Even low nanoparticle contents are sufficient to obtain new or modified material
characteristics, especially a faster crystallization rate and a higher crystallization
temperature.
To increase the stiffness of polypropylene, we investigated the in-situ polymerization of propene and silica balls (monopheres) with a diameter of 250 nm. The
zirconocene [(pMePh) 2 C(Cp)(2,7-bis-tBuFlu)]ZrCl 2 was used. The polymerizations
were carried out in toluene as solvent and TIBA as scavenger. To determine whether
MAO-impregnated silica balls are suitable for storage, 2.55 g silica balls were
impregnated with 11 mL of MAO solution (10% MAO). Polymerizations of propene
were carried out at 30
C directly after preparation, 2 weeks later, and 11 weeks later.
As can be seen from Table 5, the activities decreased only slightly, even after
11 weeks, to 81% of the original activity. This shows that nanofiller/MAO precursors
can be stored for a long period.
CNFs or MWCNTs are an especially attractive class of fillers for polymers
because of their intriguing mechanical and thermal properties [117]. CNFs were
dispersed in toluene solution, then MAO, an isotactic working zirconocene, and
propene were added and the suspension stirred for approximately 30 min. As
expected for in-situ polymerization, the polymer grew directly on the fiber surface
and covered it with a thin polypropylene layer. The dried polypropylene
nanocomposites were obtained in powder form. The morphology of the iPP/CNF
nanocomposites was investigated using transmission electron microscopy (TEM).
Figure 14 shows a TEM micrograph of iPP/CNT nanocomposite material
synthesized by in-situ polymerization. It can be seen that there is no agglomeration
of the nanofibers. The CNFs with a diameter of 100 nm are covered by a coat of
about 50 nm iPP. Separated polymerization active sites at the surface of fibers form
Fig. 13 Formation of polymerization active sites by absorption of MAO on oxidized multiwall
carbon nanotubes (MWCNT) followed by addition of a zirconocene
20
W. Kaminsky and H. Sinn
characteristics, especially a faster crystallization rate and a higher crystallization
temperature.
To increase the stiffness of polypropylene, we investigated the in-situ polymerization of propene and silica balls (monopheres) with a diameter of 250 nm. The
zirconocene [(pMePh) 2 C(Cp)(2,7-bis-tBuFlu)]ZrCl 2 was used. The polymerizations
were carried out in toluene as solvent and TIBA as scavenger. To determine whether
MAO-impregnated silica balls are suitable for storage, 2.55 g silica balls were
impregnated with 11 mL of MAO solution (10% MAO). Polymerizations of propene
were carried out at 30
C directly after preparation, 2 weeks later, and 11 weeks later.
As can be seen from Table 5, the activities decreased only slightly, even after
11 weeks, to 81% of the original activity. This shows that nanofiller/MAO precursors
can be stored for a long period.
CNFs or MWCNTs are an especially attractive class of fillers for polymers
because of their intriguing mechanical and thermal properties [117]. CNFs were
dispersed in toluene solution, then MAO, an isotactic working zirconocene, and
propene were added and the suspension stirred for approximately 30 min. As
expected for in-situ polymerization, the polymer grew directly on the fiber surface
and covered it with a thin polypropylene layer. The dried polypropylene
nanocomposites were obtained in powder form. The morphology of the iPP/CNF
nanocomposites was investigated using transmission electron microscopy (TEM).
Figure 14 shows a TEM micrograph of iPP/CNT nanocomposite material
synthesized by in-situ polymerization. It can be seen that there is no agglomeration
of the nanofibers. The CNFs with a diameter of 100 nm are covered by a coat of
about 50 nm iPP. Separated polymerization active sites at the surface of fibers form
Fig. 13 Formation of polymerization active sites by absorption of MAO on oxidized multiwall
carbon nanotubes (MWCNT) followed by addition of a zirconocene
20
W. Kaminsky and H. Sinn