Selectivity of resins

The affinity between a resin and an exchangeable ion is a function both of the resin and the ion. Ion exchange is an equilibrium process which for a cationic process can be represented by the equation 

To illustrate how different cations may be separated let us consider a column which is packed with a cation exchanger in the hydrogen form. As a solution containing M ions flows through the column the M ions will replace H ions on the resin according to the value of K. If only a small amount of the solution is used and it is washed down the column with pure water, all the M ions will eventually replace hydrogen ions, and will form a stationary adsorbed band. The distribution of the ions within this band will depend on the value of if large, the band will be narrow and concentrated if small, wide and diffuse. Thus, if a few ml of 0.1 moldm sodium chloride are placed on a column which is then washed with distilled water, the sodium ions will remain in a more or less narrow band near the top of the column and an equivalent amount of hydrochloric acid will be liberated to be eluted from the column. 

In order to make the adsorbed band of ions (M ) move down the column, water is ineffective and it is obviously necessary to elute with a solution of an acid (or a solution containing another cation), so that exchange can take place. The ions will then be washed out of the column, leaving it in its original form. The rate at which the band of ions moves will depend on the pH of the eluting acid and the value of K. Thus, two ions having different affinities for the resin will move at different rates down the column and a separation will be achieved. 

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Application. From a formulation point of view, the key application parameter is rheology, which can be adjusted by the selection of resins and reactive diluents and their levels. EB curable formulations are available covering a range of 10 to 50,000 centipoise or higher. 

Fabricators will use t]Q as a metric of melt strength for creeping flows. For example, selection of resins with higher values of tj0 should minimize sag in thermoformed parts, and allow a more uniform part wall thickness. Similarly, t and n are metrics of the onset and rate of shear thinning. They are used to identify low-f/(y) conditions (easy flow) in an extruder, which are often critical to fast part fabrication rates. 

Table 3 Selectivity of resin with 2%, 4% and 8% ciosslinking at an individual sugar concentration of200 g/1.

Ion exchange resins display preference for certain ions over others and this characteristic is extremely critical during the choice of a resin for a particular application scenario. The fundamentals of ion exchange equilibria and selectivity are explained in the entry on Ion Exchange. This subject has been studied extensively by many researchers.The following empirical rules can be used to approximate selectivities of resins. 

The selectivity of resins in the hydrogen ion or hydroxide ion form, however, depends on the strength of the acid or base formed between the functional group and the ion. The stronger the acid or base formed, the lower is the selectivity coefficient. It should be noted that these series are not followed in nonaqueous solutions, at high solute concentrations or at high temperature. 

Epoxy resins have found a broad range of applications, mainly because the proper selection of resin, modifiers, and cross-linking agent allows the properties of the cured epoxy resin to be tailored to achieve specific performance characteristics. This versatility has been a major factor in the steady growth rate of epoxy resins over the years. 

Selection of resin depends on the desired properties of the PTFE part in the application and the... 

It was by now mid-1996, a time of great excitement in the area of solid phase synthesis. A flurry of papers touted ever more diverse application the new methodology, and a large selection of resins was becoming commercially available. Inspired by all this ferment, we surmised that if amine 49 were to be anchored to a resin prior to C-deallylation, all traces of palladium and other reaction debris may be completely removed simply by repeated washings. Subsequent coupling with 126, deallylation and formation of an active ester could all be conducted on solid support. Release from the resin would then produce an activated peptide that might cyclodimerize spontaneously. 

Epoxy resins have found a wide range of applications and a steady rate of growth over the years mainly because of their versatility. Properties of the cured products can be tailored by proper selection of resin, modifier, cross-linking agent, and the curing schedule. 

Kennedy AS, Dezarn WA, McNeillie P et al (2006) Dose selection of resin 9 Y-microspheres for liver brachytherapy a single center review. Brachytherapy 5 104... 

The poor external surface can be smoothed somewhat by the proper selection of resin and fiber, the use of a surfacing mat, the use of filled smoothing compounds at some weight penalty, or by compaction and cure in a female die mold using vacuum bag or autoclave pressure. 

Pedruzzi I, Silva EAB, Rodrigues AE. Selection of resins, equilibrium and sorption kinetics of lactobi-onic acid, fructose, lactose and sorbitol. Sep PurifTechnol 2008 63(3) 600—11. 

The second division —pars. 3-7 through 3-24— presents property data relative to each resin system. Its purpose is to narrow the selection of resin-glass systems into specific commercial formulations for engineering purposes. 

This process is almost as versatile as contact moulding as regards selection of resin and reinforcement, and therefore the possible range of properties. Its primary advantage is that of reproducibility and reduced labour, though this is offset by increased tooling cost as it is a closed mould technique. 

The selection of resin type or blend of resins depends on the type of paper being coated, the kind and size of the abrasive grit used, and the parameters for the optimization of production time. 

Before discussing the function and selection of resins for adhesives, some discussion of tack... 

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