This document summarizes a study on thermoplastic polyurethane (TPU) composites reinforced with carbon nanotubes (CNTs). CNTs were incorporated into TPU at loadings from 0.5-2% by weight. Some CNTs were surface modified to improve dispersion in the TPU matrix. Mechanical, thermal, and flammability properties were evaluated. Results showed that CNTs, especially surface modified CNTs, improved tensile strength, modulus, and thermal stability while also enhancing flame retardancy at low loadings. Surface modification led to better CNT dispersion and stronger polymer-filler interactions. The highest property improvements were found at a 0.5% CNT loading for mechanical

1. Štrbské Pleso , 09.10.2017
Y.Kanbur a
*, U. Tayfun b
a
Karabuk University, Metallurgical and Materials
Engineering, Karabuk, Turkey
b
Inovasens Ltd., Izmir Technopolis, Urla, Izmir, Turkey

2. • This study was published as:
• Kanbur Y., Tayfun U., Investigating mechanical,
thermal, and flammability properties of
thermoplastic polyurethane/carbon nanotube
composites, Journal of Thermoplastic
Composite Materials, 2017.
DOI: 10.1177/0892705717743292
Štrbské Pleso

3. BACKGROUND INFORMATİON
Fundamentals of Polymer Composites
The properties of polymer composites are affected by several
factors;
• interfacial adhesion
• shape and the orientation of fillers
• properties of polymer matrix.
Reinforcer/polymer interface plays key role on mechanical
strength of the composite material since reinforcer provides
strength and stiffness by transferring load itself from the
polymer matrix.

4. THE MECHANİCAL PROPERTİES OF COMPOSİTES DEPEND ON
• filler type
• filler aspect ratio (L/D)
• orientation of filler
• filler & matrix interface (degree of adhesion between the matrix
and dispersed components.)
• The mechanical properties of the filler and matrix.

5. Štrbské Pleso
Carbon nanotube (CNT)
CNT is the most popular member of carbon nanostructures family.
CNT can add multi-functionality to composites thanks to their extraordinary mechanical and electrical properties.
CNT reinforced polymer composites having very low density, high strength and high modulus make desirable
material for aerospace and transport applications.

6. Štrbské Pleso
THERMOPLASTIC POLYURETHANESTHERMOPLASTIC POLYURETHANES
• Soft Segment:Soft Segment: Soft segment forms the rubbery (amorphous) matrixSoft segment forms the rubbery (amorphous) matrix 
Flexibility, ExtensibilityFlexibility, Extensibility
• Hard Segments:Hard Segments: Dispersed as hard domains, act as rigid filler component andDispersed as hard domains, act as rigid filler component and
physical crosslinkphysical crosslink
hard
segment
soft
segment
TPU is a linear segmented block copolymer composed of alternating hard (adduct of
diisocyanate and small glycols) and soft (e.g. polyester, polyether,
hydrocarbon,silicone, etc.) segments.
The hard segments are held together by interchain hydrogen bonds to form physical
crosslinks.
Background Information

7. •• excellent abrasion resistanceexcellent abrasion resistance
•• outstanding low-temperature performance.outstanding low-temperature performance.
•• excellent mechanical properties,excellent mechanical properties,
combined with a rubber-like elasticitycombined with a rubber-like elasticity
•• very good tear strengthvery good tear strength
•• high elasticityhigh elasticity
•• high transparencyhigh transparency
•• good oil and grease resistancegood oil and grease resistance
TPUs as “bridging the gap between rubber and
plastics”, since TPUs offer the mechanical
performance characteristics of rubber but can be
processed as thermoplastics
TPU is one of the most commonly used form of
polyurethane due their advantages
of recyclability and practical processability using
traditional methods in industry.
Tuning the properties of TPU by incorporating
different types of fillers has become trending
issue because of the opportunity for using
conventional techniques
Background Information

8. USES OF TPUSUSES OF TPUS
Background Information

9. MATERİALSMATERİALS
ExperimentalExperimental
● Polyester-based TPU (Texalan® 485A) (Covina, USA) 1.20 g/cm3 and 85
(Shore A)
-45% flexible segment and 55% of rigid segment.
● Carbon nanotube was suplied from Nanocyl SA (Belgium) under the
trade name of NC 7000.
-This CNT grade has length, diameter and carbon purity of 1.5 μm, 9.5 nm
and 90%.

10. SURFACE MODİFİCATİONSURFACE MODİFİCATİON
ExperimentalExperimental

11. PREPARATİON OF COMPOSİTESPREPARATİON OF COMPOSİTES
TPU-based composites were prepared by DSMTPU-based composites were prepared by DSM
Xplore twin screw micro compounderXplore twin screw micro compounder
Processing parameters;Processing parameters;
• Diameter of the die: 0.25 mmDiameter of the die: 0.25 mm
• Mixing unit volume: 15 ccMixing unit volume: 15 cc
• Processing temperature: 200-210 ˚CProcessing temperature: 200-210 ˚C
• Mixing speed:100 rpmMixing speed:100 rpm
• Mixing time: 5-8 minMixing time: 5-8 min
ExperimentalExperimental
Tensile test samples were prepared by Daca InjectionTensile test samples were prepared by Daca Injection
Molding InstrumentMolding Instrument
Molding parameters;Molding parameters;
•Barrel temperature: 210 ˚CBarrel temperature: 210 ˚C
•Mold temperature: 100 ˚CMold temperature: 100 ˚C
•Pressure: 8 barPressure: 8 bar

12. CHARACTERİZATİONCHARACTERİZATİON
TECHNİQUESTECHNİQUES
ExperimentalExperimental
SURFACE MODIFICATIONS:SURFACE MODIFICATIONS:
 FTIR :FTIR : ATR mode between 600-3800 cmATR mode between 600-3800 cm-1-1
wavenumbers (Bruker VERTEX 70)wavenumbers (Bruker VERTEX 70)
COMPOSITES:COMPOSITES:
 Tensile Testing:Tensile Testing: 5 kN load cell 5 cm/min speed (Lloyd LR 30 K)5 kN load cell 5 cm/min speed (Lloyd LR 30 K)
 Hardness Tests:Hardness Tests: Shore hardness tester (Zwick)Shore hardness tester (Zwick)
 DMA:DMA: Bending mode at -70°C-150°C temperature range, frequency of 1 Hz at 10°C/min heating rateBending mode at -70°C-150°C temperature range, frequency of 1 Hz at 10°C/min heating rate
(DMA 8000, Perkin Elmer)(DMA 8000, Perkin Elmer)
 MFI:MFI: at 200 and 210°C with 5 kg load (Meltfixer LT,Coesfield Material Test)at 200 and 210°C with 5 kg load (Meltfixer LT,Coesfield Material Test)
 SEM:SEM: cyro-fractured surfaces, micrographs varied from x500 to x10,000 magnificationscyro-fractured surfaces, micrographs varied from x500 to x10,000 magnifications
(FEI Quanta 400F)(FEI Quanta 400F)
 Mass Loss Calorimeter :Square test samples (100 × 100 × 3 mm3) were irradiated at a
heat flux of 35 kW/m2
, corresponding to a mild fire scenario. ( Fire Testing Technology)

13. Results & DiscussionResults & Discussion
Mechanical characterization of TPU/CNT compositesMechanical characterization of TPU/CNT composites
●Tensile strength, elongation at break and elastic modulus values are improved remarkably by the
addition of carbon nanotube as compared with neat TPU. Additionally, m-CNT containing composites
give slightly higher results in the case of tensile strength with respect to unmodified carbon
nanotube loaded TPU composites because of better interfacial interactions between TPU
and CNT surfaces after treatment.
●The highest strength, elongation and elastic modulus values are obtained for the
composites which contain 0.5 wt% CNT and m-CNT. Futher additions of m-CNT cause
decrease for percent elongation of composites which may attributed to restriction of chain
motions

14. Štrbské Pleso

15. Štrbské Pleso
Results & DiscussionResults & Discussion
Shore A Hardness Test ResultsShore A Hardness Test Results
●Hardness of TPU decreases slightly with the addition of the lowest loading level for both
cases of CNT and m-CNT.
● Hardness of the composites contain pristine CNT decreases with the increase of
filling ratio of CNT since the dispersion of pristine CNT is poor in polymer matrix and
their tendency to form agglomerate
● m-CNT shows increasing trend with increase its content due to better dispersion of
m-CNT in matrix.

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Results & DiscussionResults & Discussion
Glass Transition and Melting TemperaturesGlass Transition and Melting Temperatures
●Tm value of unmodified CNT loaded composites increases slightly with increasing CNT
composition
● m-CNT loaded composites exhibit almost identical Tm values for all loading
ratios
● Carbon nanotube additions result with the reduction for Tg of pristine TPU

17. Štrbské Pleso
Results & DiscussionResults & Discussion
Flammability Test Results of CompositesFlammability Test Results of Composites
●Addition of CNT enhances LOI of TPU slightly. Modified CNT filled composites give a
bit higher LOI values.
● The highest enhancement is obtained for TPU/1.0% m-CNT composite which has LOI
value of 21.3%. Further additions of CNT and m-CNT cause reductions.
● UL-94 rating of neat TPU increases from BC
to V2 for both cases of CNT and m-CNT additions. This result shows that CNT has
no obvious effect for the flammability properties of TPU because of only the small
changes occur in LOI values and V0 rating is not achieved during the UL- 94 test.

18. Štrbské Pleso
Results & DiscussionResults & Discussion
TGA curves of compositesTGA curves of composites
●Thermal decomposition of TPU occurs through double step at around 330oC and 400 oC with two shoulders
which can be seen at 280 0C and 460 0C. The reason for this two stage degradation is different decomposition
behavior of urethane bonds in hard segment and polyol groups in soft segment of TPU
●TGA curves of pristine CNT and m-CNT containing curves indicate that unmodified CNT favors the thermally stable
composites as compared with the same compositions of modified CNT.
●The highest shift among TGA curves is observed for TPU/2% CNT at the end of the initial decomposition
step which is related with hard domains of TPU. This result also indicates that CNT particles improve the
microphase separation by their interaction with more compatible hard domains of TPU

19. Štrbské Pleso
Mass loss calorimeter data of compositesMass loss calorimeter data of composites
Results & DiscussionResults & Discussion
●Incorporation of CNT into TPU gives decreasing trend for FPI except for TPU/2% m-CNT composite in
which the higher FPI is achieved than TPU which indicates the improvement of fire performance. It is found
that additions of pristine carbon nanotube and increase in CNT contents cause enhancement for fire
performance of TPU as an overall investigation from the mass loss calorimeter study.
●Reduction in TTI of TPU is obtained after CNT additions which mean that CNT inclusions cause the earlier
ignition with respect to TPU. The black color of CNT is the main reason for this observation which leads to
increase in absorption of radiant heat within the top layer of the material.
●TPU and its composites yield almost identical residue content at the end of the mass calorimeter test.
Modified CNT additions cause an increase in total burning time compared to pristine

20. Štrbské Pleso
Results & DiscussionResults & Discussion
HRR curves of compositesHRR curves of composites
●TPU burns very fast after ignition and one sharp HRR peak appears with pHRR
and aHRR of 454.6 and 245.8 kWm-2
, respectively.
●All of the composites show remarkable reductions in HRR curve of TPU. The
pHRR and aHRR values are drop down nearly 75 and 111 kW/m2
with the inclusion
of 2.0% m-CNT, respectively. This data displays the sharpest reduction of HRR
among all of the composites.

21. Štrbské Pleso
Results & DiscussionResults & Discussion
MFI test results of compositesMFI test results of composites
●MFI of neat TPU shows reduction trend with the addition of unmodified CNT into polymer matrix
because CNT particles prefer interparticle interactions instead of CNT-matrix adhesion.
● MFI value of TPU get much higher with the addition of m-CNT and these composites give
higher MFI values than that of unmodified ones but MFI value of modified CNT loaded
composites show decreasing trend after initial improvement through TPU/1.0% m-CNT
composites.

22. Štrbské Pleso
Results & DiscussionResults & Discussion
SEM CharacterizationSEM Characterization
●Modified CNT particles show better
dispersion in TPU matrix than the pristine
CNT particles as a result of surface
compatibility of m-CNT particles with TPU
matrix. For higher loading ratio of unmodified
CNT, CNT particles form large agglomeration
parts into TPU matrix.
●Surface modified CNT containing composites show homogeneous dispersion even at the highest loading
level as compare to unmodified CNT containing composites.

23. Štrbské Pleso
ConclusionConclusion
●Tensile test results indicate that, addition of CNT into TPU leads to distinct increase in tensile
strength, percent elongation and elastic modulus values.
● The higher mechanical properties are obtained for modified CNT containing
composites at their lowest concentrations.
● DSC analysis results show that melting temperature of TPU shifts to higher values, on
the other hand glass transition temperature shows decreasing trend with the addition of
CNT.
● TGA analysis implies that CNT containing TPU composites have better thermal stability
than neat TPU.
● Enhancement of fire performance is observed with both the pristine and modified CNT
inclusions. The highest decrease in HRR curve is found in modified CNT containing
composite at its highest loading level among all samples.
● According to morphological studies with SEM micrographs of composites, formations of
large agglomerates are observed for high loading percents of unmodified CNT. Modified
CNT containing composites shows more homogeneous dispersion homogeneity than the
unmodified ones.