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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