工厂英文Part 6 - Three Component Parameters
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Solubility behavior can be adequately described using Hildebrand values, although in some cas differences in polar composition give unexpected results (Fig. 1, for example). Predictions become more consistent if the Hildebrand value is combined with a polar value (i.e. hydrogen bonding number), giving two parameters for each liquid. Even greater accuracy is possible if all three polar forces (hydrogen bonding, polar forces, and dispersion forces) are considered at the same time. This approach assigns three values to each liquid and predicts miscibility if all three values are similar.莱昂纳多 oppo
As long as data is prented in the form of a single list, or even a two dimensional graph, it can be easily understood and applied. With the addition of a third term, however, problems ari in reprenting and using the information; the manipulation of three parate values prents certain inconveniences in practical application. It is for this reason that the development and the u of three component parameter systems has centered on solubility maps and models.
3-D MODELS
While polymer solubilities may be easily prented as a connected group of solvents on a list, or as a specific area on a graph, the description of solubilities in three dimensions is understandably more difficult. Most rearchers have therefore relied on three-dimensional constructions within which all three component parameters could be reprented at once.
In 1966, Crowley, Teague, and Lowe of Eastman Chemical developed the first three component system using the Hildebrand parameter, a hydrogen bonding number, and the dipole moment as the three components. A scale reprenting each of the three values is assigned to a parate edge of a large empty cube. In this way, any point within the cube reprents the interction of three specific values. A small ball, supported on a rod, is placed at the interction of values for each individual solvent (Figure 3).
Fig. 3 A three dimensional box ud to plot solubility information after Crowley, Teague and Lowe) = Hildebrand value, µ = dipole moment, h=hydrogen bonding value
致命译电Once all the solvent positions have been located within the cube in this way, solubility tests are performed on individual polymers. The position of solvents that dissolve a polymer are indicated by a black ball, nonsolvents by a white one, and partial solubilities are indicated by a grey ball. In this way a solid volume (or three dimensional area) of solubility is formed, with liquids within the volume being active solvents (black balls), and liquids outside the volume being non-solvents (white balls). Around the surface of the volume, at the interface between the area of solubility and the surrounding non-solvent area, the balls are grey.
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Once the volume of solubility for a polymer is established, it becomes necessary to translate that information into a form that is practical. This means transforming the 3-D model (difficult to carry around) into a 2-D graph (easier to publish). This is usually done in one of two similar ways. In both cas, the data is plotted on a rectangular graph that reprents only two of the three component parameter scales (one side of the cube).
Fig. 4 Approximate Reprentations of Solid Model and Solubility Map for Cellulo Acetate (from Crowley, et al, Journal of Paint Technology Vol 39 # 504, Jan 1967)
The polymer solubility volume takes the form of an area on the graph that reprents either a single slice through the volume at a specified value on the third component para
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meter scale, or a topographic map that indicates veral values of the third parameter at the same time (e Figure 4). Becau the volume of solubility for a polymer usually has an unusual shape, veral graphs are often needed for an individual polymer if its total solubility behavior is to be shown.三校生高复
Maps such as the can be ud in conjunction with a table of three component parameters for individual solvents, and in this way provide uable information about solvent-polymer interactions and allow the formulation of polymer or solvent blends to suit specific applications. Data prented in this way is not only conci, but saves considerable time by allowing the prediction of solubility behavior without recour to extensive empirical testing. It is for the reasons that solubility maps are often included in technical reports and manufacturer's product data sheets. How graphs are actually ud to accomplish the purpos will be described later in terms of the triangular Teas graph, in which the procedures are similar but greatly simplified.
HANSEN PARAMETERS
The most widely accepted three component system to date is the three parameter system developed by Charles M. Hann in 1966. Hann parameters divide the total Hildebrand value into three parts: a dispersion force component, a hydrogen bonding component, and a polar component. This approach differs from Crowley's in two major ways: first, by using a dispersion force component instead of the Hildebrand value as the third parameter, and cond, by relating the values of all three components to the total Hildebrand value. This means that Hann parameters are additive:
