Poly films contact angle

It is possible that such an effect may be masked by the decrease in contact angle upon the photolysis of poly(2-vinylnaphthalene) films as s lown in Figure 5. 

Upadhyay et al. [98] used primarily correlated XPS and water contact angle measurements to study the surface degradation and recovery of amorphous films of a PMMA and a poly (aryl ether ether ketone) (PEEK). Surface modification of the films was carried out in a dielectric barrier discharge (DBD) unit, samples being treated with different dose levels of dielectric discharge. The modified (treated) samples were then stored for one month and re-examined. Figure 35 shows C(ls) and 0(1 s) XPS envelopes and their curve-fitting deconvolutions,... 

The contact angle (0) by water at 25°C in air is 84° for Bisphenol A poly(carbonate) (3) film (Table 9.4).6 Introduction of 19% of Bisphenol AF unit increases the value of (0) to 90° and from that point it is almost constant irrespective of fluorine content. This abrupt increase in (0) is attributed to the migration and... 

Crystallinity of these hexafluoroisopropylidene-unit-containing poly(ketone)s is low except for poly(sulfide ketone) (13). The water contact angle for the fluorine-containing poly(ketone) films is high, being 98° for poly(ether ketone) (11), from 2,2-bis(4-carboxyphenyl)-l,l, l,3,3,3-hexafluoropropane(15) and 96° for poly(sulfide ketone) (13) from 15, whereas it is 78° for poly(ether ketone) from 2,2-bis(4-carboxy-phenyl)propane (16) and 74° for the poly(sulfide ketone) from 16. This result indicates that the substitution of isopropylidene units of poly-(ketone)s with hexafluoroisopropylidene units has a remarkable effect on the surface properties of poly(ketone) films. 

The cast films ofpoly(azomethine)s are transparent but pale to deep yellow in color. The water contact angles of fluorine-containing poly(azomethine)s films from diamine (17) are 80° for terephthalaldehye (19) and 75° for isophthalalde-hyde (20) as dialdehyde component (Table 9.9).20 These low values of water contact angles are attributed to the lower fluorine content in these polymers. 

Thin films of polyethylene, poly(ethylene-co-5-norbomen-2-yl acetate), and poly-(cthylene-co-5-norbomen-2-ol) were prepared on glass slides and contact angle measurements of water droplets determined. Testing results are provided in Table 2. 

The effect of ultraviolet irradiation in air on the wettability of thin films of amorphous polymers has been studied. With poly(vinyl chloride), poly(methyl methacrylate), poly(n-butyl methacrylate), poly (ethylene terephthalate), and polystyrene the changes in contact angles for various liquids with irradiation time are a function of the nature of the polymer. A detailed study of polystyrene by this technique and attenuated total reflectance spectra, both of which are sensitive to changes in the surface layers, indicates that the contact angle method is one of the most sensitive tools for the study of polymer photooxidation in its early stages. The method is useful in following specific processes and in indicating solvents to be used in the separation and isolation of photooxidation products. 

Procedure. With the exception of poly (ethylene terephthalate), 20/ films of each polymer were prepared by the evaporation or approximately 4% solutions in quartz or glass dishes of 50 cm.2 area for extraction experiments. For contact angle measurements, films were evaporated on acid-cleaned microscope slides by a dipping technique. Tetrahydrofuran was used with poly (vinyl chloride), methylene chloride with the other polymers. 

That photooxidation is indeed responsible for the observed changes is indicated by a comparison with the results obtained with films irradiated in vacuum. Both polystyrene and poly(n-butyl methacrylate) irradiated in vacuum showed no changes in contact angles after exposures up to 120 min. with poly (ethylene terephthalate), contact angles for all of the liquids tended to increase slightly. 

Figure 2. Contact angle changes with various liquids on a film of poly (methyl methacrylate) irradiated in air...

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Contact Angle Measurements. The angle of contact of 93° for poly(L-norleucine) has been reported previously. Problems of preparing uniform adherent films of poly(L-methionine) and hysteresis effects combined to make measurements of 0 very imprecise it is estimated at 55° 10°. No measurements at all were possible with poly(L-leucine) for similar reasons. 

GST is expressed in terms of the surface tension of a liquid which just wets the surface, i.e. has a 0 contact angle. Fig. 12 gives CST plots for the same surfaces shown in Fig. 9 and 10 before and after extraction. It can be seen that all films have lower CST values than poly(tetrafluoroethylene) before extraction, but after... 

Many soHd particles with some degree of hydrophobicity have been shown to cause the destabilisation of foams, including hydrophobic sihca and poly(tetrafluoroethylene) (PTFE) particles. The PTFE particles exhibit a finite contact angle when adhering to the aqueous interface, and it has been suggested that many such hydrophobic particles can deplete the stabilising surfactant film by rapid adsorption, causing weak spots in the film. 

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