surface measurement systems

An introduction to

DVS & iGC

Technologies

By Thomas SchmidSupport and Sales Manager SMS

And Dr. Majid NaderiPrincipal Application Specialist

SWST Conference 2010 Geneva

Introduction to SMS

• SMS are regarded as world leaders in developing and engineering DVS and iGC vapour sorption instrumentation for the physical-chemical characterisation of complex solid materials

• SMS have been providing 18 years of world-class scientific and technical solutions and support.

• SMS’s unique scientific techniques and instruments have helped solve difficult problems for leading, pharmaceutical, biomaterial, polymer, catalyst, chemical, cosmetic and food industries worldwide.

• SMS coined the phrase ‘Dynamic Vapour Sorption : DVS’ and iGC-SEA

DVS Introduction

The Effects of Moisture/Vapour

• Water Vapour (humidity) is everywhere

• Water or Solvent -Solid interactions are

important for wide range of industries:

food, pharma, biomaterials, fuel cells,

packaging, high energy materials,

personal care…

• Accurately determining water/vapor

sorption isotherms critical for proper

development and storage of these

materials

What can the DVS do for me?

– How does my material interact with moisture or solvents and temperature in the vapour phase?

– Stability, Performance and Processing issues: Reversible and Irreversible effects of moisture

– Create Moisture Isotherms – i.e. Equilibrium moisture content as a function of %RH

– Heterogeneity? – Identify the Heterogeneity of a sample batch

– Homogeneity? – Identify variance within one sample

– Kinetics – Moisture transport properties, how fast or slow?

– Energy – How strongly is the moisture bound to the material, surface or bulk?

– Identify & Characterise Phase Transition/Changes, e.g. polymorphs, amorphous stoichiometry

– Hydration and Solvate Formation

– Drying Analysis

– Diffusion and Activation Energy

– Heat of Sorption

– Moisture Content? i.e. how much moisture/vapour is taken up or release

DVS Technique

• 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 Gravimetric UltraBalance– Up to 0.1 µg sensitivity

– Allows use of small samples 1-10 mg

– Unrivaled long-term baseline stability

• ‘Real-world’ conditions– Wide range of temperatures: measurement and preheat

conditions

– Wide range of measurement pressures: atmospheric

down to 10-6 Torr (DVS-vacuum)

– Wide range of vapors: water and organic vapors

DVS – General Instrument Schematic

DVS-Advantage

Water & SOLVENTS

Temp: 5 - 60 °°°°C

Pre-heater: up to 350 °°°°C

DVS-Advantage:

The Modular Design

Raman & NIR Raman & NIR Raman & NIR Raman & NIR

PortsPortsPortsPorts

HiHiHiHi----Res. Video Res. Video Res. Video Res. Video

CameraCameraCameraCamera

Pre-Heater (up to 350°C)

Why Organic Solvents?

Unlike water vapour, organic vapour (e.g. Octane) has several advantages:

(1) For example, Octane molecule has DISPERSIVE properties, i.e. Typically wets sample surface

(2) Also, Octane does not interact strongly with material.Therefore, limits unwanted sample recrystallisation

(3) However, If there is NO recrystallisation, then Octane sorption is completely REVERSIBLE

(4) Entire P/Po range can be studied

(5) Organic Vapour (e.g. Octane) kinetics are faster than water

DVS Advantage - Video

• Microscope mounted below sample area

allows for in-situmonitoring of sample

• Up to 200x magnification

• Polarized light option

• Fully digital

• Annotated images

• Adjustable focal point

DVS Camera Assembly


Tobacco – 60% RH


Carbon Fibers – 0% RH


Maltodextrin – 0% RH Maltodextrin – 95% RH, 0 mins.

Maltodextrin – 95% RH, 30 mins. Maltodextrin – 95% RH, 50 mins.

DVS Advantage - Raman

• Two independent ports for additional in-

situmeasurements of sample

• Integrated safety locks

• Trigger from DVS control software

• Raman Spectroscopy

• NIR Spectroscopy

• UV light source

• Other probes

Ports for additional measurements

Example: Amorphous Lactose Phase Change

@ 25ºC

DVS Data

DVS Sorption Data - LACTOSE

20.5

21

21.5

22

22.5

23

23.5

0 500 1000 1500 2000 2500

Time/mins

Ma

ss

/mg

0

10

20

30

40

50

60

70

80

90

100

Ta

rge

t %

P/P

o

Mass

Target % P/Po

© Surface Measurement Systems Ltd 2008DVS - The Sorption Solution

Amorphous State Crystalline State

60% RH

Amorphous State Crystalline State

Video

Images

Raman Data

Absorption Cycle 1

0

200

400

600

800

1000

1200

1400

1600

0 500 1000 1500 2000 2500 3000 3500 4000

Raman shifts (cm-1

)

Co

un

ts

Amorphous State

Crystalline State

0% RH

40% RH

60% RH

95% RH

DVS Family of Products

SEA Introduction

SEA – Surface Energy

• Surface energy is 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

19

SEA – Why Measure Surface Energy?

• Adhesion and cohesion (composites)– J. Borch, Journal of Adhesion Science and Technology. 5 (1991) 523-541.

– R.H. Mills, D.J. Gardner, and R. Wimmer. Journal of Applied Polymer Science. 110 (2008) 3880-3888.

– B. Wang and M. Sain, BioResources, 2 (2007) 371-388.

– A. Ziani, R. Xu, H.P. Schrieber, and T. Kobayashi, Journal of Coatings Technology, 71 (1999) 53-60.

• Powder flow and powder mixing– I. Saleem, H. Smyth, and M. Telko, Drug Development and Industrial Pharmacy,

34 (2008) 1002-1010.

– I.M. Grimsey, J.C. Feeley, and P. York, Journal of Pharmaceutical Sciences, 91 (2002) 571-583.

– N.M. Ahfat, G. Buckton, R. Burrows, and M.D. Ticehurst, International Journal of Pharmaceutics, 156 (1997) 89-95.

• Static charge– N. Ahfat, G. Buckton, R. Burrows, and M. Ticehurst, European Journal of

Pharmaceutical Science. 9 (2000) 271-276.

– J.H. Clint and T.S. Dunstan, Europhysics Letters. 54 (2001) 320-322.

20

SEA – Why Measure Surface Energy?

• Milling or process-induced disorder– J.Y.Y. Heng, F. Thielmann, and D.R. Williams, Pharmaceutical Research, 23 (2006)

1918-1927.

– E. Papier, J.-M. Perrin, B. Siffert, G.I. Philipponnear, and J.-M. Lamerant, Journal of Colloid and Interface Sceince, 156 (1993) 104.

– S.P. Chamarthy and R. Pinal, Colloids and Surfaces A, 331 (2008) 68-75.

– M. Ohta and G. Buckton, International Journal of Pharmaceutics, 269 (2004) 81-88.

• Batch-to-batch variability– M. Ohta and G. Buckton, International Journal of Pharmaceutics, 289 (2005) 31-

38.

– S.P. Chamarthy, R. Pinal, and M.T. Carvajal, AAPS PharmSciTech, 10 (2009) 780-788.

• Surface Modification– C.S. Flour and E. Papier, Journal of Colloid and Interface Science, 91 (1983) 69-

75.

– E. Papier, H. Balard, E. Brendle, and J. Lignieres, Journal of Adhesion Science and Technology, 10 (1996) 1401-1411.

– J.Y.Y. Heng, D.F. Pearse, F. Thielmann, T. Lampke, and A. Bismarck, 14 (2007) 581-604.

21

Surface Energy and Wettability

22

Increasing Surface

Energy

Surface Energy and Cohesion or Agglomeration

23

Increasing Surface

Energy

Surface Energy and Particle Adhesion

24

Increasing Surface

Energy

Surface Energy and Process-Induced Disorder

25

Increasing Surface

Energy

SEA Introduction – IGC Principle

Animation by L. Teng, Surface Measurement Systems

26

27

SEA SEA Retention TimeRetention Time

Time

tMtN

�Single pulse of probe molecule

� tM is the retention time for an

inert molecule (usually methane)

� tR is the retention time for the

interacting probe

� Net retention time tN = tR - tM

tR

28

SEA Basic Configuration

Solvent

Reservoir

Colum Oven

Teflon

Insulation

29

SEA Basic Configuration

2 Columns

Fully Integrated

Colum Oven

30

SEA Add-on Options*

• Humidity Control– 0 to 90% RH (at 25 °C)

• High Temperature Oven– 2 column design

– Ambient to 600 °C

• Film Cell– Analyze flat sheets of material

– Temperature control

• Advanced methods– Increased method and analysis flexibility

– Access to broader range of surface and bulk properties

* Current Timeline: available 3rd quarter of 2010

31

SEA Properties Measured

• Surface Energy Analysis– Dispersive Surface Energy

– Specific Free Energy of Desorption

– Ability to specify desired surface coverages for analysis

• Surface Energy Heterogeneity– Ability to perform experiments over a range of surface

coverages

– ‘Energy Mapping’ of surfaces

• Surface Acid-Base interactions

• Heats of Sorption

• Glass Transition Temperatures

• Solubility Parameters

• BET Surface Area

• Henry’s Law Isotherms

32

Specific Free Energy Values

Decane

Nonane

Octane

Heptane

1,4-DioxaneDichloromethane

Acetone

Ethyl Acetate

Ethanol

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 2E-20 4E-20 6E-20 8E-20 1E-19 1.2E-19 1.4E-19

a·gamma½

RT

lnV

Specific Free Energy ∆∆∆∆GSP

Measured by determining interactions of polar or acid-base probes

with the surface.

∆GSP Ethyl Acetate

Surface Energy Heterogeneity

33

20

25

30

35

40

45

50

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Dis

pe

rsiv

e S

urf

ac

e E

ne

rgy [m

J/m

²]

Fractional Surface Coverage [-]

Dispersive Surface Energy Profile

More Defects

Less Defects

IGC-SEA

Applications

The effect of milling/grinding on surface energy

Sample Grinding

B1 None

B2 Industrial

B3 Lab-4 hrs

B4 Lab-24 hrs0

10

20

30

40

50

60

70

80

Dis

pe

rsiv

e S

urf

ace

En

erg

y (

mJ

/m2

)

B1 B2 B3 B4

Sample

Dispersive Surface Energy for Alpha-Alumina Samples

B1 B2 B3 B4

0

5

10

15

20

25

30

Sp

ecif

ic F

ree E

nerg

y (

kJ/m

ol)

Ether Dichloromethane

Probe Molecule

Specific Free Energy Values for the Alumina Samples

B1 B2 B3 B4

Grinding causes increase in dispersive surface energy

Grinding causes decrease in Lewis acidity and basicity

Conclusion: grinding leads to increase surface amorphous material

Case Study: the importance of adhesion/cohesion forcesthe importance of adhesion/cohesion forces

�1. Pack column with Material 1 (i.e. toner)

�Measure dispersive and polar (acid/base) surface energies

�2. Correlate surface energies directly with adhesive strength determined by physical/mechanical measurements

IGC Experimental Approach 1

Literature Examples

• Adhesion strength of toner to paper increases with dispersive surface energy of papers

•J. Borch, J. Adhesion Sci. Techol., 5 (1991) 523-541.

Literature Examples

• Bonding characteristics of images improve with increased dispersive surface energy of paper

•J. Borch, J. Adhesion Sci. Techol., 5 (1991) 523-541.

Case Study: the importance of adhesion/cohesion forcesthe importance of adhesion/cohesion forces

�1. Pack column with Material 1 (i.e. toner)

�Measure dispersive and polar (acid/base) surface energies

�2. Pack column with Material 2 (i.e. paper)

�Measure Dispersive and Polar surface energies

�3. Calculate Work of Adhesion using surface energy values of Material 1 and Material 2

IGC Experimental Approach 2

Adhesion and Cohesion

Compare Work of Adhesion value (WAd) with Work of Cohesion values (WCo)

High WAd values will lead to stronger toner-paperbonding strengths

High WCo values will lead to stronger toner-toner (i.e. agglomeration) or paper-paper bonding strengths

Ultimate Goal: to predict toner-paper interactions (without printing tests!) and select appropriate

toners as well as control toner properties�Same experiments can be performed on a wide range of

materials (toners, papers, fibers, wood, etc.)

41

If the surface energies of the individual compounds are known, the work of adhesion or cohesion can be obtained:

WAdhtotal = 2[(γ1

d* γ2

d)½ + (γ1+

* γ2-)½ +(γ1

-* γ2

+)½]

Work of Adhesion/CohesionWork of Adhesion/Cohesion

WCohtotal = 2[(γ1

d* γ1

d)½ + (γ1+

* γ1-)½ +(γ1

-* γ1

+)½]

Work of cohesion - between like bodiesWork of adhesion - between unlike bodies

Wd Wsp

Case Study: Granulation of glass beads

•Hydrophilic granules show finger print of HPC

•Hydrophobic granules a mixture of HPC and beads•Specific free energies show “fingerprint” of beads and binder

••MaterialsMaterials

••Hydrophilic and hydrophobic glass beadsHydrophilic and hydrophobic glass beads

••Binders: Hydroxypropylcellulose (HPC)Binders: Hydroxypropylcellulose (HPC)

Binder appears to Binder appears to ““spreadspread”” on hydrophilic glass beads on hydrophilic glass beads

which results in which results in ““coatingcoating””..

Surface Energy vs Coverage

Dispersive Surface Energy Profile for an untreated pine powder

Surface Energy vs Coverage

Linearised BET Plot from C8 Data

BET Results:Parameter: Peak Max P/P0 Range: 0.12 - 0.35

Solvent Sorption Const. 1.1837Monolayer Capacity [mMol/g] 0.01699BET Specific Surface Area [m2/g] 6.4474

R^2 0.99435

DVS Applications

Typical Temperature Stability – 24 hours

Changing Temperature: 25C-85C

Changing Temperature:25C-12C-25C

10 Avicel samples by DVS-HT

1 Avicel sample by DVS Advantage

99

101

103

105

107

109

111

113

120 320 520 720 920 1120 1320

Time / min

Mass %

Ch

an

ge

0

10

20

30

40

50

60

70

80

90

100

Targ

et

RH

(%

)

DVS - Kinetics of Moisture Sorption of Sawdust

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 4000 4500 5000

Time/mins

Ch

an

ge

In

Ma

ss

(%

) -

Re

f

0

10

20

30

40

50

60

70

80

90

100

Ta

rge

t R

H (

%)

dm - dry Target RH

© Surface Measurement Systems Ltd UK 1996-2005DVS - The Sorption Solution

Time: 16-21

File: Sawdust -

Sample: Sawdust

Temp: 25.0 °C

MRef: 10.72722

DVS- Sawdust Isotherms

DVS Isotherm Plot

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60 70 80 90 100

Sample RH (%)

Ch

an

ge

In

Ma

ss

(%

) -

Re

f

Cycle 1 Sorp Cycle 1 Desorp


Time: 16-21

File: Sawdust -

Sample: Sawdust

Temp: 25.0 °C

Meth: Sawdust.sao

MRef: 10.72722

DVS – Natural wood and Composites

• Moisture control and measurement are critical parameters

for wood and wood composites.

• moisture plays a key role in the fungal degradation and

weathering of wood-plastic composites.

• Drying kinetics i.e. moisture sorption behaviour and

diffusion processes.

• The hysteresis between sorption and desorption isotherms

provides information related to wood stability i.e. the

narrower the hysteresis, the more stable the wood sample

is to fluctuating humidities.

• water vapour diffusion coefficients are related to wood

species, wood grain direction, wood age, and tree ring

location.


0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60 70 80 90 100

Ch

an

ge In

Ma

ss

(%

) -

Re

f

Sample RH (%)

DVS Isotherm Plot



Temp: 25.0 C

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70 80 90

Ch

an

ge

In M

ass

(%

) -

Ref

Target % P/Po

DVS Isotherm Plot



Temp: 25.0 C

(b.)(a.)

Water sorption (red) and desorption (blue) isotherms at 25 °C

measured on sawdust (a.) and a solid wood sample (b.).

Different geometries can be used i.e. wood samples as sawdust, chunks, films, fibres, or slabscan be used to determine moisture sorption kinetics, diffusion coefficients and the equilibrium isotherm values (see SMS Application Notes 7, 12, 16, and 30).

Amorphous Content Determination

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800 1000 1200Time/mins

Ch

an

ge

In

Ma

ss

(%

)-D

ry

0

10

20

30

40

50

60

70

80

90

Re

lati

ve

pre

ss

ure

Increase in amorphous content and decrease in crystallinity of cellulose

∆∆∆∆ AmorphousContent

Sorption Mechanisms

Monolayer Mechanism

(typical type II/IV)

dHads >> dHcond

Using water/organic vapour isotherms to study the sorption mechanism i.e. monolayer, multilayer and bulk adsorption as well as the strength of vapour/surface interaction.

Cluster Mechanism

(typical type III/V)

dHads ≥ dHcond

Case Study: Hemp vs Hemp Lime

Hemp is porous and the lime-based binder sticks together and protects the hemp. By varying the quantities of lime, different preparations can be made.

DVS Change In Mass (ref) Plot

Hemp vs Hemp Lime

-5

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Time/mins

Ch

an

ge

In

Ma

ss

(%

) -

Re

f

0

10

20

30

40

50

60

70

80

90

100

Ta

rge

t R

H (

%)

hemp lime run 1 - Mon 20 Jul 2009 14-38-53 dm - dry hemp shiv run 3 - Tue 04 Aug 2009 09-50-21 dm - dry

hemp lime run 1 - Mon 20 Jul 2009 14-38-53 Target RH hemp shiv run 3 - Tue 04 Aug 2009 09-50-21 Target RH


Case Study: Hemp vs Hemp Lime

DVS Isotherm Plot

-5

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Ch

an

ge In

Mass (

%)

- R

ef

hemp shiv run 3 - Tue 04 Aug 2009 09-50-21 (2) Cycle 1 Sorp hemp shiv run 3 - Tue 04 Aug 2009 09-50-21 (2) Cycle 1 Desorp

hemp lime run 1 - Mon 20 Jul 2009 14-38-53 (2) Cycle 1 Sorp hemp lime run 1 - Mon 20 Jul 2009 14-38-53 (2) Cycle 1 Desorp


Heat of Sorption

DVS Isotherm Plot

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 10 20 30 40 50 60 70 80 90 100

Target RH (%)

Ch

an

ge I

n M

ass (

%)

- D

ry

25 C 35 C 45 C


Heat of Sorption

Change in mass (%) Heat of sorption (kJ/mol)

(25 and 35 °C)

Heat of sorption (kJ/mol)

(35 and 45 °C)

0.06 -46.1 -43.3

0.07 -47.3 -44.2

0.08 -47.9 -44.5

0.09 -47.4 -45.2

dHads for Water ≥≥≥≥ dHcond for Water


• Degradation of wood-plastic composites

– Kim, K.-W., Harper, D.P., and Taylor, A.M., Wood and Fiber Science, 2008. 40, 519-531.

• Swelling and dimensional instability

– Neimsuwan, T., Wang, S., and Via, B.K., Wood and Fiber Science, 2008, 40, 495-504.

• Drying kinetics

– Neimsuwan, T., Wang, S., Taylor, A.M., and Rials, T.G., Wood Science and Technology, 2008. 42, 493-506.

• Fungal growth and degradation

– ANTEC 2002 Annual Technical Conference : May 5-9, 2002, San Francisco, CA. : conference proceedings. Volume II, Materials. S.l. : Society of Plastics Engineers, 2002: p. 2219-2222

An introduction to DVS & iGC Technologies

surface measurement systems

Documents