Norihiro Inagaki

Surface modification of poly(vinylidene fluoride) film by remote Ar, H2, and O2 plasmas

Abstract The surface modification of poly(vinylidene fluoride) (PVDF) film induced by remote Ar, H2, and O2 plasmas have been investigated using contact angle measurement, X-ray photoelectron spectroscopy, and scanning probe microscope. The contact angle of water shows an improvement in the PVDF surface wettability during short plasma exposure time. Three remote plasmas treated PVDF sheet surfaces occurred dehydrofluorination and oxidation reactions simultaneously. Remote hydrogen plasma was the most effective in defluorination reactions and remote oxygen plasma was unfavorable to abstract fluorine atoms.

Surface modification of poly(tetrafluoroethylene) film by plasma graft polymerization of sodium vinylsulfonate

Poly(tetrafluoroethylene) (PTFE) surface was modified by the graft polymerization of sodium vinylsulfonate, and the chemical composition of the graft-polymerized PTFE surface was analyzed by X-ray photoelectron spectroscopy. Peroxides were formed on the PTFE surface by a combination procedure of argon plasma irradiation and air exposure, and the graft polymerization of sodium vinylsulfonate was initiated by the peroxide groups at 65–80°C. The peroxide concentration is 3 × 10+13 to 5 × 10+13 numbers/cm2. The average degree of polymerization of the graft polymers was 3.4 × 103. The graft polymer is distributed over the PTFE surface, but part of the PTFE surface remains uncovered. The coverage with the graft polymer is 43%. The PTFE surface graft polymerized with sodium vinylsulfonate was somewhat hydrophilic, but the hydrophilicity was lower than that of the PTFE surface modified by plasma treatment.

Surface modification and degradation of poly(lactic acid) films by Ar-plasma

Surface modification of poly(lactic acid) (PLA) film surface by Ar-plasma was investigated by contact angle measurements and XPS in order to answer the following two questions. (1) Could the Ar-plasma modify the PLA film surfaces? (2) What chemical reactions occurred on the film surfaces during the Ar-plasma treatment? The Ar-plasma treatment did not lead to hydrophilic modification of the PLA film surface, but to degradation reactions of the PLA film. Poor modification may be due to instability of the carbon radicals formed from C—O bond scission in the PLA chains by the Ar-plasma.

Comparative studies on surface modification of poly(ethylene terephthalate) by remote and direct argon plasmas

Surface modification of poly(ethylene terephthalate) (PET) film by an argon (Ar) plasma was investigated as a function of the distance from the Ar plasma zone. Changes in distance between the PET film and the Ar plasma zone had a strong influence on the surface modification of the film. The direct Ar plasma treatment (distance between the PET film and Ar plasma zone = 0 cm) was effective in hydrophilic surface modification, but heavy etching reactions occurred during the modification. On the other hand, the remote Ar plasma treatment (distance between the PET film and Ar plasma zone = 80 cm) modified the PET film surfaces to be hydrophilic without heavy etching reactions, although the hydrophilicity of the PET was lower than that by the direct Ar plasma. The remote Ar plasma treatment was distinguished from the direct Ar plasma treatment from the viewpoint of degradation reactions. The remote Ar plasma treatment rather than the direct Ar plasma treatment was an adequate procedure for surface modification and caused less polymer degradation on the film surface.

Surface mechanical properties of low‐molecular‐weight polystyrene below its glass‐transition temperatures

Lap shear and friction force measurements were carried out on a series of monodisperse polystyrene (PS) films below the corresponding glass-transition temperatures. It showed that adhesion between the PS/PS interface was possible at the temperature below the bulk Tg, and the lower the molecular weight of PS, the lower the temperature at which the interfacial strength was detectable. The examination of a series of molecular weights indicated both the surface molecular motion and the magnitude of the interfacial strength were dependent on molecular weight and its distribution. And a steep increase of the friction force with increasing the test temperature was observed around 0 ∼ 30 °C. The contact angle of water versus molecular weight measurements also showed a transition at room temperature. The behavior observed in this study was supposed to be due to the increased molecular mobility, and was in good agreement with the measured surface transition temperatures by DSC.

Improved adhesion of poly(tetrafluoroethylene) by NH3-plasma treatment

—Surface modification of poly(tetrafluor oethylene) (PTFE) by NH3-plasma treatment was investigated by means of contact angle measurement, XPS, and ATR FT/IR spectroscopy. The modified surfaces were adhesively bonded to nitril rubber. The NH3-plasma irradiation made PTFE surfaces hydrophilic. The contact angle of water on the modified PTFE surface was 16 deg, and the surface energy was 62-63 mJ/m2. The NH3-plasma irradiation improved adhesion between PTFE and nitril rubber using a phenol-type adhesive. The peel strength of the joints reached 8.1 × 103 N/m. Carbonyl and amido groups were created on PTFE surfaces by the NH3-plasma irradiation. The mechanism of the improvement of adhesion by the NH3-plasma irradiation is discussed.

Thermal degradation of acrylonitrile–butadiene–styrene terpolymer in bean oil

Abstract Thermal degradation of acrylonitrile–butadiene–styrene terpolymer (ABS) in bean oil has been carried out in the temperature 350 and 370°C. The degradation products have been investigated by means of gel permeation chromatography (GPC) and fourier transform infra-red spectrometry (FTIR). With the presence of bean oil, ABS thermally degrades into asphalt-like degradation residue, which is soluble in common organic solvent such as tetrahydrofuran (THF), instead of monomer and oligomers that are usually generated in direct pyrolysis of ABS. Moreover, for the system of ABS/bean oil the cross-linking reaction of ABS with bean oil takes place and forms a polymer network before the decomposition of ABS. Between the two reaction stages, the polymerization or oligomerization of sequence of adjacent nitrile groups occurs. The thermal degradation of ABS in bean oil was believed to be a radical process, which is dependent on the reaction condition, especially the concentration of bean oil, reaction temperature and time.

Preparation of oxygen gas barrier poly(ethylene terephthalate) films by deposition of silicon oxide films plasma-polymerized from a mixture of tetramethoxysilane and oxygen

To prepare silicon oxide (SiOx)-deposited poly(ethylene terephthalate) films with high oxygen gas barrier capability, SiOx deposition by plasma polymerization has been investigated from the viewpoint of chemical composition. Tetramethoxysilane (TMOS) is suitable as a starting material for the synthesis of the SiOx films. The SiOx deposition under self-bias, where the etching action occurs around an electrode surface, is effective in eliminating carbonaceous compounds from the deposited SiOx films. There is no difference in the chemical composition between the SiOx films deposited under self-bias and under no self-bias. The SiOx films are composed of a main component of SiOSi networks and a minor component of carbonized carbons. The SiOx films deposited under no self-bias from the TMOS/O2 mixture show good oxygen gas barrier capability, but the SiOx films deposited under the self-bias show poor capability. The minimum oxygen permeation rate for poly(ethylene terephthalate) films deposited SiOx film is 0.10 cm3 m−2 day−1 atm−1, which corresponds to an oxygen permeability coefficient of 1.4 × 10−17 cm3-cm cm−2 s−1 cm−1 Hg for the SiOx film itself.

Effects of surface modification by remote hydrogen plasma on adhesion in poly(tetrafluoroethylene)/copper composites

Poly(tetrafluoroethylene) (PTFE) sheet was modified with the remote hydrogen plasma, and the effect of the modification on adhesion between the PTFE sheet and copper metal was investigated. The remote hydrogen plasma was able to make PTFE surfaces hydrophilic without etching. In the modification process, defluorination and oxidation occurred on the PTFE surface. Reactivity of defluorination was 25% (estimated from the concentration of CF2 component) −39% (estimated from the F/C atom ratio). Surface modification of PTFE surface by remote hydrogen plasma contributed to the adhesion between PTFE and copper metal. Peel strength was improved from 7.5 to 92 mN/5 mm by surface modification by a factor of 12. Failure of the PTFE/copper adhesive joint occurred at the interface between the PTFE and copper metal layers, rather than in the inner layer of the PTFE polymer or copper metal layers. Remote hydrogen plasma treatment is a preferable pretreatment of PTFE surface for the fabrication of PTFE and copper metal composites.

Surface modification of aromatic polyamide film by remote oxygen plasma

Surface modification of poly(p-phenylene terephthalamide) (PPTA) film by a remote oxygen plasma treatment has been investigated from a viewpoint of comparison with a direct oxygen plasma treatment. We call the modification procedure in a space far away from the oxygen plasma zone “the remote oxygen plasma treatment,” and the modification procedure in a space just in the oxygen plasma zone (a conventional oxygen plasma treatment) “the direct oxygen plasma treatment.” In a space far away from the plasma zone, oxygen radicals rather than electrons and oxygen ions are predominant, and the PPTA film can be modified by the remote oxygen plasma treatment into a hydrophilic surface without heavy degradation of the PPTA film. The PPTA film surfaces modified by the remote oxygen plasma treatment were analyzed with contact angle measurement, scanning microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy.