Effects of Gamma Radiation on the Physicochemical Properties …
17
Environmental pollution not only occurs when polyesters are discarded, but also
during their production and final use. The pollutants are released into the air (gaseous
oxides of carbon, sulfur, nitrogen, as well as particulate solids, and even phosphorus),
into the water (such as salts and petroleum derivatives), and into the soil (chemicals
or toxic salts for animals or plants). Because, they are produced from petroleum,
and their extraction is environmentally expensive. But, the greatest concern arises,
after they have fulfilled their useful life. It is important to mention, that the world
production of polyesters was more than 76 million tons in 2016.
In the manufacturing of polyester products some harmful chemicals are used, for
example carcinogens; which are emitted into the air and untreated water, when they
are not controlled. It is estimated that most of the plastics thrown into the ocean are
polyesters, which come from the textile industry. About 70 billion of oil barrels are
necessaries for to meet the demand of them, mainly those polyester for producing
synthetic fibers [2]. The largest consumers of polyesters are the Asian countries,
where a lot of contaminants have been identified.
As it is known, the chemical reactions involved in the production of unsaturated
polyester resins are irreversible and involve a considerable energy consumption;
nevertheless, changes on the synthesis ratios can adjust chemical compositions. Then,
such resins can be used in many applications.
During the polyester elaboration through to condensation process, the reaction
water is produced (by-product), which needs to be treated as waste, for to avoid
contamination of the flows. Despite of the advances on the chemical recycling, the
waste disposal of such wastes, continue being a contamination problem.
Environmental pollution caused by the textile industry, includes the elaboration of
polyester-based textiles, which consists of many operations. In the polyester dyeing
processes are analyzed the ecological cost, mainly those related to water consumption, energy expenditure (electrical and thermal), carbon dioxide generation and the
effluent toxicity. Wastewater are a serious problem, because they contain several
chemical substances (mainly dyestuffs and surfactants), that are harmful to the flora
and fauna. In a study, concerning to dyeing polyester, the results show that polyester
requires 40 L of water per each kg of dyed material, and more consumption of electrical energy compared to the dyeing of polyamide and cotton. Moreover, thermal
energy required for polyester processing is lower compared to other materials [5].
In the industry, there are a lot of non-crosslinked unsaturated polyester resins,
whose properties decrease when they exceed the storage time, limiting their use in
several applications. The resins can be cross-linked by thermal or chemical catalysis
methods. The actions to avoid the cross-linking process includes its reformulation.
However, this action compromises its final performance. Moreover, the cost for its
reactivation is high, so it is recommendable kept in confinement, and then applying
an incineration process [6, 7].
17
Environmental pollution not only occurs when polyesters are discarded, but also
during their production and final use. The pollutants are released into the air (gaseous
oxides of carbon, sulfur, nitrogen, as well as particulate solids, and even phosphorus),
into the water (such as salts and petroleum derivatives), and into the soil (chemicals
or toxic salts for animals or plants). Because, they are produced from petroleum,
and their extraction is environmentally expensive. But, the greatest concern arises,
after they have fulfilled their useful life. It is important to mention, that the world
production of polyesters was more than 76 million tons in 2016.
In the manufacturing of polyester products some harmful chemicals are used, for
example carcinogens; which are emitted into the air and untreated water, when they
are not controlled. It is estimated that most of the plastics thrown into the ocean are
polyesters, which come from the textile industry. About 70 billion of oil barrels are
necessaries for to meet the demand of them, mainly those polyester for producing
synthetic fibers [2]. The largest consumers of polyesters are the Asian countries,
where a lot of contaminants have been identified.
As it is known, the chemical reactions involved in the production of unsaturated
polyester resins are irreversible and involve a considerable energy consumption;
nevertheless, changes on the synthesis ratios can adjust chemical compositions. Then,
such resins can be used in many applications.
During the polyester elaboration through to condensation process, the reaction
water is produced (by-product), which needs to be treated as waste, for to avoid
contamination of the flows. Despite of the advances on the chemical recycling, the
waste disposal of such wastes, continue being a contamination problem.
Environmental pollution caused by the textile industry, includes the elaboration of
polyester-based textiles, which consists of many operations. In the polyester dyeing
processes are analyzed the ecological cost, mainly those related to water consumption, energy expenditure (electrical and thermal), carbon dioxide generation and the
effluent toxicity. Wastewater are a serious problem, because they contain several
chemical substances (mainly dyestuffs and surfactants), that are harmful to the flora
and fauna. In a study, concerning to dyeing polyester, the results show that polyester
requires 40 L of water per each kg of dyed material, and more consumption of electrical energy compared to the dyeing of polyamide and cotton. Moreover, thermal
energy required for polyester processing is lower compared to other materials [5].
In the industry, there are a lot of non-crosslinked unsaturated polyester resins,
whose properties decrease when they exceed the storage time, limiting their use in
several applications. The resins can be cross-linked by thermal or chemical catalysis
methods. The actions to avoid the cross-linking process includes its reformulation.
However, this action compromises its final performance. Moreover, the cost for its
reactivation is high, so it is recommendable kept in confinement, and then applying
an incineration process [6, 7].