Grantee Research Project Results
Final Report: Plasma Polymerization: A Novel, Environmentally-Compatible Process for Surface Engineering of Metals
EPA Grant Number: R829579Title: Plasma Polymerization: A Novel, Environmentally-Compatible Process for Surface Engineering of Metals
Investigators: Boerio, F. James , Bengu, B. , Gupta, M.
Institution: University of Cincinnati
EPA Project Officer: Richards, April
Project Period: March 11, 2002 through March 10, 2006
Project Amount: $300,000
RFA: Technology for a Sustainable Environment (2001) RFA Text | Recipients Lists
Research Category: Nanotechnology , Pollution Prevention/Sustainable Development , Sustainable and Healthy Communities
Objective:
The main objective of this research was to develop environmentally compatible, all-plasma processes for surface engineering of metals prior to adhesive bonding. Plasma processes for etching or cleaning of metal substrates such as aluminum and for the subsequent deposition of plasma-polymerized primer films have been investigated. The mechanisms by which typical epoxy adhesive systems interact with plasma-polymerized primer films have also been investigated. Although most of this research involved plasma processes carried out at pressures below atmospheric pressure, the use of air plasmas at atmospheric pressure for surface engineering of metal substrates was also explored.
Summary/Accomplishments (Outputs/Outcomes):
A very effective, environmentally compatible surface engineering process for aluminum consisted of etching the aluminum in an air plasma at atmospheric pressure and then coating the aluminum with a silica-like film in an atmospheric pressure air plasma using hexamethydisiloxane as the monomer. Adhesive lap joints prepared from aluminum substrates that were engineered in this way exhibited outstanding durability when exposed to a cyclically varying corrosive environment. Other plasma-based surface engineering processes that were investigated were much less effective. Examples included etching aluminum substrates in low-pressure argon plasmas and then coating the substrates with plasma polymerized silica-like films using oxygen as a co-reactant. Also included was a process consisting of etching aluminum substrates in atmospheric pressure nitrogen plasmas and then coating the substrates with silica-like films deposited from atmospheric pressure nitrogen plasmas. Silica-like films deposited using low-pressure and atmospheric pressure plasmas had similar chemical compositions. Both types of films contained little carbon, indicating that most of the methyl groups were removed from the monomer during the deposition reaction, but both types of films also contained hydroxyl groups, showing that there were some non-bridging oxygen atoms in the silica-like structures of the films. When a typical epoxy structural adhesive was applied to plasma-polymerized, silica-like films, preferential adsorption of the curing agent dicyandiamide was observed. The extent of the preferential adsorption of the curing agent correlated with the hydroxyl content of the silica-like films. Thus, preferential adsorption of the curing agent was less in the case of films having fewer hydroxyl groups. Adsorption of the curing agent onto the silica-like films probably involved hydrogen bonding of hydroxyl groups in the films with amine and nitrile groups in the curing agent. When the same adhesive was applied to an aluminum substrate, a unique interphase having a molecular structure that was different from that of the bulk adhesive formed adjacent to the metal substrate. Formation of this interphase was mainly due to interaction between dicyandiamide and the metallic substrate through the lone-pair of electrons on the nitrogen atoms of the nitrile groups in dicyandiamide.
Conclusions:
Aluminum/epoxy adhesive bonds with outstanding durability can be prepared using substrates that are etched in atmospheric pressure air plasmas and then coated with silica-like films using hexamethydisiloxane and air as co-reactants in an atmospheric pressure plasma reactor. An all-plasma, environmentally compatible method for surface engineering of aluminum prior to adhesive bonding is thus possible. This new technique should eliminate wastes at the source that result from surface engineering of aluminum; it is compatible with continuous processing and with processing of objects with complex shapes. Moreover, with additional development, the new technique of plasma processing at atmospheric pressure may be applied to surface engineering of other substrates with similar reductions in wastes.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 9 publications | 1 publications in selected types | All 1 journal articles |
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Bengu B, Boerio FJ. Interaction of epoxy/dicyandiamide adhesives with metal substrates. The Journal of Adhesion 2006;82(12):1133-1155. |
R829579 (2004) R829579 (Final) |
Exit |
Supplemental Keywords:
plasma-polymerization, plasma-etching, adhesion, adhesive bonding, air plasmas, atmospheric pressure plasmas,, Sustainable Industry/Business, RFA, Scientific Discipline, Technology for Sustainable Environment, Chemical Engineering, Sustainable Environment, Environmental Chemistry, cleaner production/pollution prevention, Environmental Engineering, waste minimization, plasma polymerization, metal surface engineering, pollution prevention, industrial design for environment, environmentally conscious manufacturing, green design, environmentally benign coating, environmental sustainability, clean manufacturing designs, alternative materials, waste reduction, environmentally conscious design, clean technologies, clean manufacturing, industrial innovations, innovative technology, coating processes, engineeringRelevant Websites:
http://www.eng.uc.edu/~fboerio Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.