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2058. Marra, J.V., “Metallized OPP film, surface characteristics and physical properties,” J. Plastic Film and Sheeting, 4, 27-34, (Jan 1988).

Metallized OPP (oriented polypropylene) film offers exceptional gas and water vapor barrier properties, making it one of the most cost-effective flexible protective packaging materials. Its barrier properties correlate with opacity, which, in turn, de pends on the degree of coverage by the metallization. Minor defects, such as scratches, will generally represent only a small percentage of the total coverage of a package and have a proportionally small effect on the barrier properties of the pack age. The high-energy metal surface is extremely active and will wet well and adhere strongly when clean. In fact, it is so active that it is easily coated with trace amounts of any low energy organic material with which it makes contact. For assurance of consistent wetting and bonding, metallized OPP surfaces should be cleaned in-line, such as by bare-roll corona treatment.

1459. Ke-Chang, G., and Z. Shao-Hua, “Plasma treatment on polytetrafluoroethylene and the adhesion property,” in Antec '88, 1555-1558, Society of Plastics Engineers, Apr 1988.

1961. Cho, K., and A.N. Gent, “Adhesion between polystyrene and polymethylmethacrylate,” J. Adhesion, 25, 109-120, (Apr 1988).

Measurements have been made of the energy required to break through unit area of polystyrene (PS), polymethylmethacrylate (PMMA), and joints prepared by molding the two polymers in contact. The results were: 1.23 ± 0.5 kJ/m2 (PS), 0.46 ± 0.10 kJ/m2 (PMMA), and 0.22 ± 0.04 kJ/m2 for the bonded joint. Thus, the interface was significantly weaker than either adherend, but surprisingly strong for two incompatible materials. Microscopy and selective dyeing revealed that fracture took place at the interface itself, with no appreciable transfer of material from one side to the other. It is concluded that Van der Waals interactions are sufficient to create relatively strong bonds.

2379. Mita, F., K. Kitagawa, T. Arakawa, and S. Simizu, “Method of checking the degree of plasma treatment,” U.S. Patent 4740383, Apr 1988.

A method for checking the degree of plasma treatment of an article. The method comprises depositing a substance able to change color as a result of plasma treatment on a carrier, the carrier having pores having an average pore size of 0.2-3 μm, placing the carrier having said substance deposited thereon near the surface of the article, subjecting the substance carrying carrier and the article to plasma treatment, and evaluating the color change that has occurred in the substance.

185. Kaplan, S.L., and P.W. Rose, “Plasma treatment upgrades adhesion in plastic parts,” Plastics Engineering, 44, 77-79, (May 1988).

635. Gombotz, W.R., and A.S. Hoffman, “Functionalization of polymeric films by plasma polymerization of allyl alcohol and allylamine,” in Plasma Polymerization and Plasma Treatment of Polymers, Yasuda, H.K., ed., 285-303, John Wiley & Sons, May 1988.

929. Markgraf, D.A., “Statistical quality control (SQC) applied to corona treating,” Flexo, 13, (May 1988).

2989. Hillborg, H., and U.W. Gedde, “Hydrophobicity recovery of polydimethylsiloxane after exposure to corona discharges,” Polymer, 39, 1991-1998, (May 1998).

A high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer has been subjected to corona discharges for different periods of time in dry air. The loss and recovery of hydrophobicity of the surface have been characterized by contact angle measurements. Immediately after exposure to corona discharges, samples showed a low surface hydrophobicity and, on storage in dry air, a continuous increase in hydrophobicity finally approaching the hydrophobicity of the unexposed material. The activation energy of the hydrophobicity recovery was two to four times greater than the activation energy of the diffusivity of low molar mass PDMS in PDMS elastomers, indicating that the diffusivity properties of the oxidized surface layer were different from that of the bulk. PDMS elastomers quenched in liquid nitrogen or subjected to small mechanical deformation ( < 1% strain) after exposure to corona discharges for 1 h or more recovered their hydrophobicity faster than untouched specimens kept under identical conditions. X-ray photoelectron spectroscopy confirmed the early formation of a silica-like surface layer, with a thickness of at least 10–12 nm. The atomic composition of the oxidized surface layer remained essentially unchanged after the first hour of corona discharges. It is suggested that the silica-like surface layer delayed the recovery of hydrophobicity by inhibiting the transport of low molar mass PDMS to the surface. It is also suggested that thermally or purely mechanically induced stresses lead to a cracking of the brittle silica-rich layer and that this in turn facilitates the transport of low molar mass PDMS to the surface and to a more rapid recovery of the hydrophobicity. Data obtained by reflection infrared spectroscopy assessing the outermost micrometer, confirmed the oxidation and the formation of hydroxyl groups at a progressively higher concentration with increasing exposure time of corona discharges.

285. Pennance, J.R., “The role of surface tension in printing on plastic films,” ScreenPrinting, 78, 64-69, (Jul 1988).

1291. Podhajny, R.M., “Corona treatment of polymeric films,” J. Plastic Film and Sheeting, 4, 177-188, (Jul 1988).

A summary of recent studies on the corona treatment of films is presented. Chemical functional groups generated by the corona discharge on these films are identified and their effect on ink film wettability and adhesion discussed.

1982. van Oss, C.J., R.J. Good, and M.K. Chaudhury, “Additive and non-additive surface tension components and the interpretation of contact angles,” Langmuir, 4, 884-891, (Jul 1988).

1960. Dillard, J.G., T.F. Cromer, C.E. Burtoff, A.J. Cosentino, R. Cline, G. Maciver, “Surface properties and adhesion of flame treated sheet molded composite (SMC),” J. Adhesion, 26, 181-198, (Oct 1988).

The surface chemistry of sheet molded composite (SMC) following interaction with a natural gas/air flame operated under reducing, stoichiometric, and oxidizing conditions has been investigated. The SMC surface chemistry is altered to contain in addition to hydrocarbon, ether, and ester functional groups, carbonyl and a greater carboxyl concentration. The extent of surface oxidation varies with the flame condition in the manner oxidizing ∼ stoichiometric > reducing. Lap shear tests carried out at 82°C (180°F) for coupons bonded with a urethane adhesive did not fail by fiber tear. Surface analysis results indicate failure at an oxidized SMC-adhesive/non-oxidized SMC interface and within the non-oxidized SMC surface.

199. Kolluri, O.S., S.L. Kaplan, and P.W. Rose, “Gas plasma and the treatment of advanced fibers,” in SPE Advanced Polymer Composites Conference Proceedings 1988, Society of Plastics Engineers, Nov 1988.

250. Munro, H.S., and D.I. McBriar, “Influence of post treatment storage on the surface chemistry of plasma oxidized polymers,” J. Coatings Technology, 60, 41-46, (Nov 1988).

289. Podhajny, R.M., “Corona treating and press speed,” Converting, 6, 76, (Dec 1988).

628. Comyn, J., “Keynote overview on surface treatment for adhesive bonding,” Construction and Building Materials, 2, 210-215, (Dec 1988).

Improper or inadequate surface treatment is one of the commonest causes of failure in adhesive bonding, but the selection of a good surface treatment can bring marked improvements in the wet durability of adhesive bonds to metals and glasses, and can permit the bonding of otherwise unbondable materials such as polytetrafluoroethylene (ptfe) and the polyolefins. Untreated surfaces may be unsatisfactory for adhesive bonding because they may be contaminated, may lack polar chemical groups or the interface they make with an adhesive may be susceptible to hydrolysis.

76. DePuydt, Y., P. Bertrand, Y. Novis, et al, “Surface analysis of corona treated poly(ethylene terephthalate),” British Polymer Journal, 21, 141-146, (1989).

Poly(ethylene terephthalate) (PET) Mylar® samples were treated by corona discharge in order to improve their adhesive properties. The corona treatments were performed in different atmospheres including nitrogen, ammonia and air.

X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical modifications induced at the PET surface by these corona treatments. XPS results show that nitrogen incorporation takes place in the form of non-oxygenated nitrogen functionalities, like amine or cyano groups. These are present at the surface of all the corona-treated samples but in different concentrations depending on the gases used in the corona discharge. Furthermore, XPS analyses performed after heating of the treated samples show a higher thermal stability of the corona-induced surface modifications in the case of nitrogen and ammonia.

Ion scattering spectroscopy (ISS) and static secondary ion mass spectroscopy (SIMS) analyses were also performed because of their higher surface sensitivity compared with XPS: ISS reveals that nitrogen is not present at the topmost surface layer of the treated samples but is incorporated just beneath. The outermost surface layer presents a composition rich in oxygen. Finally, static SIMS spectra show that corona treatment induces more surface degradation when performed in air compared with nitrogen or ammonia.

These results are discussed in relation to adhesive properties of PET.

128. Gervason, G., J. Ducom, and H. Cheradame, “Relationship between surface energy and adhesion strength in polyethylene-paper composites,” British Polymer Journal, 21, 53-59, (1989).

This work reports adhesion behaviour of polyethylene on paper, and deals with the surface energy of the materials involved in the manufacture of these composites, and its influence on the adhesion strength, at constant roughness, for the paper substrates. The surface energy of different papers treated with various sizing agents was determined by measuring contact angles according to the Owens-Wendt method. The peeling energy was shown to follow a linear relationship versus the reversible energy of adhesion. This result is explained by the fact that rupture takes place at the interface and that the size of the defect at the interface depends on the spreading coefficient. Corona treatment, applied to strongly sized papers before making the composites, restored the adhesion strength to its original range of values, again demonstrating the thermodynamic character of adhesion in thermoplastic-paper composites.

137. Golub, M.A., T. Wydeven, and R.D. Cormia, “ESCA study of several fluorocarbon polymers exposed to atomic oxygen in low Eart h orbit or downstream from a radio-frequency oxygen plasma,” Polymer, 30, 1571-1575, (1989).

The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinyl fluoride) (Tedlar), tetrafluoroethylene-hexafluoropropylene copolymer (in the form of a Teflon FEP coating on Kapton H, i.e. Kapton F) and polytetrafluoroethylene (Teflon or Teflon TFE) exposed to atomic oxygen (O(3P)) - either in low Earth orbit (LEO) on the STS-8 Space Shuttle or within or downstream from a radio-frequency oxygen plasma - were compared. The major difference in surface chemistry of Tedlar induced by the various exposures to O(3P) was a much larger uptake of oxygen when etched either in or out of the glow of an O2 plasma than when etched in LEO. In contrast, Kapton F exhibited very little surface oxidation during any of the three different exposures to O(3P), while Teflon was scarcely oxidized.

138. Golub, M.A., and R.D. Cormia, “ESCA study of poly(vinylidene fluoride) tetrafluoroethylene-ethylene copolymer and polyethylene exposed to atomic oxygen,” Polymer, 30, 1576-1581, (1989).

The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinylidene fluoride) (PVDF), tetrafluoroethylene-ethylene copolymer (TFE/ET) and polyethylene (PE) exposed to atomic oxygen (O(3P)), in or out of the glow of a radio-frequency O2 plasma, were compared. ESCA spectra of PE films exposed to O(3P) in low Earth orbit (LEO) on the STS-8 Space Shuttle were also examined. Apart from O(3P)-induced surface recession (etching), the various polymer films exhibited surface oxidation, which proceeded towards equilibrium saturation oxygen levels. The maximum surface oxygen uptakes for in-glow or out-of-glow exposures were in the order: PE >TFEET >PVDF; for PE itself, the oxygen uptakes were in the order: in glow > out of glow > LEO. Given prior ESCA data on poly(vinyl fluoride) and polytetrafluoroethylene films exposed to O(3P), the extent of surface oxidation is seen to decrease regularly with increase in fluorine substitution in a family of ethylene-type polymers.

159. Hjertberg, Y., B.A. Sultan, and E.M. Soervik, “The effect of corona discharge treatment of ethylene copolymers on their adhesion to aluminum,” J. Applied Polymer Science, 37, 1183-1195, (1989).

The efficiency of different techniques of obtain improved adhesion in polyethylene-aluminum laminates have been studied. Both surface treatments, such as thermal oxidation and corona discharge, and the use of copolymers with polar comonomers, i.e., vinyl acetate (EVA) and butyl acrylate (EBA), have been included. Thermal oxidation performed by high temperature extrusion including an ozone shower seems to be more effective than corona discharge. In a model experiment thermal oxidation was studied in more detail. The adhesion, as measured by a T-peel test, increased with the content of carbonyl measured by reflexion IR, except for relatively long thermal treatments. In the latter case molecular scission gave a large fraction of low molecular weight material with low cohesive strength. For EBA and EVA the peel strength increased linearly with the bulk concentration of comonomer from about 100 N/m for untreated polyethylene to 450 and 300 N/m, respectively, at 5 mol % comonomer. Corona discharge treatment of these copolymers had, however, a most remarkable effect on the adhesion properties. The increases, relative to untreated EBA and EVA, were much more dramatic compared to polyethylene, e.g., three to four and less than two times, respectively. The higher values obtained with EBA are suggested to be due to the conversion of acrylate groups into carboxylic acid. In the case of EVA, loss of acetic acid might instead decrease the content of polar groups.

174. Janczuk, B., T. Bialopiotrowicz, and W. Wojcik, “The components of surface tension of liquids and their usefulness in determinations of surface free energy of solids,” J. Colloid and Interface Science, 127, 59-66, (1989).

Measurements of the interfacial tension of glycerol-dodecane, formamide-dodecane, ethylene glycol-dodecane, and aqueous ethylene glycol solution-dodecane and the surface tension of ethylene glycol-water solutions were carried out. On this basis the surface tension components of these liquids were calculated and they were compared with values from the literature. It was found that they are close to J. Panzer's (J. Colloid Interface Sci.44, 142, 1973) results obtained by using solubility parameters. In order to verify whether the determined components of the surface tension of polar liquids are valid, measurements of equilibrium contact angles for these liquids were made on the surface of paraffin, polytetrafluoroethylene, polyethylene, polyethylene terephthalate, and polymethyl methacrylate. The measured values of contact angles were compared with those calculated, using the well-known components of the surface free energy. Good agreement was achieved among measured and calculated contact angle values and those obtained by other researchers. It was found that the calculated components of the surface tension of polar liquids worked well in the studied systems, and the geometric mean used for dispersion and nondispersion interfacial interactions gives good results despite existing intermolecular forces due to hydrogen bonding.

175. Janczuk, B., and T. Bialopiotrowicz, “Surface free energy components of liquids and low energy solids and contact angles,” J. Colloid and Interface Science, 127, 189-204, (1989).

Employing the values of organic liquid surface tension and interfacial surface tension of water-organic liquid, values of dispersion and nondispersion components of these liquids were calculated and compared with those obtained in another way. For these organic liquids and water, the values of the contact angle on paraffin wax, polytetrafluoroethylene, polyethylene, polyethylene terephthalate, and polymethyl methacrylate were measured. The values of dispersion and nondispersion components of surface free energy of these polymers and paraffin wax were calculated using the measured values of the contact angle for diiodomethane and water and the calculated values of the components of their surface tension. These calculated data were in agreement with the literature data. Taking our values of free energy components of liquids and solids, the values of the contact angle for these solids were calculated and compared with those measured, obtaining good agreement. On the basis of the measurements and calculations it was found that dispersion and nondispersion components of surface free energy of liquids and solids “work well” in the systems studied.

177. Johnson, R.E. Jr., and R.H. Dettre, “An evaluation of Neumann's 'Surface equation of state' (comments),” Langmuir, 5, 293-295, (1989).

207. Ladizeski, N.H., and I.M. Ward, “The adhesion behavior of high modulus polyethylene fibers following plasma and chemical treatment,” J. Materials Science, 24, 3763-3773, (1989).

Previously published pull-out adhesion results have been substantiated by more extensive studies of chemical and plasma treatment. Particular attention has been paid to the affect of geometrical variables on the values of adhesion obtained. The effect of strain rate has also been examined. Most of the results can be understood on a semi-quantitative basis by a simple extension of lap joint theory.

221. Li, D., E. Moy, and A.W. Neumann, “The equation of state approach for interfacial tensions: comments to Johnson and Dettre,” Langmuir, 6, 885-888, (1989).

225. Lub, J., F.C.B.M. van Vroohoven, E. Brunnix, and A. Benninghoven, “Interaction of nitrogen and ammonia plasmas with polystyrene and polycarbonate studied by X-ray photoelectron spectroscopy, neutron activation analysis and static secondary ion mass spectrometry,” Polymer, 30, 40-44, (1989).

The interactions of NH3 and N2 plasmas with the surfaces of polystyrene (PS) and bisphenol-A polycarbonate (PC) have been studied with X.p.s. and SSIMS. Primary amino groups could be detected at the surfaces of both polymers after treatment with the NH3 plasma but not with the N2 plasma, with the aid of derivatization reactions with salicylaldehyde and 5-bromosalicylaldehyde. PC differs in its reactivity from PS with respect to its ease of undergoing chain scission during the plasma treatments, which results in modified structures of low molecular weight at the surface. The surface coverage of primary amino groups on PS after treatment with the NH3 plasma was determined by means of neutron activation analysis after derivatization of these groups with 5-bromosalicylaldehyde and estimated to be approximately 0.5 amino groups per nm2.

241. Morra, M., E. Occhiello, and F. Garbassi, “Contact angle hysteresis on oxygen plasma treated polypropylene surfaces,” J. Colloid and Interface Science, 132, 504-508, (1989).

PTFE was treated with oxygen plasma, and the effects of treatment time were evaluated by XPS, SEM, and the contact angles of water and CH2l2. Advancing and receding angles were interpreted in the light of current theories on contact angle hysteresis. It was found that at short treatment time wettability reflects chemical modification of the surface, while at longer treatment times surfaces are deeply etched and contact angles are controlled by roughness. With water as the wetting liquid, the typical behavior of composite surfaces was observed.

242. Morra, M., E. Occhiello, and F. Garbassi, “Contact angle hysteresis on oxygen plasma treated poly(tetrafluoroethylene) (letter),” Langmuir, 5, 872-876, (1989).

PTFE was treated with oxygen plasma, and the effects of treatment time were evaluated by XPS, SEM, and the contact angles of water and CH2l2. Advancing and receding angles were interpreted in the light of current theories on contact angle hysteresis. It was found that at short treatment time wettability reflects chemical modification of the surface, while at longer treatment times surfaces are deeply etched and contact angles are controlled by roughness. With water as the wetting liquid, the typical behavior of composite surfaces was observed.

247. Morrison, I.D., “On the existence of an equation of state for interfacial free energies,” Langmuir, 5, 540-543, (1989).

262. Occhiello, E., M. Morra, F. Garbassi, and J. Bargon, “On the application of XPS, SSIMS, and QCM to study the surface of a CF4/O2 plasma treated polycarbonate,” Applied Surface Science, 36, 285-295, (1989).

XPS, SSIMS, water contact angle and each rate measurements have been used to characterize the effect of CF4/O2 discharges on bisphenol-A-polycarbonate (PC). 1% O2 discharges resulted in the grafting of fluorocarbon radicals to the polymer surface. At higher O2 percentage in the gas feed fluorine atoms reacted with the polymer surface inducing degradation of the aromatic rings and etching. Oxidation of the PC surface was observed after all the treatments. Due to considerations based on reactivity and relative concentration in the discharge, oxygen molecules are considered more effective than oxygen atoms in inducing oxidation. Etching was found to occur as well; fluorine atoms and oxygen molecules are considered most important in promoting it.

313. Schmidt, J.J., J.A. Gardella, Jr., and L. Salvati Jr., “Surface studies of polymer blends, II. An ESCA and IR study of poly(methylmethacrylate)/poly(vinyl chloride) homopolymer blends,” Macromolecules, 22, 4489-4495, (1989).

Angle-dependent ESCA and ATR-FTIR results are presented for homopolymer blends of poly(Methyl methacrylate) and poly(vinyl chloride}. Blends over the entire composition range were cut from tetrahydrofuran (THF) and methyl ethyl ketone (MEK). Surfacee enrichment of PMMA was present at all compositions of blends cast from THF, while blends cast from MEK exhibited surface compositions that were within error limits equivalent to the bulk compositions in the blends.

437. Chen, J., and H.L. Ren, “Research of instable interface mechanism in coextrusion,” in ANTEC 89, 206-211, Society of Plastics Engineers, 1989.

487. Iriyama, Y., “Plasma polymerization and plasma treatment for modification of surfaces of polymeric materials (PhD thesis),” Univ. of Missouri, Rolla, 1989.

527. Markgraf, D.A., “Sizing: the critical element for effective corona treating,” in 1989 Coextrusion Seminar Proceedings, 17+, TAPPI Press, 1989.

541. Occhiello, E., M. Morra, G. Morini, and F. Garbassi, “Effect of oxygen plasma treatments on polypropylene - epoxy interfacial strength,” in Interfaces Between Polymers, Metals, and Ceramics, Ishida, H., 199-204, Materials Research Society, 1989.

The effect of oxygen plasma treatment on adhesion and surface properties of polypropylene (PP) was assessed. An oxygen rich modified PP layer, immiscible with bulk PP, was formed by the treatment. Contact angle measurements showed that macromolecular motions led with time to rearrangements of the surface layer drastically decreasing its wettability, while its composition, measured by XPS, remained unaffected.The shear strength of PP-epoxy joints increased after plasma treatment. The locus of failure was found to occur at the PP/epoxy interface for untreated PP, within PP in the case of oxygen-plasma-treated samples, close to the modified PP/bulk PP interface. This result suggests that the plasma treament improves the interaction at the PP/epoxy interface, but weakens the mechanical strength of the surface layer thereby creating a weak point at the modified PP/bulk PP interface.

583. Thompson, K., “Surface treatments for coextruded polymer films and coatings,” in 1989 Coextrusion Seminar Proceedings, 11-12, TAPPI Press, 1989.

587. Varughese, K.T., P.P. De, and S.K. Sanyal, “Contact angle behavior of poly(vinyl chloride)/epoxidized natural rubber miscible blends,” J. Adhesion Science and Technology, 3, 541-550, (1989).

Contact angle studies of miscible poly(vinyl chloride)/epoxidized natural rubber (PVC/ ENR) blends were carried out in air using water and methylene iodide. The solid surface free energy was calculated from harmonic mean equations. Blending of PVC and ENR decreased their contact angle or increased their solid surface free energy due to the improved chain mobility, and the accumulation of excess polar sites at the surface through conformational alterations resulting from the specific interaction of PVC and ENR. The work of adhesion, interfacial free energy, spreading coefficient, and Girifalco-Good's interaction parameter changed markedly with the blend composition. In blends, PVC and ENR improved hydrophilicity, and wettability with polar and non-polar liquids. The presence of a plasticizer in PVC, in general, further improved the wettability and hydrophilicity in blends.

609. Dick, F., “Beta Kit Wettability Test Solutions,” Marbetech, 1989.

687. Ulren, L., and T. Hjertberg, “Adhesion between aluminum and copolymers of ethylene and vinyltrimethoxysilane,” J. Applied Polymer Science, 37, 1269-1285, (1989).

The adhension between aluminum and poly(ethylene-co-vinyltrimethoxysilane) (EVS) and poly(ethylene-co-butylacrylate-co-vinyltrimethoxysilane) (EVSBA), respectively, have been studied. For comparison an ordinary low density polyethylene (LDPE), a poly(ethylene-co-butylacrylate) (EBA), and an ionomer regarded as a bonding polymer were studied as well. The peel strength of laminates obtained by pressing were measured by a T-peel test. The structure of the fracture surfaces were investigated by reflection-IR, ESCA, and SEM. The peel strength of the LDPE and the EBA samples were 100 and 700 N/m, respectively. Although the amount of vinylsilane was low, about 0.2–0.3 mol %, its presence had a pronounced influence on the adhesion: 1800 and 3000 N/m for EVS and EVSBA, respectively. This is even higher than the value observed for the ionomer, 1560 N/m. Although there was a marked difference in surface topology, the SEM and ESCA analysis showed that the fracture was cohesive for both EVS and EVSBA. Immersion in water at 85°C increased the peel strength even more, especially in the case of EVSBA (up to 9000 N/m), in contrast to what is normally observed with aluminum polyethylene laminates. The results suggest that strong and nonhydrolyzable bonds, e.g., covalent bonds, have been formed across the polymer-metal interface for the ethylene copolymers containing vinylsilane.

 

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