Vapor Sorption Characterisation of Materials...Overview 1. Vapor Sorption Techniques •Molecules as...

Vapor Sorption Characterisation of Materials

Dr. Daryl Williams

Surface Measurement Systems

Overview

1. Vapor Sorption Techniques • Molecules as Probes (DVS, iGC)

• Sorption Mechanisms

2. DVS Applications • Isotherms and Isotherm Shape

• Phase Transitions

• Sorption Kinetics

3. IGC/SEA Applications • Surface Energy

• Adhesion/Cohesion

• Bulk Properties

2

The Company

• Based in London

• Invented the Dynamic Vapor Sorption Instrument in 1993

• Currently 50 staff- London, USA, France, Germany- 7 PhD scientists

• Installed base >1000 instruments

• Technological market leader in sorption instrumentation

Characterisation of Solids

1. Radiation as a Probe • Raman, NMR, FTIR Spectroscopy • Light, x-rays, lasers, etc.

• Analytical and structural information- what where how much

2. Heat as a Probe • Calorimetry and Thermal Methods

• Thermodynamic information- rates DH DS DG

3. Molecule as a Probe • Sorption and wetting techniques

• Thermodynamic, chemical, and structural information

• Process rates, DH DS DG, diffusion constants, surface energy

4

Radiation as a Probe

1. Structural Information • XRD, XRPD

2. Chemical Information • XPS (ESCA), NMR, FTIR

3. Visual Information • Light Microscopy (polarized)

• AFM, SEM

• Particle size measurements (laser diffraction)

• Particle shape

5

Heat as a Probe

1. Thermodynamic Information • DSC (modulated; hyper)

• TGA

• DMA

• TAM

2. Chemical Reactions • Reaction Calorimetry

6

Molecule as a Probe

1. Chemical Interactions • IGC, DVS, Wetting, TAM, Chemisorption analyzers

2. Physical Structure (surface area, pore size, density, etc.) • DVS, IGC, Volumetric sorption (i.e. BET analyzers), Chemisorption,

Pycnometer

3. Thermodynamic Information • IGC, DVS, TAM

7

Types of Molecule-Solid Interactions

Adsorption

• Physisorption

• Chemisorption

Absorption

• Bulk absorption

• Absorption into lattice structure

Reactions

• Hydration and solvation

Condensation

• Pore filling

8

Adsorption

Molecules In Molecules Out

Adsorption-Physisorption

Molecules Weakly Adsorbed

9

Physisorption

•Weak interactions

•Molecules only on surface

•Probe molecules not chemically bound to surface

•Reversible sorption

•Associated properties measured

• Physical Structure: surface area, pore size, surface roughness

• Chemical Interactions: surface sorption capacity, surface energy, hydrophilicity, Lewis acidity-basicity, surface heterogeneity

• Thermodynamic: heat of sorption, free energy

10

Adsorption

Molecules In

Adsorption-Chemisorption

Molecules Covalently Bonded to Surface

11

Chemisorption

•Strong interactions

•Molecules only on the surface

•Probe molecules are covalently bound to surface

•Can be reversible or irreversible sorption


• Titrate acid-base sites

• Active surface area

• Catalyst Dispersion

12

Absorption-Bulk

Molecules In Molecules Out-Diffusion Limited

Bulk Absorption

Molecules Absorbed

Molecules Interact with Bulk

13

Absorption-Bulk

•Penetrate surface

•Desorption is often diffusion limited

•Reversible or irreversible sorption


• Physical Structure: vapor-induced phase changes (glass transition, crystallization, deliquescence), glass transition temperatures, crosslink density

• Chemical: total sorption capacity, solubility parameters

• Kinetic: diffusion coefficients, solid-solid phase transformation, drying kinetics

14

Dynamic Vapour Sorption

• Dynamic Gravimetric Vapor Sorption (DVS)

• Invented by SMS in 1993

• Long–Term Baseline Balance Stability is Key

• Controlled humidity and temperature

• Dynamic Flowing Gas System means Fast Thermal and Mass Equilibrium

• Conceptual similarities to TGA- but RH the key variable

15 Static Sorption Dynamic Sorption

DVS Introduction

16

DVS Introduction

Dynamic gravimetric Vapor Sorption (DVS)

• Fully automatic sorption instrument

• Fast equilibrium: significantly improved kinetics over static sorption systems

• SMS pioneer in vapor sorption technology

SMS UltraBalance

• Up to 0.1 µg sensitivity; unrivaled long-term baseline stability

• Allows use of small samples 1-10 mg

‘Real-world’ conditions

• Wide range of temperatures: measurement and preheat conditions

• Wide range of vapors: water and organic vapors

17

DVS Advantage

18

Experimental temperatures

System incubator: 5°C to 60°C Upper local sample temp: up to 125°C

Optional modular coil pre-heaters (large and small for temperatures up to 150°C)

Optional modular high-temperature pre-heater (for temperatures up to 350°C)

Pre-experimental temperatures

Microbalance Sample mass: up to 1g Mass change: up to ±150mg Resolution: 0.1µg High-mass option also available

Additional optional modular features Modular color video microscope for qualitative sample data

(use with a limited temperature range)

Dual fiber-optic probe adaptors for coupling with Raman/NIR spectrometers

(use with a limited temperature range)

Modular expandable manifold for use with large-sized samples

• Preconditioning with preheater 150° C or 350°C

• Vapor sorption till 85°C optional till 125°C/20%RH using 150°C preheater

• Humidity or solvent vapor steps, ramps and Isohum/Isochore measurements

• Diffusion / activation energy of diffusion

• Permeation (with Payne Cell)

• Tg versus RH or temperature

• Heat of sorption/Micro/Mesopore size distribution

• Stability tests

DVS Advantage Family

Isotherm Types (BDDT)

20

• Type I: Langmuir isotherm; chemisorption

• Type II: Monolayer formation, BET equation

• Type III: Strong sorbate-sorbate interactions; water often has this behavior

• Type IV: Monolayer formation, BET equation, capillary condensation at high pressures

• Type V: Strong sorbate-sorbate interacitons; capillary condensation at high pressures

• Type VI: only at liquid Kr temperatures

DVS-Typical Data- Kinetics

21

DVS Change In Mass (dry) Plot

-5

0

5

10

15

20

25

0 2000 4000 6000 8000 10000 12000 14000

Time/mins

Ch

an

ge

In

Ma

ss

(%

) -

Dry

0

10

20

30

40

50

60

70

80

90

100

Ta

rget

RH

(%

)

dm - dry Target RH

© Surface Measurement Systems Ltd UK 1996-2001DVS - The Sorption Solution

Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch

Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303

Moisture sorption behavior of rice starch at 25 °C- 2 cycle experiment

DVS-Typical Data-Equilibrium

22

DVS Isotherm Plot

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Ch

an

ge

In

Ma

ss

(%

) -

Dry

Cycle 1 Sorp Cycle 1 Desorp


Date: 07 Dec 2001 Time: 4:14 pm File: ricestarch071201_reduced.XLS Sample: rice starch

Temp: 24.8 °C Meth: duncan.sao M(0): 40.5303

Norit GAC-Mesopore Sorption

• Hysteresis gap suggests mesoporosity (2 to 50 nm)

23

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70 80 90 100

Ch

an

ge

In M

as

s (

%)

-R

ef

Target % P/Po

DVS Isotherm Plot



Date: 11 Mar 2010Time: 14-28File: 1 - Norit GAC - Thu 11 Mar 2010 14-28-15.xlsSample: Norit GAC

Temp: 25.0 CMeth: GAC 0-95 B.saoMRef: 7.944

Channel Hydrate

• Water sorption on Channel Hydrate

• 0.2% RH steps: 0 to 10% RH

24

0

0.5

1

1.5

2

2.5

3

3.5

4

0 10 20 30 40 50 60 70 80 90 100

Ch

an

ge

In M

as

s (

%)

-R

ef

Target RH (%)

DVS Isotherm Plot



Date: 15 Dec 2011Time: 16-13File: Channel Hydrate -

Thu 15 Dec 2011 16-13-33.xlsSample: Channel Hydrate

Temp: 25.0 °CMeth: Channel Hydrate small steps 2.sao

MRef: 13.4291

Quartz-Surface Adsorption

• Isotherm shape (Type II) and low uptake indicate surface dominated sorption

25

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100

Ch

an

ge

In M

as

s (

%)

-D

ry

Target RH (%)

DVS Isotherm Plot

Cycle 1 Sorp


Date: 05 Mar 2003Time: 3:47 pmFile: 03-05-03-quartz-gt-106.xlsSample: Quartz > 106 microns

Temp: 24.9 CMeth: BEToctane.SAOM(0): 5.9975

Fuel Cell Proton Exchange Membranes

26

Nafion-1135 sample sorbs less water than BPSH-30 sample across humidity range

DVS Isotherm Plot

0

2

4

6

8

10

12

14

16

18

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Ch

an

ge

In

Ma

ss

(%

) -

Dry

BPSH-30 Sorp BPSH-30 Desorp Nafion 1135 Sorp Nafion 1135 Desorp


Temp: 25.0 °C

Water Sorption on Hair

27

Moisture sorption behavior of three hair samples at 25 °C

DVS Change In Mass (ref) Plot

0

2

4

6

8

10

12

14

16

18

20

0 500 1000 1500 2000 2500 3000 3500

Time/mins

Ch

an

ge

In

Ma

ss

(%

) -

Re

f

0

10

20

30

40

50

60

70

80

90

100

Ta

rg

et

% P

/Po


Water Sorption on Keratinized Tissues

28

GK Johnsen, ØG Martinsen, and S Grimmes, J of Physics: Conference Series, 224 (2010) 1-4.

SC: Stratum Corneum Nail: Human Nail Hair: Human Hair

Sorption Isotherms of three different cellulose

Yanjun Xie, Callum A. S. Hill, Zaihan Jalaludin, Dongyang Sun. The water vapour sorption behaviour of three celluloses: analysis using parallel exponential kinetics and interpretation using the Kelvin-Voigt viscoelastic model. Cellulose. June 2011, Volume 18, Issue 3, pp 517-530.

sorption isotherms

Water kinetics: mass uptake vs time

-cellulose

linter

MCC

Vapor-Induced Phase Transitions

30

• Water vapor is a strong plasticiser

• Glass transitions

• Transition kinetics from glassy to crystalline phases

Material Morphology and Vapour Sorption

Amorphous- Glassy Solid

T <Tg

Mainly surface adsorption

Fast kinetics and low uptake levels

Amorphous- Rubbery Solid

T >Tg

Deep bulk sorption

Slow kinetics and large uptake levels

Crystalline

No Tg

Surface adsorption

Fast kinetics and very low uptake

Vapor-Induced Transitions

32

• RH ramping experiment (similar to DSC temperature ramp)

• Gravimetric data clearly shows moisture-induced glass transition and crystallization

DVS Change In Mass (dry) Plot

0

2

4

6

8

10

12

14

-100 100 300 500 700 900 1100 1300 1500

Time/mins

Ch

an

ge

In

Ma

ss

(%

) -

Dry

0

10

20

30

40

50

60

70

80

90

100

Ta

rge

t R

H (

%)

% Change in Mass Target RH


Date: 05 Dec 2002 Time: 11:58 am File: 12-05-02-lactoseramp900.XLS Sample: amorphous lactose

Temp: 25.1 °C Meth: lactoseramp0-90-900min.SAO M(0): 93.2048

Glass Transition

Surface Adsorption

Bulk Absorption andSurface Adsorption

Recrystallization

Spray Dried Lactose

Spray dried Lactose powder at 25C shown at a range of humidities: A: 0%RH B: 50%RH C: 60%RH D: 90%RH The formation of a gel, a solution followed by crystallisation is clearly shown.

Color Video Microscope

34

Colour Video Microscope The DVS colour vide microscope is fully

detachable with improved specifications,

coupling qualitative sample information with

DVS isotherm data.

The microscope shows visual sample changes

including swelling, deliquescence events,

cracking and phase changes.

This optional feature can also be used in

combination with some other DVS advantage

modular features.

Key Specifications • 1.3 Megapixel colour images (1280x1024)

• Adjustable focus.

• Adjustable magnification of 50x to 200x

• Picture overlay information includes: date,

sample info, experimental info, adjustable

scale marker, and overlay grid.

• Images exportable to .bmp, .tiff, and .jpeg

file formats

DVS-Microscope Accessory

35

Maltodextrin – 0% RH Maltodextrin – 95% RH, 0 minutes

Maltodextrin – 95% RH, 30 minutes Maltodextrin – 95% RH, 50 minutes

Vapor-Induced Transitions

36

• Ramping experiments at different temperatures

• 2-D stability ‘map’ for meta-stable materials

15

20

25

30

35

40

45

50

55

60

65

15 20 25 30 35 40 45 50 55

Re

lati

ve H

um

idit

y (%

)

Temperature (°C)

Humidity Induced Transitions for Spray-Dried Lactose

Humidity at Glass Transition (%) Humidity at Crystallization (%)

Stable Amorphous Region

Crystalline Region

Unstable Amorphous Region

Sorption Kinetics

37

• Bulk diffusion coefficients with fixed geometries • Film geometry (one-sided/two-sided)

• Spherical (powder) geometry

• Packaging applications • Payne style cell – MVTR determination

• Electronic packaging

Kinetics of Transitions

38

• Monitor mass loss as sample dehydrates

• Study and model drying conditions

Fraction Dehydrated

0

0.2

0.4

0.6

0.8

1

1.2

0 100 200 300 400 500 600 700 800 900 1000

Time/mins

Fra

cti

on

De

hy

dra

ted

30 °C 27.5 °C 25 °C 22.5 °C 20 °C 17.5 °C 15 °C


Two-Sided Film Diffusion

39

• Moisture gain and loss with polymer film; moisture access from both sides

• 1-D Fickian Diffusion coefficient at each step change in RH

Polyimide films

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10000 20000 30000 40000 50000 60000

Sqrt(t)/d

Mt/M

infin

ity

20% RH

20% RH (fitted)

Previous RH (%)

Target RH (%)

Diffusion Coeff. (cm²/s)

R-sq. (%)

0.0 20.0 7.63E-10 99.55 20.0 0.0 4.38E-10 99.58 0.0 40.0 9.04E-10 99.52

40.0 0.0 6.05E-10 99.59 0.0 60.0 9.30E-10 99.54

60.0 0.0 6.55E-10 99.57

Dt

dM

Mt 4

Payne-Style Cell

40

• Payne-style cell allows MVTR determination

• Can be run in dry (a) or wet (b) mode

Test Specimen

Lower O’ring

Drying Agenti.e. Zeolite, Silica Gel

Cell Lid

Cell Cup

Cell opening

Upper O’ring

Temperature & RH controlled environment

(b)(a)

100%RH

0%RH

Payne-Style Cell

41

• Payne-style cell allows MVTR determination

• Investigate surrounding RH effects

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

60 61 62 63 64 65 66 67 68 69 70

Chan

ge In

Mas

s (%

w/d

ry w

)

Time (min)

100 %RH

80 %RH

50 %RH

30 %RH

DVS Vapor Permeability-Membranes

42

DVS-Organic Vapors

• Water and Organic Vapor Control

• Proprietary optical sensor allows for real-time measurement and control of organic vapors

• Does not predict organic vapor concentration like competitive products

• Allows accurate determination of BET surface area, solvate formation, surface energetics, porosity, solid-solvent interactions

• Ethanol, Methanol, IPA, Cyclohexane, Heptane, Octane, Nonane, DCM, Ethyl Acetate, and Toluene commonly used

43

DVS-Organic Vapors

44

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250

% P

art

ial

Pre

ss

ure

Time/mins

DVS Octane Partial Pressure PlotTarget % P/Po Actual % P/Po

BET Surface Area for Hydrophobic Drug

45

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30 35 40 45 50

(P/P

o) / [(

1 -

(P/P

o) )

* M

]

Octane P/Po (%)

DVS BET Plot for Metformin Hydrochloride Fines (less thane 140 mesh)

BET Data Line Fit


Methanol Sorption on Nafion

46

Methanol sorption on different Nafion samples at 25 °C

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100

Ne

t C

ha

ng

e in

Ma

ss

(w

t%)

Methanol P/Po (%)

Methanol Sorption Isotherm at 25 °C

N117 SampleN112 SampleNR112 Sample

Amorphous Content by DVS

47

DVS Isotherm Plot

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50 60 70 80 90 100

Target p/po (%)

Ch

an

ge In

Mass (

%)

- D

ry

100% Crystalline Lactose 2.1700% Amorphous 6.017% Amorphous 24.801% Amorphous 100% Amorphous


Temp: 25.0 °C

Octane adsorption on mixtures of amorphous lactose and

-lactose monohydrate

Amorphous Content by DVS

48

Amorphous content

for mixtures of

crystalline and

amorphous (spray-

dried) Salbutamol

Sulfate

DVS-Raman Accessory

49

1. Raman spectroscopy is the measurement & detection of the wavelength and intensity of inelastically scattered light from molecules. When electromagnetic radiation passes through matter, most of the radiation continues in its original direction but a small fraction is scattered.

2. Rayleigh scattering: Light that is scattered at the same wavelength as the incoming light.

3. Raman scattering: Light that is scattered due to vibrations in molecules or optical phonons in solids.

4. The majority of scattered light is elastic and only one in 106 optical photons are scattered at frequencies different to the incident light – This is the weaker Raman scattered light.

Sample

Incident Laser Light

Rayleigh Scattering

Raman Scattering

DVS Advantage– Video and Raman

50

DVS-Raman Spectroscopy

51

DVS water sorption/desorption results (a.) and in-situ Raman spectra (b.) for MCC at 25 °C.

IGC – Surface Energy

• Surface energy is the most commonly measured property by IGC

• Analogous to surface tension of liquids

• Defined as the excess energy at the surface of a material compared to the bulk

• Directly related to the thermodynamic work of adhesion

• Can be divided into dispersive, acidic, and basic components

Measuring Surface Energy of Solids

Comparisons to Contact Angle

• Contact angle measurements are a common surface energy method

γLV

γ0SV γSL

θY Clean surface

Solid surface

• Sessile drop contact angle performed on powder compacts

• High pressure causes surface deformation; Rough surface topography

• Porous surface leading to penetration of liquid; Swelling; Dissolution

Fast penetration of water droplet into 400 MPa mannitol compacts.

Incr

easi

ng S

urfa

ce E

nerg

y

Wettability Cohesion Process-induced Disorder

Adhesion

What Does Surface Energy Affect?

IGC Principles

Animation by L. Teng, Surface Measurement Systems

iGC-SEA Instrument Overview

• Small footprint: 450 mm (18”) x 450 mm (18”) x 700 mm (27.5”)

• Variable injection sizes; wider concentration range; 1:4000 injection ratio

• 12 vapor reservoirs (50ml)

• 2 column oven design: 20 to 180 °C

• Flame Ionization Detector (FID)

• Humidity control (optional)

58

IGC Sample Preparation

Silane-treated glass tube 30cm long & 6 mm O.D. 2, 3 , 4 and 10 mm I.D. 10 mg – 500 mg of material typically

0.5 m2 of surface area

Glass wool

Sample

Schematic of IGC

IGC Principle: Retention Time

• Single pulse of probe molecule

• t0 is the retention time for an inert molecule (distribution coefficient KR = 0, CH4, Ar, N2 & H2)

• tR is the retention time for the interacting probe

• Net retention time tN = tR - t0

Detector response

Time

Methane Hexane Heptane Octane

t0 tR,OctanetR,Heptane

tR,Hexane

Detector response

Time



tR,Hexane

Detector response

Time



tR,Hexane

Isotherms

Det

ecto

r Res

pons

e

Time

Det

ecto

r Res

pons

e

Time

Det

ecto

r Res

pons

e

Time

Am

ount

Ads

orbe

d

Partial Pressure

Am

ount

Ads

orbe

d

Partial Pressure

Am

ount

Ads

orbe

d

Partial Pressure

a) b) c)

The retention time is directly related to the first derivation of the amount adsorbed

The height is related to the partial pressure

Dispersive Surface Energy

Dispersive Component of Surface Energy

Sequential injection of alkanes with increasing C-chain length at specific

surface coverage

Plot RTlnVN vs. a(γdL)

1/2 then γds = (slope/2NA)2

d

L

d

SmAN aNConstVRTG 2ln0 D

Surface Energy Heterogeneity

Decane

Nonane

Octane

Heptane

Surface Coverage

Known sample BET surface area

Known molecular size of probes

Amount/Mole of probes needed to achieve certain coverage can

be determined

Retention volumes at this coverage can be used to

determine surface energy 30% 60% 70% 75%

Surface Energy Methodology

• Specific Free Energy DGSP Measured Directly • Use polar or acid-base probes

• Use probes of specific functional groups to probe interactions with the surface

• Apply Various Acid-Base Theories • Allows determination of specific component of surface energy (using

Good-van Oss Chadury approach)

• Measurement of the Lewis acidity and basicity of the surface (using Gutmann approach)

Origins of Surface Chemistry Heterogeneity

• Almost all solid surfaces possess heterogeneous properties

• Chemical heterogeneity • Surface contaminants and impurities • Different crystal planes can exhibit different chemistry • Degree of crystallinity/amorphicity • Morphological state: polymorphs, hydrates and solvates • Surface groups/Inhomogeneous surface modification

• Structural heterogeneity • Crystals may have several defect sites

• Growth steps, crystal edges, surface pores, etc. • Irregularities of crystal lattice • Pore of different sizes and shapes

• Heterogeneous properties cause differences in adsorption energies, thus vapour sorption capacity and surface energies

Anisotropic Surface Chemistry of Crystals

• Crystallisation of macroscopic pharmaceutical crystal (Excipient) D-mannitol (AR as received D-mannitol) Silanised D-mannitol

• Characterisation of surface energy using sessile drop contact angle Following crystallisation of macroscopic crystals

• Preparation of D-mannitol powders with same particle size (45-63 m), density, shape but different surface chemistries and thus energies.

HO

OH

OH OH

OH

OH

C6H14O6(D-mannitol)

D-mannitol

5mm

(011)

(010)(120)

Contact Angle Measurement on D-mannitol Crystals

Facet Advancing Contact Angle, a(°) Surface Energy (mJ/m2) Hydrophilicity

DIM H2O d p p/

(010) 30.3 2.4 56.2 1.9 44.1 12.8 56.9 0.23

(120) 31.9 2.9 46.2 2.2 43.3 18.6 61.9 0.30

(011) 40.1 1.5 12.8 4.6 39.5 35.4 75.9 0.47

Monographs of macroscopic β mannitol crystal. Size: 8 × 8 × 60 mm.

R. Ho, S.J. Hinder, J.F. Watts, S.E. Dilworth, D.R. Williams and J.Y.Y. Heng. Int. J. Pharm (2010) 387: 1-2 pp. 79-86

D-mannitol

5mm

(011)

(010)(120)

γLV

γSV

γSL

θ Clean solid surface

Liquid drop

(cos22 LV

p

SV

p

LV

d

SV

d

LVAW

SVSLLV cosYoung’s equation:

Owens-Wendt:

282283284285286287288289290Binding Energy (eV)

C 1

s X

P S

igna

l (a.

u.)

282283284285286287288289290Binding Energy (eV)

C 1

s X

P S

igna

l (a.

u.)

ba

Facet (120)

Facet (011)

CHx

CHx

C-OH

C-OH

Surface Chemistry by XPS

SEA surface energy profile measurements

– ability to distinguish homogeneity and heterogeneity in surface free energy

SEA Dispersive Surface Energy

D-Mannitol

γ D

max γ D

min γ D

50

Silanised 33.29 33.45 33.38

AR 37.51 52.63 40.34

25.0

30.0

35.0

40.0

45.0

50.0

55.0

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Dis

pe

rsiv

e S

.E.

[mJ/

m2]

Surface Coverage [n/nm]

Silanised D-Mannitol

AR D-Mannitol

SEA Specific Surface Energy Profiles

D-Mannitol γ AB

max γ AB min

γ AB50

Silanised 1.54 1.59 1.57

AR 2.67 4.93 3.09

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Spe

cifi

c S.

E.

[mJ/

m2]

Surface Coverage [n/nm]


AR D-Mannitol

Changes in surface chemical environment - To an isotropic hydrophobic surface property

Surface Modification: Silanisation

Work required to reversibly separate an interface between two bulk phases.

WCohtotal = 2[(s

D * sD)½ + (s

+ * s-)½ +(s

- * s+)½]

0

50

100

150

200

250

300

350

400

0 2 4 6 8 10 12 16 20 24

Tota

l Flo

w E

ner

gy [

mJ]

Air Velocity [mm/s]


AR D-Mannitol

Free flowing materials fully aerate when flow energy stabilises

- Silanisation influences the dynamic flow properties, but not under consolidated conditions

Surface Modification for Improved Flow Properties

Effect of Cleaning Process on Surface Energy Heterogeneity

• Surface energy distribution of Aluminum and Teflon measured using iGC-SEA

film cell (sample area ~2” x 8”)

• Investigated cleaning proceedures effects on surface energy

• Ability to measure heterogeneity of entire surface unique to iGC-SEA

• Even simple films can be highly energetically heterogeneous

• Contact angle would require numerous droplets across the film surface. Even this would only be a gross approximate measure of heterogeneity

Dispersive Surface Energy of Aluminium

Acid-cleaned aluminium surface was energetically more active and heterogeneous, having higher mean γs

d.

Dispersive Surface Energy of Teflon®

Though bleached Teflon surface possessed higher mean γsd, nitric acid

solution has roughened the surface, inducing more surface defects and a variation of γs

d.

Planar Sample γs

d

[ mJ/m2 ]

γsab

[ mJ/m2 ]

γst

[ mJ/m2 ] γs

ab / γst

Aluminium 40.83 3.44 44.27 0.0777

Al Bleached 40.57 6.26 46.84 0.1337

Al Nitric Acid 46.15 7.24 53.39 0.1356

Teflon 38.15 2.51 40.66 0.0617

Teflon Bleached 38.96 3.84 42.80 0.0897

Teflon Nitric Acid 36.90 4.02 40.92 0.0982

Surface Energy Values (γ50) by iGC SEA

Isotherms-BET Surface Area

CnP

P

Cn

C

PPn

P

mm

11][ 00

0

5

10

15

20

25

30

35

40

45

50

0.00 0.05 0.10 0.15 0.20 0.25P/P0

P/[

n(P

0-P

)] [

g/m

Mo

l]

SEA Calculated Results : Selected P/P0 range 0.14 to 0.20 C constant 7.109 BET Surface Area: 2.9524 m2/g CRM 171 BET Surface Area = 2.95 m2/g

Selected linearization P/P0 range

IGC-BET Surface Area Standards

0% RH: IGC value of 2.95 m2/g 50% RH: IGC value of 2.73 m2/g 90% RH: IGC value of 1.45 m2/g

• As humidity increases, measured BET surface area decreases

• Water competing for sites or blocking available surface area

• Example AFM image on Graphene: JACS, 2011, 133(8), 2334-2337.

• Various pretreatments used to improve adhesion to polyolefins • Low pressure plasma

• Corona treatment

• Flame treatment

• UV irradiation

• Mechanical etching

• Priming techniques • Adhesion promoters to introduce polar functionality to TPO

• Chlorine donors

78

Polyolefin-Challenges

79

Polyolefin-Challenges

Polymer Samples Thermoplastic polyolefins (TPO) and elastomers

Different elastomer loadings (12 and 25 wt %)

Different elastomer densities

Measure mechanical adhesion to paint and compare to IGC surface energies

Polyolefin-Case Study

Dispersive Surface Energy

• TPO samples were painted with topcoat

• Comprehensive Shear Delamination Apparatus (SLIDO) as a measure of mechanical adhesion

• Traction force (or frictional force) measured by taking the peak load in compression

Mechanical Testing

Traction Force

Compressive Force

Run Length

S= v2

a

Sliding Frictional

Friction in Painted TPO

Plowing

Cohesive Failure

Mechanical Adhesion Versus Surface Energy

• Higher surface energies lead to higher practical adhesion to paint

• Higher surface energies lead to lower microhardness (lower crystallinity)

• Increase in amorphous content (lower crystallinity) allows greater penetration of paint into TPO, thus greater adhesion

• Thermodynamic adhesion agrees with practical adhesion

Polyolefin Case Study Summary

Properties measured by IGC

• Surface Energy Analysis

• Dispersive, acid-base components & total surface energy

• Acid-base Free Energy of Desorption Analysis

• Heterogeneity Mapping

• Heterogeneity profiles, heterogeneity distributions

• Gutmann Acid/Base Properties

• Isotherm Analysis

• Vapour uptake, Henry’s constant

• BET Specific Surface Area

• Thermodynamic Work of Adhesion/Work of Cohesion

• Heat of Sorption

• Bulk Solid Properties

• Glass Transition Temperature

• Solubility Parameter (Hildebrand 1D, Hansen 3D)

• Cross-linking Density

Acknowledgements

• Thank you to SMS collaborators

• SMS Colleagues: current and former team members

• London Imperial College SPEL Group

• Thank you for your time and attention

Head Office: Surface Measurement Systems, Ltd. 5 Wharfside, Rosemont Road London HA0 4PE, UK Tel: +44 (0)20 8795 9400 Fax: +44 (0)20 8795 9401 Email: [email protected]

United States Office: Surface Measurement Systems, Ltd, NA 2125 28th Street SW, Suite 1 Allentown PA, 18103 Tel: +1 610 798 8299 Fax: +1 610 798 0334

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