In-situ Small-Angle X-ray Scattering Investigation of Transient Nanostructure of Multi-phase Polymer Materials Under Mechanical Deformation

116 Pages·2013·3.89 MB·English

by  Ahmad Zeinolebadi (auth.)

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Ahmad Zeinolebadi
In-situ Small-Angle X-ray
Scattering Investigation
of Transient Nanostructure
of Multi-phase Polymer
Materials Under Mechanical
Deformation
Doctoral Thesis accepted by
the University of Hamburg, Germany
123
Author Supervisor
Dr. AhmadZeinolebadi Prof.Dr. NorbertStribeck
Instituteof Technical and Macromolecular Instituteof Technical and Macromolecular
Chemistry Chemistry
Universityof Hamburg Universityof Hamburg
Hamburg Hamburg
Germany Germany
Present address
Polymer ConsultBuchner GmbH
Hamburg
Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
ISBN 978-3-642-35412-0 ISBN 978-3-642-35413-7 (eBook)
DOI 10.1007/978-3-642-35413-7
SpringerHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2012954554
(cid:2)Springer-VerlagBerlinHeidelberg2013
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Somepartsofthisthesishavealreadybeenpublishedinthefollowingjournal
articles:
1. Zeinolebadi, A.; Stribeck, N.; Ganjaee-Sari, M.; Dencheva, N.; Denchev, Z.;
Botta,S.,‘‘NanostructureEvolutionMechanismsDuringSlowLoad-Cyclingof
Oriented HDPE/PA Microfibrillar Blends as a Function of Composition,’’
Macromol. Mater. Eng., 2012, 297, 1102–1113.
2. Stribeck, N.; Zeinolebadi, A.; Ganjaee-Sari, M.; Botta, S.; Jankova, K.; Hvil-
sted, S.; Drozdov, A.; Klitkou, R.; Potarniche, C.; Chirstiansen, J.; Ermini, V.,
‘‘Properties and Semicrystalline Structure Evolution of Polypropylene/Mont-
morillonite Nanocomposites under Mechanical Load,’’Macromolecules, 2012,
45, 962–973.
3. Stribeck, N.; Zeinolebadi, A.; Ganjaee-Sari, M.; Frick, A.; Mikoszek, M.;
Botta, S., ‘‘Structure and Mechanical Properties of an Injection- Molded
Thermoplastic Polyurethane as a Function of Melt Temperature,’’ Macromol.
Chem. Phys., 2011, 20, 2234–2248.
To my beloved family
Supervisor’s Foreword
If metal in cars is replaced with plastics, the vehicle is lighter and more fuel
efficient. The same applies to aircraft and spaceships. Nevertheless, polymers
cannot replace all the metal, because they are not as tough. Even worse: Plastics
fatigueovertime.Fatiguemay,e.g.,causethatafterdrivingayearoncobblestone
the spare wheel breaks through its well.
A European consortium of industry and academy in 2008 had taken up the
cause to reduce fatigue by incorporating reinforcing nanoparticles into the poly-
mer. The plastic is to be polypropylene (PP). If all the polymer is based on the
versatile material PP, recycling returns one single polymer. The goal is a cheap
product,thusclayischosentobeblendedwiththePP.Forpolyethylene(PE)this
method had worked well—so why should it not also work for PP? In order to
develop the reinforcing property of the clay, the clay layers are gently separated
from each other in the blender and bound to the PP by a suitable chemical. This
processtakesplaceinthemoltenPPat200(cid:2)C.Theoptimizationofthistechnology
for a new polymer grade is demanding. In our case it has succeeded after 2 years
duetothecooperationofexcellentteamsfromacrossEurope.Nowaspare-wheel
recessisinjectedfromthemelt,butthecompositeshowsfatigueanyway.Whatis
different in PP compared to PE?
Ahmad Zeinolebadi has found an answer: The PP is inherently reinforced, and
this fortification is mitigated by the clay. The reinforcement is provided by PP
crystals that are formed during cooling from the melt. Unfortunately PP crystal-
lizes slowly. Therefore, chemical companies raise the crystallization tendency of
PPbyanucleatingagent.Dr.Zeinolebadihasfoundthattheclayusedbyusisalso
a nucleating agent. It shifts the delicate balance. The crystals that are formed are
no longer a strong framework, but a multitude of small and disordered grains.
This information is contained in X-ray scattering patterns. It is evidenced by a
complex transformation. The pathway has already been pointed out by Debye in
1931.BecauseofthemathematicalcomplexityofthecorrespondingCDF-method
it is only mastered by few research groups in the world. Dr. Zeinolebadi has
studied various materials by straining and relieving them cyclically (fatigue test).
Simultaneously the samples have been irradiated and monitored by the X-rays.
ix
x Supervisor’sForeword
Ultimately he has been able to directly observe the change of the nanostructure
inside the material, and to draw his conclusions.
The implication of this study is clear: If a delicate composite of matched
components is modified by adding a new agent, then the design must be re-
optimized. This may be difficult if a natural material such as clay is added, the
properties ofwhichmay vary. Politically, one should consider extendingthe time
lineforsuchprojectsfrom3to6 years.Thentherewouldbeachancetodesignan
improved product.
Mr. Zeinolebadi has been an ideal choice for our research project. Already in
Iran, he had learned German very well. His English is professional. His out-
standingeffectivenessandabilitytothinkaheadhasbeennoticedearlyduringhis
application. His structured approach and his work ethic have helped him to
overcome setbacks during the Ph.D. thesis. Besides working on his doctorate, he
has fulfilled industrial research contracts reliably and quickly. The gained repu-
tationisanassetforhisnewjob.Fromtheyieldfundswehavebeenabletocover
travel costs to the many international conferences where he has presented the
results of his work. Also, as session chairman he has left a positive mark on his
peers.Heisskillfulinwritingandcommunication.Indiscussionandinwriting,he
structureshisthoughtsandhisnextmoves.Fromthishedrawshiscreativeability.
After his Ph.D., he took a job in a consulting company. One of his tasks is to
qualifypolymersforcustomer-definedapplications.Thusheremainsscientifically
active.Duetoinsecurity,poorremuneration,andmeageramenities,thestartofan
academic career appears to be hardly a choice.
Hamburg, November 2012 Norbert Stribeck
Acknowledgments
I would like to express my greatest thanks to Prof. Dr. Norbert Stribeck. Without
his unceasingsupportthisthesis would notbeareality.Besides the fundamentals
of X-ray scattering, he taught me scientific reasoning and organizing a research
work from the basic experimental works to interpretation of data and writing a
manuscript. I would also like to thank my colleagues at Hamburg University and
HASYLAB,DESY.Mostofthestudiedmaterialsinthisworkhavebeenprovided
by colleagues from other universities and institutes. Accordingly, I would like to
thank Prof. Achim Frick from Aalen University, Prof. Zlatan Denchev from
University of Minho, Dr. Katja Jankova from Danish Polymer Center, and Prof.
JesperdeClavilleChristiansenfromAalborgUniversityandtheircoworkers.This
work was partially supported by the European FP7 project ‘‘Nanotough’’.
xi
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Microstructure of Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Mechanical Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Constructing Structure–Property-Relationship . . . . . . . . . . . . . . 5
1.4 Structure Analysis by X-ray Scattering. . . . . . . . . . . . . . . . . . . 7
1.5 SAXS Theories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.1 Geometry of Scattering . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5.2 From the Scattering Pattern to the Materials Structure. . . 13
1.6 Objectives and Aims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2 Experimental Part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.1 SAXS Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2 Thermoplastic Polyurethane Elastomers . . . . . . . . . . . . . . . . . . 24
2.3 Polypropylene/Montmorillonite Nanocomposites. . . . . . . . . . . . 25
2.4 Microfibrillar Composites. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3 Data Evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1 Evaluation of Mechanical Parameters. . . . . . . . . . . . . . . . . . . . 29
3.2 Evaluation of Scattering Data . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2.1 Pre-evaluation of SAXS Data. . . . . . . . . . . . . . . . . . . . 32
3.2.2 Computing CDFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2.3 Computing the Scattering Power. . . . . . . . . . . . . . . . . . 37
3.2.4 Computing Isotropic Scattering. . . . . . . . . . . . . . . . . . . 38
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
xiii