HMDSO plasma

Mahlberg etal. (1998) modified the surface of birch veneer with a hexamethyldisi-loxane (HMDSO) plasma in order to improve the compatibility between the wood surface... 

Figure 30.25 depicts the correlation between the DPPH consumption and the fatigue life. Increasing trends of the fatigue life could be seen as the DPPH consumption increased regardless of the types of plasma treatments. The HMDSO plasma based treatment on the X-ray-opaque powder showed more pronounced trend in the effects of surface-bound peroxide on the fatigue properties of bone cement. 

The relation between the peroxide concentration on the X-ray-opaque powder and the gel time of bone cement could be seen in Figure 30.27, in which the time at maximal temperature was used instead of gel time or set time to avoid unnecessary error, since the temperature profiles seemed to have identical shape. As the DPPH consumption increased, the gel time decreased (i.e, faster polymerization) regardless of the types of plasma treatment, as seen in the relation between the fatigue properties and the peroxide concentration. The HMDSO plasma-based treatments showed a more pronounced effect than that by the methane plasma-based treatments. 

Figure 9-29. Water drop-induced dye removal from an HMDSO-plasma-treated eotton fabrie.

Plasma-induced hydrophobization of cottonfabric in conjunction with increased specific surface area leads to an interesting and practically important effect. Water droplets are able to effectively remove dirt particles from the surface of the cotton fabric. This phenomenon is illustrated in Fig. 9-29 for the case of HMDSO-plasma-treated cotton fabric (Hocker, 2002) and is usually referred to as the Lotus effect. Thus, the highly hydrophobic plasma-treated surface of cotton with specific plasma-modified surface topography is extremely dust- and dirt-repellant in contact with water. As an important consequence, the plasma-treated surface also becomes repellant to bacteria and fungi. The effect is relevant not only to cotton fiber but to some other materials as well. 

The hybrid films for the pinhole-free electrical insulators were prepared using hexamethyldisiloxane (HMDSO) and silicon monoxide (SiO) [64]. The HMDSO hybrid films were prepared on the substrates by evaporating SiO during HMDSO plasma polymerisation in RF discharge. SiO was evaporated by heating in RF plasma consisting of HMDSO and oxygen at a pressure of 10 Torn... 

Hegemann, D., Vohrer, U., Oehr, C., Riedel, R., 1999. Deposition of SiOx films from O2/HMDSO plasmas. Surf. Coat. Technol. 116—119, 1033—1036. 

Malmsten M, Muller D, Lassen B. Sequential adsorption of human serum albumin (HSA), immunoglobulin G (IgG) and fibrinogen (Fgn) at HMDSO plasma polymer surfaces. J Colloid Interface Sci 1997 193 88-95. 

Concerning anti-corrosion properties, Tafel curves allow the calculation that the corrosion current for this kind of coating is slightly below that for classical Ce-based ppHMDSO films. Images of HMDSO treated samples after 25 days in a salt spray chamber are shown in Fig. 12.11(c,d) which compare the resistance of HMDSO plasma treatments with and without ethanol. An increase in corrosion protection is afforded by the presence of solvent, since pitting corrosion is reduced. This last result corroborates those obtained by electrochemistry. 

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

Primary interest was in the barrier properties obtained from plasma organo-silicones and from inorganic "SIN" coatings. Spectral grade HMDSO was used in the former case, while mixtures of SiH and NH were used to produce the SIN structures. The substrate in much or the work was DuPont Kapton type H polylmide film, 51 pm thick. Substrate temperatures extended to 450 C, as described earlier (6). The thickness of plasma-polymer deposits was about 0.5 pm. Moisture permeation was evaluated by the routine of ASTME-96-53 T (water vapor transmission of materials in sheet form). Additional, more precise data, were obtained with both a Dohrmann Envirotech Polymer Permeation Analyser, modified as previously described (6), and a Mocon "Permatran W" moisture permeation apparatus. 

Finally, scanning electron microscopy (SEM) was used to study the morphology of plasma deposits obtained from HMDSO. 

Table 1. Comparison of water flux changes, AF, due to plasma deposits of HMDSO and SiN on Kapton.

Figure 9 shows the pH dependence of electro-osmosis in l mM NaCl for three plasma polymer surfaces having different functional characteristics. The respective surfaces of Fig. 9 are plasma polymerized acrylic acid, hexamethyl-disiloxane (HMDSO), and l, 2-diaminocyclohexane (DACH). It is evident from the figure that these surfaces have very different electrokinetic surface properties. This surface titration clearly distinguishes the acid-base properties of the respective surfaces. 

FIG. 9 The pH dependence of electro-osmotic fluid flow for three plasma polymer surfaces in I mM NaCl acrylic acid (O), HMDSO ( ), and DACH (A). 

Figure 11.7b shows the internal stress in LPCAT films of cyclic siloxanes 1,3,5,7-tetramethylcyclotetrasiloxane (TMTSO) and 2,4,6,8-tetravinyl-2,4,6,8-tetra-methylcyclotetrasiloxane (TVTMTSO). The large siloxane ring structure in these two monomers did not provide any decrease of internal stress in resultant plasma polymer films, compared with simple siloxane monomers, i.e., TMTSO, HMDSO, and VpMDO. 

Figure 11.8 FTIR spectra of plasma polymers prepared by cascade arc torch from (a) tetramethydisiloxane (TMDSO), (b) hexamethydisiloxane (HMDSO), and (c) vinylpenta-methyldisiloxane (VpMDSO) 750 seem argon, 4.0 A arc current, 5.0 seem monomers.

Figure 30.28 Fatigue life of plasma-treated carbon fiber reinforced PMMA bone cement at 23 MPa maximum applied stresses under flexural loading untreated untreated carbon fiber with untreated X-ray opaque powder all others are with HMDSO/O2 treated X-ray opaque powder untreated refers to untreated carbon fiber.

Figure 30.29 Effect of milled carbon fiber reinforcement and plasma treatment on the fatigue life of bone cement (a) untreated Zr02 without fiber, (b) untreated Zr02 with untreated fiber, (c) HMDSO/O2 treated Zr02 without fiber, (d) HMDSO/O2 treated Zr02 with untreated fiber, (e) HMDSO/O2 treated Zr02 with HMDSO/O2 treated fiber.

Carbon fibers treated with HMDSO/O2 plasma showed the highest DPPH consumption per unit surface (2 x 10 mol/cm ) among plasma treatments employed, and also showed a significant reduction of the time needed to reach the maximal temperature (1070 s compared to 1170 s for untreated fibers). These are the similar trends found with plasma-treated X-ray-opaque powders. All of these trends strongly indicate that the plasma-treated fillers acting as the additional initiator of MMA polymerization, i.e., PMMA polymers are covalently bonded to the LCVD-coated fillers. 

Hexamethyldisiloxane (HMDSO) is one of the simplest siloxane compounds it has been successfully used in plasma-assisted thin-film deposition applications... 

Fig. 14. Comparison of mass spectrometrically obtained ion abundances in TMS-, TEOS-, and HMDSO-containing rf discharges (open bars) with calculated ion foimation rates using measured partial ionization cross sections and a Maxwellian enetgy distribution of the plasma electrons corresponding to an average energy of 3 eV (full bars).

Ways have been investigated to reduce or avoid leaching of plasticizers. Barreto et al. (2012) deposited a barrier coating onto PVC, resulting in a reduction of more than 80% of leaching of the plasticizer. The barrier was established by means of plasma-activated CVD used to polymerize octamethylcyclotetrasiloxane (OMCTS) and hexamethyldisiloxane (HMDSO). Covalent bonding of the plasticizer to PVC... 

---