Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites
Mechanical and morphological properties of polypropylene (PP)/linear low density polyethylene (LLDPE)/ nano-sized calcium carbonate ternary composites were prepared using a twin-screw extruder. Modification of the filler nano-particle surface was pretreated with stearic acid and of the PP/LLDP...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
2013
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| Назва видання: | Проблемы прочности |
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nasplib_isofts_kiev_ua-123456789-1126702025-02-09T17:28:19Z Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites Морфологические и механические свойства смесей на основе ПП/ ЛПЭНП и тройных композиционных материалов на основе ПП/ ЛПЭНП/нано-CaCO₃ Cheraghi, H. Ghasemi, F.A. Payganeh, G. Научно-технический раздел Mechanical and morphological properties of polypropylene (PP)/linear low density polyethylene (LLDPE)/ nano-sized calcium carbonate ternary composites were prepared using a twin-screw extruder. Modification of the filler nano-particle surface was pretreated with stearic acid and of the PP/LLDPE interface by melting high crystallizable, high density polyethylene. In this research, effects of modified linear low density polyethylene (LD) and nano-CaCO₃ weight percentage on tensile strength, Young’s modulus and impact absorbed energy of composites were investigated. In addition, effect of the interaction between filler particles and polymer matrix was studied. Effect of quantity of microcracks on tensile properties of the composites was also discussed. Effect of nano-CaCO₃ and LD on the quantity of microcracks and impact- fractured surface of PP composites was studied by scanning electron microscope (SEM). The impact-fractured surface morphologies were characterized by SEM to clarify the possible mechanisms for improving the fracture resistance. Для получения полипропиленовых/линейно полиэтиленовых с низкой плотностью/наноразмерных CaCO₃ тройных композитов с соответствующими механическими и морфологическими свойствами используется двухшнековый экструдер. Исследовано влияние модифицированного линейного полиэтилена с низкой плотностью и объемного содержания нано-CaCO₃ на предел прочности при растяжении, модуль Юнга и поглощенную энергию удара композитов. Также исследовано влияние взаимодействия между частицами наполнителя и полимерной матрицей. Рассмотрено влияние количества микротрещин на механические свойства композитов при растяжении. С помощью сканирующего электронного микроскопа исследовано влияние нано-CaCO₃ с низкой плотностью на количество микротрещин и разрушенную при ударе поверхность полипропиленовых композитов. Для определения возможных механизмов улучшения сопротивления разрушению проведена сканирующая электронная микроскопия морфологии разрушенной при ударе поверхности. Результаты показали, что предел текучести смесей на основе полипропиленовых композитов с низкой плотностью и композитов на основе полипропиленовых композитов с низкой плотностью и нано-CaCO₃ с плотностью менее 10% постепенно уменьшается при незначительном увеличении модуля Юнга с повышением нагрузки. С ростом содержания CaCO₃ в обоих нанокомпозитах значение ударной вязкости увеличилось. Для отримання поліпропіленових/лінійно поліетиленових із низькою густиною/нанорозмірних CaCO₃ потрійних композитів, що мають відповідні механічні і морфологічні властивості, використовується двошнековий екструдер. Досліджено вплив модифікованого лінійного поліетилену з низькою густиною й об’ємного вмісту нано-СаСО₃ на границю міцності при розтязі, модуль Юнга і поглинену енергію удару композитів. Також досліджено вплив взаємодії між частинками наповнювача і полімерною матрицею. Розглянуто вплив кількості мікротріщин на механічні властивості композитів при розтязі. За допомогою скануючого електронного мікроскопа досліджено вплив нано-СаСО₃ з низькою густиною на кількість мікротріщин і зруйновану при ударі поверхню поліпропіленових композитів. Для визначення можливих механізмів покращання опору руйнуванню проведено скануючу електронну мікроскопію морфології зруйнованої при ударі поверхні. Результати показали, що границя текучості сумішей на основі поліпропіленових композитів із низькою густиною і композитів на основі поліпропіленових композитів із низькою густиною і нано-CaCO₃ із густиною менше ніж 10% поступово зменшується при незначному збільшенні модуля Юнга зі зростанням навантаження. Зі збільшенням вмісту СаСО₃ в обох нанокомпозитах значення ударної в’язкості зросло. 2013 Article Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites / H. Cheraghi, F.A. Ghasemi, G. Payganeh // Проблемы прочности. — 2013. — № 6. — С. 130-141. — Бібліогр.: 27 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/112670 539.4 en Проблемы прочности application/pdf Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
Научно-технический раздел Научно-технический раздел |
| spellingShingle |
Научно-технический раздел Научно-технический раздел Cheraghi, H. Ghasemi, F.A. Payganeh, G. Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites Проблемы прочности |
| description |
Mechanical and morphological properties of
polypropylene (PP)/linear low density polyethylene
(LLDPE)/ nano-sized calcium carbonate ternary
composites were prepared using a
twin-screw extruder. Modification of the filler
nano-particle surface was pretreated with stearic
acid and of the PP/LLDPE interface by melting
high crystallizable, high density polyethylene.
In this research, effects of modified linear low
density polyethylene (LD) and nano-CaCO₃
weight percentage on tensile strength, Young’s
modulus and impact absorbed energy of composites
were investigated. In addition, effect of the
interaction between filler particles and polymer
matrix was studied. Effect of quantity of microcracks
on tensile properties of the composites
was also discussed. Effect of nano-CaCO₃ and
LD on the quantity of microcracks and impact-
fractured surface of PP composites was
studied by scanning electron microscope (SEM).
The impact-fractured surface morphologies were
characterized by SEM to clarify the possible
mechanisms for improving the fracture resistance. |
| format |
Article |
| author |
Cheraghi, H. Ghasemi, F.A. Payganeh, G. |
| author_facet |
Cheraghi, H. Ghasemi, F.A. Payganeh, G. |
| author_sort |
Cheraghi, H. |
| title |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites |
| title_short |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites |
| title_full |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites |
| title_fullStr |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites |
| title_full_unstemmed |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites |
| title_sort |
morphology and mechanical properties of pp/lldpe blends and ternary pp/lldpe/nano-caco₃ composites |
| publisher |
Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| publishDate |
2013 |
| topic_facet |
Научно-технический раздел |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/112670 |
| citation_txt |
Morphology and Mechanical Properties of PP/LLDPE Blends and Ternary PP/LLDPE/nano-CaCO₃ Composites / H. Cheraghi, F.A. Ghasemi, G. Payganeh // Проблемы прочности. — 2013. — № 6. — С. 130-141. — Бібліогр.: 27 назв. — англ. |
| series |
Проблемы прочности |
| work_keys_str_mv |
AT cheraghih morphologyandmechanicalpropertiesofpplldpeblendsandternarypplldpenanocaco3composites AT ghasemifa morphologyandmechanicalpropertiesofpplldpeblendsandternarypplldpenanocaco3composites AT payganehg morphologyandmechanicalpropertiesofpplldpeblendsandternarypplldpenanocaco3composites AT cheraghih morfologičeskieimehaničeskiesvojstvasmesejnaosnovepplpénpitrojnyhkompozicionnyhmaterialovnaosnovepplpénpnanocaco3 AT ghasemifa morfologičeskieimehaničeskiesvojstvasmesejnaosnovepplpénpitrojnyhkompozicionnyhmaterialovnaosnovepplpénpnanocaco3 AT payganehg morfologičeskieimehaničeskiesvojstvasmesejnaosnovepplpénpitrojnyhkompozicionnyhmaterialovnaosnovepplpénpnanocaco3 |
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2025-11-28T17:18:51Z |
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2025-11-28T17:18:51Z |
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| fulltext |
UDC 539.4
Morphology and Mechanical Properties of PP/LLDPE Blends and
Ternary PP/LLDPE/nano-CaCO3 Composites
H. Cheraghi, F. A. Ghasemi,
1
and G. Payganeh
Shahid Rajaee Training University, Tehran, Iran
1 f.a.ghasemi@srttu.edu & faramarz_ashenai_ghasemi@yahoo.com
ÓÄÊ 539.4
Ìîðôîëîãè÷åñêèå è ìåõàíè÷åñêèå ñâîéñòâà ñìåñåé íà îñíîâå ÏÏ/
ËÏÝÍÏ è òðîéíûõ êîìïîçèöèîííûõ ìàòåðèàëîâ íà îñíîâå ÏÏ/
ËÏÝÍÏ/íàíî-CaCO3
Õ. ×åðàõè, Ô. À. Õàçåìè, Ã. Ïåéãàíåõ
Óíèâåðñèòåò Øàõèä Ðàäæàè, Òåãåðàí, Èðàí
Äëÿ ïîëó÷åíèÿ ïîëèïðîïèëåíîâûõ/ëèíåéíî ïîëèýòèëåíîâûõ ñ íèçêîé ïëîòíîñòüþ/íàíîðàçìåð-
íûõ CaCO3 òðîéíûõ êîìïîçèòîâ ñ ñîîòâåòñòâóþùèìè ìåõàíè÷åñêèìè è ìîðôîëîãè÷åñêèìè
ñâîéñòâàìè èñïîëüçóåòñÿ äâóõøíåêîâûé ýêñòðóäåð. Èññëåäîâàíî âëèÿíèå ìîäèôèöèðîâàííîãî
ëèíåéíîãî ïîëèýòèëåíà ñ íèçêîé ïëîòíîñòüþ è îáúåìíîãî ñîäåðæàíèÿ íàíî-CaCO3 íà ïðåäåë
ïðî÷íîñòè ïðè ðàñòÿæåíèè, ìîäóëü Þíãà è ïîãëîùåííóþ ýíåðãèþ óäàðà êîìïîçèòîâ. Òàêæå
èññëåäîâàíî âëèÿíèå âçàèìîäåéñòâèÿ ìåæäó ÷àñòèöàìè íàïîëíèòåëÿ è ïîëèìåðíîé ìàòðèöåé.
Ðàññìîòðåíî âëèÿíèå êîëè÷åñòâà ìèêðîòðåùèí íà ìåõàíè÷åñêèå ñâîéñòâà êîìïîçèòîâ ïðè
ðàñòÿæåíèè. Ñ ïîìîùüþ ñêàíèðóþùåãî ýëåêòðîííîãî ìèêðîñêîïà èññëåäîâàíî âëèÿíèå íàíî-
CaCO3 ñ íèçêîé ïëîòíîñòüþ íà êîëè÷åñòâî ìèêðîòðåùèí è ðàçðóøåííóþ ïðè óäàðå ïîâåðõ-
íîñòü ïîëèïðîïèëåíîâûõ êîìïîçèòîâ. Äëÿ îïðåäåëåíèÿ âîçìîæíûõ ìåõàíèçìîâ óëó÷øåíèÿ
ñîïðîòèâëåíèÿ ðàçðóøåíèþ ïðîâåäåíà ñêàíèðóþùàÿ ýëåêòðîííàÿ ìèêðîñêîïèÿ ìîðôîëîãèè
ðàçðóøåííîé ïðè óäàðå ïîâåðõíîñòè. Ðåçóëüòàòû ïîêàçàëè, ÷òî ïðåäåë òåêó÷åñòè ñìåñåé íà
îñíîâå ïîëèïðîïèëåíîâûõ êîìïîçèòîâ ñ íèçêîé ïëîòíîñòüþ è êîìïîçèòîâ íà îñíîâå ïîëè-
ïðîïèëåíîâûõ êîìïîçèòîâ ñ íèçêîé ïëîòíîñòüþ è íàíî-CaCO3 ñ ïëîòíîñòüþ ìåíåå 10%
ïîñòåïåííî óìåíüøàåòñÿ ïðè íåçíà÷èòåëüíîì óâåëè÷åíèè ìîäóëÿ Þíãà ñ ïîâûøåíèåì íàãðóç-
êè. Ñ ðîñòîì ñîäåðæàíèÿ CaCO3 â îáîèõ íàíîêîìïîçèòàõ çíà÷åíèå óäàðíîé âÿçêîñòè óâåëè-
÷èëîñü.
Êëþ÷åâûå ñëîâà: ìèêðîòðåùèíà, óäàðíàÿ âÿçêîñòü, íàíîêîìïîçèòû, êàðáîíàò
êàëüöèÿ.
Introduction. Polypropylene (PP), as one of the most important commodity
polymers, is widely used in many applications [1]. However, its application is
limited due to its high shrinkage rate and relatively poor impact resistance at room
or low temperatures. Therefore, to improve impact toughness of PP, it has received
extensive attention [2]. Recently, blending of various rubbers with PP for
improving impact resistance has been studied by several researchers [3–6].
Bertin et al. studied a virgin and recycled linear low density polyethylene
(LLDPE)/PP blends [1, 3]. Khare et al. performed thermal and dynamic analysis on
© H. CHERAGHI, F. A. GHASEMI, G. PAYGANEH, 2013
130 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2013, ¹ 6
metallocene linear low density polyethylene (LLDPE)/PP blends to optimize
impact properties [3, 7]. Also, other researchers have investigated mechanical
properties, especially impact behavior of PP/polyethylene (PE) blend and found
that, by adding PE to PP, impact resistance of PP increases [3, 8–10]. The
incompatibility between LLDPE and PP has been already reported by various
authors [11–13]. Low interfacial adhesion between the phases is responsible for the
decrease in mechanical properties, especially related to its morphology, including
impact strength, strain at break and ductile to brittle transition [11].
According to Shanks [11, 14], immiscibility between the phases makes the
rule of mixtures ineffective in predicting some properties of interest. To overcome
this difficulty, use of various coupling agents has been reported. Younesi et al. [3]
showed that addition of high crystallizable, high density polyethylene (HDPE)
improved tensile properties. Also, modification of PP/LLDPE interface increased
impact absorbed energy dramatically for these composites with all contents of
LLDPE [3]. Recently, three (and more) phase polymer composites have also
attracted the attention of researches and interest of the industry, which have been
studied in an effort to design materials with novel properties or to improve the
already existing ones [3].
The tremendous interfacial area in a polymer nanocomposite helps to affect
the composites’ properties to a great extent, even at low filler volume fractions [1,
15]. However, homogeneous dispersion of nanoparticles is very difficult because
nanoparticles with their high surface energy are easy to agglomerate. Calcium
carbonate (CaCO3) is one of the most commonly used inorganic filler in PP. Many
researchers have studied mechanical properties of PP/CaCO3 nanocomposites [1].
Thio et al. [16, 17] used three types of CaCO3 nanoparticles with average diameters
of 0.07, 0.7, and 3.5 mm to toughen PP. It was reported that the 0.7 mm diameter
particles improved Izod impact strength up to four times with respect to the
unfilled matrix. The major toughening mechanisms were interfacial debonding and
plastic deformation of inter-particle and crack deflection.
Wang et al. [18] reported that mechanical properties of PP, especially ductility,
were effectively improved by the incorporation of nano-CaCO3 pretreated with
stearic acid in an ultra-high-speed mixer (6000 rpm). Yong Lin et al. [19] aimed to
improve nano-CaCO3 dispersion in the polymer matrix and thus coated them with
stearic acid to increase their compatibility with the PP matrix and to minimize the
interactions among the particles. Ghasemi et al. [20] reported that increasing the
calcium carbonate nanoparticles improved both impact strength and the Young
modulus of PP; also, the more the PP-g-MA added to PP matrix, the more the
increase of impact strength of the samples and the less the decrease in their
Young’s modulus. Ghasemi et al. [21] also studied stiffness and damping properties
of PP/CaCO3 nanocomposites and showed that, by increasing the nanoparticles’
weight percent, tensile strength of the nanocomposites decreased and their Young’s
modulus increased.
In this work, evaluation of tensile and impact properties of PP/LD blends and
PP/LD/nano-CaCO3 was carried out to investigate composition range for better
mechanical performance. For compatibility of LLDPE with PP, HDPE was added
to LLDPE in order to result in modified linear low density polyethylene (LD). By
simultaneous change of composition of the matrix (PP/LD) and nano-CaCO3
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2013, ¹ 6 131
Morphology and Mechanical Properties of PP/LLDPE Blends ...
weight percentage, effects of composition on final properties of the composites
were investigated. The main objective of this paper was to investigate effect of
matrix composition (PP/LD) on the interaction between the particles and matrix.
Furthermore, effect of microcracks on tensile properties and fracture toughness of
the composites was studied.
1. Experimental Procedure.
1.1. Materials. PP (polypropylene, HP550j), LLDPE (linear low density
polyethylene, LL0209AA) and HDPE (high crystallizable high density polyethylene,
HD6070EA) of these ternary composites were obtained from Arak Petroleum
Company, Iran, with melt flow index of 3, 0.9, and 7 g/10 min, respectively.
CaCO3 nanoparticles, with trade name of HAKUENKA CCR, were provided by
Omya GmbH Company and the mean diameter of the particles was 80 nm.
1.2. Surface Treatment of the Nanoparticles. To improve their dispersion in
the polymer matrix, the as-received CCR nanoparticles were further coated with
2.5 wt.% stearic acid to increase its compatibility with the PP matrix and to
minimize the interactions among the particles. The coating method was as follows.
First, 100 g of CCR was mixed with a 400 ml solution mixture of water and
ethanol in the volume ratio of 3:1. The suspension was stirred by a magnetic stirrer
for 2 h to completely wet the particles. Then, the suspension was heated to and
maintained at 80�C. A fixed amount of stearic acid dissolved in the ethanol solvent
was gradually added to the suspension drop by drop. After 2 h of reaction time,
surface-treated calcium carbonate particles, which settled at the bottom of the
beaker, were dried in an oven at 105�C overnight [19].
1.3. Specimen Preparation. LLDPE and HDPE interface modifiers were first
melt-mixed in 1:4 ratio of HDPE to LLDPE; then, modified LLDPE and CCR were
directly melt-blended with PP. Compounding of the materials was done using a
Werner & Pfleiderer, Coperion EpcNTL (ZSK25) twin screw extruder. In the
extrusion step, barrel temperatures were set at 170/175/185/190/185�C and screw
speed of 300 rpm was used. L/D ratio of the screws was 40. After compounding,
the blends were injection moulded into rectangular bars and dumbbell shaped
specimens using an Emen machine injection moulding machine. The barrel had a
flat temperature profile of 180�C with injection pressure of 105 bars. A single-edge
V-shaped notch of 2 mm depth and tip radius of 0.25 mm was milled in the
moulded specimens for the notched Izod impact experiments.
1.4. Mechanical Properties. Tensile tests were performed by a Zwick/Roell
machine at crosshead speed of 50 mm/min. Tensile tests were done according to
ASTM-D638. Notched Izod impact tests were conducted using a CEAST impact
tester at room temperature using ASTM-D256. At least five samples were
conducted for each property and mean values and standard deviations (SD) were
calculated.
1.5. Scanning Electron Microscopy (SEM). Morphologies of both binary and
ternary PP composites were observed by a Hitachi S-4160, SEM with accelerating
voltage of 25 kV. To evaluate dispersion quality of the CaCO3 nanoparticles and
also extents of microcracks, 7 freeze-fractured surfaces of the nanocomposites
obtained at liquid nitrogen temperature were examined; so were the impact-
fractured surfaces in order to assess failure mechanisms. All the specimens were
coated with gold before SEM observations.
132 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2013, ¹ 6
H. Cheraghi, F. A. Ghasemi, and G. Payganeh
2. Results and Discussion.
2.1. Microcracks. Frequently, microcracks are created in the manufacturing
processes. It is crucial that microcracks reduce elastic modulus locally, resulting in
the crack attraction by the particle. When the crack approaches the particle, the
crack tip is partially unloaded because microcracks in their vicinity open as well. If
microcracks are not restricted to the vicinity of the crack tip or the particles but are
homogeneously distributed throughout the volume, they globally reduce Young’s
modulus. In a stress-controlled situation, the stored elastic strain energy increases.
Considering that all the samples were made in the same conditions, it seems that
the quantity of microcracks strongly depended on their composition. SEM
micrographs in Fig. 1 show the cryo-fractured surfaces of the nanocomposite. By
adding CaCO3 nanoparticles to the PP/LD blends, quantity of microcracks
increased (Fig. 1). Observation of the figures also showed that, for the LD10 wt.%
as a distinct behavior, nanocomposite exhibited the lowest quantity of microcracks
in comparison to other blends. It seems that compatibility between the components
was the reason for decreased quantity of microcracks in the nanocomposite.
2.2. Tensile Properties. Effect of the interaction between filler particles and
polymer matrix and quantity of microcracks on the tensile properties is discussed
in this section. Figure 2 shows the relationship between elastic modulus and weight
fraction of the fillers. The modulus is a low strain property. In this low strain
regime, the adhesion between particle and polymer 9 remains intact. The interaction
strength between polymer and particle has little effect on the modulus [5]. The
elastic modulus shows a maximum at 10 wt.% of LD content. If microcracks are
Fig. 1. Cryo-fractured surfaces of the PP/LD/CCR nanocomposites: (a) 90/10/0, (b) 90/5/5, (c)
85/10/5, (d) 75/20/5, (e) 65/20/15.
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homogeneously distributed throughout the volume, they globally reduce Young’s
modulus [22]. As seen in Fig. 1a and c, the lowest quantity of microcracks was
observed in the composites with LD content of 10 wt.%; so, the increasing Young’s
modulus can be predicted.
Effect of adding CaCO3 nanoparticles to Young’s modulus of the PP/LD
blends can be studied from two viewpoints. First, by adding the solid particles such
as calcium carbonate, the Young’s modulus improves slightly. It has been reported
by other investigators [1, 16, 22], on the other hand, that addition of CaCO3
nanoparticles increases quantity of microcracks of PP/LD blends, which results in
decreased Young’s modulus. The results of tensile tests show that addition of 5
wt.% CaCO3 nanoparticles to PP/LD decreases Young’s modulus. This result is
caused by growth of microcracks. It can be also observed that, for the LD10, a
distinct behavior, insignificant quantity of microcracks explains this behavior.
Moreover, the modulus of the nanocomposites slightly improves by further
increase of the filler content. The yield stress is measured at considerable
deformations, which leads to complete different dependency of properties on blend
composition, quantity of microcracks and particlepolymer interaction [22].
At this strain level, the particles completely or partially debond from the
polymer matrix, which leads to lowering of the yield stress through the formation
of voids, and do not contribute to the stress level. The tensile yield stress is raised
if the particles do not debond from the polymer surface, as would be the case when
the adhesion is very high [5].
Effect of increasing the LD content on yield strength of the PP/LD/CCR
nanocomposites can be studied from a different point of view:
Occurrence 1: Yield strength of PP/LD blends decreases by increasing the LD
content according to the rule of mixtures [2].
Occurrence 2: Microcracks reduce yield strength. Therefore, when LD content
is lower than 10 wt.%, microcracks decrease by increasing LD content. When LD
content is higher than 10 wt.%, microcracks increase again. Therefore, yield
strength first increases until LD 10%; then, it decreases.
Occurrence 3: The polymerparticle adhesion increases by enhancement of the
LD content. When the adhesion is low, early debonding can occur and, as a result,
the yield strength decreases.
Fig. 2. Elastic modulus of PP composites: (a) CCR = 0, (b) CCR = 5%, and (c) CCR = 15%.
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Figure 3 shows the relationship between yield strength and weight fraction of
components for these two composite systems. In Fig. 3a, it can be seen that the
yield strength of PP/LD blends decreased by increasing LD content since, in the
first case (Fig. 3a) when the weight percentage of nanoparticles was zero, only the
strength originated from occurrences 1 and 2 dominated. When LD content was up
to 10 wt.%, occurrence 1 was more effective than occurrence 2, which resulted in
diminishing of the yield strength. When LD was greater than 10 wt.%, by
increasing LD content, both occurrences 1 and 2 reduced yield strength; so, loss of
strength occurred more quickly.
Figure 3b shows that, by increasing LD content, yield strength decreases
slightly as LD content is less than 10 wt.% while increasing if LD content is more
than 10 wt.% [22]. By adding the CaCO3 nanoparticles to the composition of
PP/LD, effect of occurrence 3 should be considered along with that of occurrences
1 and 2 by the variation of yield strength.
In the nanocomposite with LD content of 10 wt.% and less than 10 wt.%,
modulus of the nanocomposite increased while yield stress was reduced by LD
content (Fig. 3b). This lowering of yield stress was connected to the early
debonding of the filler particles from the PP/LD polymer matrix because the
debonded particles did not contribute to the yield stress [22]. When the LD
percentage was less than 10 wt.%, it was not enough for preventing debonding of
the nanoparticles from the matrix; therefore, occurrence 3 had little effect in this
stage. Therefore, decreased yield strength can be explained by occurrences 1 and 2.
In the nanocomposites with more than 10 wt.% of LD content, it is believed
that the adhesion between the filler particles and PP/LD matrix was strong enough;
so, nanoparticles could bear the same fraction of the external load and the particles
did not early deboned from the matrix. Thus, the yield strength of the composite
increased [1]. In other words, in the nanocomposite with LD content of greater
than 10 wt.%, strength of occurrence 3 was dominated in comparison with
occurrences 1 and 2.
Figure 3c shows yield strength of the nanocomposites for the high CCR
contents. The yield strength decreased by increasing the CCR contents. It is
supposed that increasing of the nanoparticles, aggregate and microcracks led to this
reduction.
Fig. 3. Yield strength of PP composites: (a) CCR = 0, (b) CCR = 5%, and (c) CCR = 15%.
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The dispersion of CCR was very difficult because nanoparticles with high
surface energy were easy to agglomerate. The agglomerates were easy to debond
from the matrix and the debonded nanoparticles did not bear any fraction of the
external load; therefore, the yield strength decreased [1]. Effect of LD and CCR on
other tensile properties is shown in Table 1. By increasing LD content, a slight
decrease happened in fracture strength and elongation at break [1]. In combination
of the PP/LD/CCR (75/20/5), adhesion and compatibility between the particles and
matrix prevented early debonding of particles and led to enhancement of break
strength. Furthermore, increase of the CCR content resulted in slight decrease of
the fracture strength [3, 8].
2.3. Impact Properties. Formation of microcracks during crack propagation
can increase fracture toughness owing to additional dissipated energy. Depending
on distribution of microcracks, they may either increase or decrease fracture
toughness [23]. Figure 4a illustrates the impact absorbed energy for PP/LD blends
versus LD content wt.%. As expected, the impact absorbed energy incaresed by
increasing the LD content [3, 4, 6, 7 and 24]. Beside the effect of LD content,
quantity of microcracks can also affect impact strength [23]. Since the PP/LD10
blends have the least quantity of microcracks, PP/LD10 blends had the minimum
of impact strength. This condition can be concluded from Fig. 4a too.
Moreover, LD increase up to 20 wt.% led to improvement of the impact
strength which originated from synergistic toughening effect of both LD and
microcracks. Figure 4b illustrates the impact absorbed energy of PP/LD/CCR
nanocomposites versus LD content (wt.%). Impact strength of nanocomposites
increased slowly by increasing LD content [3, 4, 6, 7, 24]. In addition, changes in
interfacial interactions between the fillers and polymer matrix can modify the
deboning mechanism, failure behavior and thus overall performance of the
composites [22].
In PP/LD/CCR nanocomposites, increased weight percentage of LD blends
can cause changes in interaction between the matrix and nanoparticles. The
polymerparticle adhesion is lowered when the LD content decreases. When the
adhesion is low, deboning can occur, which is consistent with the cavitation
T a b l e 1
Mechanical Properties of PP Nanocomposites
Composition (weight ratio) Elongation at break (%) Break strength (MPa)
PP LD CC-R Mean SD Mean SD
95 5 0 15.4 0.6 21.4 0.9
90 10 0 15.6 1.3 19.2 0.9
80 20 0 16.7 1.6 19.0 0.9
90 5 5 17.8 1.7 19.1 1.3
85 10 5 14.2 1.6 18.2 1.2
75 20 5 14.5 0.8 20.3 0.6
65 20 15 9.9 1.0 18.8 0.6
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H. Cheraghi, F. A. Ghasemi, and G. Payganeh
mechanism of micro-sized rigid particles as summarized by Zuiderduin et al. [22],
consisting of three stages: stress concentration, debonding and shear yielding.
In composites with LD content of 10 wt.% and less than 10 wt.%, due to weak
adhesion between the particles and matrix, the filler particles debond from the
PP/LD matrix. As a result, in PP/LD/CCR (85/10/5) nanocomposites, because of
early debonding of the CaCO3 nanoparticles from the PP/LD matrix, fracture
energy of the composites stems largely from the shear yielding of the matrix.
Strong adhesion and interaction between particles and matrix are not always
conducive to toughening [25]. Vollengberg and Heikens [26, 27] reported decrease
of impact strength in chalk-filled PP composites because of strong interfacial
bonding.
Also, microcracks do not consume large quantities of energy because quantity
of the initial microcracks in PP/LD/CCR (85/10/5) nanocomposites is very low.
Furthermore, in ternary composites (PP/LD/CCR), incorporation of nanoparticles
mildly decreases impact strength of composites (Fig. 4c).
Debonding of the particles creates free volume at the particle size level;
therefore, stress state is altered in the vicinity of the particles. This mechanism is
similar to cavitation in rubber toughened blends [22]. In addition to the toughening
effect of nanoparticles, toughening effect of microcracks should be investigated
since adding CaCO3 nanoparticles to PP /LD matrix can cause dramatic increase in
microcracks.
Figure 5 shows SEM micrographs of the V-notched impact fracture surface
morphology of the composites. Two rough surfaces are demonstrated in Fig. 5a and
c; in other words, these two blends exhibit ductile fracture. Also in Fig. 5a and c,
fracture surface is composed of angular lines which are the path of crack
propagation. Having large quantity of microcracks in PP/LD20 blend, the
aggregation of the angular lines in fracture surfaces of PP/LD20 was further than
PP/LD5 blends. Thus, path length of crack propagation and 16 energy for fracture
of composite increased and, consequently, impact strength of the composites
increased as well (Fig. 4b) [3].
Figure 5b shows that PP/LD10 exhibited brittle fracture; it may be observed
that the fracture surface looked like waves [2]. It means that the PP/LD10
specimen broke relatively fast. As seen in Fig. 1d, there was a large quantity of
Fig. 4. Impact strength of PP ternary composites as a function of LD content: (a) CCR = 0, (b) CCR =
5%, and (c) CCR = 15%.
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initial microcracks in the PP/LD/CCR (75/20/5) samples; so, microcracks were
expanded upon loading. Increasing the path length of cracks led to energy
dissipation and thereby increased impact strength of the nanocomposite.
Furthermore, result of tensile tests indicated that compatibility and high adhesion
between the particles and matrix prevented debonding of the particles from matrix
in the specific compositions. Therefore, it seems that a slight improvement in the
impact strength in the PP/LD/CCR (75/20/5) samples was originated largely from
the expansion of microcracks and small fraction of the energy absorption by the
shear yielding of the matrix. Figure 5d is the SEM picture of the morphology of
V-notched impact fracture surface of the PP/LD/CCR (90/5/5) nanocomposites.
The impact-fractured surface was relatively smooth and homogeneous, indicating
that the fracture occurred at relatively high speed. In other words, the samples
exhibited brittle fracture, whcih agreed with the minimum impact strength as
observed in Fig. 4b. The fracture surface of the PP/LD/CCR (85/10/5) nano-
composites was rougher than that of the PP/LD/CCR (90/5/5) nanocomposites.
Two rough surfaces shown in Figs. 5e and 5f imply more ductile failure than the
one in Fig. 5d. This means that these two composites exhibited ductile fracture.
Conclusions. In this paper, to assess effects of matrix composition on the
mechanical properties of composites, a comprehensive experimental study was
conducted. Novelties of the present research can be summarized as follows:
1. During the manufacturing process, in all the matrices, microcracks
increased, in which the volume was influenced by the composition of composite.
2. SEM images of the samples showed that quantity of microcracks in the
PP/LD blends increased by adding the CaCO3 nanoparticles.
Fig. 5. SEM micrographs of impact-fractured surface of the PP composites: (a) 95/5, (b) 90/10, (c)
80/20, (d) 90/5/5, (e) 85/10/5, and (f) 75/20/5.
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H. Cheraghi, F. A. Ghasemi, and G. Payganeh
3. In the components with LD content of 10 wt.%, the lowest microcracks
were observed.
4. Increases in the amount of microcracks in material resulted in the reduction
of elastic modulus and yield strength of the composite.
5. Elastic modulus of the matrix decreased and increased with respect to
adding 5 and 15 wt.% CaCO3 nanoparticles, respectively.
6. Combinations with LD = 10% had the highest modulus due to the lowest
presence of microcracks in this composition.
7. Adding CaCO3 nanoparticles to PP/LD diminished yield strength.
8. Enhancement of LD content prevented early debonding.
9. The V-notched impact fracture strength of the blends increased by
increasing the nano-CaCO3.
10. Fracture surface of LD = 10% was smoother than others, indicating low
impact fracture strength.
11. Impact strength of composites increased by adding CaCO3 nanoparticles.
Ð å ç þ ì å
Äëÿ îòðèìàííÿ ïîë³ïðîï³ëåíîâèõ/ë³í³éíî ïîë³åòèëåíîâèõ ³ç íèçüêîþ ãóñòè-
íîþ/íàíîðîçì³ðíèõ CaCO3 ïîòð³éíèõ êîìïîçèò³â, ùî ìàþòü â³äïîâ³äí³ ìåõà-
í³÷í³ ³ ìîðôîëîã³÷í³ âëàñòèâîñò³, âèêîðèñòîâóºòüñÿ äâîøíåêîâèé åêñòðóäåð.
Äîñë³äæåíî âïëèâ ìîäèô³êîâàíîãî ë³í³éíîãî ïîë³åòèëåíó ç íèçüêîþ ãóñòè-
íîþ é îá’ºìíîãî âì³ñòó íàíî-ÑàÑÎ3 íà ãðàíèöþ ì³öíîñò³ ïðè ðîçòÿç³, ìîäóëü
Þíãà ³ ïîãëèíåíó åíåðã³þ óäàðó êîìïîçèò³â. Òàêîæ äîñë³äæåíî âïëèâ âçàºìî-
䳿 ì³æ ÷àñòèíêàìè íàïîâíþâà÷à ³ ïîë³ìåðíîþ ìàòðèöåþ. Ðîçãëÿíóòî âïëèâ
ê³ëüêîñò³ ì³êðîòð³ùèí íà ìåõàí³÷í³ âëàñòèâîñò³ êîìïîçèò³â ïðè ðîçòÿç³. Çà
äîïîìîãîþ ñêàíóþ÷îãî åëåêòðîííîãî ì³êðîñêîïà äîñë³äæåíî âïëèâ íàíî-
ÑàÑÎ3 ç íèçüêîþ ãóñòèíîþ íà ê³ëüê³ñòü ì³êðîòð³ùèí ³ çðóéíîâàíó ïðè óäàð³
ïîâåðõíþ ïîë³ïðîï³ëåíîâèõ êîìïîçèò³â. Äëÿ âèçíà÷åííÿ ìîæëèâèõ ìåõàí³ç-
ì³â ïîêðàùàííÿ îïîðó ðóéíóâàííþ ïðîâåäåíî ñêàíóþ÷ó åëåêòðîííó ì³êðî-
ñêîï³þ ìîðôîëî㳿 çðóéíîâàíî¿ ïðè óäàð³ ïîâåðõí³. Ðåçóëüòàòè ïîêàçàëè, ùî
ãðàíèöÿ òåêó÷îñò³ ñóì³øåé íà îñíîâ³ ïîë³ïðîï³ëåíîâèõ êîìïîçèò³â ³ç íèçü-
êîþ ãóñòèíîþ ³ êîìïîçèò³â íà îñíîâ³ ïîë³ïðîï³ëåíîâèõ êîìïîçèò³â ³ç íèçü-
êîþ ãóñòèíîþ ³ íàíî-CaCO3 ³ç ãóñòèíîþ ìåíøå í³æ 10% ïîñòóïîâî çìåí-
øóºòüñÿ ïðè íåçíà÷íîìó çá³ëüøåíí³ ìîäóëÿ Þíãà ç³ çðîñòàííÿì íàâàíòàæåí-
íÿ. dz çá³ëüøåííÿì âì³ñòó ÑàÑÎ3 â îáîõ íàíîêîìïîçèòàõ çíà÷åííÿ óäàðíî¿
â’ÿçêîñò³ çðîñëî.
1. Yang Kun, Yang Qi, Li Guangxian, et al., “Morphology and mechanical
properties of polypropylene/calcium carbonate nanocomposites,” Mater. Lett.,
60, 805–809 (2006).
2. Liang Ji-Zhao, “Impact fracture toughness and morphology of polypropylene
nanocomposites,” Polym. Bull., 65, 815–824 (2010).
3. M. Younesi and M. E. Bahrololoom, “Producing toughened PP/HA-LLDPE
ternary biocomposite using a two-step blending method,” Mater. Design, 30,
4253–4259 (2009).
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2013, ¹ 6 139
Morphology and Mechanical Properties of PP/LLDPE Blends ...
4. W. M. Speri and G. R. Patrick, “Fiber-reinforced rubber modified poly-
propylene,” Polym. Eng. Sci., 15, 668–672 (1975).
5. S. Danesi and R. S. Porter, “Blends of isotactic polypropylene and ethylene-
propylene rubbers: rheology, morphology and mechanics,” Polymer, 19, 448–
457 (1978).
6. J. Karger Kocsis, A. Kallo, A. Szafner, et al., “Morphological study on the
effect of elastomeric impact modifiers in polypropylene system,” Polymer, 20,
37–43 (1979).
7. R. A. Khare, P. S. Westphal, T. K. M. Ling, et al. “Thermal and dynamic
mechanical analysis on metallocene ULDPE/PP blends to optimize impact
properties,” Thermochim. Acta, 357-358, 155–160 (2000).
8. C. M. Tai, R. K. Y. Li, and C. N. Ng, “Impact behaviour of polypropylene/
polyethylene blends,” Polym. Test., 19, 143–154 (2000).
9. J. Loos, M. Bonnet, and J. Petermann, “Morphologies and mechanical
properties of syndiotactic polypropylene (sPP)/polyethylene (PE) blends,”
Polymer, 41, 351–356 (2000).
10. R. Strapasson, S. C. Amico, M. F. R. Pereira, and T. H. D. Sydenstricker,
“Tensile and impact behavior of polypropylene/low density polyethylene
blends,” Polym. Test., 24, 468–473 (2005).
11. N. K. Madi, “Thermal and mechanical properties of injection molded recycled
high density polyethylene blends with virgin isotactic polypropylene,” Mater.
Design, 46, 435–441 (2013).
12. J. W. Teh, A. Rudin, and J. C. Keung, “A review of polyethylene poly-
propylene blends and their compatibilization,” Polym. Tech., 13, 1–23 (1994).
13. S. Bertin and J. J. Robin, “Study and characterization of virgin and recycled
LDPE/PP blends,” Eur. Polym. J., 38, 2255–2264 (2002).
14. R. A. Shanks, J. Li, F. Chen, and G. Amarasinghe, “Time-temperature-
miscibility and morphology of polyolefin blends,” Chin. J. Polym. Sci., 18,
263–270 (2000).
15. Chan Chi-Ming, Jingshen Wu, Li Jian-Xiong, and Ying-Kit Cheung, “Poly-
propylene/calcium carbonate nanocomposites,” Polymer, 43, 2981–2992 (2002).
16. Zhang Qing-Xin, Yu Zhong-Zhen, Xie Xiao-Lin, and Mai Yiu-Wing,
“Crystallization and impact energy of polypropylene/CaCO3 nanocomposites
with nonionic modifier,” Polymer, 45, 5985–5994 (2004).
17. Y. S. Thio, A. S. Argon, R. E. Cohen, and M. Weinberg, “Toughening of
isotactic polypropylene with CaCO3 particles,” Polymer, 43, 3661–3674
(2002).
18. Wang Gang, Chen Xiao Y., Huang Rui, and Zhang Ling, “Nano-CaCO3/
polypropylene composites made with ultra-high-speed mixer,” J. Mater. Sci.
Lett., 21, 985–986 (2002).
19. Lin Yong, Chen Haibin, Chan Chi-Ming, and Jingshen Wu, “High impact
toughness polypropylene/CaCO3 nanocomposites and the toughening
mechanism,” Macromolecules, 41, 9204–9213 (2008).
140 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2013, ¹ 6
H. Cheraghi, F. A. Ghasemi, and G. Payganeh
20. F. A. Ghasemi, Gh. Payganeh, and M. Rahmani, “The effect of stearic acid
surfasmodified calcium carbonate nanoparticles and PP-g-MA on the
mechanical properties of PP/CaCO3/PP-g-MA nanocomposites,” J. Modares
Mech. Eng., 13, No. 4, 139–152 (2013).
21. F. A. Ghasemi and R. E. Farsani, “Effect of nano-CaCO3 on dynamic
mechanical properties of polypropylene,” J. Modares Mech. Eng., 13, No. 6,
1–10 (2013).
22. W. C. J. Zuiderduin, C. Westzaan, J. Huetink, and R. J. Gaymans, “Toughening
of polypropylene with calcium carbonate particles,” Polymer, 44, 261–275
(2003).
23. J. Rosler, H. Harders, and M. Baker, Mechanical Behaviour of Engineering
Materials: Metals, Ceramics, Polymers, and Composites, Springer, New York
(2007).
24. Shu-Lin Bai, Gong-Tao Wang, J.-M. Hiver, and C. G’Sell, “Microstructures
and mechanical properties of polypropylene/polyamide 6/polyetheleneoctene
elastomer blends,” Polymer, 45, 3063–3071 (2004).
25. B. Pukanszky, “Particulate filled polypropilene composites,” in: J. Karger-
Kocsis (Ed.), Polypropylene: Structure, Blends, and Composites, Vol. 3,
Chapman and Hall, London (1995), pp. 574–580.
26. P. H. T. Vollenberg and D. Heikens, “The mechanical properties of chalk-
filled polypropylene: a preliminary investigation,” J. Mater. Sci., 25, 3089–
3095 (1990).
27. C. M. Tai and R. K. Y. Li, “Mechanical properties of flame retardant filled
polypropylene composites,” J. Appl. Polym. Sci., 80, 2718–2728 (2001).
Received 08. 08. 2013
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