Introduction Introduction to to Plastic FoamsPlastic Foams
AndrAndréé MoreiraMoreiraPolymer Polymer PhysicsPhysics, BASF AG, BASF AG
Ludwigshafen, GermanyLudwigshafen, Germany
Les Les HouchesHouches, Jan. 2006, Jan. 2006
AcknowlegmentsAcknowlegments::
H.H. WeiWeißß V. V. SchSchäädlerdlerP. P. MMüüllerller M. M. RRüüllmannllmannE. E. WaWaßßnerner H. H. SchuchSchuchK. HahnK. Hahn C. C. ExnerExnerM. M. AllmendingerAllmendinger P. LopesP. LopesB. B. SowartSowart A. A. AlteheldAlteheldD. LongoD. Longo K.K.--H. H. WaWaßßmermerT. FrancisT. Francis F. F. HeilmannHeilmannM. M. RRüüllmannllmann M. M. BotheBothe
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Global summaryGlobal summary
Introduction
Plastic foams: Physics and Chemistry
Plastic foams: industrial processes
Mechanical properties
Acoustic properties
Thermal properties
Nanoporous foams: the future?
Part I
Part II
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Summary: Part ISummary: Part I
IntroductionWhat are polymers?What are plastic foams?Open and closed cell foamsApplications and Markets
Plastic foams: Physics and ChemistryNucleationBubble growthStabilization (solidification)
Plastic foams: industrial processesExtrusion process (XPS)Expandable beads (EPS)Reactive foams (PUR)
IntroductionIntroduction
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
What are polymers?What are polymers?
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
What are polymers?What are polymers?
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
What are polymers?What are polymers?
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Some usual monomersSome usual monomers
Source: Cowie, Polymers: Chemistry & Physics of modern materials. , Blackie (1991)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Mechanical behavior Mechanical behavior of polymersof polymers
Source: Gibson & Ashby, Cellular solids , 2nd Ed., Cambridge (1997)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
World polymers marketWorld polymers market
World plastics production
1
10
100
1000
1950 1960 1970 1980 1990 2000 2010 2020
year
mill
. to
ns
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Plastic consumption worldwidePlastic consumption worldwide
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
What are foams & cellular materials?What are foams & cellular materials?
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
What are foams & cellular materials?What are foams & cellular materials?
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Closed and open foam-structures
cork sponge
cakecrisp
Natural cellular structuresNatural cellular structures
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Styrodur®(XPS) closed-cell polystyrene foam
Basotect®open cell Melamine polycondensate
Closed and open foam-structures
Artificial cellular structuresArtificial cellular structures
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Polyurethane foams Styropor® (EPS)Polystyrene (closed-cell)
Neopolen®
Polypropylen (closed-cell )
Foams@BASFFoams@BASF
Styrodur®(XPS) polystyrene (closed-cell)
Neopor® (EPS)Polystyrene (closed-cell)
Basotect®Melamine (open cell)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
ApplicationsApplications……
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Savings after
50 years93 100 l
oil
Energy and Material needed to production of EPS (equivalent in oil)
670 loil
Foams and the environmentFoams and the environment
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Foams and the environmentFoams and the environment
IR Camera
Plastic foamsPlastic foams::Physics Physics and and ChemistryChemistry
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Bubbles growFluid is initially sturated with a blowing agent. Bubbles nucleate.
Bubbles touch each other: "Polyhedralfoam„, closed cells - 100-600 µm.Exs.: XPS (Styrodur), EPS (Styropor), some PUR foams
Open cellsEx.: MF foam(Basotect)
Cell w
alls b
reak
up
The making ofThe making of…… cellular plasticscellular plastics
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Phase diagram PS-CO2 (T=150 C)
0
150
300
450
600
750
0 0.05 0.1 0.15 0.2
w-fraction CO2
P (
bar
)
liquid-gas
single phase
Thermodynamics of bubblingThermodynamics of bubbling
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
σππ 23 4)(3
4RPPRG ei +−−=∆
ei PPR
−=
σ2*
2
3*
)(316
eiB PPTkG
−=
∆ σπ
∆−=
TkG
JJB
*
0 exp
0 0.5 1 1.5 2RêR*
-200
-100
0
100
DG
êkT
0 200 400 600 800 1000DPêk T
0
0.20.40.6
0.81
JêJ 0
Classical nucleation theory (homogeneous)Classical nucleation theory (homogeneous)
0 5 10 15 20gêk T
00.20.40.60.8
1
JêJ 0σ/ k T
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
With η~5x103 Pa s and a pressure difference of 200 bar. This means that this characteristic time is of the order of τη~10-3 s
Bubble growthBubble growth
BEB
B
B RPP
dtdR
Rση 24
−−=
1) Viscosity-dominated regime
−
−−+= )(
4exp)( 00 tt
PPRRRR EB
crcrB η
EB PP −=
ητη
4ητDlc ≈
tDFRR mB 220 +≈
)( inf sE
gm cc
P
TRF −=
2) Diffusion-dominated regime
Doelder, Sammler, Koopmans, Paquet, Cellular Polymers 21, 99 (2002)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Bubble coalescenceBubble coalescence
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Bubble coalescenceBubble coalescence
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
n Up to a gas volume of ~ 64% (random packing of spheres), bubbles are still spherical.
n Thereafter bubbles are deformed into polyhedron structures and cell lamellae and struts.
Polyhedron foamPolyhedron foam
Pentagondodekaeder Tetrakaidekaeder
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Stabilization of polymer foamsStabilization of polymer foams
1) Viscoelastic stabilization (self healing)
Entropic force (chains stretched)
< 1 due to extrudateswelling
Melt strength
Dra
wab
ilityfo
rce
F
Draw down ratio v / v0(~1 / thickness)
1
Filament break
with:
v0 ... average velocity at die exit
v ... velocity at draw down wheels
F ... forceConstant accelaration of wheels
v0
v
F
Extrudate strand
Rheotens MACCARONE effect
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Stabilization of polymer foamsStabilization of polymer foams
1) “Anti-Plasticizer” effect
The blowing agent molecules
(when also plasticizers) leave
the thinner parts faster than the
thicker ones, contributing to
hardening in those areas!
Effect of a plasticizer/blowing agent over PS (fixed shear rate)
100
1000
10000
0 2 4 6 8 10
weight% blowing agent
η (
Pa
s)
M. Rüllmann, BASF
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
If it survives all that, one getsIf it survives all that, one getssomething like thissomething like this……
Plastic foamsPlastic foams::Industrial Industrial processesprocesses
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Melting
Mix blowing agent
Pressurize
Melt mixed with blowing agent
III. IV. V. I. II.
Foam
Extrusion foams (XExtrusion foams (X--Foams, XPS)Foams, XPS)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Phase diagram PS-CO2 (T=150 C)
0
150
300
450
600
750
0 0.05 0.1 0.15 0.2
w-fraction CO2
P (
bar
)
liquid-gas
single phase
Adiabatic expansion of an ideal gas:
5/2
=
I
F
I
F
PP
TT
Ex. (lower limit):TI=150 CPI=150 barPF=1 bar
TF=20 C
Thermodynamics of XPSThermodynamics of XPS
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
StyrolStyrol
WasserWasser
AdditiveAdditive
StyrolStyrol
WasserWasser
AdditiveAdditive
Styrol/Polystyrol-Perlen + Treibmittel Pentan
Styrol/Polystyrol-Perlen + Treibmittel Pentan
Expandable foams (EExpandable foams (E--Foams, EPS)Foams, EPS)
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
PackagingBlocks Parts
Raw material (Ø 1 mm) Pre foaming Storage Fusion
EPSEPS
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Phase diagram PS-n pentane (P=1 bar)
-20
0
20
40
60
80
100
120
140
160
0 0.2 0.4 0.6 0.8 1
w-fraction pentane
T (C
)
"liquid"-gas
liquid-liquid
single phase(glas/gel)
Thermodynamics of EPSThermodynamics of EPS
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
• unlimited variety of structural building blocks
• wide range of different properties adjustable ⇒ tailor-made polymers
catalyst, blowing agent
Difunctional or polyfunctional aromatic, (cyclo)aliphatic residue
Polyether/polyester of different functionality, molecular weight, reactivity
OO
NH
OO
NH
+ OH OHOCN NCO
Polyurethane foamsPolyurethane foams
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
Polyurethane foamsPolyurethane foams
Iso Polyol
Air
Dr. AndrDr. Andréé MoreiraMoreira, BASF AG, BASF AG
PU70 %
XPS5 %
EPS23 %
Others2 %
n 40 Mill. tons polymeric materials
n 3.6 Mill. tons polymer foams
Market in western Europe (2004)Market in western Europe (2004)