Combination of polymers

Daylight fluorescent pigments (qv) are considered to be nontoxic. Since they are combinations of polymers and dyestuffs, the combined effect of the ingredients must be taken into account when considering the net toxic effect of these materials. Table 5 gives results of laboratory animal toxicity tests of standard modified melamine—formaldehyde-type pigments, the Day-Glo A Series, and the products recommended for plastic mol ding, Day-Glo Z-series. 

Phosphate—Chelant—Polymer Combinations. Combinations of polymer, phosphate, and chelant are commonly used to produce results comparable to chelant—polymer treatment in boilers operating at 4137 x 10 Pa or less. Boiler cleanliness is improved over phosphate treatment, and the presence of phosphate provides an easy means of testing to confirm the presence of treatment in the boiler water. 

Alloys are combinations of polymers that are mechanically blended. They do not depend on chemical bonds, but do often require special compatibilizers. Plastic alloys are usually designed to retain the best characteristics of each constituent. Most often, property improvements are in such areas... 

Combinations of polymers are widely used as overlays in phosphate or chelant programs, or as the primary ingredients in all-polymer and mixed-organic/inorganic multifunctional program product ranges. These combinations may offer new or additional technical benefits and are marketed as such. 

Thus, confirmation of whether the product obtained in an attempted reaction in a true random copolymer is important to clarify the mechanism of the propagation reaction and to correlate structure and reactivity in ring-opening polymerizations. Considering that apparent copolymers may be formed by reactions other than copdymerization, for example, by ionic grafting or by combination of polymer chains, characterization of cross-sequences appears to be one of the best ways to check the formation of random copolymers. 

In this section, we will review the application of the combination of polymer-supported reagents and/or scavengers with microwave irradiation to the syn-... 

Modem floor finishes contain mixtures of ingredients that when applied as a liquid dry to give a clear, durable film coating. Most floor finishes are combinations of polymers blended to provide unique and desirable characteristics such as durability, gloss retention, resistance to scuffing, fast-drying, and ease of removal. Polymers made up of more than one monomer or repeating unit are called copolymers. 

Stable microcapsules require the combination of polymer solutions containing both flexible and rigid chains. 

As for any chain reaction, radical-addition polymerization consists of three main types of steps initiation, propagation, and termination. Initiation may be achieved by various methods from the monomer thermally or photochemically, or by use of a free-radical initiator, a relatively unstable compound, such as a peroxide, that decomposes thermally to give free radicals (Example 7-4 below). The rate of initiation (rinit) can be determined experimentally by labeling the initiator radioactively or by use of a scavenger to react with the radicals produced by the initiator the rate is then the rate of consumption of the initiator. Propagation differs from previous consideration of linear chains in that there is no recycling of a chain carrier polymers may grow by addition of monomer units in successive steps. Like initiation, termination may occur in various ways combination of polymer radicals, disproportionation of polymer radicals, or radical transfer from polymer to monomer. 

Applications of the combination of polymer-supported triarylphosphines (82) with carbon tetrachloride for the synthesis of peptides76 and acid chlorides,77 involving a simple filtration and evaporation process for product isolation, have been reported. 

Finally, we should mention the phenomenon of incompatibility of mixtures of polymer solutions. It applies to nearly all combinations of polymer solutions when the homogeneous solutions of two different polymers in the same solvent are mixed, phase separation occurs. For example, 10% solutions of polystyrene and poly(vinyl acetate), each in benzene, form two separated phases upon mixing. One phase contains mainly the first polymer, the other phase mainly the second polymer, but in both phases there is a certain amount of the other polymer present. This limited compatibility of polymer mixtures can be explained thermodynamically and depends on various factors, such as the structure of the macromolecule, the molecular weight, the mixing ratio, the overall polymer concentration, and the temperature. 

Static mixers offer an alternative route to enhancing mixture uniformity, through repeated division and combination of polymer passing through a tube containing motionless profiled elements (Fig. 23g). Mixers of this type closely control the applied shear strain developed and are positioned between the extruder and die [96]. 

Combination of Polymers with Other Compatible Soft Polymers... 

General rules for the occurrence of stress corrosion cannot be given, since the phenomenon is very specific for certain combinations of polymer and environment, and is also dependent on the processing conditions in manufacturing the article (such as the occurrence of cooling stresses and orientations). When plastics are used in articles which are subjected to mechanical stress, such as pipes, crates, bottles, screw-caps, etc., the risk of stress corrosion in the presence of fat, soap or organic liquids, should always be taken into account. Proper choice of material and dimensions can minimize the occurrence of crack formation. 

Evidently, the most important application of the solubility parameters to be discussed in this chapter is the prediction of the solubility of polymers in various solvents. A first requirement of mutual solubility is that the solubility parameter of the polymer <5P and that of the solvent <5S do not differ too much. This requirement, however, is not sufficient. There are combinations of polymer and solvent for which solvent for which rip <5S, but yet do... 

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