In Situ Resorcinol Formaldehyde Coatings

1. In Situ Resorcinol Formaldehyde Coatings John Karnes1, Jon Streit1, Don Bittner1, Nicole Petta1, Shannan Downey2, Mike Droege2, Jared Hund3, Dan Goodin3 1Schafer Corporation, Livermore, CA 2Ocellus Inc., Livermore, CA 3General Atomics, Inertial Fusion Technology, San Diego, CA

2. HAPL Shell Specifications • Out of round • Wall uniformity • Non-concentricity • Gas tight • Smooth surface < 50nm RMS Foam + DT DT DT Vapor ~ 2.3 mm A problematic shell specification is the gas tight, smooth permeation barrier. Our work focuses on new methods to solve this problem.

3. Skin Provides Smoother Initial Substrate RF with Skin as Coating Substrate DVB as Coating Substrate RF as Coating Substrate • DVB with PVP coating was the original design. • Large DVB pores (>1 µm) make it difficult to coat. • RF is being investigated as an alternative (smaller pore size). • Formation of a smooth skin on RF may be beneficial.

4. Origin of the Skin • R&D large pore RF for NRL’s Nike laser • Obvious smooth skin • Usefulness? • Skin reported in the literature • On walls of vessel1 • At oil-water interface2 Skin formation on large pore RF at Schafer. Bulk foam “Skin” 1.) S. A. AL-Muhtaseb and J. A. Ritter Adv. Mater., 2003, 15, 101 2.) K. Nagai, et. al. Macromol. Chem. Phys.2005, 206, 2171 Skin scraped away to reveal bulk RF at ILE2.

5. Conventional & Skin Forming RF Synthesis Initial steps of both methods are the same. dissolve monomer nucleation clustering F F F R R F R R F=formaldehyde R=resorcinol acid in oil oil Acid is added to the aqueous phase in the conventional method. Acid is added to the oil phase in the skin forming method.

6. Possible Skin Formation Mechanism aqueous phase oil phase F • Free monomer is far more mobile than the RF clusters • High acid concentration available at oil-water interface acid acid R acid acid R F R acid acid R F Initial acid attack may encounter free monomer before reaching the RF colloid particles • Acid may catalyze a membrane analogous to phenol-formaldehyde resins

7. The Standard RF Shell’s Surface is Hard to Quantify Surface roughness data cannot be obtained with an interferometer without gold coating due to low reflectivity. Interferometer surface data from a gold coated RF shell with no skin. Surface roughness is 401 nm over a 61 x 46 µm area. Surface of a standard RF shell.

8. Initial Experiment Shows the Formation of Skin Skin Bulk material Initial experiment yielded an optically shiny RF bead. SEM demonstrates the difference between the bulk RF material and the skin.

9. 2mm 2mm 2mm Varying the Acid May Change Skin Morphology acetic acid propanoic acid hexanoic acid

10. The RF Bead with Skin Looks Smooth • Interferometer data from an early RF bead with skin had an 81 nm RMS over an 92 x 122 µm area. • A new RF bead had a 21 nm RMS over a 46 x 61 µm area.

11. Laser Microscopy Confirms the Smooth Skin • Data acquired with a Keyence scanning laser confocal microscope • RMS data is similar to that obtained by interferometry 59 nm RMS RF bead with skin, 202 x 270 µm scan. 26 nm RMS RF bead with skin, 67 x 90 µm scan.

12. Summary • We have developed an RF synthesis technique that produces a thin “skin” at the oil-water interface. • Preliminary experiments have produced samples with RMS surface roughness under 30nm in some areas. • We have synthetic control over this skin- we have identified processing variables that alter the skin morphology.

13. Future Work – RF Skin Technique • Altering the acid species and concentration may allow us to tailor the characteristics of the skin • Adding additional monomer prior to droplet generation may favor a thicker skin • More detailed experiments and thorough characterization is required

14. Future Work - Interfacial Chemistry • Free monomer can also participate in interfacial reactions • We can revisit DVB ideas with the RF system • Preliminary results show that the monomer can react with other agents polyurethane skin