M. KASZONYIOVÁ et al.: EFFECT OF BETA IRRADIATION ON THE STRUCTURAL CHANGES OF ISOTACTIC ...
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EFFECT OF BETA IRRADIATION ON THE STRUCTURAL
CHANGES OF ISOTACTIC POLYPROPYLENE
VPLIV RADIOAKTIVNEGA SEVANJA BETA NA STRUKTURNE
SPREMEMBE IZOTAKTI^NEGA PROPILENA
Martina Kaszonyiová, Frantisek Rybnikar, Milena Kubi{ová, David Maòas
Tomas Bata University in Zlin, Faculty of Technology, Vavreckova 275, Zlín 76001
mhribova@ft.utb.cz
Prejem rokopisa – received: 2017-06-30; sprejem za objavo – accepted for publication: 2017-10-11
doi:10.17222/mit.2017.089
The electron -irradiation of isotactic polypropylene (iPP) influenced the sample chemical structure because it mostly caused
the crosslinking of the polymer chains beside the macromolecule degradation. The irradiation effect led to the corresponding
changes in physical properties (crystallinity, crystal size, melting and crystallisation temperatures). The amount of the -phase
in the samples decreased with the increasing -irradiation dose, changing into the 
- and amorphous phase. After the irradiation,
the iPP melting and crystallisation temperatures decreased, and the spherulitic structure was partially decomposed. The
imbibition of boiling xylene proved that the highest degree of crosslinking took place in the samples irradiated with a dose of 33
kGy, showing the highest crystallinity and melting temperature.
Keywords: isotactic polypropylene crystal modifications, -irradiation, structure and properties
Elektronsko radioaktivno -obsevanje vzorcev izotakti~nega polipropilena (iPP) vpliva na njihovo kemijsko zgradbo, ker to
povzro~a pre~no vezavo polimernih verig, povezano z degradacijo (kraj{anjem) makromolekul. Vpliv obsevanja vpliva skladno
s tem tudi na fizikalne lastnosti polimera (kristalini~nost, velikost kristalov, tali{~e in temperatura kristalizacije). S pove~e-
vanjem doze obsevanja  se koli~ina -faze zmanj{uje zaradi njenega spreminjanja v 
 in amorfno fazo. Po obsevanju se tali{~e
in temperatura kristalizacije iPP zni`ata, sferuliti~na (krogli~na) struktura pa delno razpade. Imbibicija (razmikanje molekul)
med vretjem ksilena je pokazala, da nastopa ve~ja stopnja pre~ne vezave molekul pri vzorcih, ki so jih avtorji prispevka obsevali
s 33kGy dozo, kar ka`e na ve~jo kristalini~nost in vi{je tali{~e.
Klju~ne besede: kristalne modifikacije izotakti~nega propilena, radioaktivno sevanje , struktura in lastnosti
1 INTRODUCTION
The properties of semicrystalline polymers prepared
with usual technologies can be influenced by several
factors such as time, temperature, moisture and other
environmental factors, where the radiation is significant.
In this contribution, we studied the effect of the
-radiation on some principal characteristics of isotactic
polypropylene (iPP) and its basic structural changes.1–5
2 EXPERIMENTAL PART
Commercial isotactic polypropylene V-PTS–Cre-
alen-EP-2300L1 M800 (PTS Plastic Technologie
Service, Germany; MFR (230 °C, 2.16 kg) = 6 g/10 min;
 = 0,9 g/cm3) containing 5 % of volume fractions of a
crosslinking agent (TAIC – triallylisocyanurate) enabling
the crosslinking with the -irradiation, was used.2 The
tested samples were prepared with the injection-
moulding technology at a temperature in the range of
210–240 °C, injection pressure of 80MPa and injecting
rate of 50 mm/s3. Subsequently, the samples were
irradiated at the company BGS Beta-Gamma-Service
GmbH & Co. KG, Saal an der Donau, Germany, with
electron rays, with an energy of 10 MeV and doses of
(33, 66 and 99) kGy in air at room temperature.4
Xylene imbibition – An experiment was carried out
according to ^SN EN 579 1996 to prove the iPP sample
crosslinking at the degrees of imbibing Q achieved by
boiling xylene at 140 °C for 30 min and 60 min.
Fourier transform infrared spectroscopy – An infra-
red analysis was made using a FTIR spectrometer
Nicolet 6700 FTIR (Thermo Nicolet Instruments Co.,
USA). The following degradation functional groups were
identified: –OH from the FTIR bands of 3600–3080 cm–1
and –CO- from 1800–1500 cm–1 bands.
Wide-angle X-ray scattering – Wide-angle X-ray
diffraction measurements were made using the PAN-
alytical X’Pert PRO X-ray diffraction system (Nether-
land) with Cu-K
 Ni-filtered radiation. Diffraction
patterns were obtained in the reflection mode in a range
of 5–30° 2 (4.5° 2/min). The total crystallinity (X) was
calculated as the ratio of the areas of crystal diffraction
peaks and the total scattering area. Crystal size L110 of
the 
 most intensive peaks was calculated using the
Scherrer equation.6 As the standard, perfect-crystal
terephthalic-acid peak at 2 = 17.4° and the half-maxi-
mum breadth at 0.3° 2 were chosen. The amounts of 

and  were calculated as the areas of the corresponding
Materiali in tehnologije / Materials and technology 52 (2018) 1, 15–18 15
UDK 620.179.155.5:67.017:547.313.3 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(1)15(2018)
peaks (
 = 110, 040, 130 and  = 300) from the total
crystallinity. The results in Table 1 are arithmetic ave-
rages of three measurements.
Differential scanning calorimetry – The melting and
crystallisation of iPP were analysed using DSC Q 100
(TA INDUSTRIES, USA) with the heating and cooling
rate of 10 °C/min in a N2 atmosphere. The enthalpy of
fusion was 148 J/g for 100 % 
-phase and 113 J/g for the
-phase.7
Morphology – Sample micrographs were charac-
terised with a transmission electron microscope Tesla BS
500 (Czech Republic) at 90 kV using replicas of selec-
tively etched sample surfaces. Selective etching was
carried out using a 1-% solution of KMnO4 in 85-%
H3PO4 for 1–10 min at room temperature.8 The samples
were consequently gold or platinum vacuum shadowed
and covered with a thin layer of vacuum-evaporated
carbon. For obtaining sample replicas, a 5-% water
solution of polyacrylic acid was used. The magnification
on the micrographs is indicated with 1-μm bars.
3 RESULTS AND DISCUSSION
The samples of iPP containing 5 % of volume frac-
tions of the crosslinking agent were -irradiated using
dose intensities of (33, 66 and 99) kGy. The sample
crosslinking was confirmed by measuring the degree of
imbibition (Q) when boiling xylene for 30 min and 60
min. The crosslinked-sample network was proportional
to the amount of the retained quantity of the solvent. The
non-irradiated sample dissolved (Q = 0) after 60 min.
The sample irradiated with 33 kGy had the largest sieve
mesh (Q = 4.0567) and the sample irradiated with 99
kGy had a small sieve mesh (Q = 3.0130), therefore, the
highest network density. This confirmed that the
-irradiation formed a 3D network in iPP (Table 1).
Table 1: Xylene imbibition and X-ray structure analysis
Irradiatio
n dose
Q after 60
min in
xylene
XX-ray, % L110, nm 
,% , %
0 kGy 0 51.53 29.9 48.00 3.53
33 kGy 4.0567 50.90 29.95 47.53 3.37
66 kGy 3.6432 48.20 24.9 45.44 2.76
99 kGy 3.0130 41.85 19.8 41.85 x
Decreased melting (Tm) and crystallisation tempera-
tures (Tc), total crystallinity (X) and the presence of –OH
and –CO- groups confirmed that, together with chain
crosslinking, the chain degradation also took place.
Typical wide-angle X-ray diffraction patterns (Figure
1) show the characteristic peaks of the 
-phase and -iPP
while Table 1 summarises the results of the X-ray anal-
ysis. The applied -irradiation dose decreased the initial
total sample crystallinity X (from 51 % (0 kGy) to 42 %
(99 kGy)) and the crystallinity of both iPP crystal
phases, mostly the -phase that completely disappeared
(confirmed with the diminishing of the -300 peak). It is
evident that  of the iPP phase is more sensitive to the
-irradiation than the 
-phase. The amorphous part (A)
is affected by the iPP crosslinking and degradation. The
highest crystal size of 
 characterised with L110 was
found in the case of the non-irradiated sample (29.9 nm)
and at a higher irradiation dose, it decreased (to 19.8
nm).
DSC measurements (Tables 2 and 3) confirmed the
results of the X-ray analysis indicating that the -irradi-
ation had a profound effect on the iPP structure. The
crystal peaks and areas confirmed that the -irradiation
decreased the total crystallinity and the amount of the
M. KASZONYIOVÁ et al.: EFFECT OF BETA IRRADIATION ON THE STRUCTURAL CHANGES OF ISOTACTIC ...
16 Materiali in tehnologije / Materials and technology 52 (2018) 1, 15–18
Figure 2: The DSC diagram of the melting (a) and crystallizaton (b)
peaks of phases 
 and  for non-irradiated sample
Figure 1: X-ray diffraction patterns of the original non-irradiated
sample and sample irradiated by 99 kGy dose.
-phase. Besides the peaks of the 
- and -phases, DSC
diagrams (Figures 2a to 2b) showed mainly small peaks
for the non-irradiated sample in the vicinity of 121 °C,
which belonged to another substance than the iPP. For
the -irradiated samples, these peaks were missing and
we assumed that they belonged to the crosslinking agent,
as did the small oval structures seen in TEM images
(described below).
Table 2: DSC melting
Irradiat-
ion dose
Melt-
ing

 Tm,
°C
H,
J/g X
, %
 Tm,
°C
H,
J/g X, %
XDSC,
%
0 kGy
1st 163.66 71.68 50.84 148 3.11 5.06 55.89
2nd 161.44 76.07 53.95 145 2.20 3.58 57.53
33 kGy
1st 161.89 72.41 51.35 148 0.97 1.58 52.93
2nd 159.95 74.23 52.65 143 0.69 1.12 53.77
66 kGy
1st 159.64 72.73 51.58 145 1.98 3.22 54.80
2nd 157.49 73.06 51.82 142.5 0.82 1.33 53.15
99 kGy
1st 157.97 71.83 50.94 142.3 0.61 1.00 51.94
2nd 155.96 71.91 51.00 142.5 0.46 0.75 51.75
Table 3: DSC crystallization
Irradiat-
ion dose

 Tc,
°C
H,
J/g X
, %
 Tc,
°C
H,
J/g X, %
X DSC,
%
0 kGy 114.94 76.45 54.22 101.39 3.2 5.20 59.42
33 kGy 112.75 78.66 55.79 95.89 1.1 1.79 57.58
66 kGy 113.17 75.42 53.49 95.18 1.8 2.93 56.42
99 kGy 112.99 72.64 51.52 93.99 1.6 2.60 54.12
Tm – melting temperature, Tc – crystallization temperature, H –
melting or crystallisation heat
The iPP morphology was studied in several publi-
cations.1,8 For free-melt crystallised samples, the surface
was characterised mostly by lamellar spherulites belong-
ing either to the 
- or -crystal modifications. TEM
images of the studied, selectively etched samples are
shown in Figures 3a to 3c. The non-irradiated sample
(Figure 3a) shows oval structures (dimensions of
0.57 μm × 0.4 μm) situated against a lamellar back-
ground (the thickness of the lamellae of 0.015 μm). The
ovals are not structurally connected to the large sphe-
rulite background. We conclude that the ovals represent
the particles of the crosslinking agent. This suggestion is
confirmed by the fact that the ovals are not present in any
further TEM image of the -irradiated samples. The
-irradiation process destroyed this crosslinking agent,
and the non-reacted agent was degraded similarly, re-
sembling the parts of the lamellae of the large spherulitic
support material.
Figure 3b shows the iPP irradiated with 33 kGy of
the -irradiation. The substrate including large thick
lamellar blocks is significantly changed and the thick
lamellae are divided into small lamellar blocks. In the
sample irradiated with a 99-kGy dose (Figure 3c), the
oval structures are not present and the lamellar substrate
is even more etched and destroyed than before. It is
evident that the original morphology was largely
changed and destroyed by the -irradiation. The lamellar
ends and edges look like melted areas. The question
arises whether the small oval lamellae were melted and
evaporated or degraded. Also, did the surface parts of the
large spherulites undergo the same process?
All the mentioned results confirm that the -irradi-
ation caused a significant increase in the sample tempe-
rature, which may have led to partial sample melting and
recrystallization, sample crosslinking and chain destruc-
tion.
4 CONCLUSIONS
The effect of the -irradiation on iPP was dual: At
first, there were chain crosslinking and partial chain de-
gradation due to the presence of –OH and –CO- groups
in the sample. Simultaneously, the irradiation process
warmed up the sample and partially melted or even
M. KASZONYIOVÁ et al.: EFFECT OF BETA IRRADIATION ON THE STRUCTURAL CHANGES OF ISOTACTIC ...
Materiali in tehnologije / Materials and technology 52 (2018) 1, 15–18 17
Figure 3: The surface of: a) non-irradiated sample, b) irradiated
sample by 33 kGy, c) irradiated sample by 99 kGy
evaporated the oval structures and lamellar ends of
spherulites. This process inevitably changed the sample
morphology, decreased the total crystallinity values, the
melting and crystallisation temperatures. The degra-
dation also decreased the crystal size and diminished the
-phase amount. The -irradiation mostly degraded the
free crosslinking agent and the -phase of iPP more than
the 
-phase.
Acknowledgment
This work was supported with a grant from the
Tomas Bata University in Zlin, IGA/FT/2017/002, and
financed from the funds for specific academic research.
5 REFERENCES
1 B. Lotz, Molecular aspects of structure and morphology of isotactic
polypropylene, J. Macromol. Sci., Part B, 41 (2002) 4–6, 685
2 D. Manas, M. Manas, M. Stanek, M. Danek, Improvement of plastic
properties, Arch. Mat. Sci. Eng., 32 (2008) 2, 69
3 E. Ragan, P. Baron, J. Dobransky, Sucking Machinery of Transport
for Dosing Granulations of Plastics at Injection Molding, Adv. Mat.
Research, 383–390 (2011), 2813, doi:10.4028/www.scientific.net/
AMR.383-390.2813
4 M. Ovsik, D. Manas, M. Manas, M. Stanek, M. Hribova, K. Kocman,
D. Samek, Irradiated polypropylene studied by microhardness and
WAXS, Chemicke listy, 106 (2012), 507
5 B. Ameduri, Crosslinking in materials science, New York, Springer,
2005
6 P. Scherrer, Alexander Leroy E., X-ray diffraction methods in
polymer science, New York, Wiley-Interscience, 1969, 582
7 J. Varga, -modification of isotactic polypropylene: preparation,
structure, processing and application, J. Macromol. Sci., Part B, 41
(2002), 4–6, 1121
8 F. Rybnikar, Selective etching of polyolefines. I. Isotactic polypro-
pylene, J. App. Pol. Sci., 30 (1985) 5, 1949, doi:10.1002/app.1985.
070300513
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