some North Sea fields the opposite was true. Corrosion inhibitor replacement was the best way to deal with the incompatibility problem. 

Wang and Chen [41] studied the compatibility problems of incompatible NBR-PVC blends. Poly(vinyl-idene chloride-covinyl chloride) is reported to act as an efficient interfacial agent. Blends of PVC, NBR, and the copolymer were prepared by the solution casting technique using THE as a solvent. Improvement in mechanical properties can be achieved in NBR-PVC blend by the addition of different types of rubbers [42]. Different rubbers include NR, styrene butadiene (SBR) and butadiene (BR). Replacement of a few percent of NBR by other rubbers will improve the mechanical properties and at the same time reduce the cost of the blend. 

The different food products discussed below illustrate compatibility/ incompatibility problems and solutions in flexible packaging. 

Seven different LC-MS interfaces are described in Chapter 4, with particular emphasis being placed on their advantages and disadvantages and the ways in which the interface overcomes (or fails to overcome) the incompatibilities of the two techniques. The earlier interfaces are included for historical reasons only as, for example, the moving-belt and direct-liquid-introduction interfaces, are not currently in routine use. The final chapter (Chapter 5) is devoted to a number of illustrative examples of the way in which LC-MS has been used to solve various analytical problems. 

Incompatibility with fluid formulations is one disadvantage of this chemistry, another is its potential to induce skin sensitisation. Benzisothiazolinone, (see Figure 6) is a chemically more stable isothiazolinone. This material can be incorporated into most metalworking fluid concentrates, over coming the stability problems seen with other isothiazolinones. However, this higher stability is reflected in higher in-use levels required to control micro-organisms. Typical in-use levels are between. ... 

Coupling of CE with MS is a difficult task, because of the incompatibility of the EOF (100 500 nl min ) and optimal ESI ionization conditions. Moreover, a stable current for reproducible electrophoretic separations must be ensured. Fortunately, both these problems can be solved by adding make-up solution (10 100 g min ), which also ensures an electric connection between the nebulizer and the tip of a capillary. 

Aqueous two-phase hydrogenation may be a method of choice for synthetic purposes when no incompatibility problems between water and the substrates, products, or catalyst arise. It has already been proven by the success of the Ruhrchemie-Rhone-Poulenc hydroformylation process, that the catalyst can be retained in the aqueous phase with very high efficiency, and that aqueous-organic biphasic processes using organometallic catalysts are suitable for indus-... 

Recently however, it has been recognized that liquid extraction is a potential method in the primary recovery of fermentation cell culture products, such as proteins and amino acids. The separation problem, however, is difficult because the product mixtures are often complex, including cell debris and enzymes. Proteins are not suitable for conventional solvent extraction because of incompatibility with organic solvents, but can be handled in aqueous two-phase systems or by extraction in reverse micellar systems (Chapter 15). 

Reports of incompatibility between Portland cement and chemical admixtures have increased over the past 10 years. Rapid set, accelerated stiffening, increase in time of set, lack of water-reduction are some of the reported problems. Such effects produced by the interaction of the composition of the cement and that of the chemical admixtures has been often referred to as cement-admixture incompatibility . This is discussed below. 

In essence, all of the environmental problems associated with coal mining and the disposal of the lithic wastes to which it gives rise can be attributed to a single cause the incompatibility... 

This approach eliminates the problem of the low solubility of TV-acylaminonitriles in HC1 saturated CH2C12 used in the classical Pinner reaction. Overall yields were greatly improved with more reactions in the 60-70% range. The only limitation of this method is the incompatibility of some N-protecting groups with HF. 

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