T3B) How to get the best from your carbon black

Report
How to get the Best From
Your Carbon Black
PNW Coatings Society
October 2014
Agenda
• Review of Carbon Black Fundamentals
• Dispersion Process and Optimization
• Process
• Wetting
• Dispersion
• Stabilization
• Correct Carbon Black Product
• Dispersant types
• Examples
• Summary
2
Review of Carbon
Black
Fundamentals
Four Fundamental Properties of Carbon Black
• Fineness
• Particle Size Distribution
• Structure
• Aggregate Size/Shape Distribution
• Porosity
• Pore Size Distribution
• Surface Activity
• Surface Functionality Distribution
4
Properties of Carbon Black - Primary Particle Size
• Measured directly by Electron Microscope or indirectly by tint test, ISA, NSA
• A wide distribution of particle sizes within a product, but similar particle
size within an aggregate
• Birla Carbon make blacks with mean particle sizes from 8 nm to 100 nm
Raven 410
100 nm
Raven 1255
21 nm
Conductex 7055 Ultra
42 nm
Raven 5000 Ultra II
8nm
5
Surface area and its influence
• Smaller particle diameter generally leads to high surface area
• Surface area typically measured by nitrogen absorption (ASTM
D6556) or iodine titration (ASTM D1510)
• Birla Carbon’s carbon blacks have surface areas ranging from 25580+ m2/g
• High surface area is the single biggest predictor of
color performance (masstone and tint)
• Higher surface area increase viscosity and
conductivity and UV protection
• High surface area lower dispersibility
6
Carbon Blacks
7
Structure – Oil Absorption Number (ASTM D2414)
• Oil Absorption Number, primarily influenced by aggregate
size/shape, may be influenced by porosity
• The amount of oil to reach a peak torque, results given as cubic
centimetres of oil per 100 g carbon black
8
Effect of Structure on Performance
Higher structure (OAN) leads to
• Slightly lower blackness and tint strength
• Better dispersibility
• Higher viscosity and vehicle demand
• Higher electrical and thermal conductivity
9
Porosity and its Influence
• Porosity is caused by oxidation in the reactor and is controlled
by residence time
• Indicated by a difference between Nitrogen Surface Area (NSA)
& Statistical Thickness Surface Area (STSA)
• High porosity gives an increase in
• Conductivity
• Viscosity
• Moisture pick up
• High porosity
• Enables a low loading in conductive applications
• Decreases gloss
10
Surface Activity and its Influence
• Property describing the interaction
of a carbon black surface with its
surroundings
• Furnace carbon blacks can be
chemically surface treated after
production to mimic channel blacks
Carbon Black
as produced
Oxidation
• Increase of surface activity by an
increased number of acid groups
leads to improved dispersion
• Improves wetting of the carbon
black by most vehicle systems
• Reduces viscosity in liquid systems
950 OC
No Oxygen
Post treatment adds oxygen
groups to the surface
• Reduces conductivity
11
Measurement of Surface Activity
• Volatile (Mass loss at 950 °C)
• Usually indicative of oxygen function groups, sometimes influenced by
moisture, sulfur and toluene extract
• pH (ASTM D1512)
• Generally assumed to indicate surface acidity by oxygen functional
groups, often strongly influenced by sulfur levels
• Oxygen Content
• Direct measure of bulk oxygen
• XPS Analysis
• Measure of surface composition by atomic type, and some qualitative
information on oxygen functionalities
12
Oxygen Functionality – Volatile
Increasing Acidity
Carboxyl
Phenol
Aldehyde
Lactone
Quinone
Anhydride
Ether
13
Dispersion
Optimization
Stages of Dispersion Process
Premixing
Grinding
Depends on
- Premixing
- Grinding
- Letdown
15
Correct Carbon Black Product
• For full color coatings, a high surface area product, which gives a
jet color and blue shade
• For tint applications, there is a tradeoff between strength and
blue shade. Higher tint products giver a browner shade, lower
strength products give a blue shade.
16
Full Color Performance
0.6
10
9
0.4
Untreated Products
Treated Products
0.2
Blueness
Hunter b
8
7
6
5
0.0
-0.2
-0.4
-0.6
4
-0.8
-1.0
3
0
50
100
150
200 250
STSA
2
m /g
300
350
0
400
50
100
150
200 250
STSA
2
m /g
300
350
400
0.6
Untreated Products
Treated Products
0.4
0.2
Blueness
Hunter b
Jetness
Hunter L
Untreated Products
Treated Products
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
3
4
5
6
7
Jetness
Hunter L
8
9
10
17
Tint Color Performance
120
0.00
Hunter Undertone (b)
90
60
-2.00
-3.00
-4.00
30
-5.00
0.0
40.0
80.0
120.0
STSA (m²/g)
160.0
200.0
0.0
40.0
80.0
120.0
STSA (m²/g)
160.0
200.0
0.00
-0.50
-1.00
-1.50
Hunter Undertone (b)
Tinting Strength (%)
-1.00
-2.00
-2.50
-3.00
-3.50
-4.00
-4.50
-5.00
0
20
40
60
Tinting Strength (%)
80
100
120
18
Dispersant Choice
• Surfactants
Low molecular weight dispersing agent which can modify the
properties between the pigment and resin solution by lowering
their interfacial tension.
• Polymeric Dispersants
Higher molecular weight dispersing agents, composed of
anchoring groups and polymeric chains that stabilize
dispersions via a steric stabilization mechanism.
19
Surfactants Can be Classified by Head Group Type
•
•
•
•
Anionic – negative charge
• Sodium dodecylsulfate (SDS) also called sodium lauryl sulfate
• (C12H25)OSO3Na
• Good for basic pigment surfaces
Cationic – positive charge
• Cetyltrimethylammonium bromide (CTAB)
• (C16H33)N(CH3)3Br
• Good for acidic pigment surfaces
Nonionic – No charge
• Octaethylene glycol monododecyl ether
• (C12H25)(OCH2CH2)8OH
• Good for neutral pigment surfaces
Zwitterionic – both postive and negative charge (on different parts of the molecule)
• Phosphatidylcholine (as seen in lecithin)
• Good for neutral pigment surfaces
20
Surfactants Can be Classified by Tail Type
• Saturated
–
• Unsaturated
– Monounsaturated
– Polyunsaturated
21
Phosphatidylcholine Structure
22
Polymeric Dispersants
Polymeric dispersants are at least a two-component structure which combines
the following requirements:
a) Specific Anchor Groups
The dispersant must be capable of being strongly adsorbed into the
carbon black surface via the anchoring groups.
b) Polymer Chains
The dispersant must contain polymeric chains that give steric stabilization
in the required solvent or resin system.
23
Effect of Dispersant Choice : Leather Coating
10.99
4.50
10.00
4.00
9.00
3.50
8.00
3.00
7.00
6.27
6.00
1.85
5.56
5.83
1.00
0.90
5.66
4.89
1.43
5.00
4.00
2.50
6.51
1.12
2.00
Bluness Hunter b
Jetness Hunter L
11.00
1.50
1.01
1.00
0.78
3.00
0.50
2.00
0.00
Reference
"Drop In"
A
B
C
Y
Z
24
Effect of Dispersant Choice : WB Automotive
6.00
1.6
L
b
5.00
1.2
3.93
0.8
3.64
3.49
3.02
3.04
3.00
2.94
2.81
0.4
2.61
0.09
2.00
0.0
-0.05
-0.05
-0.08
-0.18
1.00
-0.42
0.00
Bluetone Hunter b
Jetness Hunter L
4.00
-0.40
-0.19
-0.4
-0.8
25
Effect of Dispersant Loading: WB Automotive
3.90
3.70
Jetness Hunter L
3.50
3.30
3.10
2.90
2.70
2.50
60
70
80
90
100
Dispersant Amount Wt %
110
120
130
26
Effect of Dispersant Loading: SB Automotive
305
300
Jetness My
295
290
285
280
275
0%
20%
40%
60%
Dispersant Amount
80%
100%
120%
27
Summary
• The first stage in getting the best from your carbon black, is
choosing the right carbon black initially
• Tailor dispersant and resin chemistry to optimize performance
• Ladder study to optimize loading
28
Further Information : Thank you
• MSDS, brochures and other
information is available at
birlacarbon.com
• The International Carbon Black
Association website carbonblack.org also contains useful
health and safety information
including a users guide
29

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