poss for surface modification and and corrosion prevention
TRANSCRIPT
POSS for Surface Modification and and Corrosion Prevention
Bill Reinerth
18237 Mount Baldy CircleFountain Valley, CA 92708
www.hybridplastics.com
Presented at the Nanostructured Chemicals WorkshopSeptember 7th - 8th, 2000
General Types of Surface Treatment
• All filler treatments in commercial use are chosen to bond an organic molecule to
molecule to a filler surface.
• Monofunctional coatings aid filler incorporation and dispersion.
• Bifunctional coatings are known as “Coupling Agents” because of their ability to
ability to chemically couple the filler to the polymer.
Silanes
Surfactants
Polymers
Fatty Acids
Titanates
Zirconates
Phosphate Esters
Inorganic
Silane Treatment of Surfaces
Y = Organic functional group
(vinyl, methacryl, epoxy,
amine, thiol, etc.)
X = Cl, OMe, OEt, acetoxy,etc.
Y SiX
XX
Substrates
SilicaQuartzGlassAluminumCopperAlumino-Silicates (clays)MicaTalcInorganic OxidesSteel, IronAsbestosNickelZincLeadCaCO3CaSO4BaSO4GraphiteCarbon Black
Excellent
Good
Slight
Poor
Why use Silanes?
• Surface Modifiers (hydrophobicity, low surface free energy, oleophobicity, etc.)
• Dispersion Agents (Improve wetting and dispersion of filler)
• Coupling Agents (Change a non-reinforcing filler into a reinforcing material)
• Crosslinking Agents
• Adhesion Promoters
• Co-monomers
• Moisture Scavengers
• Corrosion Protection
Benefits of Silanes in Polymer Composites
• Increased strength and toughness (tensile, tear, abrasion, impact)
• Better filler wet-out and dispersion
• Water repellant filler/polymer interphase region
• Lower viscosity of filled resin
• Protection of composite properties against hydrous attack
• Reduce cure inhibition of filler
• Improve electrical properties of filled polymers
• Overall Cost Reduction- Silane treatment enables polymer composites to
composites to be used in new ways.
Mode of Silane Action
Step-by-Step Hydrolysis
• Covalent Bonding
• Hydrogen Bonding
• Electrostatic Interaction
• Interpenetrating Polymer Network
• Modification of Polymer Crystallinity
Coupling by Interaction
Bonding by Condensation
Y Si(OR)3 Y Si(OH)3
Y Si(OH)3 Y SiO
O
Y SiO
O
Polymer
HO
InorganicSubstrate
Catalyst
+ 3 H2O/ - 3 ROH
- x H2O+
Mode of Silane Action-The Real World
• Oligomerization vs. Condensation
• Catalyst, pH, water, time, temperature
• Multiple (>8) ill-defined layers of silane form IPN with
polymer matrix.
OH O O O
SiHO
R
O SiO
Si
O
R
O
SiR
O
O
Si
R
O OHSi
R
O
O
R
Si
Si
O
O
R
R
SiO
Si
O
SiHO
RHO
HO
R
O
R
HO R
InterphaseIPN
Interface
Silanes vs. POSS™-Silanols
• Moisture sensitive
• Volatile liquid (Fp = 27 °C)
• Water required for complete silane
hydrolysis (365 g water/kg Silane)
• Volatile organic by-product released
released (648 g MeOH/kg Silane)
• Moisture stable
• Non-volatile solid or oil
• No activation required
• No VOCs released
Si
Si
O
O
Si
Si Si
O
O
O
OH
SiO
Si
O
OO
O OH
R R
R
R
R
R
R Si
MeMe
Si(OMe)3
POSS™-Silanol Surface Modifiers
Si
Si
O
O
Si
Si Si
O
O
OH
OH
SiO
Si
O
OO
O OH
R R
R
R
R
R
R
Si
Si
O
O
Si
Si
Si
Si
O
O
OH
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R R
OH
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R OH
R = Cyclopentyl, i-Butyl, i-Octyl, Ethyl, Cyclohexyl
Si
Si
O
O
Si
Si Si
O
O
OH
SiO
Si
O
OO
OOH
R R
R
R
R
R
R
O
Si(CF2)5CF3
Me MeSi
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R OSi
Me
Me H
POSS™-Silanol Coupling Agents
• POSS cages can be tailored with virtually any reactive functionality for interaction interaction with a polymer matrix.
• Surface modification can be accomplished before or after polymerization.
Si
Si
O
O
Si
Si Si
O
O
O
OH
SiO
Si
O
OO
O OH
R R
R
R
R
R
R Si
MeMe Si
Si
O
O
Si
Si Si
O
O
O
OH
SiO
Si
O
OO
O OH
R R
R
R
R
R
R Si
MeMe
Si
Si
O
O
Si
Si Si
O
O
O
OH
SiO
Si
O
OO
O OH
R R
R
R
R
R
R Si
MeMe
O
O
Silanes vs. POSS: Monolayer Comparison
• The well-defined polyhedral structure leads to a more well-ordered, regular regular surface.
• POSS cages provide increased surface coverage leading to a more hydrophobic surface.
Si
Si
OO
Si
Si
Si
OO
O O
Si
O
Si
OO
O
O
O
R
R
RR
R
R
R
Si
Si
OO
Si
Si
Si
Si
OO
O O
Si
O
Si
OO
O
O
O
R
R
R
R
R
R
R
O
SiOO
O
5.5 Å
8.1 Å
17.2 Å
12.5 Å
17.2 Å
14.4 Å
POSS: The Hydrophobic “Umbrella”
• POSS acts a hydrophobic “umbrella” covering surface Si–OH groups (Approx. (Approx. 10-12 Si–OH groups/POSS nanostructure)
• The surface coverage provided by a single POSS cage is approximately 8-1058-105 that provided by a typical silane. (2.32 nm2 vs. 0.24 nm2)
OH OH O OH OH
POSS
Multiscale Reinforcement
• POSS can stabilized and reinforce interphase region.
• POSS cages could provide nanoscopic reinforcement of polymer chains which chains which may complement the filler’s macroscopic reinforcement.
• POSS surface treatment can provide added value to traditional fillers.
Macroscopic Filler
POSS
POSS
POSS
POSS
POSS
Polymer
Polymer Polymer
Polymer
Interphase RegionIPN
“Traditional” POSS Surface Modifiers
X = Cl, OMe, OEt
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
SiX
MeMe
1 or 2
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
SiX
MeX
1 or 2
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
R R
R
R
R
R
R
SiX
XX
1 or 2
“Traditional” POSS Crosslinkers
X = Cl, OMe, OEt
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
Si
X
X
X
SiX
XX
SiX
X X
Si
X
X
X
SiX
XX
SiX
XX
SiX
XX
Si
X
X
X
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
Si
X
X
Me
SiX
XMe
SiX
X Me
Si
X
X
Me
SiX
XMe
SiX
XMe
SiX
XMe
Si
X
Me
X
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
Si
X
Me
Me
SiX
MeMe
SiMe
X Me
Si
X
Me
Me
SiMe
XMe
SiX
MeMe
SiX
MeMe
Si
Me
Me
X
(RO)3SiSi(OR)3
Si(OMe)3
Compare with:
Crosslinker
Moisture
Scavenger
POSS for Corrosion Prevention
(HSiO1.5)x x = 8, 10, 12, 14
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
H H
H
H
H
H
H H
• Hydrosilsesquioxane cages form corrosion resistant coating on a variety of metal surfaces by interacting with metal oxides on the surface.
• Coating can be applied by a number of methods but CVD is preferred.
• The nanoscopic size and hydrophobic nature of the POSS coating very effectively prevents the diffusion of water and ions to the surface.
• Residual Si—H groups allow coating to function as a primer layer.
Banaszak Holl,et al US Patent 5,858,544
2283
1175
1013
889
1: chromium oxide
2: H 8Si 8O12 on chromium oxide
Banaszak Holl et al. University of Michigan
Appl. Organomet. Chem. 1999, 13, 279-285.
RAIRS of H8Si8O12 on Chromium Oxide
Chromium Oxide
Line Scan 1 Line Scan 2
STM Image of a H8Si8O12 Cluster Chemisorbed on Si(100)-2x1
Phys. Rev. Lett. 2000, 85, 602.Banaszak Holl et al. University of Michigan
H8Si8O12 on Si(100)-2x1
Phys. Rev. Lett. 2000, 85, 602.University of Michigan
Three Geometrical Constraints:1) Position of features with respect to dimer rows2) Pattern of features
3) Relative height of features within pattern
Monovertex Binding Geometry
Phys. Rev. Lett. 2000, 85, 602.University of Michigan
cracked-cluster monovertex cluster
• Cracked Cluster Bonding Geometry Consistent with No Constraints
• Monovertex Geometry Bonding Geometry Consistent with All Constraints
POSS for Corrosion Prevention
OctaSilane-POSS™
SH1310
• OctaSilane-POSS™ has a more hydrophobic nature than (HSiO1.5)x which should result in even less surface corrosion.
• Spraying would likely be the preferred coating method.
• Residual Si—H groups allow coating to function as a primer layer.
• OctaSilane-POSS™is approximately one tenth the cost of (HSiO1.5)x.
Si
Si
O
O
Si
Si
Si
Si
O
O
O
O
SiO
Si
O
OO
OO
HMe2SiO OSiMe2H
OSiMe2H
HMe2SiOOSiMe2H
HMe2SiO
HMe2SiO OSiMe2H
Why use Silanes?
• Surface Modifiers — POSS provides a more well-defined surface.
• Dispersion Agents — POSS provides a more hydrophobic surface.
• Coupling Agents — POSS changes a filler into a multiscale reinforcement.
• Crosslinking Agents — POSS increases 45 (8 groups vs. 2)
• Adhesion Promoters — POSS™-Silanols — No activation/No VOCs
• Co-monomers — POSS can be tailored with virtually any polymerizable group.
• Moisture Scavengers — POSS increases 85 (24 hydrolyzable groups vs. 3)
• Corrosion Protection — POSS provides a tailorable surface.