Solubility parameters Hansen

CHEMICAL COMPATIBILITY OF POLY(LACTIC ACID) A PRACTICAL FRAMEWORK USING HANSEN SOLUBILITY PARAMETERS 

In an ideal world, a chapter such as this would provide the reader with the ability to know how any chemical will interact with PLA. There are two possible ways of doing this. The first is to provide an overwhelming amount of detail over a large range of chemicals, allowing the experienced reader to extrapolate to their own area of interest. For a comparatively young polymer such as PLA, this is simply not possible. The second approach is to provide a perfect theoretical framework from which the reader can calculate whatever they require. No such framework exists. 

The approach adopted instead is closer to the second than the first. It starts from a rather simple thermodynamic approach and shows that over a broad range of chemicals and applications this approach yields practical insights that are frequently reliable or, at the very least, point the practical scientist in the right direction. Such frameworks are worthless without experimental validation, so the relatively sparse real-world data are used to check the framework. 

If one wants a framework for understanding chemical interactions, thermodynamics has a lot going for it it is a fundamental grounding for science it is often amenable to calculations and it has separable terms (enthalpy and entropy) that are deeply insightful into many phenomena. On the other hand, we all know that kinetic effects can dominate results in the short timescale of experiments. This is partic- 

Ideally, all thermodynamic approaches should lead to the same conclusion, so it should not matter too much which is adopted. But within a practical framework, the choice has to be something that is not only thermodynamically justified but also easy to use, and applicable, over a wide range of topics. 

According to the regular solution theory of Hildebrand the f-parameter can be approximated by Eq. (41) [8], where Vs is the molar volume of the solvent and 4 and Sp are the solubility parameters of solvent and polymer, respectively. Since these solubility parameters are pure component parameters, Eq. (41) combined with Eq. (27) results in a predictive model. However, since many simplifications are involved, the results of this model can be considered as only a rough estimate. Following the slogan like dissolves like , a good solvent for a polymer is a solvent for which Ss and Sp have similar values. 

Hansen suggested refining the solubility parameter theory by the introduction of contributions from dispersive interactions (d), polar interactions (p) and hydrogen bond formation (hb), as in Eq. (42) [33]. 

Recently, Lindvig et al. [34, 35] showed that Eq. (42) systematically overestimates the infinite dilution activity coefficient of the solvent and proposed an alternative expression, Eq. (43). 

These authors showed that for a number of polymer-solvent system with a = 0.6 this method performs similarly to group contribution methods using volume fractions to represent the segment fractions in the Flory-Huggins model. Values of solubility parameters are tabulated by Barton [36]. 

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Paine et al. [85] extensively studied the effect of solvent in the dispersion polymerization of styrene in the polar media. In their study, the dispersion polymerization of styrene was carried out by changing the dispersion medium. They used hydroxypropyl cellulose (HPC) as the stabilizer and its concentration was fixed to 1.5% within a series of -alcohols tried as the dispersion media. The particle size increased from only 2.0 /itm in methanol to about 8.3 /itm in pentanol, and then decreased back to 1 ixm in octadecanol. The particle size values plotted against the Hansen solubility parameters... 

Figure 13 The variation of particle size with the Hansen solubility parameter of the n-alcohols. (Adapted from Ref. 85 with the permission of John Wiley Sons, Inc.)...

Hansen solubility parameters. A convenient scheme for the evaluation of solvency is the use of the Hansen plot, a 3D diagram positioning 8, 5p and of polymer and solvent. 

C. Hansen, Hansen Solubility Parameters. A User s Handbook, CRC Press, Boca Raton, FL (2000). 

Hansen CM, Smith AL (2004) Using Hansen solubility parameters to correlate solubility of C60 fullerene in organic solvents and in polymers. Carbon 42 1591-1597. 

In the context of the TMS investigated here, a mediator was needed with a Hansen solubility parameter (HSP) closer to that of the catalyst solvent than to that of NOP. A detailed database of HSPs can be found in the literature [30-32]. 

Table 9 Hansen solubility parameters of some solvents...

Pioneering work on the application of this theory for correlating and predicting distribntion ratios was done in the 1960s [38a-40c]. Several reviews on the nse of this theory for two-phase distribution processes are also available [41,42]. Recently this theory has been refined by the use of Hansen solubility parameters [6,43,44], according to which... 

Hansen C (2007) Hansen solubility parameters a user s handbook, 2nd Ed. CRC Press Inc, Taylor Francis Group, Boca Raton FL... 

Belmares, M., M. Blanco, W. A. Goddard, R. B. Ross, G. Caldwell, S.-H. Chou, J. Pham, P. M. Olofson, and C. Thomas. 2004. Hildebrand and Hansen solubility parameters from molecular dynamics with applications to electronic nose polymer sensd>.r omputat. Chen25 1814-1826. 

Predictions of Woo could be performed using global (Hildebrand) or partial (Hansen) solubility parameters, but these are very difficult (and perhaps impossible) to determine accurately from solvent-sorption experiments, so that this way is not realistic. The best experimental approach is, in our opinion, using the ultrasonic modulus. 

In another study Slobodian et al. (57) found that the percolation threshold for electrical conductivity of MWCNT-PMMA composites depends on the solvent used. The lowest percolation threshold was achieved for toluene where percolation was found to be at 4 wt% of MWCNT, for chloroform at 7 wt% and for acetone at 10 wt%. The highest conductivity was obtained at 20 wt% of MWCNT at values around 4x 10 5 Sc nr1 for composite prepared from toluene solution. They observed that the Hansen solubility parameters of individual solvent play an important role in the dispersion of MWCNT in PMMA. 

Slobodian et al. 2007(57) MWCNT Sun Nanotech Co. Ltd. Purified Solvent Casting Followed by compression molding CNT loading levels 2 to 20 wt% Bulk Composites Percolation threshold Solvent Percolation MWCNT [Pg.214]

Solvating efficiency of the plasticiser for PVC -predicted using Hansen solubility parameters (350) and the Hildebrand solubility parameter (442)... 

New York City, 2nd-6th May 1999, p.3512-25. 012 PREDICTION OF PLASTICISER SOLVENCY USING HANSEN SOLUBILITY PARAMETERS... 

Hansen CM, Just L (2001) Prediction of environmental stress cracking in plastics with Hansen solubility parameters. Ind Eng Chem Res 40( 1) 21—25... 

Hansen, C.M. and Just, L. (2001) Prediction of Environmental Stress Cracking in Plastics with Hansen Solubility Parameters, Ind. Eng. Chem. Res. 40,21-25. 

Frank et aL reported examples of quickly screening solvents for organic solids. In one particular example, solubilities of aspirin in four different solvents (acetone, ethanol, chloroform, and cyclohexane) were used to regress the Hansen solubility parameters for the solute, aspirin. Once the Hansen solubility parameters are identified for aspirin, Frank et al. showed that one could quickly estimate the solubilities of aspirin in any solvent or solvent mixture as long as the Hansen solubility parameters are also available for the solvents. 

Hansen nonpolar (dispersion) solubility parameter dh Hansen solubility parameter... 

A number of methods based on regular solution theory also are available. Only pure-component parameters are needed to make estimates, so they may be applied when UNIFAC group-interaction parameters are not available. The Hansen solubility parameter model divides the Hildebrand solubility parameter into three parts to obtain parameters 8d, 5p, and 5 accounting for nonpolar (dispersion), polar, and hydrogenbonding effects [Hansen,/. Paint Technot, 39, pp. 104-117 (1967)]) An activity coefficient may be estimated by using an equation of the form... 

Dispersive Forces. In the absence of permanent or induced dipoles, London dispersive forces (17) become important. Random fluctuations in the electron cloud produce a time-varying, temperature-independent intermolecular force of attraction termed the dispersive force. The magnitude of these dispersive forces (typically 0.1 to 2 kcal/mole) can be represented by a variety of cohesive parameters Including the dispersive component of the Hansen solubility parameter (16). 

The solubility parameter has found previous use in membrane science. Casting solution components and composition have been selected using the Hansen solubility parameters (68-71). The total Hansen solubility parameter, which is equivalent to the Hildebrand parameter (.72), has been used to explain permeation and separation in reverse osmosis (23). Hansen s partial parameters have also been used to explain permeation and separation in pervaporatlon (61). The findings of these studies (61,73) plus those reported elsewhere in this volume (74) do lend credence to the use of 6, 6, and 6, for membrane material selection. 

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