Critical surface tension of poly

THE EFFECT OF COMPOSITION ON THE CRITICAL SURFACE TENSION OF POLY/VINYL BUTYRAL/. 

The bonding of a viscoelastic material (a film of glue) onto a solid surface can only be expected, then, when the surface tension of the liquid is lower than the critical surface tension 7. of the solid body. According to equation (13-3), these two quantities are related to the contact angle S and the interfacial surface tension between solid and adhesive film. Since a chemical variation in the surface can also cause the surface tension to change, it is often possible to obtain better bonding through chemical modification of a surface. An example of this is the oxidation of the surface of polyolefins [see the critical surface tensions of poly(ethylene) and poly-(vinyl alcohol) in Table 13-3]. 

The critical surface tension of poly(methy 1 methacrylate) (PMMA) is 39 mN m , of polyethylene (PE) is 31 mN m of poly(vinyl chloride) (PVC) is 40 mN m and that of Teflon (PTFE) is 18. Which of the five polymers, PS, PMMA, PE, PVC and PTFE is easiest to wet and which one is the most difficult to wet Explain briefly your answer. 

Allcock and Smith118 have prepared a series of poly(organophosphazenes) containing siloxane grafts and/or trifluoroethoxy side groups (31-34). Polymers 31 and 32 had critical surface tensions of 16-17 rn N rn 1 and surface layers which were enriched in fluorine. In the case of 32, silicone was not observed at the surface. Polymer 33 had a critical... 

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. 

TgS for polymers with architectures similar to PDMS are given in Table XII 21, 81). The TgS of poly(dimethylsilazane) and poly(dimethyl-silmethylene) lie between those of PDMS and poly(isobutylene) (critical surface tensions of wetting of 24 and 27 mN/m, respectively [70]). These values suggest that poly(dimethylsilazane) and poly(dimethylsilmethylene) will have critical surface tensions of wetting in the 25-26-mN/m range. 

Attenuated total reflection infrared critical micelle concentration electron spectroscopy for chemical analysis hydrophilic-lipophilic balance poly(chlorotrifluoroethylene) poly(dimethylsiloxane) poly(tetrafluoroethylene) poly(trifluoropropylmethylsiloxane) glass transition temperature critical surface tension of wetting Owens-Wendt solid surface tension surface tension of aqueous solution surface tension of liquid... 

The present investigation describes the successful modification of the surface properties of polymeric solids by the adsorption of appropriate partially fluorinated compounds at polymer-air interfaces during the formation of the polymer surfaces. The extent of additive adsorption was foxmd to be dependent upon the molecular structure, fluorine content, and solubility of the additives in the solute—i.e., their organophilic-organophobic balance with respect to the solute. Certain effective additives were able to decrease the critical surface tension, of such polymers as poly(methyl methacrylate) and polyacrylamide to 20 and 11 dynes per cm., respectively. These low values correspond to surfaces containing closely packed CF2 and CF3 groups. 

Four polymers with different surface compositions were used in this study—polystyrene (PS), poly(methyl methacrylate) (PMMA), polyacrylamide (PAM), and a poly(vinylidene chloride) (PVeC) copolymer (containing 20% polyacrylonitrile). Polystyrene has essentially a hydrocarbon surface, whereas the surfaces of poly (methyl methacrylate) and polyacrylamide contain ester and amide groups, respectively. The surface of the poly(vinylidene chloride) copolymer on the other hand will contain a relatively large number of chlorine atoms. The presence of acrylonitrile in the poly(vinylidene chloride) copolymer improved the solubility characteristics of the polymer for the purposes of this study, but did not appreciably alter, its critical surface tension of wetting. Values of y of these polymers ranged from 30 to 33 dynes per cm. for polystyrene to approximately 40 dynes per cm. for the poly(vinylidene chloride) copolymer. No attempt was made to determine e crystallinity of the polymer samples, or to correlate crystallinity with adsorption of the fluorocarbon additives. 

From the contact angles in Table III, cos 6 vs. Vly was plotted in Figure 2 for clean PMMA. From the intercept it is seen that 7c is approximately 39 dynes per cm., well within the range of 33 to 44 dynes per cm. recently reported by Wolfram [24]. Ellison and Zisman [9] also obtained a critical surface tension of between 39 and 40 dynes per cm. for poly (ethylene ter ephthalate), another polymer containing a large number of carboxylic ester groups. 

PVeC copolymer surface are in good agreement, generally within the limits of experimental error. These values of 6 are very similar to those reported previously by Ellison and Zisman[S] on a poly(vinylidene chloride) surface, which for comparison are plotted in Figure 3 along with the present results. The plot of cos 6 vs. in Figure 3 shows the critical surface tension of the additive-free PVeC copolymer surface to lie between 38 and 44 dynes per cm. 

Partially fluorinated oligomers derived from hexafluoropropylene oxide je.g., F[C(CF3)FCF20]9C(CF3)FC00CH2CH2(0CH2CH2)60CH3 lower the critical surface tension of polymers on which they are adsorbed [e.g., polystyrene, poly (methyl methacrylate), and a vinyl chloride-vinylidene copolymer] [282]. 

Table III. Estimate of Critical Surface Tensions for Undissociated Poly R4N-X Surfaces0...

The wettability of plasma deposited coatings can be compared with poly(tetrafluoroethylene) and poly(ethylene). When the cosine of contact angles obtained with non-hydrogen bonding liquids are plotted against their surface tension, extrapolation of the resulting straight line to cos 0=1 yields a term called the critical surface tension (CST) which is characteristic of that surface (ll). 

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