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6 Waste Plastics Management and Conversion into Liquid …
(1) Filling materials
A filling material (or filler) slows down the flow between the molecular compounds
and helps to improve the strength, stiffness, and heat resistance of the synthetic
resin. The filling materials can be either organic such as wood flour and wastepaper
or inorganic such as talcum powder, diatomite, mica, limestone powder, and glass
fiber [3].
(2) Plasticizers
Plasticizers reduce the density, brittleness, melt viscosity and glass transition temperature of the polymers, while they improve the plasticity, flexibility and deformation
at the break of the final product. Plasticizers form secondary bonds with the polymer
chains and increase the distance of neighbor chains, reducing their interaction and
increasing their mobility, but they have the disadvantages of reducing the mechanical properties and heat resistance of the plastics. The most popular plasticizers are
dibutyl phthalate (DBP), dioctyl phthalate (DOP), and camphor [3, 5].
(3) Flame retardants
Flame retardants prevent or slow down the formation of toxic and harmful
compounds and retard the development of ignition by different chemical and physical
methods. Combustion of hydrocarbons results in the breakage of polymeric chains,
forming smaller detrimental molecules composed of elements such as nitrogen,
oxygen, sulfur, fluorine and chlorine. Flame retardants are added to the plastics
to prevent/retard the formation and spread of these compounds [5].
(4) Heat stabilizers
Heat stabilizers improve the quality of the plastics and prevent the thermal degradation of polymers when exposed to elevated temperatures. Heat stabilizers can
be classified as the primary stabilizers such as mixed metal salt blends, organotin
compounds, and lead compounds and secondary stabilizers such as alkylorganophosphites, epoxy compounds, and beta diketones [3, 6].
(5) Antioxidants and UV stabilizers
Antioxidants and UV stabilizers inhibit the oxidative degradation of the plastics and
degradation when exposed to ultraviolet (UV) light. Polymer degradation is caused by
the highly reactive free radicals formed by heat, UV radiation, and mechanical shear.
The potential of oxidation increases when the plastics are exposed to air under high
temperatures, infrared heating and microwave heating. Based on their protection
mechanism, the anti-oxidants can be classified into two groups: (1) the primary
anti-oxidants or the chain-breaking anti-oxidants that scavenge the free radicals by
chain-breaking electron donor mechanism, (2) the secondary anti-oxidants or the
hydroperoxide decomposers that decompose the polymer hydroperoxides (POOH)
and form inert secondary products. The most common anti-oxidants are (BHT, BHA,
6 Waste Plastics Management and Conversion into Liquid …
(1) Filling materials
A filling material (or filler) slows down the flow between the molecular compounds
and helps to improve the strength, stiffness, and heat resistance of the synthetic
resin. The filling materials can be either organic such as wood flour and wastepaper
or inorganic such as talcum powder, diatomite, mica, limestone powder, and glass
fiber [3].
(2) Plasticizers
Plasticizers reduce the density, brittleness, melt viscosity and glass transition temperature of the polymers, while they improve the plasticity, flexibility and deformation
at the break of the final product. Plasticizers form secondary bonds with the polymer
chains and increase the distance of neighbor chains, reducing their interaction and
increasing their mobility, but they have the disadvantages of reducing the mechanical properties and heat resistance of the plastics. The most popular plasticizers are
dibutyl phthalate (DBP), dioctyl phthalate (DOP), and camphor [3, 5].
(3) Flame retardants
Flame retardants prevent or slow down the formation of toxic and harmful
compounds and retard the development of ignition by different chemical and physical
methods. Combustion of hydrocarbons results in the breakage of polymeric chains,
forming smaller detrimental molecules composed of elements such as nitrogen,
oxygen, sulfur, fluorine and chlorine. Flame retardants are added to the plastics
to prevent/retard the formation and spread of these compounds [5].
(4) Heat stabilizers
Heat stabilizers improve the quality of the plastics and prevent the thermal degradation of polymers when exposed to elevated temperatures. Heat stabilizers can
be classified as the primary stabilizers such as mixed metal salt blends, organotin
compounds, and lead compounds and secondary stabilizers such as alkylorganophosphites, epoxy compounds, and beta diketones [3, 6].
(5) Antioxidants and UV stabilizers
Antioxidants and UV stabilizers inhibit the oxidative degradation of the plastics and
degradation when exposed to ultraviolet (UV) light. Polymer degradation is caused by
the highly reactive free radicals formed by heat, UV radiation, and mechanical shear.
The potential of oxidation increases when the plastics are exposed to air under high
temperatures, infrared heating and microwave heating. Based on their protection
mechanism, the anti-oxidants can be classified into two groups: (1) the primary
anti-oxidants or the chain-breaking anti-oxidants that scavenge the free radicals by
chain-breaking electron donor mechanism, (2) the secondary anti-oxidants or the
hydroperoxide decomposers that decompose the polymer hydroperoxides (POOH)
and form inert secondary products. The most common anti-oxidants are (BHT, BHA,