Polymer in water

Instrumental methods for the determination of water in polymeric materials often rely on heat release of water from the polymer matrix. However, in some cases (e.g. PET) the polymer is hydrolysed and a simple Karl Fischer method is then preferred. Small quantities of water (10 pg-15mg) of water in polymers (e.g. PBT, PA6, PA4.6, PC) can be determined rapidly and accurately by means of a coulometric titration after heating at 50 to 240 °C with a detection limit in the order of 20 ppm. 

Water in polymer to dryer, at 5 per cent (neglecting polymer loss)... 

P. Lillford, A. H. Clark and D. V. Jones, Water in Polymers, ACS Symposium Series, American Chemical Society, Washington, D.C., 1980, 177. 

One further attraction of the Raman technique for vibrational studies is that water of bonded OH groups does not cause obscuration of the spectrum but, of course, Raman spectroscopy is useless for studies on water in polymers. At Southampton, excellent spectra of numerous solid mono-, di-, and trisaccharides have been recorded as well as aqueous solutions of some species. It is quite probable that Raman spectra of biologically interesting polymers may be produced shortly8. The ability to examine samples in aqueous regimes obviously has its attractions to the biochemist 1... 

Luck WA (1980) In Rowland SP(ed) Water in polymers, ACS symposium series 127. American Chemical Society, Washington DC, p 43... 

Table 9-2 Permeability coefficients P (cnr (STP)cm cm 2s Pa 1) of gases and water in polymers.

G. L. Brown, Clustering of water in polymers, in Water in polymers, edited by S. P. Rowland (ACS Symposium Series 127, American Chemical Society, Washington, DC,... 

The behaviour of water in polymers presents a special case, due to the nature of the water molecule. This molecule is relatively small and has a strong tendency towards hydrogen bond formation in its own liquid and solid state as well as with other polar groups. 

Also the diffusivity of water in polymers is highly dependent on the polymer-water interaction. When a polymer contains many hydrogen-bonding groups (cellulose, poly (vinyl alcohol), proteins, etc., and to a lesser extent synthetic polyamides) the diffusivity increases with the water content. This is explained by the strong localisation of the initially sorbed water over a limited number of sites, whereas at higher water contents the polymer... 

Lillford, P.J., Clark, A.H., and Jones, D.V. (1980). Distribution of water in heterogeneous food and model systems, ACS Symposium Series 127, In S.P. Rowland (ed.) Water in Polymers. Ameriean Chemical Society, Washington DC, pp. 177-195. 

Obviously, one solvent, ideal from many points of view, is water. Nobody cares about trace amounts of water in polymer films that might be used to wrap food, for example. Trace amounts of benzene (a grade A carcinogen) would be unacceptable, however. The problem is, of course, that most polymers (or monomers for that matter) do not dissolve in water. This brings us to the topic of multiphase processes where polymerizations are performed in water with the monomer or polymer suspended in the form of droplets or dispersed in the form of an emulsion. 

The figures show that Eq. (4) coupled with the Flory-Huggins equation for the activity coefficient of water in polymer + water mixed solvents provides a minimum for the Henry constant at high (>95 wt%) polymer compositions. Because gas solubility data are not available for such high polymer compositions, one cannot determine whether this minimum is due to the empirical nature of the adjustable parameter x or reflects an experimental feature of the gas... 

Starkweather, H. W. In Water in Polymers-, ACS Symposium Series 127 American Chemical Society Washington, DC, 1980 p 433. 

The partitioning of water may be determined from the equality of the chemical potentials of water in polymer and microemulsion phases existing in equilibrium. The two chemical potentials may be obtained as follows ... 

In a novel process, FIPI was also applied to the emulsiflcation of polymer melts in water, thus providing an alternative method to emulsion polymerization for the production of latexes. " " In fact, some thermoplastic melts (such as polyethylene) cannot be obtained through the emulsion polymerization route hence, the present technique is an example of PI providing a novel product form. To achieve the emulsiflcation of thermoplastics, it is necessary to operate near or above 100°C and at elevated pressures, which necessitates the use of polymer processing equipment fitted with a MFCS mixer at the outlet. It was found that molecular surfactants could not be used to obtain the initial (water-in-polymer melt) emulsion. Instead, hydrophobically modified water-soluble polymers were used as the surface active material. After the phase inversion in the MFCS mixer, the resulting emulsion was diluted to the level required. This also freezes the molten latexes. The important attributes of FIPI emulsification include a low level of surfactant use, low temperature processing, production of submicrometer particles with a narrow size distribution, and production of novel products. 

Maeda, Y. and Kitano, H. The structure of water in polymer systems as revealed by Raman spectroscopy, Spectrochim. Acta Part A-Mol. Biomol. Spectrosc., 51, 2433, 1995. 

---