5.2 Weakly Interacting Compatibilizers in Polyolefin
Composites
The polyolefin composites are usually modified by a compatibilizer that contains
some Lewis-basic reactive groups. Still, when a Lewis-acidic phenylsilanefunctionalized compatibilizer, PE-co-SiPh, was used in a polyethylene/aluminum
hydroxide composite, there were, indeed, some marks of influenced interaction at
the filler/matrix boundary layer [28]. It was also found that phenylsilanefunctionalized compatibilizer can actually react and form a covalent bond with
the microsilica (μSi) filler. When polypropylene with pendant phenylsilane groups
(PP-co-SiPh) was used as compatibilizer in a PP/μSi composite, the improved
interaction between matrix and filler was seen as an increase in the crystallization
temperature, i.e., stronger nucleation effect (Fig. 23) [25].
As an extension to this study, the μSi concentration in the composite was
increased (from 4 wt% to 30 wt%), whereafter the influence of the PP-co-SiPh
was also seen in the mechanical properties of the composites (Table 8, compare run
2 with run 3, increased yield and tensile values). A similar kind of increase in the
mechanical properties was also achieved when a highly reactive Lewis-basic
fluorosilane analogue was used in parallel (Table 8, compare run 3 .with run 4).
This clearly supports the assumption that the PP-co-SiPh is able to form a strong
bond with the μSi filler [29].
0
10
20
30
100
105
110
115
120
125
130
135
140
Temperature / °C
Heat flow / mW
A
B
C
Fig. 23 DSC-cooling curves
for (A) PP, (B) PP/μSicomposite (4 wt% of μSi),
and (C) PP/μSi/PP-co-SiPh
composite (4 wt% of μSi and
0.4 wt% of compatibilizer).
Reprinted from [25], with
kind permission from
Elsevier
Table 8 Tensile properties of PP/μSi composites modified by functional PP
Run
Composition
Modulus
(MPa)
Yield
Tensile
Strain (%)
Strength
(MPa)
Strain (%)
Strength
(MPa)
1
PP
860 Æ 30 12.8 Æ 0.3 29.1 Æ 0.2 >1,500
~50
2
PP/μSi (30 wt%)
1,260 Æ 30
5.2 Æ 0.1 28.1 Æ 0.1 500 Æ 110 ~26
3
+1.5 wt% PP-co-SiPh 1,250 Æ 20
7.9 Æ 0.2 31.9 Æ 0.2 740 Æ 30 ~34
4
+1.5 wt% PP-co-SiF 1,240 Æ 10
8.2 Æ 0.1 32.3 Æ 0.3 750 Æ 30 ~35
Data from [29]
226
J. Seppa ¨la ¨ et al.
Composites
The polyolefin composites are usually modified by a compatibilizer that contains
some Lewis-basic reactive groups. Still, when a Lewis-acidic phenylsilanefunctionalized compatibilizer, PE-co-SiPh, was used in a polyethylene/aluminum
hydroxide composite, there were, indeed, some marks of influenced interaction at
the filler/matrix boundary layer [28]. It was also found that phenylsilanefunctionalized compatibilizer can actually react and form a covalent bond with
the microsilica (μSi) filler. When polypropylene with pendant phenylsilane groups
(PP-co-SiPh) was used as compatibilizer in a PP/μSi composite, the improved
interaction between matrix and filler was seen as an increase in the crystallization
temperature, i.e., stronger nucleation effect (Fig. 23) [25].
As an extension to this study, the μSi concentration in the composite was
increased (from 4 wt% to 30 wt%), whereafter the influence of the PP-co-SiPh
was also seen in the mechanical properties of the composites (Table 8, compare run
2 with run 3, increased yield and tensile values). A similar kind of increase in the
mechanical properties was also achieved when a highly reactive Lewis-basic
fluorosilane analogue was used in parallel (Table 8, compare run 3 .with run 4).
This clearly supports the assumption that the PP-co-SiPh is able to form a strong
bond with the μSi filler [29].
0
10
20
30
100
105
110
115
120
125
130
135
140
Temperature / °C
Heat flow / mW
A
B
C
Fig. 23 DSC-cooling curves
for (A) PP, (B) PP/μSicomposite (4 wt% of μSi),
and (C) PP/μSi/PP-co-SiPh
composite (4 wt% of μSi and
0.4 wt% of compatibilizer).
Reprinted from [25], with
kind permission from
Elsevier
Table 8 Tensile properties of PP/μSi composites modified by functional PP
Run
Composition
Modulus
(MPa)
Yield
Tensile
Strain (%)
Strength
(MPa)
Strain (%)
Strength
(MPa)
1
PP
860 Æ 30 12.8 Æ 0.3 29.1 Æ 0.2 >1,500
~50
2
PP/μSi (30 wt%)
1,260 Æ 30
5.2 Æ 0.1 28.1 Æ 0.1 500 Æ 110 ~26
3
+1.5 wt% PP-co-SiPh 1,250 Æ 20
7.9 Æ 0.2 31.9 Æ 0.2 740 Æ 30 ~34
4
+1.5 wt% PP-co-SiF 1,240 Æ 10
8.2 Æ 0.1 32.3 Æ 0.3 750 Æ 30 ~35
Data from [29]
226
J. Seppa ¨la ¨ et al.