P1259078426IsTUR

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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
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HAPL Shell Specifications

• Out of round
• Wall uniformity
• Non-concentricity
• Gas tight
• Smooth surface lt 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.
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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 (gt1 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.

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Origin of the Skin

• RD large pore RF for NRLs 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.
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Conventional Skin Forming RF Synthesis
Initial steps of both methods are the same.
dissolve monomer
nucleation
clustering
F
F
F
R
R
R
F
R
Fformaldehyde Rresorcinol
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.
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Possible Skin Formation Mechanism
oil phase
aqueous 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

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The Standard RF Shells 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.
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Initial Experiment Shows the Formation of Skin
Bulk material
Skin
Initial experiment yielded an optically shiny RF
bead. SEM demonstrates the difference between
the bulk RF material and the skin.
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Varying the Acid May Change Skin Morphology
acetic acid
propanoic acid
hexanoic acid
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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.

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Laser Microscopy Confirms the Smooth Skin
59 nm RMS RF bead with skin, 202 x 270 µm scan.
26 nm RMS RF bead with skin, 67 x 90 µm scan.

• Data acquired with a Keyence scanning laser
  confocal microscope
• RMS data is similar to that obtained by
  interferometry

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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.

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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

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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