Casting Solvents for membrane

HSP Application note #61

2010.11.19

HSPiP Team Senior Developer, Dr. Hiroshi Yamamoto

I got interesting paper.

Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) membranes for ethyl acetate removal from water
Xiuzhi Tian ∗, Xue Jiang
School of Textiles & Clothing, Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi 214122, China

Journal of Hazardous Materials 153 (2008) 128–135

SEM pictures of PVDF-HFP membranes’ cross-sections prepared under different conditions.
DMAc, vacuum, 60 ◦ C.

They cast PVDF-HFP polymer with several conditions.

In this paper, author use Hansen solubility parameters (HSP) of PVdF-HFP [17.2, 12.5, 8.2].
But reference paper, it is not PVdF-HFP but pure PVdF.
And the HSP value is [17.2, 12.5, 9.2] in original paper.

Hansen Solubility Parameters (HSP)

Hansen Solubility Parameters(HSP) were developed by Charles M. Hansen as a way of predicting if one material will dissolve in another and form a solution. They are based on the idea that "like dissolves like" where one molecule is defined as being 'like' another if it bonds to itself in a similar way.
Specifically, each molecule is given three Hansen parameters, each generally measured in MPa0.5:
dD:The energy from dispersion bonds between molecules
dP:The energy from dipolar intermolecular force between molecules
dH:The energy from hydrogen bonds between molecules.
These three parameters can be treated as Vector for a point in three dimensions also known as the Hansen space. The nearer two molecules HSP Vector are in this three dimensional space, the more likely they are to dissolve into each other.

What can perhaps be surprising is that one can assign HSP to so many different things. Gases like carbon dioxide, solids like carbon-60, sugar, and biological materials like human skin, depot fat, DNA, and even some proteins all have HSP. The list can be continued with drugs, polymers, plasticizers, and in fact any organic material and even many inorganic materials like salts. The only requirement for an experimental confirmation is that the material must behave differently in a sufficient number of test solvents upon contact.

Pirika JAVA Demo Applet calculate HSP. HSPLight is available here.
Please refer to e-Book of HSPiP if you want know more about HSP.
About the Power Tools that handle HSP more effectively.

The distance calculation is wrong with this paper.

δiP = [(δpi − δpP)2 + (δdi − δdP)2 + (δhi − δhP)2]1/2 (7)

It need 4* before δd term.

HSP Distance

To calculate the distance (Ra) between Hansen parameters in Hansen space the following formula is used:

HSP distance(Ra)={4*(dD1-dD2)2 + (dP1-dP2)2 +(dH1-dH2)2 }0.5

Anyway, I try to use HSP for “Choice of Solvents for membrane preparation”.

<p>Please Use HTML5 Browser</p>

Drag=Rotate, Drag+Shift=Larger/Smaller, Drag+Alt or Command(Window key)=Translate.

If you are using HTML5 enable browser such as Chrome, Safari or FireFox (IE9 is out of support), you will see the Canvas. If you pick solvent, solvent name will appear.

As I wrote at PVdF binder resin, this polymer has double natures.
1st Large Green Sphere, [19.1, 15.6, 10.2] Radius 8.45
2nd Small Green Sphere, [17.5, 6.3, 9.0] Radius 4.63

Hcode	Name	dD	dP	dH	DistSP-A	Dis/RA	DistSP-B	Dist/RB
417	hexane	14.9	0	0	20.44	2.42	12.15	2.63
181	cyclohexane	16.8	0	0.2	19.09	2.26	10.91	2.36
456	methyl alcohol	14.7	12.3	22.3	15.32	1.81	15.63	3.38
325	ethyl alcohol	15.8	8.8	19.4	13.21	1.56	11.22	2.42
569	propyl alcohol	16	6.8	17.4	12.95	1.53	8.93	1.93
92	butanol	16	5.7	15.8	12.95	1.53	7.46	1.61
182	cyclohexanol	17.4	4.1	13.5	12.44	1.47	5.01	1.08
46	aniline	20.1	5.8	11.2	10.05	1.19	5.67	1.22



11	acetophenone	18.8	10	4	8.38	0.99	6.74	1.46
363	ethylene carbonate	18	21.7	5.1	8.25	0.98	15.92	3.44
584	Propylene Carbonate	20	18	4.1	6.80	0.80	13.63	2.94
115	gamma-butyrolactone	18	16.6	7.4	3.70	0.44	10.47	2.26
617	tetrahydrofuran	16.8	5.7	5.7	11.81	1.40	3.63	0.79
285	N,N'-dimethylacetamide	16.8	11.5	10.2	6.16	0.73	5.52	1.19
521	N-methyl-2-pyrrolidone	18	12.3	7.2	4.97	0.59	6.34	1.37
303	dimethyl sulfoxide	18.4	16.4	10.2	1.61	0.19	10.33	2.23
624	Tetramethylurea	16.7	8.2	11	8.86	1.05	3.19	0.69
416	hexamethyl phosphoramide	18.5	11.6	8.7	4.44	0.53	5.67	1.23
659	triethyl phosphate	16.7	11.4	9.2	6.46	0.76	5.35	1.16
671	trimethyl phosphate	15.7	10.5	10.2	8.50	1.01	5.66	1.22
297	N,N'-dimethylformamide	17.4	13.7	11.3	4.05	0.48	7.75	1.67
183	cyclohexanone	17.8	8.4	5.1	9.20	1.09	4.47	0.97

If JAVA 3D is already installed in your machine, please try 3D view of this Sphere.

Hansen Sphere

To determine if the parameters of two molecules (usually a solvent and a polymer) are within range a value called interaction radius (R0) is given to the substance being dissolved. This value determines the radius of the sphere in Hansen space and its center is the three Hansen parameters.

From version 3.1.X, Double Spheres function is available.

Pirika provide JAVA 3D Demo Applet to browse the Sphere(s).
The HTML5 Sphere Viewer examples are available here.
Now we have Power Tool "Sphere Viewer", GUI HTML5 software on HSPiP ver. 4.

I selected several solvents and calculate (solvent-polymer) distance.
If the Distance is within sphere radius, that solvent is good solvent. So I append 2 column Ra=Distance/Radius.
If Ra<1.0, then that is good solvent.

There is no solvent that dissolve both parts of polymer.
Maybe, N,N’-Dimethylacetamide (DMAc) is the most good balanced solvent.

The second example is,

MIT OpenCourseWare
2.500 Desalination and Water Purification
Amphiphilic Graft Copolymers for Nanofiltration Membranes with Tunable Pore Size

How can we use HSP designing solvents for this purpose?

At first, we need to determine HSP of PEG.
I got Solubility data from Polymer Handbook.

Hcode	Name	dD	dP	dH	Vol	Score
417	hexane	14.9	0	0	131.4	0
7	acetone	15.5	10.4	7	73.8	0
481	methyl ethyl ketone	16	9	5.1	90.2	0
255	diethyl ether	15.49	2.9	4.6	104.7	0
522	methyl tert-butyl ether	14.8	4.3	5	119.8	0
306	1,4-dioxane	17.5	1.8	9	85.7	0
52	benzene	18.4	0	2	89.5	1
637	toluene	18	1.4	2	106.6	1
456	methyl alcohol	14.7	12.3	22.3	40.6	1
10	acetonitrile	15.3	18	6.1	52.9	1
524	dichloromethane	17	7.3	7.1	64.4	1
156	chloroform	17.8	3.1	5.7	80.5	1
122	carbon tetrachloride	17.8	0	0.6	97.1	1
183	cyclohexanone	17.8	8.4	5.1	104.2	1
202	diethylene glycol dimethyl ether	15.7	6.1	6.5	142.9	1
328	ethyl acetate	15.8	5.3	7.2	98.6	1
617	tetrahydrofuran	16.8	5.7	5.7	81.9	1
285	N,N'-dimethylacetamide	16.8	11.5	10.2	93	1
297	N,N'-dimethylformamide	17.4	13.7	11.3	77.4	1
303	dimethyl sulfoxide	18.4	16.4	10.2	71.3	1
598	pyridine	19	8.8	5.9	80.9	1
1016	ethylacetoacetate	16.5	7.3	8.3	127.3	1

And calculate with Sphere program.
The result is [20.0, 11.2, 2.3] Radius 12.2

Only N-methylacetamide is good solvents for PVdF, and bad solvent for PEG.
So, this solvent might make phase separation most effectively.
(At least, you would better use RED SOLVENTS )