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PREFACE
1. Urgency of the thesis
Reinforcement of thermoplastic by using particle has studied in few decades ago. Until now, it
plays an important role in as well [1]. The flexibility of thermoplastic composite materials expands the
scope of application in the life and research field. When the materials are reinforced by fillers, their
properties are changed. Typically, the filler impacts in hardness, thermal conductivity, thermal expansion.
However, they improve strength and elasticity as well because of the filler properties and the changing of
morphology matrix. The inorganic filler are used wide in thermoplastic such as CaCO3, talc, SiO2, mice
and Mg(OH)2.
Most of the researches carried paying attention on the factors such as (i) component; (ii) shape and
size; (iii) composition; (iv) compatibility of matrix and filler. Some of them showed a polymer layer
locating aninteraction phase between filler surface and matrix which have special property. However, the
role, influenceand a parameters relationship ofthe phase interaction betweenthe filler and the matrix on
the mechanical properties (i.e. tensile strength, impact resistance) is not determined clearly.
Thus, supervisor and PhD student carried on a thesis:” Effect of surface fillers modification on
phase interaction and mechanical properties of thermoplastic materials”
2. The aim of thesis
To study relation of molecular structural changing between polypropylene microcomposite system
and the particle fillers with varies phase interactions by using solid-state NMR(ssNMR) spectra.Therein,emphasizing the molecular flexibility on mechanical properties of materials.
3. Main contents of thesis
a. Preparing polypropylene composites materials by using the filler was modified/unmodified
surface at varies contents.
b. Research phase interaction morphology, determine the mechanical properties of materials
including tensile strength and impact resistance (integral J).
c. Application of solid-state nuclear magnetic resonance (ss-NMR) method to determine molecular
mobility in polymer composite materials, study the relation of mechanical properties of material.
Outline of the thesis: The thesis has 24 pages including introduction, 4 chapters of content, contributions
and a list of publication.
The main results of the thesis are published in:
- 01 article in an international journal in the ISI list (IF = 3.7)

expectant researches. In reality, application and the growth rate of fiber glass for PP are lower than that of
particle fillers.
Nowadays, not only the technical and aesthetic requirements but also the costs of processing and
raw materialsare increasing. To meet these requirements, the researchers need understanding the relevant
properties of fillers as well as their influence on the structure and properties of composite materials touse
all the advantages of fillers or just use them as diluents forreducing costs.
1.3 . Solid state magnetic resonance spectroscopy and its application for molecular mobility in
polypropylene composites
Today, the high-resolution 13 C NMR spectrum is a common tool for studying the structure of
polymers. 1 H-NMR isa standard technique in structural analysis of liquid-state substances, but in solidstate substances. Isotactic polypropylene isa polymorphic material due to a modifying arrangement of
polymer chains. Hence, ss-NMR spectroscopy technique showed complicatedanalysis for
polypropylene.It is more complicated particularlyif the composition of these components that plays a
decisive role changing the properties of polymer is significantly lower than composition of the matrix.
This difference prevents the use calibration curve analysis. Therefore, special method must be used to


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describe the small differences between the amorphous and crystals disordering in the phase interaction
region.
However, the less attention has been paid to the multi-molecular analysis of the ss-NMR spectrum
for amorphous or disordered solids, which can be considered an extreme limit due to the frequency range
being too much for signals for which only one signal is available are defined. Therefore, the thesis also
demonstrates that 13 C MAS ss-NMR spectrocopy is a fast, reliable tool for describing extremely
complex crystal forms in PP material for clarifying the relationship between spectral data at the
molecular level and the macroscopic properties of materials such as mechanical properties.
1.4 . These studies were carriedon in Vietnam
The basic researches in Vietnam on thermoplastic composite materials in general and
polypropylene in particular were studied by Hoang Thai and et al at the Institute of Tropical Technology
and Dieu Tran Vinh and et al at Hanoi University of Technology.
Hoang Thai et al treated titan dioxide or nano BaSO4 surface by silane coupling agent for studying

fibers and determined the effect of this process on the reinforcement of polypropylene based composite
material. Acetylation reduces the hygroscopic of bamboo fibers, increases the adhesion between bamboo
fibers and PP resin. 50% of short bamboo fibers reinforced PP composites has the highest tensile strength
(36.45 MPa), increase of 2% compared with its raw PP.
Chapter 2. EXPERIMENTAL
2.1. Materials
2.1.1. Polymer
Isotactic polypropylene homopolymer Mosten 52.412 (Chemopetrol, Czech Republic) was used
as a matrix in this study.
2.1.2. Fillers
Glass beads, average size ~ 20 µm supplied by SOVITEC, France.
Calcium carbonate, average particle size ~ 1.7 µm (1VA) and ~ 12 µm (15VA), supplied by
Omycarb, Switzerland.
Talc mineral originated from Thanh Son district, Phu Tho province, Vietnam. The main
components of this mineral are SiO2 (60,82 %) and MgO (32,16 %). Average particle size ~ 6,58 µm.
2.1.3. Surface modification agents
Vinyltriethoxysilane
supplied
by
Momentive
(Switzerland)
and
methacryloxy
propyltrimethoxysilane supplied by DowCorning (USA). Oleic and stearic acids (technical grade products
supplied by Sigma-Aldrich) were used for calcium carbonate surface modification.
2.1.4. Other materials
Dicumyl peroxite (technical grade ) supplied by Sigma-Aldrich.
2.2. Methods
2.2.1. Surface modification
The surface modification of filler particles is carried out in 96% ethanol solution containing 2%

differences between the prepared PP/CaCO3 microcomposites in 2D or 3D maps.
Chapter 3: RESULS AND DISCUSION
3.1. Composite based on polypropylene and glass beads
3.1.1. Morphology observation
The introduction of inorganic filler into a polymer matrix results in a heterogeneous system.
Adhesion among different materials is created by physical or chemical bonds between the adhesive and
the substrate, and this depends on the selection of coupling agent. Figure 3.1 presents structure
morphology taken of the impact fracture cross section of PP/glass beadcomposites with 20% of filler
content.

a)

b)

c)

Fig. 3.1. Degree of interfacial adhesion between glass bead and PP matrix.
As revealed by SEM in the cases of non-treated and NO adhesion, there was a poor interfacial
with the strong debonding of particles. While in case of GOOD adhesion, a strong bonding achieved
between glass bead particles and PP matrix, coated spheres adhere to the matrix.
3.1.2. Tensile properties
The effects of glass bead with different surface properties on the mechanical properties of
composites are showed in Fig. 3.2. It can be sheen that the tensile moduli in all cases of composites


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increase with increasing filler loading. Generally, the addition of rigid particulate fillers increases
stiffness, which is measured through Young's modulus. This is due to the fact that fillers often exhibit
higher stiffness compared matrix polymer. Besides, Young's modulus is measured at the very beginning
of a tensile test, where deformation is insufficient to cause particle-matrix debonding. However, obtained


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3.1.3. Impact properties
The J-integral was used to characterize the energy absorption of polymer materials at the initial
stage of crack and the resistance for crack initiation. Figure 3.3 showed Jld values of polypropylene and
glass bead composites.

Fig. 3.3. Impact strength of PP/glass beads composites
The fracture behavior of polymers is strongly affected by the addition of rigid particles. The
incorporation of them into the polypropylene matrix leads to differences in the overall process of crack
propagation and fracture. The process starts with the plastic deformation of the matrix ahead of the initial
crack. The adsorption of polymer molecules on the filler surface through chemical bonds leads to the
rigidity in structure of polymer chains. This leads to earlier crack initiation and propagation with
dramatically decreasing of J-integral value in case of GOOD adhesion (Figure 3.3). Plastic deformation of
the matrix polymer is the main energy absorbing process in impact and this increases when the interaction
between particles and polymer matrix is lowered in case of non-treated and NO adhesion.
3.1.4. ss-NMR
In general, narrowing of 1H lineshapes indicates the increase in global segmental dynamics as 1H1
H dipolar couplings are motionally averaged out. As demonstrated in Figure 3.4 in our particular case,
the most mobile polymers segments were found in parent PP. Slightly hindered segmental dynamics in
the composites Non-treated and NO-adhesion is reflected by the broadening of the corresponding signals.
The most rigid polymer segments were found in the composite GOOD-adhesion that is reflected by the
broadest 1H MAS NMR line


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GOOD-adhesion

Non-treated and

protocrystalline phases etc….).

GOOD-adhesion
Non-treated
NO-adhesion
PP
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Fig. 3.6. C CP/ MAS NMR spectra of the parent PP and composites recorded at 300 K and MAS 6
kHz.
3.3. Composite based on polypropylene and calcium carbonate
3.3.1. Morphology observation
The introduction of inorganic filler into a polymer matrix results in a heterogeneous system.
Adhesion between different materials is created by physical or chemical bonds between the adhesive and
the substrate, and this depends on the selection of coupling agent.
The morphology of the compounds up to concentration of 40 wt% treated and untreated CaCO3
are shown in Figure 3.7 and Figure 3.8. The CaCO3 particles are generally supplied as agglomerates,
however, it can be seen that aggregates are broken up to the primary particles during the extrusion
process. In the case of CaCO3 with average particle size ~ 1.7 µm, the interaction between untreated filler
particles with the polymer matrix is stronger compared with treated filler particles (Figure 1a). The strong
debonding of particles can be observed in cases of treated particles (Figure 3.7-b and 3.7-c).
a

b

c

Figure 3.7. SEM images of morphology of PP filled with a) untreated CaCO3, b) oleic acid
treated CaCO3 and c) stearic acid treated CaCO3, average particle size ~ 1.7 µm, filler content 40 wt%


The extent of plastic deformation characterized by strain at break is then very sensitive to
composition and morphology of the composites. As shown in Figure 3.9, various types of calcium
carbonate fillers have distinctly different effects in strain at break values.


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Figure 3.9. Effects of particle size, surface modification and filler loading on the tensile mechanical
behaviour of injection-moulded specimens.
3.3.3. Độ bền va đập
J-integral was originally defined by Rice as a contour integral independent on the path, which
express the energy per unit area necessary to create new fracture surfaces in a loaded body containing a
crack. Figure 4 show J-integral values of PP/CaCO3 composites with different types of particle size, filler
loading and surface properties.


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Figure 3.10. Fracture behaviour of PP/CaCO3 composites.
The addition of calcium carbonate led to a change in the fracture mode from brittle fracture for
virgin PP to ductile fracture for the filled composites, which was attributed to the changes of stress fields
in the PP matrix around the filler particles. For the unfilled PP, when the notched composite specimen
receives an impact load, the crazes will be rapidly developed cracks, and then will propagate toward the
whole cross section. The incorporation of rigid particles into the polypropylene matrix leads to
differences in the overall process of crack propagation and fracture. The process starts with the plastic
deformation of the matrix ahead of the initial crack. Assuming a poor bonding between filler and matrix
in cases of treated calcium carbonate, the filler particles detach easily from the matrix by creating voids as
observed by SEM. These voids be formed will absorb impact deformation energy. Otherwise, the particle
will block the propagation of the crack developed from the crazes to increase the fracture resistance.
Jilken et al. [8] also observed that the high impact strength, at high filler content, could be obtained for

3.13, the amount of the highly mobile amorphous r.c. fraction systematically decreased as the critical
value of the J-integral increased, which represents a measure of the composite. The neat, unfilled PP
surprisingly had a dependence in the middle of the other dependences, and regardless of the amount of
filler particles the composite systems that were modified by larger particles (12 mm) nearly exclusively
exhibited a lower J-integral critical value in comparison with the systems that were modified by smaller
particles (1.7 mm).


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: Jid [N/m] is calibrated to [%]
: Highly-mobile fraction of CH %

Figure 3.13. Graph of the toughness expressed as the J-integral (JId) critical value and the contents of the
highly mobile amorphous fractions in the PP systems calculated from the integral intensities of the CH
signal in the 13C MAS NMR spectra. The maximum integral intensity value was calibrated to the
maximum content (100%) of the highly mobile fraction. The maximum J-integral value was normalized
to 100%.
To find other consistent trends and characteristic spectral features related to the changes in the
mechanical properties of the samples, we used FA to extract the key information from the relatively large
experimental data sets that were obtained. The recorded 13C CP/MAS NMR and/or 13C MAS NMR
spectra were separately analyzed in sets representing each temperature.
Subsequently, the FA generated subspectra, Sj, and the corresponding singular values, wj, for
each set of NMR spectra. Because only the singular values w1 - w4 were significantly high (Fig. 3.14, left
panel), the spectral variation in the analyzed dataset was completely described by the corresponding
subspectra, S1eS4
Sau đó, FA tạo ra các phổ thế, Sj và các giá trị bất thường tương ứng, wj cho mỗi phổ NMR. Do
chỉ các giá trị đơn w1 – w4 ở mức cao đáng kể (hình 3.26), biến thể phổ trong tập dữ liệu được phân tích
đã được mô tả hoàn toàn bởi phổ thế tương ứng, S1 – S4.


MAS NMR data using FA for the full spectra
MAS NMR data using FA for the single CH3
signals at 355 K.


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Fig. 3.17. 3D correlation plots of the Vi1, Vi2 and Vi4 coefficients evaluated from the 13C MAS
NMR data at 355 K using FA.
The FA results also give information on the addition of fatty acids into the PP/CaCO3
microcomposites. In this case, at high temperatures (330-355 K), clustering of the systems based on the
surface treatment of the CaCO3 particles was not observed. However, at lower temperatures (325 K),
clustering based on the surface treatment, i.e., with OA or SA and without an acid treatment, was
observed (Fig. 3.18). This clustering was likely revealed by the lower temperatures because the
amorphous phase segmental motion in the systems is not completely free, and the full differences in the
chain mobility and the trans-crystalline layer are not yet well resolved. Therefore, the samples are
clustered based on the subtle differences in the system homogeneity, which is influenced by the nontreated or treated regimes of the two fatty acids.


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Fig. 3.18. 3D correlation plot of the Vi1, Vi2 and Vi4 coefficients evaluated from the 13C MAS NMR data
at 325 K using FA. The plot shows the PP samples based on the fatty acid treatment and the
corresponding 13C MAS NMR spectra of the grouped systems and the pure PP sample.
When searching for the molecular origin of the toughness differences in the prepared PP/CaCO3
microcomposites, we determined that the systems with a higher toughness (higher JId) mostly contained
filler particles with a smaller diameter (1.7 mm), smaller amounts of these particles (80/20), and smaller
amounts of the highly mobile r.c. amorphous fraction based on the 13C MAS NMR spectra at 355 K. The
key role of the amorphous phase in understanding the toughness of the PP/CaCO3 composites was further
evidenced by the FA, which highlighted the prominent spectral differences between the prepared
composite systems. In particular, the subspectrum S4 unambiguously identified the signal at 22 ppm as



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Fracture surface morphology of polypropylene composites containing 40% talc mineral powder
non-modified surface is shown in Figure 3.19.

Fig. 3.19. SEM images of morphology of PP filled with 40% untreated talc
SEM images of the fracture surface of the material samples show that talc minerals are not
denatured, the surface is unevenly dispersed in the polypropylene substrate with the appearance of
agglomerated particles in the substrate. In addition, the interaction between the phases is poor when gaps
appear between the filler particles and the polymer substrate.

Fig. 3.20. SEM images of morphology of PP filled with 40% silane treated talc.
In the case of modified talc mineral powders (Figure 3.20), the dispersion and phase
interoperability were improved. Thus, it is clear that the surface modification process has been shown to
be effective when increasing the adhesion between the surface of the talc and the polypropylene substrate.
3.3.2. Tensile properties
a. Young’s modulus
Effects of talc content and surface modification on mechanical behaviour of polypropylene based
composites were investigated. Figure 3.21 showed Young’s modulus of composites. The results showed
that Young’s modulus values of composites increased as a function of filler content. Generally, the
addition of rigid particulate fillers increases stiffness, which is measured through Young modulus. This is
due to the fact that fillers often exhibit higher stiffness compared matrix polymer. On the other hand,
Young’s modulus is measured at the very beginning of a tensile test, where deformation is insufficient to
cause particle-matrix debonding


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Fig. 3.21. The effects of content and filler surface on the Young’s modulus of PP based composites

stress maximums developing in the composite influence its deformation and fracture behaviour as well as
its overall performance. Also, any influence on the crystalline structure produced by the filler addition
will have an influence on the fracture behaviour and deformation mechanisms of the composite.
Some authors reported a maximum of the notched impact strength at a talc content in range of 10 –
20 %. Results in figure 3.24 had a similar trend. Maximum of the notched Charpy impact strength at talc
content of 10%. After this concentration, notched impact toughness decreased with increasing talc
content.
On the other hand, the adsorption of polymer molecules on the filler surface through stronger bonds
leading to the rigidity in structure of polymer chains. This leads to earlier crack initiation and propagation
with decreasing of impact strength values in case of PP/talc/T2Mt composites compared with PP/talc
composites at corresponding concentration (figure 4). Plastic deformation of the polymer matrix is the
main energy absorbing process in impact and this increases when the interaction between particles and
polymer is lowered in case of PP/talc composites.

Fig. 3.24. Effects of talc content and filler surface on the values of notched Charpy impact strength of PP
based composites


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Chapter 4: CONCLUSIONS AND RECOMMENDATIONS
A. Conclusion
The thesis investigated the effect of phase interaction, molecular mobility on the mechanical
properties of polypropylene basedcomposite materials reinforcing with three typical fillers such as glass
beads, calcium carbonate and talc mineral powder. Glass beads are surface treated with silicone oil and
vinyl silane, calcium carbonate are surface treated withstearic acid and oleic acid and talc are surface
treated withmetacryloxypropyltrimetoxy silane.
Strong phase interaction increases the modulus of elasticity and tensile strengbut reduces the
elongation at break. , the value of impact energy absorptionis higher with weak phase interaction. Of
Among of 3 fillers, talc is the best reinforced filler for polypropylene, the tensile and impact strength
composite increase with loadingof 10% talc.

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LIST OF PAPERS PUBLISHED
A. List of papers
1. Olivia Kukackova, Nguyen Viet Dung, Sabina Abbrent, Martina Urbanova, Jiri Kotek, Jiri Brus. “A
novel insight into the origin of toughness in polypropyleneecalcium carbonate microcomposites:
Multivariate analysis of ss-NMR spectra”. Polymer 132 (IF = 3,7), 106-113, 2017.
2. Nguyen Viet Dung, Ngo Ke The and Jiri Kotek. “Effect of particle size and fatty surface treatment of
calcium carbonate on the deformation and fracture behaviour of polypropylene-based composites”,
Vietnam Journal of Chemistry, Vol. 53 (2e1), 26-30, 2015.
3. Nguyen Viet Dung and Ngo Ke The. “Effects of talc content and interfacial adhesion on mechanical
behaviour of polypropylene-based composites”, Vietnam Journal of Chemistry, Vol. 53 (4A), 2015.
4. Nguyen Viet Dung, Ngo Ke The and Jiri Kotek. “A solid-state NMR study of molecular mobility and
resulting deformation and fracture behaviour of glass beads filled polypropylene composites”,
Vietnam Journal of Chemistry, Vol. 53(6e4), 240-244, 12/2015.
5. Nguyen Viet Dung, Ngo Ke The and Jiri Kotek. “Effect of interfacial adhesion on deformation and
fracture behaviour of composites based on polypropylene and galss beads”, Journal of Science and
Technology, Vol. 54(1A), 300-307, 2016.
B. List of papers in Conference
1. Nguyen Viet Dung, Libor Kobera and Jiri Kotek. “Effects of filler surface on molecular mobility and
resulting deformation and fracture behaviour of thermoplastic polymer composites”. Carreer in
Polymer VI, Prague, Czech Republic, ISBN 978-80-85009-79-8, 18-19 July 2014.
2. Nguyen Viet Dung, Ngo Ke The and Jiri Kotek. "Effects of filler surface on crack initiation and
propagation of particulate filled polymer composites". 7th International Workshop on Advanced
Materials Science and Nanotechnology, Ha Long city, Vietnam, 2-6 November 2014.
3. Nguyen Viet Dung, Ngo Ke The and Jiri Kotek. "Effect of particle size and fatty acid coatings of
calcium carbonate on the deformation and fracture behaviour of polypropylene-based composites".
Vietnam Malaysia International Congress 2014, Ha Noi, Viet Nam, 7-9 November 2014.
4. Nguyen Viet Dung, Ngo Ke The. “Deformation and fracture behaviour of isotactic polypropylene
reinforced particle fillers”, The 5th Asian Materials Data Symposium, Hanoi, Vietnam, Oct 30th –
Nov 02nd 2016.