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Assessing Tack, Print and
Block of New High-Gloss
Architectural Binders using
Rheological and Mechanical
Measurements
Tessie Ewert
Challenges with Low-VOC High Gloss Paints
2
Poor Properties
Difficult to Differentiate
Similar Samples with
Current Test Methods
ASTM D 4946 – 89:
Block resistance
Tackiness Poor Block
Resistance Low Hardness
ASTM D 2064 – 91:
Print Resistance
Ideal Test Method
Objective
Quantitative
Provides Insight into Structure-Property Information
Need for Better Test Methods
3
Measuring Viscoelastic Properties using Rheology
4
Oscillatory rheology experiments measure
– E′ : Storage (Elastic) Modulus (solid-like character)
– E′′: Loss Modulus (liquid-like character)
– tan(δ) = E′′E′ : Relative liquid-like/solid-like character
δ
RSA-G2 Film Tension
time
am
plit
ude
Strain
Stress
How are Rheology and Tack Related?
5
Substrate Substrate
Paint Film
High E′ : resists deformation
and limits wetting of probe
Step 1: Bonding
Paint Film
High E′′: increases
energy dissipation
Step 2: Debonding
E′ : Elastic Modulus
Solid-like character E′′ : Loss Modulus
Liquid-like character
Probe Probe
Validating the Relationship between Viscoelasticity and
Tack
Tack Experiment
• 25 participants
• Each participants asked to – Contact paint films for 3 seconds with
thumb
– Rank paints from least to most tacky
(1-5 scale)
Rheology Experiment
• Films run at 25 °C
• Measured Eʹ and Eʹʹ
6
• Tested 5 low VOC paints with differences in perceived tack
• Samples dried for 24 hours before testing
• Two parallel experiments
Comparison of E' Measurements to Perceived Tack
Survey
7
Rating
1 = Least Tacky
5 = Most Tacky
Tack ratings correlate well with E′ measurements
Less Tacky More Tacky
* 25 testers asked to rate
samples 1-5 based upon 3
seconds of contact with
thumb
1.0E+06
1.0E+07
1.0E+08
0 1 2 3 4 5 6
E′ at
2.5
rad
/s a
nd
25 °
C (
Pa)
Tack Rating
• Reproducible
• Repeatable
• Ability to relate tack to
material properties
• Understand impact of
bonding time
Advantages of Rheological Measurements for Tack
8
𝝎𝒃𝒐𝒏𝒅𝒊𝒏𝒈 ≅𝟐𝝅
𝒕𝒃𝒐𝒏𝒅𝒊𝒏𝒈
𝑡𝑏𝑜𝑛𝑑𝑖𝑛𝑔 ≅ 3 sec 𝑡𝑏𝑜𝑛𝑑𝑖𝑛𝑔 ≅ 1 hr 𝑡𝑏𝑜𝑛𝑑𝑖𝑛𝑔 ≅ 0.1 sec
Viscoelastic Measurements for Quantitative
Benchmarking and Screening Tool
9
0.0E+00
1.0E+07
2.0E+07
3.0E+07
4.0E+07
5.0E+07
6.0E+07
7.0E+07
8.0E+07
9.0E+07
1.0E+08
EPS Experimental1
EPS Experimental2
EPS Experimental3
EPS Experimental4
Commercial 150g/L
Commercial 50 g/L
Eʹ at
2.1
rad
/s a
nd
25 °
C (
Pa)
YOX Low VOC Colorant
Black Low VOC Colorant
Red Low VOC Colorant
EPS
Samples
Competitive
Benchmarks
Viscoelastic measurements help rapidly screen formulas
Rheology and Print Resistance
10
Rank = 1 Rank = 9
ASTM D4946
• 60 °C, 60 minutes
• Cheesecloth with 500 g weight on top of
1.25 inch stopper
• Visual evaluation of print
Creep and Recovery
• RSA-G2, 8 mm parallel plates 60 °C
• At t1, apply compressive force applied
• At t2, stress removed
• Strain measured during the experiment
time
str
ess
t1 t2
Creep and Recovery Experiments
11
time
str
ess
t1 t2
t = t1: Step stress applied
t > t1: Creep (strain measured)
t = t2: Step stress removed
t > t2: Recovery (strain measured)
time
str
ain
t1 t2 time
str
ain
t1 t2 time
str
ain
t1 t2
Elastic Viscous Viscoelastic
Modeling Creep Behavior
12
Instantaneous
Response
Viscous Flow
Maxwell Model
𝜀 = 𝜎1
𝑬+𝑡
𝜼
Spring
(Elastic)
Dashpot
(Viscous)
Stress, 𝜎
Modeling Creep Behavior
13
Viscous Flow Delayed
Elastic
Response
Burgers Model
𝜀 = 𝜎1
𝑬𝟏+
𝑡
𝜼𝟏+
1
𝑬𝟐1 − 𝑒
−𝑡𝝉
𝝉 =𝜼𝟐𝑬𝟐
Maxwell
Element
Voigt
Element
Stress, 𝜎
Instantaneous
Response
Behavior modeled well by multiple viscous and elastic elements
Modeling Creep Behavior
14
Linear Elastic Spring
Stress, 𝜎
𝜀 =𝜎
𝑬
Spring
(Elastic)
Instantaneous
Response
Behavior modeled well by single elastic element
Creep Behavior and Print Resistance
15 15
Stress, 𝜎 • Only elastic deformation
• Recoverable deformation
• Print Resistance = 9
Stress, 𝜎
• Viscous and elastic response
• Non-recoverable deformation
• Print Resistance = 6
Creep experiment explains print resistance ratings
Tan(δ) and Print Resistance
16
tan(δ)=𝐸′′
𝐸′=𝐿𝑖𝑞𝑢𝑖𝑑 − 𝑙𝑖𝑘𝑒
𝑆𝑜𝑙𝑖𝑑 − 𝑙𝑖𝑘𝑒
• Viscous (non-recoverable)
• Predict lower print
resistance
• Elastic (recoverable)
• Predict higher print
resistance
tan(δ) quickly differentiates samples with differences in print
resistance rating
0
2
4
6
8
10
0.00 0.10 0.20 0.30 0.40 0.50
Pri
nt
Resis
tan
ce R
an
kin
g
tan(δ)
Print Resistance >5
Print Resistance 0-5
Print Resistance > 5
Print Resistance ≤ 5
• Cheesecloth print resistance measured on
• 15 commercial samples
• 2 EPS experimental samples
• Print resistance ratings compared to measured tan(δ)
EPS
Experimental
Samples
A More Quantitative Block Test
17
ASTM D 4946 – 89:
Block resistance T-peel Tests
Sample
Block is influenced by:
• Viscoelastic properties
• Tg
• Molecular weight
• Surface-active additives
T-peel Tests and Block Resistance
18
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 50 100 150 200 250 300
Fo
rce/w
idth
(N
/mm
)
Extension (mm)
Block Rating = 8
Block Rating = 8
T-peel tests differentiate samples which are indistinguishable
by standard methods
Summary
19
Rheology (Tack) Rheology (Print
Resistance)
T-Peel Block
Tests
Quantitative? Objective? Structure
Property
Information?
• EPS has developed rheological and mechanical tests for
• Tack
• Print Resistance
• Block
• EPS developed tests have many advantages compared to standard
industry tests
• Tests are helpful development and benchmarking tools