• Calcium Carbonate
• Cavitation
• Debonding
• Interface
• Nanocomposite
• Polypropylene (PP)
• Polystyrene (PS)
• Toughening

The objective of this PhD thesis is to develop new tough and rigid
nanocomposites based on polypropylene (PP) and polystyrene (PS) which are two
of the polymers with the highest demand and growth rates worldwide. Recently,
attempts have been made to improve the mechanical properties and
processability of PP and PS through several procedures. Nowadays the market
of fillers for polyolefines is dominated by calcium carbonate which is one of
the most widely used particulate fillers for polymer applications due to it’s
low cost, ready availability and useful properties. However, even if CaCO₃
enhances the Young’s modulus it is often reported that decreases impact
strength. Thus, researchers are studying to improve the mechanical properties
of polymers toughened with CaCO₃ nanoparticles so they are expected to be
very desirable materials. In fact, previous results from our work in
collaboration with Solvay Advanced Functional Minerals have shown that a
dry-coated PCC substantially enhances impact in both homopolymer and
copolymer iPP and so this result encourage us to continue these studies and
to extend its use on both PP and PS. So we studied the possibility to tough
some polyolefines mixed with different type of CaCO₃ nanoparticles (PCC) and
the mechanism that explains their mechanical deformation. In this way we
tested the effect of the different characteristics of the powders on the
final properties of the nanocomposites, as the various particles differ for
shape, granulometric size, surfactant agent and kind of process utilized to
prepare them.
This work is divided into three main parts: the first regards the fracture
behaviour of polyproylene filled with different kinds of CaCO₃ powders, the
second the development of a new alternative procedure to produce
nanocomposites (based on PP and PS matrices) with the relative comparison
with the extrusion method and the third the interface characterization with
various techniques.