Environmental Engineering Reference
In-Depth Information
4.5.1 Fillers for Plastics
Fillers are low-cost, mostly inorganic, powders that are used in plastic
formulationstoeitherreducetheamountofplasticresinusedandhencethe
cost (called extender fillers) or to improve performance of the compound.
Carbon, glass fiber, mica, talc, glass, titania, clays, and silica are well-known
reinforcing fillers used to increase the modulus and strength of plastics.
With these, the amount, particle size (and its distribution), particle shape,
and compatibility with the polymer matrix determine the level of
reinforcement. In general, the improvement obtained is proportional to the
volume fraction of the filler used. Maximum performance of a functional
filler at a given volume fraction is fully expressed only if it is well dispersed
in the plastic matrix. Therefore, the processing method also influences filler
performance. Chemical modification (or functionalization) of the filler
surface and the use of a dispersants are common methods to ensure
improved compatibility between phases and therefore superior
reinforcement in filled plastics. In both instances, the surface of filler
particle is covered with a hydrophobic layer that has better compatibility
with the polymer matrix.
With emerging nanoscale fillers where the particle sizes are in the 100s
of nanometers, the specific surface area of filler particles can be orders of
magnitude larger than that for conventional fillers. As fractional volume
of matrix-filler interphase determines the level of reinforcement achieved
in the composite, nanofillers can achieve superior properties at relatively
low volume fractions, provided they are adequately dispersed in the base
polymer.
4.5.2 Plasticizers in PVC
Plasticizers arecommonlyusedinplasticstechnologyandespeciallyinPVC,
a plastic produced in high volume. They are used at high volume fractions;
phthalate levels can be as high as 60-70% by weight in some “soft” or
flexible PVCproducts(RudelandPerovich, 2009). Productsthatconsumers
are routinely exposed to include shower curtains, toys, floor tiles,
containers, sealants, and automotive interior trimming that are made from
plasticized PVC. Phthalates are the most commonly used plasticizer in PVC,
though others such as epoxides, trimellitates, and phosphates can also be
globally produced in 2011, for instance, 87% were phthalates. Plasticizers
