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Plastics play an important role in the modern world. They have been
found to be extremely versatile materials with many useful uses for human
life since the 1950s. In 2015, 322 million tonnes of plastics were produced
throughout the world. Average plastic consumption per capita in 2015 is 69.7
kg/person in the world, 48.5 kg/person in Asia, 155 kg/person in USA, 146
kg/person in Europe, 128 kg/person in Japan, 41 kg/person in Vietnam (a
significant increase by 33 kg/person compared to 2010). Polyethylene is the
most widely used thermoplastic in the world, consumed more than 76 million
tons per year, accounting for 38% of total plastic consumption. Increased
demand for plastics causes increase in waste and global environment
pollution. In 2012, the amount of plastic waste dumped into the environment
was 25.2 million tons in Europe, 29 million tons in the United States.
According to environmental reports of the United Nations, around 22- 43%
of the world's waste is buried in the landfill and 35% of waste in ocean. In
Vietnam, the average annual volume of solid waste has increased by nearly
200% and will increase in the near future, estimated at 44 million tons per
annum. According to the Marine Conservation Organization and the
McKinsey Center for Business and Environment, plastic waste of Vietnam is
the world's fourth largest by volume (0.73 million tons/year, representing 6%
of the total in the world) in 2015. To solve this problem, in the past few
decades, scientists have focused on the development of plastic materials
which decompose easily. Adding pro-oxidant additives is the most interesting
method.
Prooxidant additves are usually transition metal ions introduced in the
form of stearates or complexes with other organic compounds. Transition
metals are used as prooxidant additves, including Ti, V, Cr, Mn, Fe, Co, Ni,
Cu, Zn, Ca ., the most effective of which are the stearate of Co, Mn and Fe.
Under the influence of ultraviolet (UV) radiation, temperature or mechanical
impacts, prooxidant additives promote the oxidation of polymer chains to
form functional groups such as carbonyl, carboxyl, hydroxide, ester, etc.
which can be consumed by microorganisms. In the presence of prooxidant
additives, the degradation time of plastics from hundreds of years decreased
to several years or even several months.
For the above reasons, we propose the dissertation: “Study on the
biodegradability of polyetylene in the presence of transition metal
stearates (Mn, Fe, Co)”.
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