amounts of well-dispersed natural clay can lead to environmentally friendly
and inexpensive plastic composites with improved specialized properties,
according to a University researcher.
"Adding very small
amounts of natural clays to plastics changes some of their physical properties,"
said Evangelos Manias, assistant professor of materials science and engineering.
"While we can tune the chemical interactions between the clays and some
polymers, it is the general changes due to the nanometer fillers in all
plastics that may be the most interesting."
Addition of clay can
make plastics less permeable to liquids and gases, more flame retardant
and tougher. Lower permeability can make plastics like PET, the standard
plastic used in soft drink bottling, suitable for bottling beer or wine.
The clay-enhanced product would protect the beverages from the effects
of oxygen. At the same time, the addition of small amounts of clay does
not affect the transparency of plastics.
Adding clay to polymer
blends is not a simple process as polymers and clays mix about as well
as oil and water. However, if the clay is treated with an organic surfactant,
a compound that allows the inert clay to mix with the polymers, much as
soap allows oil and water to mix, the clays can be incorporated into the
An inexpensive, more
environmentally clean method of producing flame retardant plastics could
eventually save lives. Because the addition of clay into plastics reduces
flammability in a wide range of plastics, it may have universal application
as a general flame retardant additive.
used to make plastics flame retardant contain bromine, which produces poisonous
combustion gases when burned," Manias said. "Using clay is a green alternative
to current practices and reduces flammability in a wide range of plastics."
The polymer clay blends,
while containing only 1 percent to 5 percent clay, are
actually nanocomposites. The addition of clay into the polymer blend does
not alter the normal production and processing of the clayless polymer.
"The clay can be added
at the final stages of polymer processing without any change in the current
industrial practices," Manias said. "The thermodynamics drive the nanometer
the clay through the polymer and the small amounts of clay do not cause
any wear in the equipment. Manufacturers can use the same equipment, timing
and settings as in their normal process.