Graft-copolymerized PTFE Film Research Articles

Thermal imidization of poly(pyromellitic dianhydride-4,4′-oxydianiline) precursors on fluoropolymers modified by surface graft-copolymerization with glycidyl methacrylate

Composite films of polyimide (PI) and poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) or of PI and poly(tetrafluoroethylene) (PTFE) were prepared by thermal imidization of the poly(amic acid) (PAA) precursors of poly(pyromellitic dianhydride-4,4′-oxydianiline) (PMPA-ODA) on glycidyl methacrylate (GMA) graft-copolymerized FEP and PTFE films. The resulting PI/GMA-g-FEP and PI/GMA-g-PTFE composites exhibited T-peel adhesion strength of approximately 7.0 and 6.5 N/cm, respectively, compared to negligible adhesion strength for the laminates prepared from thermal imidization of the PAA on the pristine and the Ar plasma-treated FEP and PTFE films. X-ray photoelectron spectroscopy (XPS) results revealed that both the PI/GMA-g-FEP and PI/FEP-g-PTFE composite films delaminated by cohesive failure inside the FEP and PTFE films, respectively. The so-delaminated PI films with a covalently tethered FEP or PTFE surface layer were highly hydrophobic, having static water contact angles above 140°. The highly hydrophobic property depends on both the composition and roughness of the delaminated surface.

Electroless deposition of copper and nickel on poly(tetrafluoroethylene) films modified by single and double surface graft copolymerization

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films via UV-induced graft-copolymerization with glycidyl methacrylate (GMA) and 1-vinylimidazole (VIDz) was carried out to improve the adhesion with the electrolessly deposited copper and nickel. The surface compositions and microstructure of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), respectively. Prior to the electroless deposition of the metals, the graft-modified PTFE surfaces were sensitized by SnCl 2, followed by activation with PdCl 2. The electroless plating of Cu and Ni on the VIDz graft-copolymerized PTFE (VIDz-g-PTFE) film could also be carried out in the absence of sensitization by SnCl 2 (the Sn-free activation process). The adhesion strength of the electrolessly deposited metal on the PTFE surface was affected by the type of monomers used for graft copolymerization and the surface graft concentration. The optimum T-peel adhesion strengths of the electrolessly deposited Cu on the VIDz and GMA graft-copolymerized PTFE films were about 2.7 and 6.3 N/cm, respectively. The T-peel adhesion strengths of the electrolessly deposited Ni on the corresponding PTFE surfaces were slightly lower. The T-peel adhesion strengths of the electrolessly deposited Cu and Ni were further enhanced to about 10 N/cm on the PTFE surfaces modified by consecutive graft copolymerizations (double graft copolymerization) with GMA and VIDz.

Interaction of copper atoms with surface graft-copolymerized poly(tetrafluoroethylene) film: an in situ X-ray photoelectron spectroscopic study

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were carried out via UV-induced graft copolymerization with 1-vinyl imidazole (VIDz), acrylic acid (AAc) and glycidyl methacrylate (GMA). The interaction of deposited copper atoms with surface graft-copolymerized PTFE film was studied in situ by X-ray photoelectron spectroscopy (XPS). Functional groups, such as imidazole, carboxyl, and epoxide groups, on the graft chains were found to interact chemically with the deposited copper atoms. The interfacial interactions helped to account for the enhanced adhesion of copper to the graft-copolymerized PTFE surfaces.

Electroless Plating of Copper and Nickel on Surface-Modified Poly(tetrafluoroethylene) Films

Chemical modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced graft copolymerization with glycidyl methacrylate (GMA), followed by reactive coupling of 3-aminopropyltriethoxysilane (APS), or reactive immobilization of polyaniline (PANI) chains had been carried out to improve the adhesion of the electrolessly deposited copper and nickel to PTFE film. The surface compositions and microstructures of the modified PTFE films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The PANI-modified PTFE surface was susceptible to the electroless deposition of copper and nickel in the absence of sensitization by The adhesion strength of the PANI-modified or silane-modified PTFE film with the electrolessly deposited metal was affected by the graft concentration of the GMA polymer, the Ar plasma post-treatment, the graft-modified PTFE surface, and the extent of thermal post-treatment after metallization. The optimum T-peel adhesion strength of the electrolessly deposited metal on the graft-copolymerized and APS-coupled PTFE film could reach about 13 N/cm. This adhesion strength represented a more than tenfold increase over that obtained when the PTFE film was modified by Ar plasma treatment alone. The mechanisms of the adhesion strength enhancement, thermal stability enhancement, and cohesive failure of the metal-PTFE interface were also investigated. © 2001 The Electrochemical Society. All rights reserved.

Grafting of Epoxy Resin on Surface-modified Poly(tetrafluoroethylene) Films

An epoxy/PTFE composite was prepared by curing the epoxy resin on the surface-modified PTFE film. Surface modification of PTFE films was carried out via argon plasma pretreatment, followed by UV-induced graft copolymerization with glycidyl methacrylate (GMA). The film composite achieved a 90°-peel adhesion strength above 15 N/cm. The strong adhesion of the epoxy resin to PTFE arose from the fact that the epoxide groups of the grafted GMA chains were cured into the epoxy resin matrix to give rise to a highly crosslinked interphase, as well as the fact that the GMA chains were covalently tethered on the PTFE film surface. Delamination of the composite resulted in cohesive failure inside the PTFE film and gave rise to an epoxy resin surface with a covalently-adhered fluoropolymer layer. The surface composition and microstructures of the GMA graft-copolymerized PTFE (GMA-g-PTFE) films and those of the delaminated epoxy resin and PTFE film surfaces were characterized by X-ray photoelectron spectroscopy (XPS), water contact angle and scanning electron microscope (SEM) measurements. The delaminated epoxy resin surfaces were highly hydrophobic, having water contact angles of about 140°C. The value is higher than that of the pristine PTFE film surface of about 110°. The epoxy resin samples obtained from delamination of the epoxy/GMA-g-PTFE composites showed a lower rate of moisture sorption. All the fluorinated epoxy resin surfaces exhibited rather good stability when subjected to the Level 1 hydrothermal reliability tests.

Consecutive Graft Copolymerization of Glycidyl Methacrylate and Aniline on Poly(Tetrafluoroethylene) Films

Chemical modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced graft copolymerization with glycidyl methacrylate (GMA), followed by oxidative graft copolymerization of aniline and reactive immobilization of polyaniline (PANI) chains have been carried out to render the PTFE surface conductive. The surface compositions and microstructures of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The PANI chains grafted onto PTFE film surface were similar to the PANI homopolymer. The surface resistance of the aniline graft-copolymerized PTFE film could be reduced to the order of about 104 Ω/sq, compared to the order of 1016 Ω/sq for the pristine PTFE film. Cohesive failure occurred inside the bulk of PTFE film when an epoxy adhesive was applied to peel off the grafted PANI layer from the GMA graft-copolymerized PTFE substrate. The strong adhesion arose from the fact that the PANI chains were...

Surface Functionalization of Poly(tetrafluoroethylene) Films via Consecutive Graft Copolymerization with Glycidyl Methacrylate and Aniline

Chemical modification of argon-plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced surface graft copolymerization with glycidyl methacrylate (GMA), followed by epoxide-ring-opening reaction with aniline (An), and finally oxidative graft polymerization with aniline had been carried out to render the PTFE surface conductive. The surface composition and microstructure of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The graft concentration of the GMA polymer and An polymer increased with increasing concentration of the respective monomer used for graft polymerization. Ethanol, when used as a solvent, catalyzed the coupling reaction of epoxide with An and should be of more than 40 vol % in concentration to achieve the optimum effect. The physicochemical characteristics of the polyaniline (PANI) chains grafted onto PTFE film surface were grossly similar to those of the PANI homopolymer. The surface resistance of the aniline graft-polymerized PTFE film was reduced to the order of about 104 Ω/square, in comparison to the value of 1016 Ω/square for the pristine PTFE film.

Thermal imidization of poly(amic acid) precursors on surface-modified poly(tetrafluoroethylene) films via graft copolymerization with glycidyl methacrylate

A novel method for preparing composites of polyimides (PI) laminated to poly(tetrafluoroethylene) (PTFE) films is reported. PI/PTFE composites were developed through thermal imidization of poly(amic acid) (PAA) precursors on surface-modified PTFE films. Surface modification of PTFE films was carried out via Ar plasma pretreatment of the films, followed by UV-induced graft copolymerization with glycidyl methacrylate (GMA). The surface composition and topography of the graft copolymerized PTFE films and the delaminated PI and PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The adhesion strengths of the PI (imidized PAA) on the GMA graft copolymerized PTFE films were evaluated as a function of various thermal imidization schedules. The adhesion reliability of the PI/PTFE composites was tested by a series of hydrothermal cycles. The development of strong Tpeel adhesion strengths of about 8 N/cm with excellent reliability for the PI/PTFE composites was attributable to the synergistic effect of coupling the curing of the epoxide functional groups of the grafted GMA chains with the imidization process of the PAA and the fact that the GMA chains were covalently tethered onto the PTFE surface. The PI/PTFE composites delaminated via cohesive failure inside the PTFE substrates. The delaminated PI film with a covalently adhered 'rough' PTFE surface layer exhibited a water contact angle as high as 140°.

Surface modification of poly(tetrafluoroethylene) films by graft copolymerization for adhesion enhancement with electrolessly deposited copper

The surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films via UV-induced graft copolymerization with either 3-(trimethoxysilyl)propyl methacrylate (TM-SPMA) or glycidyl methacrylate (GMA) was carried out to enhance their adhesion to electrolessly deposited copper. The surface compositions of the PTFE films at various stages of surface modification and electroless plating were studied by X-ray photoelectron spectroscopy (XPS). The adhesion strength of the graft-copolymerized PTFE film to the electrolessly deposited copper was affected by the type of monomer used for graft copolymerization, the graft concentration, the plasma post-treatment time after graft copolymerization, and the extent of thermal post-treatment after metallization. The maximum T-peel strength achieved between the electrolessly deposited copper and the GMA graft-copolymerized PTFE film was about 11 N/cm. This adhesion strength represented a more than 20-fold increase over what could be achieved when the PTFE film was treated by Ar plasma alone. The mechanisms of the adhesion strength enhancement and the failure mode in the metal-polymer laminates were also investigated. It was found that the failure was cohesive in nature within the PTFE film.

Reactive adsorption of aminosilane onto the glycidyl methacrylate graft‐copolymerized poly(tetrafluoroethylene) film surface for adhesion enhancement with evaporated copper

Surface modification of argon-plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced graft copolymerization with glycidyl methacrylate (GMA) was carried out first. Reactive adsorption of γ-aminopropyltriethoxysilane (APS) onto the GMA graft-copolymerized PTFE (GMA-g-PTFE) film surface was performed by the simple immersion of the film in the APS solution. The adsorption process was studied as a function of the APS concentration, the immersion time of the graft-modified PTFE film in the APS solution, and the washing protocol. The chemical composition and morphology of the silane-modified surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The performance of the silane-modified PTFE surface in adhesion promotion was investigated. The T-peel adhesion strength of the evaporated Cu on the PTFE film with the reactively adsorbed organosilane increased significantly to about 12.5 N/cm. This adhesion strength was more than twice that of the assembly involving evaporated Cu on the GMA-g-PTFE film and about 10 times that of the assembly involving evaporated Cu on the Ar-plasma-treated PTFE film. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 80–89, 2000

Reactive adsorption of aminosilane onto the glycidyl methacrylate graft-copolymerized poly(tetrafluoroethylene) film surface for adhesion enhancement with evaporated copper

Surface modification of argon-plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced graft copolymerization with glycidyl methacrylate (GMA) was carried out first. Reactive adsorption of γ-aminopropyltriethoxysilane (APS) onto the GMA graft-copolymerized PTFE (GMA-g-PTFE) film surface was performed by the simple immersion of the film in the APS solution. The adsorption process was studied as a function of the APS concentration, the immersion time of the graft-modified PTFE film in the APS solution, and the washing protocol. The chemical composition and morphology of the silane-modified surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The performance of the silane-modified PTFE surface in adhesion promotion was investigated. The T-peel adhesion strength of the evaporated Cu on the PTFE film with the reactively adsorbed organosilane increased significantly to about 12.5 N/cm. This adhesion strength was more than twice that of the assembly involving evaporated Cu on the GMA-g-PTFE film and about 10 times that of the assembly involving evaporated Cu on the Ar-plasma-treated PTFE film. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 80–89, 2000

Adhesion and adhesion reliability enhancement of evaporated copper on surface modified poly(tetrafluoroethylene) films from graft copolymerization

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced graft copolymerization were carried out to improve the adhesion and adhesion reliability with evaporated copper. The PTFE film surface was modified by graft copolymerization with a monomer, such as 2-hydroxylethyl methacrylate (HEMA), acrylic acid (AAc), methacrylic anhydride (MAAn), and glycidyl methacrylate (GMA). A double graft copolymerization process, involving initially the graft copolymerization with HEMA, AAc or MAAn, which contained the functional moities for curing the epoxide groups, and subsequently by graft copolymerization with GMA, which contained the epoxide group, was also employed. The adhesion strength of the evaporated Cu on the singly and doubly graft-copolymerized PTFE film was affected by the type of monomer used during graft copolymerization, the concentration of the graft, the extent of O/sub 2/ plasma post-treatment after graft copolymerization, and the extent of thermal treatment after metallization. The T-type peel adhesion strength of the Cu/PTFE laminate obtained under the optimum conditions was about 19 N/cm. The adhesion strengths of the Cu/PTFE laminates remained practically unchanged after the Level I test (85/spl deg/C and 85% relative humidity for 168 h). The good adhesion strength and adhesion reliability must have resulted from the strong affinity of the graft chains for Cu, the extensive crosslinking of the graft chains at the metal/polymer interface, and the fact that the graft chains where covalently tethered on the PTFE surface. The cohesive failure of the metal/polymer laminates was also investigated.

Surface Modification of Poly(Tetrafluoroethylene) Films by Graft Copolymerization for Adhesion Improvement with Sputtered In-Sn Oxides

Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films was carried out via UV-induced graft Copolymerization with glycidyl methacrylate (GMA), acrylamide (AAm) and hydroxylethylacrylate (HEA) to improve the adhesion strength with sputtered indium-tin-oxide (ITO). The surface compositions of the graftcopolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The graft yield increases with increasing monomer concentration and Ar plasma pre-treatment time of the PTFE films. The T-peel adhesion strength was affected by the type of monomer used for graft Copolymerization, the graft concentration, and the thermal post-treatment after ITO deposition. A double graft-copolymerization process, which involved initially the graft copolymeri/ation with AAm or HEA, followed by graft Copolymerization with GMA. was also employed to enhance the adhesion of sputtered ITO to PTFE. T-peel adhesion strengths in excess of 8 N cm were achieved in the ITO graft-modified PTFE laminates. The adhesion failure of the ITO/PTFE laminates in T-peel tests was found to occur inside the PTFE films. The electrical resistance of ITO on all graft-modified PTFE surfaces before and after thermal post-treatment remained conslant at about 30 Ω square, suggesting that the graft layer did not have any significant effect or. the electrical properties of the deposited ITO.

Surface modification of poly(tetrafluoroethylene) films by double graft copolymerization for adhesion improvement with evaporated copper

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced double graft copolymerization were carried out to improve the adhesion with evaporated copper. The PTFE film surface was first modified by graft copolymerization with a monomer, such as hydroxylethylacrylate and acrylamide, which contained functional moities for curing the epoxide groups. The so-modified PTFE surface was subsequently re-exposed to Ar plasma and subjected to UV-induced graft copolymerization with glycidyl methacrylate. The surface compositions of the PTFE films from single and double graft copolymerization were studied by X-ray photoelectron spectroscopy. The adhesion strength of the evaporated copper on the double graft copolymerized PTFE film was affected by the type of monomer used during the first graft copolymerization, the concentration of the first and second graft, the extent of O2 plasma post-treatment after the second graft copolymerization, and the extent of heat treatment after metallization. The T-type peel strength of the Cu–PTFE laminate obtained under optimum conditions was about 19N/cm, which represented a more than ten-fold increase over that obtained when the PTFE film was treated by plasma alone. The mechanism of the peel strength enhancement and the cohesive failure of the metal–polymer laminate were also investigated.

Adhesion enhancement of thermally evaporated aluminum to surface graft copolymerized poly(tetrafluoroethylene) film

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV-induced graft copolymerization with glycidyl methacrylate (GMA) and 1-vinylimidazole (VIDz) were carried out to improve the adhesion with evaporated aluminum metal. The surface compositions of the graft copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The adhesion strength of the evaporated aluminum to the surface graft copolymerized PTFE film was affected by the type of monomer used for graft copolymerization, the graft concentration, the plasma post-treatment of the graft copolymerized PTFE surface prior to metallization, and the extent of thermal treatment after metallization. The optimum T-peel adhesion strengths of the Al/PTFE laminates were in excess of 10 and 5 N/cm, respectively, for the GMA and VIDz graft copolymerized PTFE films. These adhesion strengths are significantly higher than those obtained between the evaporated aluminum and the pristine or plasma-pretreated PTFE film. The mechanism of adhesion enhancement and the failure of the metal-polymer assembly were also investigated. It was observed that the failure occurred within the PTFE film. The strong adhesion between Al and PTFE arises from the charge-transfer interaction between the Al atom and the epoxide moiety of the grafted GMA polymer, as well as from the fact that the graft chains are covalently tethered on the PTFE film surface as a result of the grafting process.

Surface Modification of Poly(tetrafluoroethylene) Films by Graft Copolymerization for Adhesion Improvement with Evaporated Copper

Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV light-induced graft copolymerization with 1-vinylimidazole (VIDz) and glycidyl methacrylate (GMA) were carried out to improve the adhesion with evaporated copper. The surface compositions of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The graft yield increases with the monomer concentration. The adhesion strength of the graft-copolymerized PTFE film and the evaporated copper is affected by the type of monomer used for graft copolymerization, the graft concentration, the plasma posttreatment time after graft copolymerization, and the extent of heat posttreatment after evaporation of copper. A double graft copolymerization process, which involved first the graft copolymerization with VIDz, followed by graft copolymerization with GMA, was also employed to enhance the adhesion of evaporated Cu to PTFE. The T-type peel strength of the PTFE/Cu interface so obtained is about 15 N/cm, which represents a 10-fold increase over that obtained when the PTFE film was treated by plasma only. The mechanism of the peel strength enhancement and the cohesive failure of the polymer−metal interface were also investigated.