Microfibrillar composites (MFCs) are advantageous polymer-polymer composites with in situ formed reinforcing fibrils. The range of applications of MFCs is limited by their low thermal resistance and me-chanical parameters of polymeric microfibres, which are formed by melt or cold drawing of the polymer blend. This study addresses improving MFCs based on HDPE matrix with 20% polyamide 6 microfibrils using organophilized montmorillonite. The complex effect of the nanofiller on the structure and parameters of the MFCs is investigated.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3545

Kelnar, I.

Microfibrillar composites (MFCs) are advantageous polymer-polymer composites with in situ formed reinforcing fibrils. The range of applications of MFCs is limited by their low thermal resistance and me-chanical parameters of polymeric microfibres, which are formed by melt or cold drawing of the polymer blend. This study addresses improving MFCs based on HDPE matrix with 20 % polyamide 6 microfibrils using organophilized montmorillonite. The complex effect of the nanofiller on the structure and parameters of the MFCs is investigated

I. Kelnar

CiteSeerX

Polymer-polymer Microfibrillar Composites: Effect of Nanofillers on Structure and Properties

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 3, 03NCNN25(3pp) (2013)   2304-1862/2013/2(3)03NCNN25(3) 03NCNN25-1  2013 Sumy State University Polymer-polymer Microfibrillar Composites: Effect of Nanofillers  on Structure and Properties  I. Kelnar  Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Heyrovsky Sq. 2, Prague, Czech Republic  (Received 06 May 2013; published online 01 September 2013)  Microfibrillar composites (MFCs) are advantageous polymer-polymer composites with in situ formed reinforcing fibrils. The range of applications of MFCs is limited by their low thermal resistance and me-chanical parameters of polymeric microfibres, which are formed by melt or cold drawing of the polymer blend. This study addresses improving MFCs based on HDPE matrix with 20% polyamide 6 microfibrils using organophilized montmorillonite. The complex effect of the nanofiller on the structure and parameters of the MFCs is investigated.  Keywords: Microfibrillar Composite, Layered nanosilicate, Drawing.   PACS number: 81.05.Qk   1. INTRODUCTION  Microfibrillar composites (MFCs) are polymer-polymer composites based on blends of ideally semi-crystalline polymers with a marked difference in melting points [1]. Their melt or cold drawing can  transform the original spherical inclusions of dis-persed polymer, such as polyamide or poly(ethyleneterephthalate to fibre-like microfibrils, which are preserved during the subsequent pro-cessing step at lower temperature to only melt the matrix  (usually polyethylene or polypropylene). The advantages of MFCs are their mechanical properties, which are  analogous to those of glass  or carbon fibre  composites, and their lower density, zero abra-sion of equipment, improved processability and cost effectivity. Further advantages represent fair recy-clability and application of conventional processing equipment. Of importance is the very high interfacial bonding of the fibrils formed directly inside  the ma-trix (created together with the matrix similarly to natural composites), which arises from the formation of a transcrystalline layer  of matrix around the fi-brils or chemical bonding in case of condensational polymers [2] and also through the use of the func-tionalized components. The limitations of MFCs include a reduced applicable temperature range, due to their relatively low thermal resistance, and a low strength and stiffness of the polymeric fibrils in comparison with inorganic or carbon fibres. These shortcomings can be successfully eliminated through the use of nanofillers (NF) of various geometries, i.e., by combination of MFC and nanocomposite concepts. In polymer nanocomposites [3], plate-, tube- or fibre-type nanofillers can significantly enhance the mate-rial’s mechanical properties, influence the crystallin-ity and flow characteristics, and so on. Moreover, even more significant and complex changes can occur in the case of multiphase polymer systems [4], where the regulation of the phase structure by influencing the dynamic phase behaviour can be accompanied by the formation of new effective morphologies of the dispersed phase, increasing the toughening efficiency [5]. As a result, systems with a unique balance of mechanical parameters may be obtained. Nanofillers close in size to that of the macromolecules also sup-port drawing of the polymers [6], especially fibre formation due to the enhancement of the chains ori-entation along draw axis and the oriented crystalli-sation. As a result, the effect of using NF in MFC may be even more complex than the mere combina-tion of reinforcement and structure directing effect. At the same time, the numerous, and  in some cases contradictory, effects of NF must be perfectly har-monised to upgrade MFCs and/or to eliminate possi-ble antagonistic effects. This study addresses with the potential of layered nanosilicate montmorillonite to improve an MFC based on the combination of an HDPE matrix with PA6 microfibrils.  2. EXPERIMENTAL  2.1 Materials  High density polyethylene (HDPE) HYA 800 (Exxon Mobil), copolymer ethylene-glycidymethacrylate (Al-drich), Polyamide/6 (PA6) Ultramid B5 (BASF), Clays based on natural montmorillonite: Cloisite 15A(modified with dialkyldimethylammonium chloride 95 meq/100g) (C15), Cloisite 30B (modified with al-kylbis(2-hydroxyethyl)dimethylammonium chloride 90 meq/100g, with alkyl  derived from tallow) (C30), (Southern Clay Products, Inc.)  2.2 MFC preparation  Prior to mixing, PA6 and clay were dried at 85 °C and 70 °C, respectively, for 12 h in a vacuum oven.  Mixing proceeded in a counter rotating segmented twin screw extruder (L/D 40) Brabender TSE 20 at 400 rpm and temperature of respective zones 230, 235, 240, 245,  245 and 250 °C. The extruded bristle was melt-drawn using adjustable take-up device. Dog-bone specimens (gauge length 40 mm) were prepared in a laboratory micro-injection molding machine (DSM). The barrel temperature was 200 °C, that of mold 70 °C.   I. KELNAR PROC. NAP 2, 03NCNN25 (2013)   03NCNN25-2 2.3 Testing  Tensile tests were carried out at 22 °C using an In-stron 5800 apparatus at a crosshead speed of 20 mm/min. At least 8 specimens were tested for each sample. Structure of fibrils was observed using scan-ning electron microscopy (SEM), HDPE matrix re-moved by boiling xylene for 10 hours.   3. RESULTS AND DISCUSSION  From Fig. 1 it can be observed that the addition of 3% C 30 (in the course of simultaneous mixing of all components) to the 80/20 HDPE/PA6 mixture leads to a minor increase in the stress at break, accompanied by a significant gain in stiffness with increasing draw ratio. The relatively higher parameters of the undrawn sam-ple without nanofiller results from the significant fibril formation due to flow through the die; this effect is apparently reduced by the nanoclay. This is a conse-quence of the clay affecting rheological parameters of components.  0 5 801020304050Stress at break (MPa)Draw ratio   0 5 80200400600800100012001400160018002000E (MPa)Draw ratio   Fig. 1 – Stress at break and stiffness of HDPE/PA6 80/20 system without and with 3% clay (white) in dependence on draw ratio  From Fig. 2, it follows that with the analogous sys-tem containing pre-made polyamide nanocomposite containing 1 % C30 and an HDPE matrix with 5% of copolymer ethylene-glycidyl methacrylate (for reactive compatibilisation) the positive effect of NF occurs at a lower draw ratio only. This indicates a more complex effect of the nanoclay on these systems, which may in-clude antagonistic effects. 0 5 80102030405060Stress at break (MPa)Draw ratio  0 5 8020040060080010001200140016001800E (MPa)Draw ratio   Fig. 2 –  Stress at break and stiffness of HDPE/PA6 80/20 with 5% epoxidized HDPE and analogous system with PA6 nanocomposite (white) in dependence on draw ratio  Fig. 3, shows the microfibril structure of the above mentioned samples (Fig. 2). There is a marked effect of the nanoclay on the diameter and length of the microfi-brils. The finer microfibrils formed in the case of   PA6 nanocomposite result from the structure-directing effect of the clay in the multiphase system, which leads to a finer size of the PA6 domains in the original blend. At the same time, the length of the fibrils formed from the polyamide nanocomposite at a high draw ratio is lower than from neat PA6. The reduced parameters of this system at a high draw ratio (Fig 2) are undoubtedly a consequence of the clay-affecting the elongational flow of PA6 and its ability to form fibrils. Additionally, the effect of the molecular weight of PA6 and effect of the nano-filler on crystallinity will be discussed.        Fig. 3 – Structure of original blends (above) and  PA6 microfi-brils in  HDPE/PA6 80/20 containing 5% epoxidized HDPE and analogous system with PA6 nanocomposite (right), draw ratio  POLYMER-POLYMER MICROFIBRILLAR COMPOSITES:… PROC. NAP 2, 03NCNN25 (2013)   03NCNN25-3 of both samples was 8 4. CONCLUSIONS  The enhanced mechanical behaviour of microfibril-lar composites with HDPE matrix suggests that nano-fillers may be used to improve polymer-polymer compo-sites. The explanation for the improved mechanical properties is the combination of reinforcement and structure-directing effects of the rigid nanoplatelets,  hich also affect the formation of polyamide fibrils dur-ing melt drawing. At the same time, the complex effects of nanofillers must be harmonised to avoid antagonistic effects such as the unfavourable alteration of  the rheo-logical parameters of the components.  AKNOWLEDGEMENTS  This work was supported by Czech Science Founda-tion (Grant No 13-15255S).   REFERENCES  1. S. Fakirov,  H. Kamo,  M. Evstatiev,  K. Friedrich,, J. of Macromolec. Sci., Part B 43, 1281 (2008). 2. M. Evstatiev , S. Fakirov, Polymer 21, 877 (1992). 3. S. Sinha Ray, K. Okamoto, Prog. Polym. Sci. 28, 1539 (2003). 4. I. Kelnar, J. Rotrekl, J. Kotek, L. Kaprálková, Polym. Int. 57, 1281 (2008) 5. I. Kelnar, V. Khunová, J. Kotek, L. Kaprálková, Polymer 48, 5332 (2007). 6. B. Na, R. Lv, N. Tian, W. Xu, Z. Li, Q. FU, J. of Polym. Sci.: Part B: Polym. Phys. 47, 898 (2009).  

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 3, 03NCNN25(3pp) (2013) 
 
 
2304-1862/2013/2(3)03NCNN25(3) 03NCNN25-1  2013 Sumy State University 
Polymer-polymer Microfibrillar Composites: Effect of Nanofillers  
on Structure and Properties 
 
I. Kelnar 
 
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Heyrovsky Sq. 2, Prague, 
Czech Republic 
 
(Received 06 May 2013; published online 01 September 2013) 
 
Microfibrillar composites (MFCs) are advantageous polymer-polymer composites with in situ formed 
reinforcing fibrils. The range of applications of MFCs is limited by their low thermal resistance and me-
chanical parameters of polymeric microfibres, which are formed by melt or cold drawing of the polymer 
blend. This study addresses improving MFCs based on HDPE matrix with 20% polyamide 6 microfibrils 
using organophilized montmorillonite. The complex effect of the nanofiller on the structure and parameters 
of the MFCs is investigated. 
 
Keywords: Microfibrillar Composite, Layered nanosilicate, Drawing. 
 
 PACS number: 81.05.Qk 
 
 
1. INTRODUCTION 
 
Microfibrillar composites (MFCs) are polymer-
polymer composites based on blends of ideally semi-
crystalline polymers with a marked difference in 
melting points [1]. Their melt or cold drawing can  
transform the original spherical inclusions of dis-
persed polymer, such as polyamide or 
poly(ethyleneterephthalate to fibre-like microfibrils, 
which are preserved during the subsequent pro-
cessing step at lower temperature to only melt the 
matrix  (usually polyethylene or polypropylene). The 
advantages of MFCs are their mechanical properties, 
which are  analogous to those of glass  or carbon 
fibre  composites, and their lower density, zero abra-
sion of equipment, improved processability and cost 
effectivity. Further advantages represent fair recy-
clability and application of conventional processing 
equipment. Of importance is the very high interfacial 
bonding of the fibrils formed directly inside  the ma-
trix (created together with the matrix similarly to 
natural composites), which arises from the formation 
of a transcrystalline layer  of matrix around the fi-
brils or chemical bonding in case of condensational 
polymers [2] and also through the use of the func-
tionalized components. The limitations of MFCs 
include a reduced applicable temperature range, due 
to their relatively low thermal resistance, and a low 
strength and stiffness of the polymeric fibrils in 
comparison with inorganic or carbon fibres. These 
shortcomings can be successfully eliminated through 
the use of nanofillers (NF) of various geometries, i.e., 
by combination of MFC and nanocomposite concepts. 
In polymer nanocomposites [3], plate-, tube- or fibre-
type nanofillers can significantly enhance the mate-
rial’s mechanical properties, influence the crystallin-
ity and flow characteristics, and so on. Moreover, 
even more significant and complex changes can occur 
in the case of multiphase polymer systems [4], where 
the regulation of the phase structure by influencing 
the dynamic phase behaviour can be accompanied by 
the formation of new effective morphologies of the 
dispersed phase, increasing the toughening efficiency 
[5]. As a result, systems with a unique balance of 
mechanical parameters may be obtained. Nanofillers 
close in size to that of the macromolecules also sup-
port drawing of the polymers [6], especially fibre 
formation due to the enhancement of the chains ori-
entation along draw axis and the oriented crystalli-
sation. As a result, the effect of using NF in MFC 
may be even more complex than the mere combina-
tion of reinforcement and structure directing effect. 
At the same time, the numerous, and  in some cases 
contradictory, effects of NF must be perfectly har-
monised to upgrade MFCs and/or to eliminate possi-
ble antagonistic effects. This study addresses with 
the potential of layered nanosilicate montmorillonite 
to improve an MFC based on the combination of an 
HDPE matrix with PA6 microfibrils. 
 
2. EXPERIMENTAL 
 
2.1 Materials 
 
High density polyethylene (HDPE) HYA 800 (Exxon 
Mobil), copolymer ethylene-glycidymethacrylate (Al-
drich), Polyamide/6 (PA6) Ultramid B5 (BASF), Clays 
based on natural montmorillonite: Cloisite 
15A(modified with dialkyldimethylammonium chloride 
95 meq/100g) (C15), Cloisite 30B (modified with al-
kylbis(2-hydroxyethyl)dimethylammonium chloride 90 
meq/100g, with alkyl  derived from tallow) (C30), 
(Southern Clay Products, Inc.) 
 
2.2 MFC preparation 
 
Prior to mixing, PA6 and clay were dried at 85 °C 
and 70 °C, respectively, for 12 h in a vacuum oven.  
Mixing proceeded in a counter rotating segmented 
twin screw extruder (L/D 40) Brabender TSE 20 at 
400 rpm and temperature of respective zones 230, 
235, 240, 245,  245 and 250 °C. The extruded bristle 
was melt-drawn using adjustable take-up device. Dog-
bone specimens (gauge length 40 mm) were prepared 
in a laboratory micro-injection molding machine 
(DSM). The barrel temperature was 200 °C, that of 
mold 70 °C.  
 I. KELNAR PROC. NAP 2, 03NCNN25 (2013) 
 
 
03NCNN25-2 
2.3 Testing 
 
Tensile tests were carried out at 22 °C using an In-
stron 5800 apparatus at a crosshead speed of 20 
mm/min. At least 8 specimens were tested for each 
sample. Structure of fibrils was observed using scan-
ning electron microscopy (SEM), HDPE matrix re-
moved by boiling xylene for 10 hours.  
 
3. RESULTS AND DISCUSSION 
 
From Fig. 1 it can be observed that the addition of 
3% C 30 (in the course of simultaneous mixing of all 
components) to the 80/20 HDPE/PA6 mixture leads to a 
minor increase in the stress at break, accompanied by a 
significant gain in stiffness with increasing draw ratio. 
The relatively higher parameters of the undrawn sam-
ple without nanofiller results from the significant fibril 
formation due to flow through the die; this effect is 
apparently reduced by the nanoclay. This is a conse-
quence of the clay affecting rheological parameters of 
components. 
 
0 5 8
0
10
20
30
40
50
S
tr
e
s
s
 a
t 
b
re
a
k
 (
M
P
a
)
Draw ratio  
 
0 5 8
0
200
400
600
800
1000
1200
1400
1600
1800
2000
E
 (
M
P
a
)
Draw ratio  
 
Fig. 1 – Stress at break and stiffness of HDPE/PA6 80/20 
system without and with 3% clay (white) in dependence on 
draw ratio 
 
From Fig. 2, it follows that with the analogous sys-
tem containing pre-made polyamide nanocomposite 
containing 1 % C30 and an HDPE matrix with 5% of 
copolymer ethylene-glycidyl methacrylate (for reactive 
compatibilisation) the positive effect of NF occurs at a 
lower draw ratio only. This indicates a more complex 
effect of the nanoclay on these systems, which may in-
clude antagonistic effects. 
0 5 8
0
10
20
30
40
50
60
S
tr
e
s
s
 a
t 
b
re
a
k
 (
M
P
a
)
Draw ratio  
0 5 8
0
200
400
600
800
1000
1200
1400
1600
1800
E
 (
M
P
a
)
Draw ratio  
 
Fig. 2 –  Stress at break and stiffness of HDPE/PA6 80/20 
with 5% epoxidized HDPE and analogous system with PA6 
nanocomposite (white) in dependence on draw ratio 
 
Fig. 3, shows the microfibril structure of the above 
mentioned samples (Fig. 2). There is a marked effect of 
the nanoclay on the diameter and length of the microfi-
brils. The finer microfibrils formed in the case of   PA6 
nanocomposite result from the structure-directing effect 
of the clay in the multiphase system, which leads to a 
finer size of the PA6 domains in the original blend. At 
the same time, the length of the fibrils formed from the 
polyamide nanocomposite at a high draw ratio is lower 
than from neat PA6. The reduced parameters of this 
system at a high draw ratio (Fig 2) are undoubtedly a 
consequence of the clay-affecting the elongational flow of 
PA6 and its ability to form fibrils. Additionally, the effect 
of the molecular weight of PA6 and effect of the nano-
filler on crystallinity will be discussed. 
 
  
 
  
 
Fig. 3 – Structure of original blends (above) and  PA6 microfi-
brils in  HDPE/PA6 80/20 containing 5% epoxidized HDPE and 
analogous system with PA6 nanocomposite (right), draw ratio 
 POLYMER-POLYMER MICROFIBRILLAR COMPOSITES:… PROC. NAP 2, 03NCNN25 (2013) 
 
 
03NCNN25-3 
of both samples was 8 
4. CONCLUSIONS 
 
The enhanced mechanical behaviour of microfibril-
lar composites with HDPE matrix suggests that nano-
fillers may be used to improve polymer-polymer compo-
sites. The explanation for the improved mechanical 
properties is the combination of reinforcement and 
structure-directing effects of the rigid nanoplatelets,  
hich also affect the formation of polyamide fibrils dur-
ing melt drawing. At the same time, the complex effects 
of nanofillers must be harmonised to avoid antagonistic 
effects such as the unfavourable alteration of  the rheo-
logical parameters of the components. 
 
AKNOWLEDGEMENTS 
 
This work was supported by Czech Science Founda-
tion (Grant No 13-15255S). 
 
 
REFERENCES 
 
1. S. Fakirov,  H. Kamo,  M. Evstatiev,  K. Friedrich,, J. of 
Macromolec. Sci., Part B 43, 1281 (2008). 
2. M. Evstatiev , S. Fakirov, Polymer 21, 877 (1992). 
3. S. Sinha Ray, K. Okamoto, Prog. Polym. Sci. 28, 1539 
(2003). 
4. I. Kelnar, J. Rotrekl, J. Kotek, L. Kaprálková, Polym. Int. 
57, 1281 (2008) 
5. I. Kelnar, V. Khunová, J. Kotek, L. Kaprálková, Polymer 
48, 5332 (2007). 
6. B. Na, R. Lv, N. Tian, W. Xu, Z. Li, Q. FU, J. of Polym. 
Sci.: Part B: Polym. Phys. 47, 898 (2009). 
 


English

https://essuir.sumdu.edu.ua/bitstream/123456789/35451/1/Kelnar_Drawing.pdf

Polymer-polymer Microfibrillar Composites: Effect of Nanofillers on Structure and Properties

Abstract

Similar works

Full text

Available Versions

CiteSeerX

Electronic Sumy State University Institutional Repository

SocioEconomic Challenges Journal (Sumy State University)