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The theoretical studies on this project demonstrate the feasibility of delaminating PCB boards when PCB bonding materials (resins) are dissolved and removed by the supercritical fluid. Rapid depressurizations in the process can cause foaming effects and hence accelerate the delaminating effect. Addition of a small amount of co-solvent can largely enhance the interactions between supercritical fluid and PCB resins. In the research, carbon dioxide is selected as the supercritical fluid substance to treat the board because of its economic and environmental advantages. 7 mole % of water is added as co- solvent to enhance the PCB interactions with SCF CO2. Some exploratory studies validate the theoretical assumptions and the delaminating effect is confirmed from supercritical fluid treatment when a temperature test at the same conditions fails to obtain the same result. With a supercritical fluid system used at the Advanced Manufacturing Laboratory at Texas Tech University, the research is systematically studied to explore all input variables including pressure, temperature, time, and co-solvent effect with three rapid depressurizations conducted in each experiment. The experiments are designed based on factorial experiment method and totally 36 runs are selected for a fractional test. The weight reduction percent of PCBs is selected as the indication of PCB dissolution effect in SCF CO2 treatment. The analysis on WRP data at various experimental conditions states that the PCB dissolution in SCF CO2 is dependent on pressure but highly related to temperature, especially when temperature is above 200 C. Heavy increase of pressure can induce slight increase of WRP but time increase from 3 hours to 6 hours does not cause any more changes on WRP. Although small increases are induced in WRP analysis, addition of 7 mole % of water can greatly enhance the delaminating effect and surface cracking which is significant for real applications of the process. References [1] Taberman SO, Carlsson B, Erichson H, Brobech J, Gregersen JC. Environmental Consequences of Incineration and Landfilling of Waste from Electr(on)ic Equipment. Copenhagen: the Nordic Council of Ministers; 1995. [2] Martin Goosey, Rod Kellner. A Scoping Study End-of-Life Printed Circuit Boards. London: Intellect & Shipley Europe Limited; 2001. 7 p. [3] Stanford Resources Inc. Electronic product recovery and recycling baseline report: Recycling of Selected Electronic Products in the United States. Washington, D.C.: the National Safety Council; 1999. [4] Nagel N, Nilsson J, Boks C. European end-of-life systems for electrical and electronic equipment. Proceedings of the First International Symposium on EcoDesign; 1999 February 1-3; Tokyo; Japan. Tokyo: EcoDeNet; 1999: p 197-202. [5] Zong Gao, Jianzhi Li, Hong C. Zhang. Printed Circuit Boards Recycling: A State-of-Art Survey. Proceedings of IEEE International Symposium on Electronics and the Environment; 2002 May 6-9; San Francisco; U.S.A. San Francisco: IEEE; 2002: p 234-241. [6] Legarth JB. Recycling of Electronic Scrap [dissertation]. Copenhagen: The Technical University of Denmark; 1996. [7] Prausnitz JM, Lichtenthaler RN, Gomes EA. Molecular thermodynamic of fluid-phase equilibria. In: Turton R, Bailie RC, Whiting WB, Shaeiwitz JA, Editors. International Series in the Physical and Chemical Engineering Sciences: second edition. New Jersey: Prentice-Hall; 2000. 30PDF Image | Recycling Printed Circuit Board Wastes Through Supercritical Fluid Delaminating
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