NH3-plasma treatment

Li et al. have reported results from tensile and pull-out tests on plasma-treated polyethylene fiber eonerete eomposites (/= 12.7mm, if=38pm, Ff = 2%) [32]. Among the three treatments (NH3, CO2, and Ar) investigated, NH3 plasma treatment provided the best improvement in bond strength (up to 35% over untreated fiber eomposites). 

It is worth noting that the amino groups introduced by the NH3 plasma treatment made possible the immobilization of various compounds on the membrane surfaces (Ldvesque et al. 2002 Lopez et al. 2006 Liu et al. 2006 Buonomenna et al. 2007). Also, the action of the nitrogen plasma on the PP membranes was investigated in detail to apply it to bacteria sterilization (Ricard and Canal 2010). 

After one minute of NH3 plasma treatment he found a 114% inaease in T-peel, a 31% increase in interlaminar strength and, a 5% decrease in toughness. However, he also found the major changes in failure mechanisms already mentioned and attributed the low loss in toughness to those changes. 

FIG. 29 Auger analysis of the Al-PP interface after (a) NH3 plasma treatment, (b) He plasma pretreatment. AlmetLW-l. A1oxlvv-2, Ckll"3- (Adapted from Ref. 123.)... 

In [123] the difference in the Auger profiles of the Al metallized PP following different low-pressure corona discharge treatments is shown. In the case of NH3 plasma-treated PP a broader interface is observed (Fig. 29a). The Alj etLvv (63.5 eV) peak persists for higher ion doses (Fig. 29a, curve 1) which allow measurement of the carbon (Fig. 29a, curve 3). The interdiffusion of Al in the subsurface layers of NH3-treated PP is also shown by the Al yv (52 eV) peak evolution with dose (Fig. 29a, curve 2). In contrast, in the case of NH3 plasma treatment with a He plasma pretreatment, AES shows a sharp interface (Fig. 29b). A drastic decrease of Al et peak is observed and no intermixing of Al with carbon was observed. 

Williams and coworkers utilized low-powered plasma treatment in the presence of four different gases (O2, Ar, N2, and NH3) to treat with the surface of the medical-grade silicone mbber. 

Besides the changes in wettability, they found that the hemocompatibility was significantly affected by plasma treatment. Treatment of PDMS with both Ar and O2 induced a decrease in hemocompatibility, leading to shorter clotting times. The N2 and NH3 treatments had a significantly beneficial effect on the activation of the coagulation cascade. 

The adhesion between phases and the dispersion state seem to play a very important role. To improve wetting behavior, dispersion, and adhesion by grafting reactions, a plasma treatment (02/N2/NH3) of the TP powders can be performed in a fluidized bed (Lennon et al., 2000a). 

In a related study [62], similar effects on conductivity of SWCNTs were reported, but here a comparison was also made between the effects of nitric acid reflux and air plasma treatment, and an attempt was made to relate the changes observed to the creation of defect sites. The authors did not offer a more concrete proposal regarding the nature of the sites involved in these treatments. After the acid treatment, Raman microscopy results indicated a dramatic change in SWNT electronic structure, and both treatments enhanced the electron transfer kinetics for the oxidation of inner-sphere dopamine. By contrast, both treatments had a negligible effect on the voltammetric response of a simple outer-sphere electron-transfer redox process Ru(NH3)63+/2+. ... 

Analysis of the Non Metallized. Pretreated Polypropylene. In a previous paper (1), we have shown that for very short treatment times (23 ms) in N2 or NH3 plasma, the first observed effect of the plasma was an increase of the dispersive component (y ) of the polypropylene surface tension. Since almost no nitrogen nor oxygen were detected by XPS for treatment times shorter than 0.7 s, it was concluded that the plasma had first a physical effect rather than a chemical one, although the efficiency of the treatment on the Al-PP adhesion was high (as proven by the use of a scotch-tape test). 

Polyacrylic acid (PAA)—P2VP mixed brushes were prepared by a similar synthetic procedure, by grafting of carboxyl-terminated poly(ferf-butyl acrylate) (PtBuA) and P2VP. Afterwards, PtBuA was hydrolyzed in the presence of p-toluene sulfonic acid. The same strategy was employed to graft mixed PEL brushes on polymer surfaces. In this case plasma treatment was used to functionalize surface of polymer substrates. We introduced amino groups on the surface of PA-6 and PTFE by treatment of the polymer samples with NH3 plasma. Then the carboxyl terminated homopolymers were grafted step by step from the melt to the solid substrate via amide bonds. 

The same protocol was used for the grafting from procedure to graft mixed brushes on to polymeric substrate. Plasma treatment was used to introduce hydroxyl (oxygen plasma) and amino (NH3 plasma) functional groups on to the polymeric surfaces and then Cl-ABCPA and two different homopolymers were grafted by polymerization from the functionalized surface. 

Biocompatibility and adhesion of different cells to the polystyrene surface is significantly enhanced by the formation of amine groups on the surfaee during treatment in NH3 plasma. Similarly, the amine groups ereated inNHs plasma on the surfaee of PTFE provide adhesion of collagen. 

The hydrophilicity of the NH3 plasma-treated PP membranes increased with the increase in plasma treatment time and decreased with the increase in storage time (Yan et al. 2008). The adsorption of BSA on the modified membranes was lower than that on the unmodified-membrane surface and the flux recoveries after water and caustic cleaning for the NH3 plasma-treated membranes for 1 min were 51.1% and 60.7% higher than those for the unmodified membrane. However, the mechanical properties of the membranes decreased after prolonged plasma treatment, thus the optimal plasma treatment time for membrane modification was taken as 1 min. 

Poly(phenylene oxide) (Kumazawa and Yoshida 2000), PMMA (Yamamoto et al. 2003), and PES (Iwa et al. 2004) membranes were treated with NH3 plasma and the gas separation properties of the modified membranes were examined. The treatment resulted in an increase in the CO2/N2 separation factor as well as the permeability to CO2. 

In the case of the PDMS gas, the membrane permeability of CO2 decreased, but the selectivity of CO2 over CH4 was found to be remarkably improved irrespective of the plasma gas used (NH3, Ar, Nj, O2). The nitrogen plasma treatment seemed to give better selectivity than the ammonia plasma (Matsuyama et al. 1995). The NH3 and N2 plasma treatment of the dense PE (Nakata and Kumazawa 2006) and PP (Teramae and Kumazawa 2007) membranes increased both the permeation coefficient for CO2 and the ideal separation factor for CO2 relative to N2. The effects of both plasma gases are very similar. 

Smith [43] also reports the results of the plasma treatment of high modulus graphite in high modulus epoj (Thomel T-300 in DER 332/T403). He found the following T-peel results for different plasma gases dry air, +41%, Ar, +32%, NH3, +22% and, O2, -18%. 

Hydrophilic modification of the membrane surface is also a promising method to control membrane fouling because the surface properties of membranes dominate the membrane characteristics. Plasma treatment is a widely used and effective technique to create polar organic functional groups on the membrane surface. Membrane hydrophilicity can be drastically improved by plasma treatment using various gases such as NH3 and CO2, and plasma treated membranes show better filtration performance and antifouling characteristics compared with unmodified ones (Yu et al., 2005). 

Different snrface treatments have been compared alkaline hydrolysis in presence of NaOH, H O plasma, and NH plasma. The physicochemical characteristics of the modified snrfaces were correlated to the adhesion of endothelial cells and to the FN (purified from adult human plasma) reorganization by the adherent cells [29], When compared to the amount of FN remaining on the surfaces after 24 h, a decreasing amount was observed in the order unaltered >NH3 plasma >HjO plasma > NaOH. Cells adhered very well on all FN precoated PHAs surfaces. 

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