Gradient block copolymers | ResearchGate

BEHAVIOUR OF BLOCK COP0LYMERS IN SUPERCRITICAL CO2 and MICRO CELLULLAR FOAMING of their blends with homo polymers Michel Dumon a), José Antonio Reglero Ruiz a), Matthieu Pedros b), Jean-Marc Tallon b), Eric Cloutet a), Javier Pinto Sanz c), Miguel Angel Rodriguez Perez c), Philippe Viot d) a

Laboratoire de Chimie des Polymères Organiques, Bordeaux, France

b Département

Science et Génie des Matériaux , IUT Université Bordeaux 1 Materials Laboratory (CellMat), Condensed Matter Physics Dept, Universidad de Valladolid, Spain Institut de Mécanique et Ingénierie I2M, ENSAM Paris TECH, site de Bordeaux Talence, France

c Cellular d

DSL 2011, Algarve Portugal, June 29th 2011

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Behaviour of block copolymers in supercritical CO2 ; micro cellular foaming of their blends with homo polymers

Contents, Issues 1. Introduction and Objectives 2. Block copolymer behaviour in CO2: summary of recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of block copolymers under study : SM, PS-PFA, SBM, MAM; core shell particles >>> Differences in CO2 absorption. Role of the CO2-philic blocks,

4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends; 5. rubbery – glass transition vs. CO2 saturation, vs. Foaming. Role of nano structure type on foams 6. Conclusions


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Objectives 

General objective : Design and fabrication of micro and nano cellular polymer foams from amorphous polymers (PS, PMMA, ...) in supercritical CO2 on thick pieces through blends with the addition of well selected nano structured block copolymers.



Technical objectives , applications : improvement of mechanical properties,



Scientific questions : study of the foaming mechanism and foaming process of

energy absorption or fatigue life, increased toughness, thermal insulating properties

polymer blends (matrix : PS, PMMA, ...) with CO2-philic nano or micro structured block copolymers. (variable % of copolymer type, showing different nano structures or morphologies)


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Strategy : synergetic use of 3 phenomena (attemptively) 1- Nano structuration of organic block copolymers (self assembly, ‘ordered’ structures) >> micro phase separation in a polymer matrix, perfect dispersion of organic moities >> generate thermoplastic polymer foams from ordered structures 2- Control of CO2-philicity by the block’s choice in the copolymer >> enhancement of CO2 absorption, restriction of CO2 diffusion ? (e.g due to a glassy shell layer) 3- Organic nucleating agents which also may play the role of CO2 reservoirs >> induce a heterogeneous nucleation on copolymers, thus an enhancement of bubble nucleation and an increase in cell density (from 109 to1016 cells/cm3) >> reduce the cell size (down to 50nm), in any case cells are in microcellular range: below 10mm, >> improve the foam homogeneity (lower dispersion of cell size and cell geometry)


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Gas process, Nucleation – Growth : micro / nano cellular range : high nucleation rate + high gas concentration >> micro /nano polymer foams Ideally … heterogeneous nucleation on CO2-philic, size-monodisperse, well dispersed agents with a simultaneous initiation of their blowing activity

Siripurapu, DeSimone, Spontak, 2005 macromolecules

Organic block copolymers : good nano dispersability of organic moities in polymer matrices, better than inorganic moities (micro sized or sub micronic particles of talc, kaolin, silica, TiO2, …)


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Contents, Issues 1. Introduction and Objectives

2. Block copolymer behaviour in CO2: summary of recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of block copolymers under study : SM, SBM, MAM, PS-PFA; core shell particles >>> Differences in CO2 absorption. Role of the CO2-philic blocks,

4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends; 5. rubbery – glass transition vs. CO2 saturation, vs. Foaming. Role of nano structure type on foams 6. Conclusions


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Different types of block copolymers => nano or molecularly dispersable organic polymeric moieties with a potential high CO2 philicity and a nucleating activity

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v v

Di or Tri block copolymers, nano structuration into cylinders hexagonal, lamella, gyroids, micelles, onion-like structures

Gradient block copolymers

Schematic of AB block copolymers

Schematic of ABA or ABC block copolymers

Schematic of a core/shell particle


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block copolymer behaviour in CO2 : literature (2005-2011)

solubility in CO2

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Previous works

Block copolymers used in CO2 (supercritical): di or tri or gradient blocks of AB, ABA, ABC type >> polymers having the highest solubility in CO2 are : :

fluoro polymers, polysiloxanes, polyacrylates, polyethers,

(apart from low molar mass fluorinated surfactants)

Homopolymers : Polydimethylsiloxane PDMS Polymethylmethacrylate PMMA Ethylene Propylene EP Polyvinylpyridine PVP Polybutylacrylate PBA Polytetrahydro perfluoro decylacrylate PFDA* Polydihydro perfluoro octyl acrylate PFOA*

Copolymers : PS-PMMA PS-PDMS PS-PB-PMMA (SBM) PS-EP PS-PVP PMMA-PBA-PMMA PS-PFDA PS-PFOA

*PFDA is semi crystalline, PFOA is amorphous, PS = poystyrene

>> Copolymer solubility in CO2 depends on molar mass, composition, block length DSL 2011, Algarve Portugal, June 29th 2011

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block copolymer behaviour in CO2 : literature (2005-2011)

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solubility in CO2 and phase separation (a) PFDA (n = 8) polytetrahydro perfluoro decyl acrylate; (b) PS-b-PFDA block copolymer, m and p are the number of monomer units for each block; (c) PFOA polydihydro perfluoro octyl acrylate (n = 7 and methylene spacer, 25% of branched side chains); (d) PTAN (n = 4–18 with a mean value n = 8) Lacroix Desmazes, Boutevin J. of Supercritical Fluids 2006

TEM micrograph of the disordered cylindrical micelles obtained for PS-b-PFDA 22. PS, stained with RuO4 vapor, appears black Lacroix Desmazes, Boutevin, DeSimone, J. of Polym.Sci A 2004

Cloud point curves for PFDA homopolymer (■) and PS-b-PFDA block copolymer (▲), performed at 3.9% (w/w) in neat CO2 The lines stand for constant CO2 density stated in g/mL on their left Lower CO2 density is required to reach the PFDA one-phase region than PTAN DSL 2011, Algarve Portugal, June 29th 2011

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block copolymer behaviour in CO2 , literature (2005-2011)

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structuration in CO2

(a) General schematic phase diagram in the polymer volume fraction-pressure plane for a polymer in scCO2 at a given temperature. (b) Phase diagram for the copolymers of FDA and VBPDE at T = 40 C: gradient copolymers G4 and G3 and block copolymers B3 and B4 Lacroix Desmazes et al. J. of Phys Chem 2011 DSL 2011, Algarve Portugal, June 29th 2011

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structuration in CO2

Normalized small-angle neutron scattering (SANS) for a PS-b-PFOA diblock copolymer dissolved in scCO2 at 65°C and 34 MPa. A schematic of the micellar model for monodisperse and polydisperse micelles Spontak et al. Adv Mater 2008

Phase diagram generated by light scattering for a PVAc-b-PTAN diblock copolymer in high-pressure CO2 at 45°C. The conditions signifying phase separation (o), the micelle–unimer transition (), and the overlap concentration (C*,) have been identified. Spontak et al. Adv Mater 2008


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phase transition in CO2

Schematic representation of the proposed mechanism of the HEX - LAM transition of PDMS58-bPMPCS66 induced by scCO2 Shi, Fan 2011 Macromolecules

Simplified phase diagram of PDMS-bPMPCS showing the orderorder transition of PDMS58-bPMPCS66 (case 1) and the periodic size changes of PDMS58-bPMPCS54 (case 2) and PDMS58b-PMPCS75 (case 3) induced by scCO2


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Neat block copolymer behaviour in CO2 , recent literature (2005-2011) nano cellular foaming in CO2

Topographic AFM images of nanocellular structures in PS-PFMA thin films after the scCO2 process at saturation pressure of 8 MPa with full-scale height of 18 nm (a), 10 MPa with full-scale height of 22 nm (b), 15 MPa with full-scale height of 25 nm (c), 20 MPa with full-scale height of 27 nm (d). SEM images of the same films processed at 8 MPa (e), at10 MPa (f), at 15 MPa (g), at 20 MPa (h) The bars indicate 200 nm Sugiyama, Yokoyama 2006 Macromolecules


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Short summary of the review on block copolymers in sc CO2

▪ Mc Clurg, Macosko 2004 Macromolecules ◉

PS + PS-PDMS or + PS-PMMA or + PS-EP; study of NG of cells in CO2, very little effect of these copolymers on foam cell size , little nucleation activity except PS-PDMS but bimodal distribution

▪ Siripurapu, Spontak, DeSimone 2004 Macromolecules, 2005 Adv. Mater., ◉

PMMA + Commercial fluorinated surfactants or + designed fluoro or siloxane blocks, increase in Nc over large T and P ranges, self organization into micelles

▪ Yokoyama 2009 Macromolecules nano porous films of PS-PVP in sc (C02 /methanol ) ▪ Lacroix-Desmazes 2011 J. Phys.Chem.; polyperfluorodecylacrylate PFDA Polymer 2004 PFDA-g-acetoacetoxy ethyl methacrylate, PFDA-g-vinylphosphonic acid diethylester, gradient copolymers : better solubility than block copolymers, and also self assembled

▪ Shin, Fan 2011 Macromolecules orderorder transition OOT in block copolymers induced by C02; series of PDMS-PMPCS rod coil di blocks, Hexagonal - Lamellar phase transition at low content of PDMS ( (foam) Ncfoams F=15 to 30 nm DSL 2011, Algarve Portugal, June 29th 2011

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Contents, Issues 1.

Introduction and Objectives

2.

Block copolymer behaviour in CO2 : recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of the block copolymers under study : SM, SBM, MAM, PS-PFA; core shell particles >>> Role of the CO2-philic blocks, structuration of blocks

4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends; 5. rubbery – glass transition vs. CO2 saturation, vs. Foaming ; role of nano structure type on foams 6. Conclusion


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3. Case of different block copolymers : SM, SBM, MAM, PS-PFA; core shell particles

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Nano structured polymers: Blends of PS or PMMA + SBM or MAM or SM

Block Copolymers self assembly (or core shell particles)

MAM

• Triblock styrene-butadienemethylmethacrylate terpolymer (SBM)

PS + SBM (90/10)

• Triblock methylmethacrylatebutylacrylate-methylmethacrylate terpolymer (MAM)

SBM

•Diblock styrene-methylmethacrylate copolymer (SM)

100 nm

PMMA + MAM (90/10) high impact PMMA = PMMA + core shell 200 nm

100 nm

DSL 2011, Algarve Portugal, June 29th 2011 PMMA+MAM

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Behaviour of block copolymers in supercritical CO2, and micro cellular foaming of their blends with homo polymers

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1) HIPMMA high impact transparent polymethylmethacrylate Altuglas CompanyArkema, modified with core/shell rubber particles of diameter 250-300 nm composed of a PMMA core, a Styrene-Butylacrylate rubbery inner shell and grafted PMMA chains on the outer shell

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2) PS high molecular weight transparent polystyrene (PS Crystal) Total Petrochemicals

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3) SBM triblock styrene-butadiene-methylmethacrylate terpolymer (polystyreneblock-polybutadiene-block-polymethylmethacrylate) 52wt% stryrene- 30wt% butadiene- 18wt% methylmethacrylate with a PS block of molar mass equal to 30000 g/mol



4) MAM triblock methylmethacrylate-butylacrylate-methylmethacrylate terpolymer (poly methylmethacrylate-block-polybutylacrylate-block-polymethylmethacrylate) with - 35wt% methacrylate- 30wt% butylacrylate- 35%wt methacrylate, with a PMMA block of molar mass equal to 90000 g/mol

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5) SM diblock styrene-methylmethacrylate copolymer ( 58wt% styrene- 42wt% methylmethacrylate), with a molar mass of 90000 g/mol


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CO2 saturation and foaming process Evolution of the (Polymer-CO2) system

CO2 Phase Diagram

Saturation of the polymer Time t, Temperature T, Pressure P

Depression of Tg by CO2 > possibility to use vitrification of the polymer or the copolymer

Supersaturated state and swelling of the polymer

Depressurization - dP/dt RT, atm pressure phase separation

Foaming controlled by dP/dt Chemical modification reactions

scCO2

but also by the blocks

Foaming agent


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EQUIPMENT

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Equipment to process raw materials and blends Mini extruder twin screw single screw extruder

SCAMEX CE02 • Temperature Profile 165°C to 225°C • screw Velocity 65 rpm • 1,5 to 5 Kg of material extruded and blended

Mini injection machine 1 cm

DSM Xplore extruder

DSM Xplore injection machine

• Twin – Screw extruder

• 3 moulds available

• screw Velocity 100 rpm

Capacity  10 samples/h

• Capacity  200 g/h

• Mould temperature up to 80°C • Mass temperature up to 260°C


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EQUIPMENT and PROCESS

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Foaming equipment Foaming reactor

Experimental parameters

Pressure and temperature controller

One Step-Process Fixed Depressurization Rate (60 bar/min) Saturation Temperatures Tsat /°C

25

40

50

60

70

80

One Step-Process TCP Industrie Model V570 Teledyne ISCO Model 260D • Pressure control up to 450 bar at RT • Volume  400 cm3 • Pressure and Temperature controled up to 24 h • Ethanol refrigerated

• Pressure and temperature monitoring • Temperature up to 250°C

Fixed saturation Temperature (40°C)

• Temperature dispersion +-2°C • Electrical resistance for heating • Termocouple inside reactor

• Fixed saturation Pressure 300 bar and saturation time 24 h •Cells triggered by dP/dt (variable) and different initial Tsaturation =? foaming


Depressurization Rate, dP/dt (bar/min)

150

75

50

20

12

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CO2 absorption in blends , 10wt% of copolymer in the homopolymer

Characteristic curves for mass loss as a function of time, measured at room temperature RT, out of the CO2 vessel, in samples analysed after a scCO2 saturation at 40°C, 24h, 300 bar

Deformation state (swelling) of two specimens of polystyrene after saturation at 40°C and 50°C DSL 2011, Algarve Portugal, June 29th 2011

Constant values of CO2 mass uptake measured at RT, out of the vessel, after scCO2 exposure at different times (saturation values, 300 bar, 40°C)

Depressed glass transition temperature ranges estimated after CO2 absorption and saturation at different temperatures

w%CO2 (in block copolymer) >> w%CO2 (in matrix)

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Solubility of carbon dioxide in several homopolymers and copolymers

Spitael, Macosko, Clurg 2004 Macromolecules

Carbon dioxide solubility is significantly larger in fluoro and MAM based blends, at only 10wt%

Material

w () (%)

w () (%)

w () (%)

w () (%)

w () (%)

w () (%)

PS

10.4

10.3

10.1

9.4

9.2

8.9

PMMA

16.9

16.4

16.2

16.1

15.9

15.6

PS + SBM

12.1

10.9

10.5

10.4

10.2

9.7

PMMA + MAM

22.3

21.2

20.4

20.1

19.3

19.2

Weight gain ratio of CO2 after saturation (300bar) at different temperatures DSL 2011, Algarve Portugal, June 29th 2011

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Contents, Issues 1.


2.

Block copolymer behaviour in CO2 : recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of different block copolymers : SM, SBM, MAM, PS-PFA; core shell particles >>> Differences in CO2 absorption. Role of the CO2-philic blocks,

4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends; 5. rubbery – glass transition vs. CO2 saturation, vs. foaming; role of nano structure type on foams

6. Conclusion


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Foaming of NEAT vs. NANSTRUCTURED polymers (PS, PMMA),

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morphologies

Polystrene based blends : PS vs. PS-SBM

PS Tsat = 25°C

PS SBM Tsat = 25°C

PS SBM dP/dt = 12 bar/min

PS, dP/dt = 12 bar/min, Tsat = 40°C

50 mm

PS Tsat = 80°C

50 mm

100 mm

PS SBM Tsat = 80°C

200 mm

PS, dP/dt = 150 bar/min Tsat = 40°C

PS SBM dP/dt = 150 bar/min

100 mm

PS Tsat = 60°C

300 mm

50 mm

100 mm

10 mm

Tsat=40°C

dP/dt=60bar/min

neat PS vs. PS + SBM 10wt%  2-30 mm / 5–10 mm

50 mm

• Foaming not possible under 60°C, due to poor plasticization effect and early vitrification, higher temperatures increase cell size.



• PS is weakly sensitive to CO2 swelling / foamimg

Nc

0.9-1.0 g/cm3 / 0.6-0.9 g/cm3 10 8-10 9 cells/cm3 / 10 8-10 9 cells/cm3


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Foaming of NEAT vs. NANO STRUCTURED polymers (PS, PMMA), morphologies

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polymethylmethacrylate based blends : PMMA vs. PMMA-MAM PMMA, Tsat = 25°C

PMMA MAM, Tsat = 25°C

PMMA, dP/dt = 150 bar/min

PMMA MAM dP/dt = 150 bar/min

30 mm

20 mm 2 mm

PMMA, Tsat = 60°C PMMA MAM, Tsat = 80°C

PMMA, dP/dt = 12 bar/min

PMMA MAM dP/dt = 12 bar/min

100 mm

PMMA, Tsat = 80°C 20 mm

dP/dt=60bar/min

500 mm

Tsat=40°C

50 mm

neat PMMA vs. PMMA+MAM 10wt%  1 - 25 mm / 0.2 - 5 mm

• Foaming is possible all over the whole temperature range, due to the high CO 2 affinity of the methacrylate groups. Higher process temperature increases cell size.



• Foaming at lower temperatures increase the cell density and decrease the cell size, due to the higher solubility and reduce growth.

Nc


0.7 - 1.0 g/cm3 / 0.3 - 0.8 g/cm3 10 7-10 10cells/cm3 / 10 7-10 12 25

Foaming of NEAT vs. NANO STRUCTURED polymers : cellular

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parameters

characteristics of cellular polymer blends based on PS, PMMA and SBM, MAM PS + SBM 10%

DP/Dt bar/min 150 75 50 20 12

F mm

12 20

foam g/cm3

0,90 0,82

Nc cells/cm3

1,2 1011 4,5 1010

PMMA + 10%MAM

F mm 0,3 2 10 20 80

PS + SBM 10%

Tsat °C

F mm

foam g/cm3

Nc cells/cm3

25

No foam No foam No foam

No foam

No foam

No foam

15 20 30

40 50 60 70 80

foam g/cm3 0,71 0,65 0,63 0,60 0,53

Nc cells/cm3 2,1 1013 8,6 1010 7,3 108 9,8 107 1,7 106

PMMA + 10%MAM

F mm 1

foam g/cm3 1

Nc cells/cm3

No foam

2

0,93

4,8 1010

No foam

No foam

3

0,92

1,5 1010

0,94 0,85 0,76

3,9 1010 3,8 1010 1,8 1010

4 5 7

0,83 0,78 0,65

5,3 109 3,5 109 2 109


3,7 1010

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Case of a fluoro neat copolymer

SEM micrographs of PS-b-PFDA (50/50) copolymer solid dense film,  250 microns (before foaming)


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Case of a fluoro neat copolymer

Comparative CO2 absorption of the bulk PS and PS-b-PFDA polymers films,  250 microns

SEM images of the neat PS sample after saturation in scCO2 and depressurization

SEM images of foamed PS-b-PFDA after saturation in scCO2 and depressurization


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Contents, Issues 1.


2.

Neat block copolymer behaviour in CO2 : recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of different block copolymers : SM, SBM, MAM, PS-PFA; core shell particles >>> Saturation at ≠ T, P. Differences in CO2 absorption. Role of the CO2-philic blocks, 4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends;

5. rubbery – glass transition vs. CO2 saturation, vs. foaming ; role of nano structure type on foams

6. Conclusions


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Typical temperature-drop curves from an initial constant saturation temperature of 40°C, at variable depressurization rates. Note thatTemperature is only affected by dP/dt 60 40

T (°C)

20 0 0 -20 -40

3

6

9

12

15

18

21

24

27

t (min) 75 bar/min 50 bar/min

-60 -80

20 bar/min 12 bar/min 150 bar/min


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Nano structure effects …

Possible mechanism of activity of a block copolymer micelle during CO2 saturation and foaming

Micelle (radius: rm) with a glassyfying shell (ex. PMMA, PS)

rm

block copolymer micelle

rc

Nucleus (rm > rc) and rubbery CO2 reservoir / concentrator (e.g blocks of PBA, PFDA)

blocks of e.g PMMA, PS)

Polymer matrices (PS, PMMA, …) role of nano structures, example of micellar objects : rubbery phase in the core (PBA) >> swelling, growth. glassy / glassyfying shell (PS, …) >> restricted diffusion. DSL 2011, Algarve Portugal, June 29th 2011

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Contents, Issues 1.


2.

Neat block copolymer behaviour in CO2 : recent literature (2005-2011) >>> solubility in CO2, structuration in CO2, micro and nano cellular foaming

3. Case of different block copolymers : SM, SBM, MAM, PS-PFA; core shell particles >>> Saturation at ≠ T, P. Differences in CO2 absorption. Role of the CO2-philic blocks, 4. homopolymer / block copolymer Blends: interplay between CO2 Solubility and Nucleation-Growth Foaming of the blends;

5. rubbery – glass transition vs. CO2 saturation, foaming and vs. diffusion of CO2 ; role of nano structure type on foams

6. Conclusions


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Comparison of structures before foaming, variable location for morphology characterization within a sample

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Homogeneity of morphologies in injection molded thick samples, preferential diffusion ?

Direction of injection molding

H1

1/8 1/2

H4

V2 H2 H5

90/10 H2

90/10 H1

25/75 V2

25/75 V3

H3

1/8 1/4 1/2 3/4


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different compositions of PMMA / MAM blends, Comparison of structures before foaming

HORIZONTAL

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90/10

80/20

50/50

25/75

VERTICAL

95/5


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Change of structure during CO2 saturation or foaming

Saturation at 23°C: 24 h, 300 bar, PMMA/MAM 25/75wt%

Saturation at Room temperature, probably no change of nano structure under CO2


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Change of structure during CO2 saturation or foaming

Saturation at 40°C : 24 h, 300 bar, PMMA/MAM 25/75wt%

Saturation at temperature of 40°C, probably change of nano structure under CO2*, change from dispersed to lamellar structures, but at which step ? *always at contents of MAM > 50wt%, micellar behaviour is preserved DSL 2011, Algarve Portugal, June 29th 2011

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Rubbery and CO2-philic (nano separated) inner blocks acting as CO2 concentrators and nucleating agents. They enable cell growth (rubbery inner blocks) to a limited extent due to vitrification of hard blocks and size of nano objects. w%CO2 (in block copolymer) > w%CO2 (in matrix) e.g. MAM, PFDA CO2 reservoirs / concentrators

Polymer matrix

Polymer matrix (PS, PMMA, …) + block copolymer additives dispersed at nano level as nano structures, stabilized in the matrix by matrix-like blocks which vitrify before the inner blocks DSL 2011, Algarve Portugal, June 29th 2011

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CONCLUSIONS

▲ Advantages of Block copolymers in CO2 : they show a panel of various nano structures either preserved, or enhanced or modified in CO2 1- blocks may show selective absorption and localize CO2 in domains depending on the nano structure type and the block type, length. 2- blocks may reduce diffusion during foaming. ▲ Block copolymers can considered as neat polymers or polymer additives (by blending) used for thermoplastic polymer foams; e.g in Styrene and MethylMethacrylate polymers to improve their foaming behaviour towards micro cellular foams (increase in the cell density with respect to the neat polymer) e.g. tri-block MAM to a PMMA matrix resulted in a remarkable reduction of the average cell size, especially at high depressurization rates, showing the effect of the nanostructuration; producing an ultra microcellular foam with an average cell size close to 0.1mm and cell densities of 1016 cells/cm3. ▲ The use of nano structuring CO2-philic copolymers is a versatile route to produce micro, ultra micro or nano cellular polymer foams from several commodity polymers with an easy mixing by extrusion followed by a batch foaming one or two-step scCO2 process. Thick homogeneous samples can be produced. DSL 2011, Algarve Portugal, June 29th 2011

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PERSPECTIVES

▲ characterization of nano structures during saturation, during and after foaming step ▲ Homogeneity of foams, control of foaming (diffusion) in thick samples ▲ modeling of CO2 solubility and diffusion in heterogeneous blends ? ▲ new thermoplastic polymer foams : “ordered”, micro porous, gradient


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acknowledgements

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Thank for your attention Listrac* project, ANR funded project (2008-2012), partners : CRPP, LCPO, ICMCB Tomomat, ENSAM

* LightenIng of StrucTuRes And Composites

Ph.D collaboration at CellMat laboratory, University Valladolid, Spain


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Evolution of mean diameter, skin effect

SEM micrograph showing a solid outer skin presented in the samples, diffusion of CO2


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different compositions of PMMA / MAM blends, observation by different microscopies

PMMA / MAM (95 / 5 wt%) HR SEM polished sample + RuO4 treatment

PMMA / MAM (75 / 25 wt%) HR SEM polished sample + RuO4 treatment

Comparison of morphologies before foaming,

PMMA / MAM (75 / 25 wt%) AFM ultracut+ image treatment

At the same wt%, an identical structure is observed by different techniques, although poorly defined on injected bulk thick sample


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LCPO Advantages of CO2 : 1- possible « retrograde behaviour » at low temperature and pressure on thin films; 2- induced annealing (phase separation assisted) of phases (high copolymer contents)


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MATERIALS Some Chemical and Physical data before foaming : homo polymers, core shell particles, block copolymers Standard values

Tg homo PBA= -45°C Tg homo PB =