case studies: reduction of thermal conductivity ... · case studies: reduction of thermal...

CASE STUDIES: REDUCTION OF THERMAL CONDUCTIVITY &

IMPROVEMENT OF MECHANICAL PERFORMANCE OF POLYMERIC

FOAMS BY USING NANOSTRATEGIES

Technology and Innovation for Cellular Materials at Industry Service

Cristina Saiz-Arroyo1, Alberto López-Gil2, Josías Tirado2, Sergio Estravís2, Javier Escudero2, Miguel Angel Rodríguez-Pérez2

1 CellMat Technologies SL, Valladolid-Spain2 CellMat Laboratory-University of Valladolid, Valladolid- Spain

13-14 MAY- VIENNA, AUSTRIA

o CELLMAT TECHNOLOGIES

o POLYMER NANOCOMPOSITE FOAMS

o CASE STUDY #1: RIGID PU FOAMS WITH IMPROVED THERMAL

INSULATING PERFORMANCE

o CASE STUDY #2: HIGH DENSITY LDPE FOAMS WITH IMPROVED

MECHANICAL BEHAVIOUR

o SUMMARY & CONCLUSIONS

CELLMAT TECHNOLOGIES

CELLULAR MATERIALS LABORATORY

UNIVERSITY OF VALLADOLID- SPAIN

• ∼∼∼∼145 scientific papers

• 10 patents and several novel technologies

• 16 Ph D thesis

• More than 55 research projects

• Strong collaborations with companies around the world

Established in 1999.

International recognized laboratory in the

area of cellular materials. o Transferring knowledge and

technology on cellular materials to

industrial partners.

o Advising to plastics producers in

manufacturing better and cheaper

materials using specific know-how.

o Producing advanced foams and/or

formulations for foaming

applications

Established in October 2012.

Spin-off company of the

University of Valladolid.

SPECIFIC AND NOVEL

KNOW-HOW AND

TECHNOLOGIES ON

ADVANCED CELLULAR

MATERIALS

LICENSES

TRANSFER

AGREEMENTS


CELLMAT PRODUCTS

o IMPLEMENTATION OF FOAMING PROCESSES

o TECHNICAL CONSULTANCY IN HALOGEN FREE

FLAME RETARDANCY

o SPECIFIC TRAINING COURSES


o STAGES MOULDING

o ANICELL

o OPENCELLMAT

SOLID PLASTIC PARTS PRODUCERS

o OPTIMIZATION OF CELLULAR MATERIALS:

PROCESS & PRODUCT

o SUBSTITUTION OF OIL-DERIVED PRODUCTS

BY BIOPLASTICS

o TECHNICAL CONSULTANCY IN HALOGEN FREE

FLAME RETARDANCY

o SPECIFIC TRAINING COURSES

FOAM PRODUCERS

WHAT DO WE OFFER?

POLYMER NANOCOMPOSITE FOAMS

CLASSIC APPROACH: OBTENTION OF TAILORED POLYMERIC FOAMS WITH IMPROVED PROPERTIES FOR A CERTAIN APPLICATION

PROCESSING

PARAMETERSCELLULAR

STRUCTURE

MORPHOLOGY

POLYMERIC

MATRIX

PHYSICAL

PROPERTIES

MARKET,

APPLICATIONMODIFICATIONS

POLYMERIC MATRIX

• Temperature

• Pressure

• Time

• Blowing Agent Amount

• …

• Modification of polymer molecular architecture, (Crosslinking, Branching…)

• Modification of chemical composition: NANOPARTICLES

MICROSCOPIC

LEVEL

MACROSCOPIC

LEVEL

D. Klempner, V. Sendijarevic. Handbook of Polymeric Foams and Foam Technology. 2nd Edition. (Hanser Publishers)


WHY NANOPARTICLES?

PROCESSING

PARAMETERS

CELLULAR

STRUCTURE

MORPHOLOGY

POLYMERIC

MATRIX

PHYSICAL

PROPERTIES

MARKET,


POLYMERIC MATRIX

MICROSCOPIC LEVEL MACROSCOPIC LEVEL

NANOPARTICLES

• Nucleating agents

• Improved rheology

• Improved barrier properties

• Modifications polymeric

matrix

IMPROVEMENTS IN THE SOLID POLYMERIC

MATRIX, (Solid Nanocomposite in Cell Walls)

• Thermal stability

• Mechanical properties

• Fire retardancy

• Thermal

• Mechanical

• Fire retardantSYNERGISTIC

EFFECTS

MULTIFUNCTIONAL ROLE OF NANOPARTICLES IN CELLULAR POLYMERS

C. Saiz-Arroyo, M.A. Rodríguez-Pérez, J.I. Velasco, J.A. De Saja. Influence of foaming process on the structure-property relationship of LDPE/SIO2 foamed nanocomposites. Composites Part B, Engineering 48:40-50, (2013))



o CASE STUDY ####1: RIGID PU FOAMS WITH IMPROVED THERMAL





CASE STUDY ####1: PUR FOAMS WITH REDUCED λλλλ

CASE STUDY ####1: RIGID POLYURETHANE FOAMS/NANOCLAYS

PROCESSING

PARAMETERS

CELLULAR

STRUCTURE

MORPHOLOGY

POLYMERIC

MATRIX

PHYSICAL

PROPERTIES

MARKET,


POLYMERIC MATRIX

MICROSCOPIC LEVELMACROSCOPIC LEVEL

• NUCLEATING EFFECT

• THERMAL CONDUCTIVITY

PUR FOAMS WITH IMPROVED

INSULATION PROPERTIESFOAMING MECHANISMS

• Commercial polyurethane rigid

formulation blown with water

• NANOCLAYS: 0.5, 1, 3 & 5 wt.%


NANOFILLER/POLYURETHANE REACTIVE FOAMING

POLYOLADDITIVES

WATER

NANOFILLERS(Nanoclays)

STEP 1: NANOFILLERS

ADDITION/DISPERSIONDispersion / exfoliation

(mechanical stirring)

STEP 2: FOAMING PROCESS

Mechanical stirring to

activate/promote the

reaction

ISOCYANATE

Reactive foaming expansion


0 1 2 3 4 524

25

26

27

28

29

The

rmal

Con

duct

ivity

(m

W/m

·K)

Nanoclays Concentration (wt%)

Thermal Conductivity

0 1 2 3 4 5

0

1

2

3

4

5

6

7

8

9

10

Red

uctio

n The

rmal

Con

duct

ivity

(%

)


RESULTS: THERMAL CONDUCTIVITY

Effective reduction of λλλλ due to the introduction of nanoclays.

Optimum content- Minimum in λλλλ- 1wt%- 8% Reduction


0 1 2 3 4 5

24

26

28

30

32

34

36

38

The

rmal

Con

duct

ivity

(m

W/m

·K)


λ- 2 Days After Production λ- 40 Days After Production

0 1 2 3 4 5

24

26

28

30

32

34

36

38

The

rmal

Con

duct

ivity

(m

W/m

·K)


λ- 2 Days After Production λ- 40 Days After Production

DIFFUSION OF BLOWING AGENT

λ- Air: 25.3 mW/m·K

λ- CO2: 14.5 mW/m·K

0 1 2 3 4 5

0

1

2

3

4

5

6

7

8

9

10

Red

uctio

n The

rmal

Con

duct

ivity

(%

)


Reduction λ- 2 Days After Production Reduction λ- 40 Days After Production

RESULTS: THERMAL CONDUCTIVITY

Effective reduction of λλλλ due to the introduction of nanoclays.

Optimum content- Minimum in λλλλ- 1wt%- 8% Reduction

� � ��

Thermal Conductivity in Polymeric Foams

λλλλs: Conduction through solid phase

λλλλg: Conduction through gas phase

λλλλr: Thermal radiation

λλλλc: Convection within the cells, negligible φφφφ < 4mm.

IN WHICH MECHANISM ARE NANOCLAYS ACTING?

� ��

� �2

3�

��

3��

� �16��

3�

� � ��, ��, !, ", ��, �#$

O. Almanza, M.A. Rodríguez-Pérez, J.A. de Saja. Prediction of the radiation term in the thermal conductivity of crosslinked closed cell polyolefin foams. Journal of Polymer Science Part B: Polymer Physics 38:993-1004, (2000).R.A. Campo-Arnaiz, M.A. Rodríguez-Pérez, B. Calvo, J.A. de Saja. Extinction coefficient of polyolefin foams. Journal of Polymer Science, Part B: Polymer Physics 43: 1608-1617, (2005).


PHYSICS IN POLYMER FOAMS: NANOPARTICLES COULD ACT IN MOST OF THE

MECHANISMS TAKING PLACE

CELL SIZE

EVOLUTION

DENSITY

DISTRIBUTION

COALESCENCE

EVENTS

COALESCENCE DRAINAGE

NUCLEATIONSOLIDIFICATION

MELTING

DIFFUSION

COARSENING

CELL DENSITY


Microfocus

X-Ray source

Source:5 µm Spot20-100KV0-200µA

ANALYSIS OF THE FOAMING PROCESS: X-RAY RADIOSCOPY SET UP

Flat panel

detector

Detector:2240x2344

12bits9fps max

50 µµµµm

%&'()�)*&+),( �-..

-/.CONE BEAM

SEQUENCE OF RADIOGRAPHIES ADQUIRED ON REAL TIME


FOAMING PROCESS: NEAT PU VS PU + 3wt% NANOCLAYS

NEAT PU PU + 3wt% NANOCLAYS

Qualitative analysis: Cell size reduction due to the addition of nanoclays


NUCLEATING EFFECT OF NANOCLAYS: QUANTITATIVE ANALYSIS (X-RAY + IMAGE ANALYSIS)

30 40 50 60 70 8090100

200

300

400

10

20

30

40

50

60

708090

100

Rela

tive d

ensit

y /

%

Time /s

neat PU

0.5% clays

1% clays

3% clays

5% clays

30 40 50 60 70 8090100

100

200

300

400

500

50

100

150

200

250

300

350

400

450 neat PU

0.5% clays

1% clays

3% clays

5% clays

Cell s

ize /

µµ µµm

Time /s

DENSITY EVOLUTION CELL SIZE EVOLUTION

40% CELL SIZE REDUCTION

CELL DENSITY, (Nc , cells/cm3)

50 100 150 200 250 300 350 400 450

0.0

4.0x106

8.0x106

1.2x107

1.6x107

2.0x107

Cell d

ensit

y /

cm

3

Time /s

neat PU

0,5% clays

1% clays

3% clays

5% clays


NUCLEATING EFFECT OF NANOCLAYS: QUANTITATIVE ANALYSIS (X-RAY + IMAGE ANALYSIS)

Nc = 6

πφ 3

ρsolid

ρ foam

−1

COALESCENCE ABSENCE

Constant Cell Density

ENHANCED NUCLEATION

Increase in the number of cells per unit volume


MEAN CELL SIZE AS A FUNCTION OF NANOCLAYS CONTENT AND REPRESENTATIVE

AVERAGE CELL, (Obtained by Tomography)

0 1 2 3 4 5

300

400

500

600

700

800

900

cell s

ize /

µµ µµm

nanoclays content /%

o 2 TIMES CELL SIZE REDUCTION

o 8 TIMES CELL VOLUMEN REDUCTION

REDUCTION OF THE

RADIATION TERM

CELL WALL THICKNESS


STRUTS MASS FRACTION, (fs) & CELL WALL THICKNESS (δδδδ)

2D Slice of a single cell after having applied

the struts identification methodology

0 1 2 3 4 5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

cell w

all thic

kness /

µµ µµm

Nanoclays content /%

Nanoclays Content (wt%) fs

0 0.66

0.5 0.62

1 0.66

3 0.78

5 0.76

Fraction of material in the edges increases

and cell wall thickness decreases in a

significant way0 1 2 � 3� 1 4� � 567

The presence of the nanoparticles seems to

affect the kinetics of polyurethane formation

reaction.

FTIR evidences of a delay in the gelling reaction leading to an

increase of the time at which the material is in a non-

crosslinking stage favoring drainage and hence leading to a

reduction of cell wall thickness to values lower than expected.

CELL WALL THICKNESS


STRUTS MASS FRACTION, (fs) & CELL WALL THICKNESS (δδδδ)

2D Slice of a single cell after having applied

the struts identification methodology

0 1 2 3 4 5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

cell w

all thic

kness /

µµ µµm

Nanoclays content /%

Nanoclays Content (wt%) fs

0 0.66

0.5 0.62

1 0.66

3 0.78

5 0.76

0 1 2 � 3� 1 4� � 567LOWER ATTENUATION OF

RADIATION

Fraction of material in the edges increases

and cell wall thickness decreases in a

significant way


EXPERIMENTAL DETERMINATION OF EXTINCTION COEFFICIENT (K)

FTIR Espectrometer, Transmission Mode.

Ke,λλλλ

( )K

Ln

Le

n

,

,

λλτ

=− ( )

τ λλ

λn

I x

I,,

=0

-1.2

-0.2

0.8

1.8

2.8

0 1 2 3 4 5

L (mm)

Ln

€€ €€

Beer-Lambert Law

Samples with different thicknesses Experimental

determination of Ke,λλλλ

R.A. Campo-Arnaiz, M.A. Rodríguez-Pérez, B. Calvo, J.A. de Saja. Extinction coefficient of polyolefin foams. Journal of Polymer Science, Part B: Polymer Physics 43: 1608-1617, (2005


EXPERIMENTAL DETERMINATION OF EXTINCTION COEFFICIENT (K)

λλ

λ

de

e

KK b

b

eRe ∂∂

= ∫∞

,

0 ,,

11

2

2,2

2,4

2,6

2,8

3

3,2

3,4

3,6

400900140019002400290034003900

Wave Number (cm -1)

Ke,

λ (m

-1)

K e,λλλλ AS A FUNCTION OF WAVE NUMBER

ROSSELAND MEAN EXTINCTION COEFFICIENT

89,:: Spectral black body emissive power.λ: Wavelength

� Diffussion approximation, (Radiation travels only a short distance before being scattered or absorbed. The energy transfer depends only on the intermediate vicinity of the position being considered).

� Foams used in real applications thick enough, considered optically thick, radiative flux, Rossland equation.

� Refraction index for foam, close to one. � Medium absorbs and scatters isotropically.



EXTINCTION COEFFICIENT: COMPARISON WITH THEORETICAL MODEL, (GLICKSMAN MODEL)

15,00

20,00

25,00

30,00

35,00

0,00 0,50 1,00 3,00 5,00

nanoclays concentration (wt %)

K (c

m-1

)

Experimental

Glicksman

Sample (nanoclays con.

%wt.)K (exp.) (cm-1) K Gliks. (cm-1) Variation % K

ω(m-1) exp.

0 23.18 25.40 9.56 462660.5 25.47 28.53 11.99 429461 30.42 28.91 -4.94 689453 33.68 29.59 -12.14 975055 27.31 28.93 5.95 46488

THEORETICAL EXPRESSION FOR K, GLICKSMAN MODEL

Differences between experimental and

theoretical values: CHANGES IN Kw

Kw increases up to 3wt%

�; � �<=>� � �?�#

�; � 4.10

��

��

��

"� �1 � ��$

��

��

�#

o Poorer dispersion (SAXS confirmed a

good level of dispersion and exfoliation.)

o Preferential location of

nanoparticles in the struts as the

cell wall thickness is reduced.

NO ATTENUATION OF RADIATION,

NANOCLAYS CONCENTRATION >3



COALESCENCE DRAINAGE

NUCLEATIONSOLIDIFICATION

DIFFUSION

COARSENING

REDUCED CELL SIZE: Heterogeneous Nucleation (Increase in the number of cell per unit volume) & Coalescence Absence (constant

cell density). REDUCTION OF RADIATION

CONTRIBUTION.

Clays are “correctly” distributed until 3wt%, INCREASING THE EXTINCTION

COEFFICIENT OF THE POLYMERIC MATRIX

(Kw). REDUCTION OF THE RADIATION

CONTRIBUTION

INCREASE IN fs as the nanoclays concentration increases. Thinner cell walls has lower ability to

attenuate thermal radiation. HIGHER

CONTRIBUTION TO RADIATION THERM.

The CONDUCTIVITY OF SOLID PHASE

INCREASES and this has a negative influence. It is more important at high filler content.

HIGHER CONTRIBUTION OF CONDUCTION

THROUGH SOLID PHASE

RESULTS FOR λλλλ A COMBINATION OF POSSITIVE AND NEGATIVE EFFECTS

MELTING





o CASE STUDY ####2: HIGH DENSITY LDPE FOAMS WITH IMPROVED



CASE STUDY ####2: LDPE/SiO2 FOAMS WITH IMPROVED MECHANICAL PERFORMANCE

CASE STUDY ####2: HIGH DENSITY LDPE/SiO2 FOAMS

PROCESSING

PARAMETERS

CELLULAR

STRUCTURE

MORPHOLOGY

POLYMERIC

MATRIX

PHYSICAL

PROPERTIES

MARKET,


POLYMERIC MATRIX

MICROSCOPIC LEVELMACROSCOPIC LEVEL

• NUCLEATING EFFECT

• MECHANICAL PROPERTIES

HIGH DENSITY LDPE FOAMS WITH

IMPROVED MECHANICAL PERFORMANCE

DISPERSION/COMPATIBILIZATION

• LDPE FOAMS

• WITH (NC) & WITHOUT LLDPE-g-MA

• SILICA NANOPARTICLES: 0, 1, 3, 6, 9 wt%,

Surface treated with dimethyldichlorosilane

• In mould gas

dissolution, pressure

quench method

• Fixed density, ρρρρr=0.6

• CRISTALLINITY DEGREE

• MECHANICAL PROPERTIES OF

SOLID NANOCOMPOSITES

VS SYNERGISTIC

EFFECTS


MICROGRAPHS: CELLULAR STRUCTURE OF LDPE/SiO2 FOAMS

WITH

LLDPE-g-MA

WITHOUT

LLDPE-g-MA

NEAT LDPE


CHEMICAL COMPOSITION VERSUS NUCLEATING EFFECT

0 1 2 3 4 5 6 7 8 9 10

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Nuc

leat

ion

Rat

io

Contenido de Silice (wt%)

WITHOUT LLDPE-g-MA WITH LLDPE LLDPE-g-MA

OptimumSiO2

concentration: 1wt%

CD*E8&+),(F&+), �G8EEDE&H.8(I)+J � C&(,*,KL,I)+8M,&K

G8EEDE&H.8(I)+J � C8&+N,EJK8HM,&K

WITH LLDPE-g-MA: Values around 2 for

optimum content. At higher SiO2

concentrations, worst results than for

neat LDPE.

WITHOUT LLDPE-g-MA: Values of

nucleation ratio higher than 1.4 in any

case


MECHANICAL PROPERTIES. SOLID VERSUS NANOCOMPOSITES: SYNERGISTIC EFFECTS

0 1 2 3 4 5 6 7 8 9 10

-505

10152025303540

15.5%

∆ ∆ ∆ ∆ E-FOAMED NANOCOMPOSITES

∆ ∆ ∆ ∆ E-SOLID NANOCOMPOSITES

∆ E-L

DP

E /

E-N

S (%

)

Silica Content (%)

39.8%

19.8%

0 1 2 3 4 5 6 7 8 9 10

0

5

10

15

20

25

∆ ∆ ∆ ∆ E-FOAMED NANOCOMPOSITES ∆ ∆ ∆ ∆ E-SOLID NANOCOMPOSITES

∆ E-L

DPE

/ E-N

C (%

)

Silica Content (wt%)

10.6%

18.2%

WITH LLDPE-g-MA

WITHOUT LLDPE-g-MA

∆P �PQRSP/UVWX

YPQRSP

PQRSPx100

SYNERGISTIC EFFECTS due to the

combination of nanoparticles and

foaming processes.

LOWER SILICA CONTENT TO ACHIVE

HIGHER LEVELS OF IMPROVEMENT.

Higher reinforcement in the solids.

Better compatibilization (bonding)

polymer/particle

SUMMARY & CONCLUSIONS

NANOPARTICLES INDUCE TECHNICAL

IMPROVEMENTS IN POLYMERIC FOAMS.

BUT… WHAT ABOUT THE NUMBERS????


RIGID POLYURETHANE FOAM/NANOCLAYS: THE NUMBERS

PUR: 4 €/kgNanoclays: 7 €/kgPUR + 1wt% Nano: 4.03 €/kg

1wt% Nanoclays→→→→8 % reduction in λλλλ

10 mm

Neat PU

9.25 mm

PU + 1wt% Nanoclays

Wall- PUR: 10m x 2.5 m x 10 mm

Wall- PUR + 1wt% Nano: 10 m x 2.5 x 9.25

Density-PUR: 53.1 kg/m3

Density-PUR + 1wt% Nano: 54.07 kg/m3

Wall- PUR: 53.10 €Wall- PUR + 1wt% Nano: 50.11 €

SAVINGS PER WALL: 2.99 €→→→→ ∼∼∼∼5.5%

HOW MANY WALLS ARE THERE IN A BUILDING? AND IN A CITY

FULL OF BUILDINGS? …

SAME THERMAL INSULATION ABILITY !!


LDPE/SiO2 FOAMS: THE NUMBERS

Z�

Z�

~��

��

\

GIBSON & ASHBY MODEL

Ef: Elastic modulus foamEs: Elastic modulus solidρf: Density foamρs: Density solid

LDPE + 3 wt% SiO2, <]

<^� 0.5619

Corresponds to a ρρρρr: 0.749

LDPE + 3 wt% SiO2: r: 0.649

BY ADDING A 3wt% OF SiO2 PARTICLES: ∼∼∼∼12% LIGHTER PART WITH SAME

MECHANICAL PERFORMANCE!!

LDPE: 1.5 €/kgSiO2: 5 €/kgLDPE + 3 wt% SiO2: 1.60 €/kg

FOAMED PART- Volume 0.1 m3

LDPE: 68.9 kgLDPE + 3 wt% SiO2: 61.4 kg

LDPE: 103.44 €LDPE + 3 wt% SiO2: 98.33 €

SAVINGS PER PART: 5.10 €

∼∼∼∼7.5%LET’S THINK… ABOUT CARS….

CELLMAT TECHNOLOGIES S.L.

CENTRO DE TRANSFERENCIAS Y TECNOLOGÍAS APLICADAS (CTTA)

PASEO DE BELÉN 9A OFFICE 10547011, VALLADOLID-SPAIN

Phone:+34 983 189 [email protected]

www.cellmattechnologies.com

ACKNOWLEDGEMENTS

o CellMat Laboratory.o Prof. Miguel Angel Rodríguez-Pérezo Sergio Estravís, Samuel Pardo, Alberto López-Gil, Josías Tirado, Javier Escudero.o Spanish Ministry of Economy and Competitiveness: Program Torres Quevedo PTQ-12-05504

THANK YOU SO MUCH FOR YOUR

ATTENTION!!

case studies: reduction of thermal conductivity ... · case studies: reduction of thermal...

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