calcium carbonates for sealants redefining...

Calcium Carbonates for Sealants

Redefining Performance

Kalena Stovall, PhD

Imerys Carbonates

October 19, 2016

Calcium Carbonates in Sealants

Caulks and sealants use high levels of calcium

carbonate for desired performance and cost reduction

Reactive sealants often need very low moisture content for

processing and shelf stability

Specialty engineered carbonates are incorporated to control

rheology and mechanical properties

Higher brightness calcium carbonates offer better color match

and surface finish

Typical carbonates in caulks and sealants

Water-borne caulks: medium PSD GCC

Reactive sealants: fine PCCs and GCCs, treated carbonates

10/19/2016Calcium Carbonates for Adhesives, Caulks &

Sealants

GCC and PCC Manufacturing

Ground Calcium Carbonate (GCC)

3 10/19/2016Calcium Carbonates for Adhesives, Caulks &

Sealants

2.5” and smaller pebbles 1 mm and smaller (0.4 µm)

particles

Crush,

Pulverize,

Grind

Precipitated Calcium Carbonate (PCC)

Big rock Pebble Powder

Final powders made by wet or dry grinding

Calcite, only

Purity impacted by nature and processing

Chemically prepared in aqueous solution

Multiple polymorphs and crystal shapes

Finer PSD options than GCC

Purer calcium carbonate than most GCCs

Higher surface area than GCC

Ultrafine PCC

Polymorphs: Vaterite,

Aragonite, Calcite

Can surface treat either product (with fatty acid or other)

All Calcium Carbonates Are Not the Same..

10/19/2016Calcium Carbonates for Adhesives, Caulks &

Sealants

Typical Differentiation Properties between PCC and GCC

Particle or granular size

Morphology / aspect ratio

Brightness

Surface functionality

Chemical purity

Moisture content

Surface area

Porosity

Oil absorption


Sealants

Silicone and modified

silicones

Polyurethane and

silane-terminated

Water-borne Acrylics

Polysulfide

Butyl

Cost

Manufacturing cycle

Package stability

Application

Adhesion

Tensile properties

Chemical resistance

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100

% p

as

s

Particle Diameter (µm)

3 µm untreated GCC

3 µm fatty acid treated GCC 1

3 µm fatty acid treated GCC 2

3 µm GCC treated withengineered treatment

Particle Size Distribution: More than d50 Matters (Example 3 µm GCCs)


Sealants

Treated GCC 1 and untreated GCC contain more fines may be higher surface area GCC may

have higher viscosity sealant

Fines can be viewed two ways:

1. Overall steepness of the curve more steep = less fines = likely lower viscosity/ faster extrusion rate

2. % of particles passing at 1 µm

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100

% p

as

s

Particle Diameter (µm)

Treated PCC, PPS: 0.06 µm




Particle Size Distribution: More than d50 Matters (Example PCCs)


Sealants

PSD curve and primary particle size (PPS) in PCCs should be considered together available surface area

sealant rheology, mechanical properties

Inflections of particle sizes in a single batch particle packing in sealant and sealant viscosity

Calcium Carbonate Differentiation Study


Sealants

Calcium Carbonate Differentiation – Looking Beyond PSD

Known: PSD and moisture content can influence sealant performance

Manufacturers use untreated and treated GCC, PCC or both to optimize sealant properties

Curiosity/ Hunch: Surface area and surface treatment impact sealant:

Processing time

Rheology

Mechanical properties

To probe this, tested GCCs of varying surface area and surface treatment in a SPUR construction

sealant

Fixed GCC PSD at 3 microns, and examined:


Sealants

GCC Surface Treatment Surface Area

Untreated Naked surface High surface area

Classically treated Excess carboxylic acid* Low surface area

Classically treated Excess carboxylic acid* Low surface area

Engineered product No excess treatment Medium surface area

*Classical carbonate treatment to obtain a monolayer of fatty acid

coverage typically yields an excess of unreacted carboxylic acid

SPUR Sealant Formulation


Sealants

Component Wt %

SPUR+ 1015LM prepolymer 22.2

Plasticizer (DIDP) 18.5

Moisture scavenger (Silquest A-171* silane) 1.0

Calcium Carbonate (PCC) 30.0

Calcium Carbonate (GCC) 25.5

UV Stabilizers 0.5

Thixatropic Agent (SiO2) 0.2

Colorant (TiO2) 1.2

Adhesion Promoter (Silquest* A-1110 silane) 0.6

Catalyst (dibutyltin dilaurate) 0.3

SPUR Sealant Formulation GCCs and PCCs Tested

Product PPS, µm Treatment

level, wt %

Surface

Area, m2/g

GCC A 3 0 4.9

GCC B 3 1.0 2.5

GCC C 3.5 0.9 3.5

GCC D 3.2 2.5 1.8

PCC 1 0.07 2.6 24.5

PCC 2 0.06 2.7 19.5

PCC 3 0.07 2.8 22.6

PPS = primary particle size

Calcium Carbonate Influence on Silylated Polyurethane (SPUR)

Sealant Pre-Batch Processing Time


Sealants

Calcium Carbonate Influence on SPUR Sealant Pre-Batch Processing/

Drying Time

Pre-batched GCC and PCC with DIDP, TiO2 and anti-oxidant package

GCC and PCC not pre-dried

Compounded in mixer with high speed disperser blade (1000 rpm) and scraper

blades (60 rpm)

Mixed under vacuum at 93C until 800 ppm reached

Time to reach 800 ppm tracked

Moisture level checked using volumetric Karl Fisher titration


Sealants

100

150

200

250

300

350

0

500

1000

1500

2000

2500

1 2 3 4

Tim

e to

Red

uce

Moi

stur

e to

800

ppm

(m

ins)

Sea

lant

Initi

al M

oist

ure

(ppm

)

Se…

Calcium Carbonate Influence on Pre-Batch Processing/ Drying Time

Pre-batch processing target: 800 ppm moisture

Surface area is not the clear influencer


Sealants

GCC surface area (m2/g):

PCC surface area (m2/g):

2.5 2.5 3.5

19 19.5 1818

4.9

GCC D

PCC 3GCC B

PCC 2

GCC C

PCC 1

GCC A

PCC 1

100

150

200

250

300

350

0

500

1000

1500

2000

2500

1 2 3 4

Tim

e to

Red

uce

Moi

stur

e to

800

ppm

(m

ins)

Sea

lant

Initi

al M

oist

ure

(ppm

)

Se…

Calcium Carbonate Treatment Influences Pre-Batch Processing/

Drying Time

Pre-batch processing target: 800 ppm moisture

Engineered treatment reduces processing/drying time compared to traditionally treated carbonates


Sealants

GCC D

PCC 3

GCC treatment: Fatty Acid Fatty AcidNone

GCC B

PCC 2

GCC C

PCC 1

GCC A

PCC 1

Unreacted Treatment (wt%): n/a 0.40

Engineered Treatment

0

Calcium Carbonate Influence on SPUR Sealant Rheology & Mechanical

Properties


Sealants

SPUR Sealant Rheology

Sealant based on SPUR+ 1015LM prepolymer compounded with GCC and PCC

Rheology:

Extrusion rate/ gunnability (ASTM C1183)

Slump (ASTM D2202)

Brookfield viscosity


Sealants

Extrusion rate

Semco nozzle, cartridge, instrument

40 psi, 0.318 mm nozzle tipSlump

Mixing / Compounding

0

50

100

150

200

250

1 2 3 4

Ext

rusi

on

Rat

e (g

/min

)

2.5 2.5 3.5

19 19.5 1818

4.9

Influence on Extrusion Rate


Sealants

373k cP 329k cP 290k cP390k cP Brookfield Viscosity

GCC D

PCC 3



GCC B

PCC 2GCC C

PCC 1

GCC A

PCC 1

GCC treatment: Fatty Acid Fatty AcidNone Engineered

Treatment

In general, higher GCC surface area higher Brookfield viscosity and lower extrusion rate

Having no unreacted treatment may influence rheology differently

SPUR Sealant Mechanical Properties

SPUR sealant cured for 2 weeks at 23C and 50% RH

Mechanical Properties:

Tensile (ASTM D412)

Tear (ASTM D624)


Sealants

Tensile Testing

Tear, Die B

0

100

200

300

400

500

600

700

1 2 3 4

% Elongation @ Break

Tensile @ Break, psi

2.5 3.5

19.5 1818

4.9 2.5

19

Influence on Mechanical Properties (Medium Modulus Sealant)

Increase elongation for similar tensile behavior using treated GCC

As-good-as or better tensile performance with untreated GCC versus treated GCC


Sealants

GCC D

PCC 3



GCC treatment: Fatty Acid Fatty AcidNone Engineered

Treatment

GCC B

PCC 2

GCC C

PCC 1

GCC A

PCC 1

Summary

Surface area and surface treatment DO impact sealant processing time, rheology, and

mechanical properties

Specifically,

‒Surface treatment Processing time

‒Surface area Rheology

‒Surface treatment Mechanical properties and rheology

Engineered product provides:

Lower processing and drying time

Good mechanical properties

Rheology modification


Sealants

Thank you for your attentionFor more information, visit: www.imerys-carbonates.com

[email protected]

calcium carbonates for sealants redefining...

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