Poly iodides 662 -methylenes

Estimate the surface tension of solid poly(methyl methacrylate) and its contact angle with methylene iodide (y = 50.8 mN/m). 

Surface tension studies of the most common fluorosilicone, poly(3,3,3-trifluoropropylmethylsiloxane) (PTFPMS), give unexpected results. Compared with (PDMS), PTFPMS has a higher liquid surface tension, a similar critical surface tension of wetting, and a considerably lower solid surface tension, as determined by water and methylene iodide contact angles and the method of Owens and Wendt (67). These results are summarized in Table X (7, 67, 72-74, 76, 77), in which PTFPMS is compared with two other fluorocarbon polymers, poly(tetrafluoroethylene) (PTFE) and poly(chlorotrifluoroethylene) (PCTFE). PTFE behaves like PTFPMS, whereas PCTFE behaves like PDMS. 

Sensitive extraction-spectrophotometric methods are based on the extractable (into CHCI3, 1,2-diehloroethane, benzene, or toluene) ion-associates of basic dyes and anionic Ag complexes with cyanide [35,36], iodide [37,38], and bromide [39]. In these methods, use has been made of such dyes as Crystal Violet [35,39], Brilliant Green [38,39], Malachite Green [39], Methylene Blue [36], and Nile Blue A [37]. In some of these methods the molar absorptivities are elose to MO [36,39]. A flotation method has been proposed, based on the addition compound [R6G ][Ag(SCN )2] [R6G ][SCN ] which is formed by silver ions (at pH 2-5) in the presence of thiocyanate and Rhodamine 6G (flotation with DIPE, the precipitated compound is washed and dissolved in acetone, e = 1.5-10 ) [40]. The complex Ag(CN)2 , associated with Crystal Violet, has been utilized in another flotation-spectrophotometric method of determining silver [41]. Silver has been determined also in a system comprising thiocyanate and Rhodamine B, as an aqueous pseudo-solution, in the presence of poly(vinyl alcohol) [42]. 

Equilibrium contact angle data are available for methylene iodide on a somewhat smaller number of solid surfaces than for water (about 80) they range from a maximum of 101° to 103° on a condensed film of -CF3 terminal groups to a minimum of 29° on surfaces not dissolved or attacked by the sessile drop [poly (vinylidene chloride), y = 0 dynes per cm.]. 

The poly(MPC) brush gave a quite wettable surface. The contact angle of the water droplet (2.0 pL) on poly(MPC) brush surface was very low (below 5°). The contact angles of methylene iodide and hexadecane were 45° and <5°, respectively. Using the Owens-Wendt equation [49], the surface free energy of the poly(MPC) brush surface was estimated to be 73 mJ/m, which is quite similar to that of water. Therefore, water plays the role of a good solvent, resulting in low friction of the poly(MPC) brush. Ho et al. [50] prepared a low-friction surface on polyurethane... 

Problem 6.2 Characterization of a PVC surface with the Owens-Wendt theory The contact angles of water and methylene iodide have been measured on a PVC (poly(vinyl chloride)) surface to be equal to 87° and 36°, respectively. The surface tension of water is at 25 °C equal to 72.8 with a dispersion part equal to 21.8. For methylene iodide, the surface tension is 50.8, and the dispersion part is 49.5. All surface tension values are in mN m. Assuming the validity of the Owens-W endt theory, calculate the surface tensions (total, dispersion and specific) of the sohd PVC surface and comment briefly on the results. 

The solid-surface tension, indicated by a contact angle of a liquid drop (e.g., n-hexadecane, water, and methylene iodide) on the fluorosiloxane film on glass is different from the liquid-surface tensions. Siloxanes containing trifluoropropyl groups have a lower surface tension than the nonfluorinated siloxane [poly(dimethylsiloxane)] [152]. 

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