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2826. Sabreen, S.R., “Advances in atmospheric plasma treatment for polymer adhesion,” https://plasticsdecorating.com/enews/2018/advances-in-atmospheric-plasma-treatment-for-polymer-adhesion, Dec 2018.

2837. Sabreen, S.R., “Improving polymer adhesion: Advancements for low surface energy plastics applications,” Plastics Decorating, 48-51, (Oct 2020).

2877. Sabreen, S.R., “Industrial liquid coating of plastic products - adhesion surface science,” Plastics Decorating, 50-52, (Oct 2021).

2878. Sabreen, S.R., “Single-pass UV LED inkjet printing on 3D plastics - ink chemistry and polymer surfaces,” Plastics Decorating, 44-46, (April 2021).

2909. Sabreen, S.R., “UV/ozone surface pretreatment to improve adhesion of polymers,” Plastics Decorating, 40-44, (Apr 2022).

2931. Sabreen, S.R., “Advanced technologies for decorating polyethylene,” Plastics Decorating, 30-33, (Jan 2022).

1414. Sabreen, S.R., and N. Roobol, “Preparing plastics for painting,” Plastics Decorating, (Apr 2003).

1989. Sachler, E., “The possibility of 'standard' surface tension values for polymers,” J. Colloid and Interface Science, 92, 275-276, (Mar 1983).

708. Sadras, B., P. Laurens, and F. Decobert, “Excimer laser treatment of thermoplastics for adhesive bonding,” Presented at First International Congress on Adhesion Science and Technology, Oct 1995.

3026. Sagit-Levanon, S., and M. Marmur, “Validity and accuracy in evaluating surface tension of solids by additive approaches,” J. Colloid and Interface Science, 262, 489-499, (2003).

1380. Sahil, S., A. Bellel, Z. Ziari, A. Kahlouche, and Y. Segui, “Measure and analysis of potential decay in polypropylene films after negative corona charge deposition,” J. Electrostatics, 57, 169-181, (Feb 2003).

Surface potential decay after negative corona charge deposition has been studied for polypropylene films 50μm thick, over a wide range of decay times and charging voltage (500–2800V). At low initial potential (500–800V), the surface potentials were stable and did not decay. At high initial potential (1200–2800V), the surface potential decay has been clearly observed with differences in the decay rate. The observed decay behavior has been computer simulated to elucidate the transport mechanism in polypropylene films. A good agreement between measured and calculated decay curves was obtained with a model in which charges are transported by hopping of injected carriers between localized trapping centers. The model is characterized by parameters such as the free carrier mobility, the mean free time of carrier between traps and the mean capture time in trap. The transport parameters have been determined by a fitting procedure.

974. Saito, D., “Surface modification by corona discharge,” Nippon Gomu Kyokaishi, 70, 333-339, (1997).

2039. Saito, M., and A. Yabe, “Dispersion and polar force components of surface tension of some polymer films,” Textile Research Journal, 53, 54-59, (1983).

The surface tension and the dispersion and polar components of the surface tension for solids and liquids were estimated by contact angle measurement in order to apply these concepts to a detergency study. Two approximation methods, the extended Fowkes' equation and Wu's equation, were adopted for the calculations. Among the twelve experimental liquid pairs, methylene iodide/water and tricresyl phosphate/water gave values for paraffin, polyethylene, and polystyrene close to the average for the twelve pairs. Values for cellulost acetate and cellophane were there fore obtained using these two pairs. The results showed that the dispersion force component becomes larger with increasing degree of acetylation, while the polar force component becomes smaller.

307. Sakata, I., M. Morita, H. Furuichi, and Y. Kawaguchi, “Improvement of plybond strength of paperboard by corona treatment,” J. Applied Polymer Science, 42, 2099-2104, (1991).

It was found that the treatment of the surfaces of wet pulp sheets (moisture content; up to 85%) in a corona discharge improved greatly the plybond strength of the paperboard obtained when the treated wet pulp sheets were laminated together, pressed, and then dried. Treatment was carried out by use of a corona apparatus which had variable driven roll electrodes for transporting the wet pulp sheets through a corona field and was attached to a high-voltage generator (∼ max 500 W, ∼ 16 kV at 5 kHz). The plybond strengths of the paperboards were examined by means of Tappi RC-273 and JIS P8139 methods. Some experiments regarding the chemical effects of the corona treatment on the surface modification of wet pulp sheets were made with the aid of dye adsorption methods. Both untreated and corona-treated pulps adsorbed basic dyes, methylene blue, etc., with the same extent of dyeing. This indicates that no measurable acidic sites (carboxyl groups) increased on the surfaces of the pulp sheets during the corona treatment. To detect aldehyde groups, the dyeing examination of the pulps with Schiff's reagent was made, and the results showed a higher dyeing ability for the corona-treated pulps compared to the untreated, indicating that aldehyde groups on the pulp surfaces increased with an increase in the degree of corona treatment. The corona treatment seems to produce on the surface layer lightly oxidized and fairly degraded polysaccharide chains, which will tend to swell in water and thus act as an adhesive in plybonding the pulp sheets.

308. Sakata, I., M. Morita, N. Tsurata, and K. Morita, “Activation of wood surface by corona treatment to improve adhesive bonding,” J. Applied Polymer Science, 49, 1251-1258, (1993).

Oxidative activation of resinous wood surfaces by a corona treatment to improve adhesive bonding was studied. It was found that the wettability of the veneers, including hardwoods, softwoods, and tropical woods increased with an increase in the degree of treatment, and the gluability increased rapidly after the initial mild treatment. To elucidate the nature of any chemical change occurring on the wood surface, the dyeing examination of the wood and its components with Schiff's reagent was made, and the results showed a higher dyeing ability for corona-treated samples compared to untreated ones, indicating that aldehyde groups increased by the corona treatment. The treatment affected the alcohol-benzene extractives, and oxidized them to produce aldehyde groups. Especially, the neutral fraction in the extractives was significantly affected. On the other hand, negligible chemical effects of the treatment on the surface modification of the wood's main components were seen. Both the untreated and corona-treated samples adsorbed basic dye to the same extent of coloration. Thus, no measurable carboxyl groups increased on the surface of the samples. It seems that an increase in the wettability of corona-treated wood veneers resulted mainly from the oxidation of the high hydrophobic surface layer of neutral fraction substances in the extractives, and from the reduction in their hydrophobicity. © 1993 John Wiley & Sons, Inc.
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.1993.070490714

2053. Sakhalkar, S.S., K.B. Walters, D.E. Hirt, N.R. Miranda, and W.P. Roberts, “Surface characteristics of LLDPE film containing glycerol monostearate,” J. Plastic Film and Sheeting, 18, 33-43, (Jan 2002).

Glycerol monostearate (GMS) can serve as an anti-fogging agent by increasing the hydrophilic nature of a film surface. In this study, blends of GMS and LLDPE were extruded into film and the GMS was allowed to migrate to the surface over time. The surface was characterized by measuring the static water contact angle, which was then used to calculate the surface free energy of the film. Results showed that the equilibrium wettability of the film deviated dramatically from that of neat LLDPE when the GMS concentrations were greater than about 1900 ppm. Time-dependent studies demonstrated that the rate of surface-energy change was significantly influenced by the GMS concentration.

554. Sakjhalkar, S.S., and D.E. Hirt, “Surface segregation of erucamide in LLDPE films: Thermodynamic analysis and experimental verification,” in ANTEC 98, Society of Plastics Engineers, Apr 1998.

998. Sako, N., T. Matsuoka, and K. Sakaguchi, “Changes and control of plasma modified surface energy of polypropylene with aging time and temperature,” in Adhesion '99, 395-400, Institute of Materials, 1999.

1035. Sako, N., T. Matsuoka, and K. Sakaguchi, “Effect of interface on fracture mechanism of GF/PP composites using O2 plasma treatment,” Composite Interfaces, 4, 401-415, (1997).

Polypropylene sheets are treated with oxygen plasma for the interfacial control of GF/PP composites. The interfacial strength between glass fabric and PP resin is estimated by the T-peel test method. The evaluation of T-peel test data is done by both the T-peel strength method and the T-peel amplitude method. The T-peel strength value and T-peel amplitude value were respectively increased to about 50% and 120% compared with each value of non-treated specimens. The T-peel strength relates to the surface energy on the PP-sheet and the T-peel amplitude relates to the fracture pattern of the delamination surface. From SEM observations on the delamination surface, many voids in the space enclosed with fiber bundles are observed in the case of non-treated specimen and no void and fiber bridging are observed on the plasma treated specimens. It is found that interfacial properties between fiber and resin are improved by this plasma process.

3032. Salapare III, H.S., G.Q. Blantocas, .R. Noguera, and H. J. Ramos, “The porosity and wettability properties of hydrogen ion treated poly(tetrafluoroethylene),” in Contact Angle, Wettability and Adhesion, Vol.6, K.L. Mittal, ed., 207-218, VSP, 2009.

The porosity and wettability properties of hydrogen ion treated poly(tetrafluoroethylene) (PTFE) materials are related using contact angle, scanning electron microscopy (SEM) and ellipsometry techniques. PTFE samples are irradiated using a low-energy hydrogen ion shower (LEHIS) produced by a Gas Discharge Ion Source (GDIS). The plasma discharge current (Id) is varied at intervals of 1 mA. Results show that treatment using lower Id improved the hydrophobic property of the PTFE material with water contact angle increasing from 102◦ to 119◦. It also becomes less porous as indicated by the increase in the index of refraction, decrease in optical transmittance, and increased fissures and striations in the SEM images. Opposite effects are observed for higher Id.

927. Salmaggi, H.L, “Flexo finds the answer: How does the treater roll get affected by dirt, dust, or ink, and how should it be cleaned?,” Flexo, 21, 96, (Feb 1996).

2891. Samuel, B., H. Zhao, and K.-Y. Law, “Study of wetting and adhesion interactions between water and various polymer and superhydrophobic surfaces,” J. Physical Chemistry C, 115, 14852-14861, (Jun 2011).

The wetting and adhesion characteristics of 20 different surfaces have been studied systematically by both static water contact angle (θ) and dynamic contact angle measurement techniques: sliding angle (α) and advancing (θA) and receding (θR) contact angles. These surfaces cover surfaces of all traits, from smooth and flat to rough and artificially textured. Fourteen of the surfaces are flat, and they range from molded plastic sheets to solution coated polymer films to chemical vapor deposition polymerized polymer films and to self-assembled monolayers on Si wafers. The rest of the surfaces include 4 fluorosilane coated textured Si wafer surfaces and two natural surfaces derived from the front and back side of the rose petal. Static water contact angle data suggest that these surfaces vary from hydrophilic with θ at ∼71° to superhydrophobic with θ exceeding 150°. Plots of θ of these surfaces versus α, (cos θR – cos θA), and the contact angle hysteresis (θA – θR) all yield scattered plots, indicating that there is little correlation between θ and α, (cos θR – cos θA) and (θA – θR). Since the later three parameters have been mentioned to relate to adhesion semiempirically between a liquid droplet and the contacting surface, the present work demonstrates with generality that contact angle indeed does not relate to adhesion. This is consistent with a known but not well recognized fact in the literature. In this work, we study both the wetting and adhesion forces between water and these 20 surfaces on a microelectromechanical balance (tensiometer). When the water drop first touches the surface, the attractive force during this wetting step was measured as the “snap-in” force. The adhesion force between the water drop and the surface was measured as the “pull-off” force when the water drop separates (retracts) from the surface. The snap-in force is shown to decrease monotonously as θA decreases and becomes zero when θA is >150°. The very good correlation is not unexpected due to the similarity between the wetting and the “snap-in” process. The analysis of the pull-off force data is slightly more complicated, and we found that the quality of the water–surface separation depends on the surface “adhesion”. For surfaces that show strong adhesion with water, there is always a small drop of water left behind after the water droplet is pulled off from the surface. Despite this complication, we plot the pull-off force versus α, (cos θR – cos θA) and (θA – θR), and found very little correlation. On the other hand, the pull-off force is found to correlate well to the receding contact angle θR. Specifically, pull-off force decreases monotonically as θR increases, suggesting that θR is a good measure of surface adhesion. Very interestingly, we also observe a qualitative correlation between θR and the quality of the pull-off. The pull-off was found to be clean, free of water residue after pull-off, when θR is >∼90° and vice versa. The implications of this work toward surface contact angle measurements and print surface design are discussed.

2635. Samuel, J., and J. Renner, “UV inkjet label printing: Getting it right on the customer's substrate,” Radtech Report, 11-14, (Jul 2011).

Drop-on-demand inkjet printing, familiar to most of us from small home and office printers, is taking an increasing role in printing for the broader commercial and industrial market. Inkjet printing has made serious inroads into the market for printing banners and signs of all sorts. Wide-format and super wide-format printing is now the norm and has, to an increasing degree, superseded analog printing as the method of choice for printing large format and point-of-purchase signage. Overall, inkjet printing has now taken over 30 percent of the general sign and banner market. One area of printing that holds promise for future growth is that of packaging and labels. Many forms of commercial printing, although a huge market today, are threatened on multiple fronts from various forms of electronic media. Printing and decoration for packaging, on the other hand, is expected to increase in volume in the foreseeable future. In spite of this great promise, penetration of digital printing, in general, and inkjet printing, in particular, into packaging and label printing is still in the low single digits. This article will focus on the label market as an example of printing for packaging. Printing for packaging is a much broader and diverse subject than just labels, but many of the conclusions that follow can be extrapolated to the broader packaging market. Toner-based methods, both wet and dry, have been at the vanguard of penetrating the label market. Today, inkjet is slowly gaining market share. Inkjet has great potential because there is more flexibility in the type and characteristics of fluids that can be applied from an inkjet head. While there are many possible explanations for the relatively low penetration of digital printing into this market, this article will concentrate on the technical challenges involved in reliably printing labels of acceptable quality with inkjet printing. Only now is the inkjet printing industry overcoming these challenges.

1094. Sancaktar, E., and N. Sunthonpagasit, “Surface modification of polypropylene for improved adhesion,” in Polymer Surface Modification: Relevance to Adhesion, Vol. 3, K.L. Mittal, ed., 285-324, VSP, Sep 2004.

The objectives of this work were to identify, develop and compare methods for opti-mized welding of polypropylene using the ultrasonic method. The methods considered include: modification of surface polarity by grafting monomers onto polypropylene backbone, thermal and chemical surface pretreatments and surface pretreatment by excimer laser ablation. The weld joint tensile strength was chosen as the optimization criterion for ultrasonic welding. The thermal properties and weld morphology obtained using Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), respectively, were correlated to weld strength. It was determined that proper surface modification improved material weldability. The results suggest that increased polarity and roughness and decreased melting temperature and heat of melting increase the weld strength.

309. Sanchez-Rubio, M., J.R. Castellanos-Ortega, and J.E. Puig, “An analytical balance as tensiometer and densimeter,” J. Chemical Education, 68, 158-160, (1991).

How to convert an analytical balance into an accurate ring tensiometer or densimeter.

555. Sanchez-Valdes, S., et al, “Characterization of LLDPE-LLDPEgMA blends by contact angle and FTIR-ATR,” in ANTEC 97, Society of Plastics Engineers, Apr 1997.

2018. Sanchis, M.R., O. Calvo, O. Fenollar, D. Garcia, and R. Balart, “Surface modification of a polyurethane film by low pressure glow discharge oxygen plasma treatment,” J. Applied Polymer Science, 105, 1077-1085, (2007).

Low pressure oxygen plasma has been used to improve the surface wettability of a polyurethane film. The modifications induced by the plasma treatment in the material were analyzed using contact angle measurements. X-ray photoelectron spectroscopy technique was used for surface characterization of the plasma-treated films. Atomic force microscopy and scanning electron microscopy were used to analyze topography changes due to the plasma-etching mechanism. The results show a much better surface wettability of the film even for short exposure times, with a considerable increase in the surface energy values. As expected, functionalization with oxygen plasma is mainly because of surface oxidation with species like (CO, CO, OH, etc). An aging process with regard to polar groups rearrangement has been observed, thus promoting a partial hydrophobic recovery. Besides functionalization, the surface wettability of the material improves as a consequence of a slight increase in surface roughness because of the etching effect of oxygen plasma.

2089. Sanchis, M.R., O. Calvo, O. Fenollar, D. Garcia, and R. Balart, “Characterization of the surface changes and the aging effects of low-pressure nitrogen plasma treatment in a polyurethane film,” Polymer Testing, 27, 75-83, (Feb 2008).

In this work, low-pressure nitrogen plasma has been used to improve wettability in a polyurethane film. Evaluation of wettability changes has been carried out using contact angle measurements. Furthermore, plasma-treated films have been subjected to air aging to evaluate the extent of hydrophobic recovery. X-ray photoelectron spectroscopy (XPS) has been used to study surface functionalization; surface topography changes related with the etching mechanism have been followed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and weight loss study. The results show a considerable improvement in surface wettability even for short exposure times, as observed by a remarkable decrease in contact angle values. The aging study shows a partial hydrophobic recovery due to the re-arrangement of polar species and migration of low molecular oxidized material (LMWOM). In addition to surface activation, SEM and AFM analyses show slight changes in surface topography as a consequence of the plasma-etching mechanism.

2062. Sanchis, M.R., V. Blanes, M. Blanes, D. Garcia, and R. Balart, “Surface modification of low density polyethylene (LDPE) film by low pressure O2 plasma treatment,” European Polymer J., 42, 1558-1568, (Jul 2006).

In this work, low pressure glow discharge O2 plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O2 plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O2 plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.

816. Sanchis, R.M., O. Calvo, L. Sanchez, D. Garcia, and R. Balart, “Enhancement of wettability in low density polyethylene films using low pressure glow discharge N2 plasma,” J. Polymer Science Part B: Polymer Physics, 45, 2390-2399, (2007).

Low pressure glow discharge nitrogen plasma has been used to improve wettability in a low density polyethylene (LDPE) film for technical applications. The plasma treatment was carried out at a power of 300 W for different exposure times in the 1–20 min range. Wettability changes were analyzed using contact angle measurements. In addition to this, plasma-treated samples were subjected to an aging process to determine the durability of the plasma treatment. X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy were used for surface characterization. The nitrogen plasma treatment considerably reduced contact angle values thus indicating an increase in surface wettability. The spectroscopic study showed presence of oxygen-based species on the plasma-treated samples, which are mainly generated after the plasma treatment as a consequence of air exposure. These polar species contribute to improve surface functionalization, but this is almost lost during aging due to the hydrophobic recovery process. Microscopic studies revealed that also small changes in surface roughness occurred during the plasma treatment but these are very low compared to surface activation. The results confirmed that low pressure nitrogen can be considered as an environmentally efficient process to improve wettability in low density polyethylene films. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2390–2399, 2007

1633. Sapieha, S., J. Cerny, J.E. Klemberg-Sapieha, and L. Martinu, “Corona versus low pressure plasma treatment: Effect on surface properties and adhesion of polymers,” J. Adhesion, 42, 91, (1993).

Low density polyethylene (PE) and polyethylene terephthalate (PET) films were treated in air plasma of a low pressure (500 mTorr) large area microwave (2.45 GHz) discharge, or in a corona discharge at atmospheric pressure. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for their oxygen content [O] and surface chemical structure, which were related to the corresponding peel strength of PE/PE and PE/PET laminates. Although the oxygen concentration at the surface increased monotonically with the degree of treatment, the peel force reached a maximum and then sharply decreased. Regardless of the treatment type, the maximum peel force occurred for [O] values between 10-15 at.%. The highest peel force has been found to occur when the concentration of CSingle BondO (hydroxyl, ether, epoxy,…) groups is highest and that of OSingle BondCSingle BondO (carboxyl) groups is lowest, which corresponds to the situation when the effect of a weak boundary layer, due to low molecular weight materials, is minimal (low OSingle BondCSingle BondO concentration).

556. Sarabia, A., “Plasma surface treatment of poly(phenyl sulfide) and poly(etheretherketone) prior to adhesive bonding (MS thesis),” MIT, 1987.

1130. Sardella, E., R. Gristina, G.S. Senesi, R. d'Agostino, and P. Favia, “Plasma-aided micropatterning of polystyrene substrates for driving cell adhesion and spreading,” in Plasma Processes and Polymers, d'Agostino, R., P. Favia, C. Oehr, and M.R. Wertheimer, eds., 373-388, Wiley-VCH, 2005.

Coatings with polyethylene oxide (PEO)-like films deposited by RF (13.56 MHz) glow discharges and featuring a total cell-repulsive effect were deposited on polystyrene (PS) samples. Substrates containing tracks of PS of petri dishes surrounded by PEO-like domains have been prepared with a good spatial resolution by using a masking procedure. The behavior of the substrates after seeding NCTC2544 human keratinocytes and 3T3Murine fibroblasts has been studied. It has been found that also PS tracks are able to drive cells up to confluence, provided that a longer incubation time is provided. A phenomenological interpretation is suggested.

2527. Sarmadi, A.M., T,.H. Ying, and F. Denes, “HMDSO-plasma modification of polypropylene fibers,” European Polymer J., 31, 847-857, (Sep 1995).

A hexamethyldisiloxane (HMDSO)-RF plasma was used to treat polypropylene (PP) fabrics to achieve an inorganic type surface. The properties of the plasma modified PP were investigated through demand wettability and contact angle techniques. ESCA and ATR-IR spectroscopy indicated the presence of Si  O  Si and Si  O  C based structures. The influence of treatment time on the level of deposition and surface atomic composition was established. Plasma induced molecular fragmentation of HMDSO was determined through GC-MS and high resolution MS analyses of the molecular structures produced from recombination of active species, in the cold trap.

310. Sarmadi, M., and F. Denes, “Surface modification of polymers under cold plasma conditions,” TAPPI J., 79, 189-204, (Aug 1996).

2528. Sarra-Bournet, C., G. Ayotte, S. Turgeon, F. Massines, and G. Laroche, “Effects of chemical composition and the addition of H2 in a N2 atmospheric pressure dielectric barrier discharge on polymer surface functionalization,” Langmuir, 25, 9432-9440, (2009).

We examined the effect of hydrogen content in various polymers in a N2/H2 discharge for surface amine functionalization. Three polymers (polyethylene (PE), polyvinylidene fluoride (PVDF), and poly(tetrafluoroethylene) (PTFE)) containing various amounts of hydrogen and fluorine were treated with an atmospheric pressure dielectric barrier discharge (DBD). While surface modification was observed on the PE and the PVDF in a pure N2 discharge, adding H2 in a N2 discharge was necessary to observe the fluorine etching on the surface of the PVDF and PTFE polymers. The presence of a slight amount of hydrogen in the gas mixture was also a prerequisite to the formation of amino groups on the surface of all three polymers (max NH2/C ∼ 5%). Aging revealed that the modified polymer surfaces treated in a N2−H2 discharge were less prone to hydrophobic recovery than were surfaces treated in pure N2, due primarily to the presence of a higher density of polar groups on the surfaces. We demonstrated that H atoms in the discharge are necessary for the surface amine functionalization of polymers in a N2 atmospheric pressure DBD, regardless of polymer chemical composition. It is therefore possible to control the plasma functionalization process and to optimize the concentration and specificity of NH2 grafted onto polymer surfaces by varying the H2 concentration in a N2 atmospheric pressure DBD.

2276. Sarra-Bournet, C., S. Turgeon, D. Mantovani, and G. Laroche, “Comparison of atmospheric-pressure plasma versus low-pressure RF plasma for surface functionalization of PTFE for biomedical applications,” Plasma Processes and Polymers, 3, 506-515, (Aug 2006).

PTFE surface modifications have been realized using low-pressure RFGD, DBD and APGD in different atmospheres. Compared to the RFGD NH3 plasma, the DBDs operating in H2/N2 lead to similar surface concentrations of amino groups and similar surface damage, but with a much higher specificity. Both APGDs in H2/N2 and NH3/N2 lead to lower concentrations of amino groups, but with similar specificity, and with lower surface damage than the RFGD treatment. A method is proposed to evaluate the efficiency of the different discharges for amine surface functionalization of PTFE, and it is concluded that the NH3/N2 APGD discharge is the one that give the best results for an effective surface treatment.

2558. Sarra-Bournet, C., S. Turgeon, D. Mantovani, and G. Laroche, “A study of atmospheric pressure plasma discharges for surface functionalization of PTFE used in biomedical applications,” J. Physics D: Applied Physics, 39, 3461-3469, (2006).

Plasma polymer surface modification is widely used in the biomedical field to tailor the surface properties of materials to improve their biocompatibility. Most of these treatments are performed using low pressure plasma systems but recently, filamentary dielectric barrier discharge (FDBD) and atmospheric pressure glow discharge (APGD) have appeared as interesting alternatives. The aim of this paper is to evaluate the potential of surface modifications realized with FDBD and APGD in different atmospheres (N2+ H2 and N2+ NH3 mixtures) on poly(tetrafluoroethylene) to determine the relative influence of both the discharge regime and the gas nature on the surface transformations. From XPS analysis, it is shown that the discharge regime can have a significant effect on the surface transformation; FDBDs operating in H2/N2 lead to a high concentration of amino-groups with high specificity but also important damaging on the surface. Glow discharges in both H2/N2 and NH3/N2 lead to lower concentrations of amino-groups with lower specificity but lower surface damaging. Therefore, this simple surface treatment seems to be an effective, low cost method for the production of uniform surface modification with amino-groups that can subsequently be used to graft various chemical functionalities used for biomaterial compatibility.

1837. Sauer, B.B., and N.V. Dipaolo, “Surface tension and dynamic wetting on polymers using the Wilhelmy method: Applications to high molecular weights and elevated temperatures,” J. Colloid and Interface Science, 144, 527-537, (Jul 1991).

A technique was developed to rapidly measure surface tensions (γ) of viscous molten polymers and polymer solutions. The usual problems of slow meniscus equilibration and low signal-to-noise levels due to thermal convection currents at elevated temperatures have been overcome. Small-diameter fibers were used as vertical probes in the Wilhelmy technique to facilitate rapid equilibration of the wetting meniscus, and a “baffle tube” surrounding the electrobalance wire was implemented to suppress noise from thermal convection currents from the oven. Even with the baffle tube, it was found that computer averaging of the measured wetting force was necessary to obtain the desired precision precision atT 250°C. Measurements of γ up to ∼400°C were routinely made with η> 50 P polymers. Data are given for a molten fluoropolymer, a thermoplastic, and a liquid crystalline polymer. Room-temperature polymer fluids with viscosities extending to η = 500,000 P were studied; at η ⩽ 5000 P the precision was better than 0.04mNm. The dynamic contact angle versus time was measured as a function of fiber diameter, giving a relationship between the rate of meniscus equilibration and fiber diameter. Contact angles of polymer fibers immersed in water and methylene iodiode were used to calculate the surface free energies of the polymer in the solid state. These values are consistent with the extrapolated molten surface tension data and help to characterize the trend in γ over a wide range ofT.

311. Savolainen, A., J. Kuusipalo, and H. Karhuketo, “Extrusion coating: corona after-treatment of LDPE coating,” TAPPI J., 73, 133-139, (Jul 1990).

 

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