Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly ...Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly contributes to the loss of valuable resources and environmental pollution.Thermoplastics may be readily recycled,but because of their flammability,large amounts of flame retardant(FR)ad-ditives are required for many applications.This results in a significant volume of FR polymeric wastes too,particularly halogenated plastics,which are subject to severe recycling regulations.In general,ther-moplastics containing FRs are raising concerns,as their effective recycling is strongly influenced by the chemical composition,additive content,and physicochemical characteristics of the waste stream.The recycling of FR thermosets is even more challenging due to their crosslinked and cured nature,which makes them resistant to melting and reprocessing.In many cases,traditional mechanical recycling meth-ods,such as grinding and melting,are not applicable to thermosetting polymers.Current recycling meth-ods do not always consider the recovery of the thermosetting/thermoplastic matrix and the presence of toxic FRs in the polymer network.Sorting and solvent washing treatment are important steps,which are usually performed before recycling the FR polymeric waste to reduce contamination in the following steps.展开更多
Flame-retarded polymers,such as polyester textiles and sheets,are attracting attention with regard to their sustainability.Mechanical recycling is currently the most frequently used technique for improving the circula...Flame-retarded polymers,such as polyester textiles and sheets,are attracting attention with regard to their sustainability.Mechanical recycling is currently the most frequently used technique for improving the circularity of plastics.However,one complication of mechanical recycling is associated with the(still)inevitable mixtures of polymers and additives,which can influence material stability and significantly de-teriorate the mechanical properties of recycled products.In this study,we aim to specifically investigate the interactions between mixtures of phosphorus flame retardants(FRs)in polyethylene terephthalate(PET)and evaluate their potential role in the mechanical recycling of melt-spun fibers.Two highly rel-evant commercial FRs,namely a DOPO-derivative(DOPO-PEPA or DP)and Aflammit PCO 900(AF),are added to PET compounds as additives using a melt compounder.The melt stability of PET/FR compounds over extended processing time is assessed by chemical,thermal,and rheological measurements.DP shows a molecular lubrication effect,lowering the melt viscosity of PET,while AF promotes chemical changes(i.e.,chain branching/crosslinking).Interestingly,a PET compound containing hybrid mixtures of DP/AF 20/80(wt.%/wt.%)shows the most stable behavior at high temperatures under both nitrogen and air at-mospheres,thus showing a synergistic effect.Most importantly,in a recycling scenario,the stabilization effect persists at diluted concentrations below the typical FR contents in PET.Multiple extrusion cycles are used to assess the repeated processing behavior of the compounds,and the mechanical properties and fire behavior of melt-spun fibers are compared before and after recycling.The results reveal that DP can maintain the mechanical performance of recycled PET/FR fibers,even if it is mixed(contaminated)with AF.展开更多
基金the Italian Ministry of Ed-ucation and Research,PON R&I 2014-2020-Asse IV“Istruzione e ricerca per il recupero-REACT-EU”-Azione IV.6-“Contratti di ricerca su tematiche Green”,for the financial support concerning his employment contractThe work was partially supported by funds from the Zuercher Stiftung fuer Textilforshung(Winterthur,Switzerland).
文摘Polymers are indispensable to humans in different applications due to their ease of manufacturing and overall performance.However,after a material lifetime,there is a large amount of polymer-based waste,which greatly contributes to the loss of valuable resources and environmental pollution.Thermoplastics may be readily recycled,but because of their flammability,large amounts of flame retardant(FR)ad-ditives are required for many applications.This results in a significant volume of FR polymeric wastes too,particularly halogenated plastics,which are subject to severe recycling regulations.In general,ther-moplastics containing FRs are raising concerns,as their effective recycling is strongly influenced by the chemical composition,additive content,and physicochemical characteristics of the waste stream.The recycling of FR thermosets is even more challenging due to their crosslinked and cured nature,which makes them resistant to melting and reprocessing.In many cases,traditional mechanical recycling meth-ods,such as grinding and melting,are not applicable to thermosetting polymers.Current recycling meth-ods do not always consider the recovery of the thermosetting/thermoplastic matrix and the presence of toxic FRs in the polymer network.Sorting and solvent washing treatment are important steps,which are usually performed before recycling the FR polymeric waste to reduce contamination in the following steps.
文摘Flame-retarded polymers,such as polyester textiles and sheets,are attracting attention with regard to their sustainability.Mechanical recycling is currently the most frequently used technique for improving the circularity of plastics.However,one complication of mechanical recycling is associated with the(still)inevitable mixtures of polymers and additives,which can influence material stability and significantly de-teriorate the mechanical properties of recycled products.In this study,we aim to specifically investigate the interactions between mixtures of phosphorus flame retardants(FRs)in polyethylene terephthalate(PET)and evaluate their potential role in the mechanical recycling of melt-spun fibers.Two highly rel-evant commercial FRs,namely a DOPO-derivative(DOPO-PEPA or DP)and Aflammit PCO 900(AF),are added to PET compounds as additives using a melt compounder.The melt stability of PET/FR compounds over extended processing time is assessed by chemical,thermal,and rheological measurements.DP shows a molecular lubrication effect,lowering the melt viscosity of PET,while AF promotes chemical changes(i.e.,chain branching/crosslinking).Interestingly,a PET compound containing hybrid mixtures of DP/AF 20/80(wt.%/wt.%)shows the most stable behavior at high temperatures under both nitrogen and air at-mospheres,thus showing a synergistic effect.Most importantly,in a recycling scenario,the stabilization effect persists at diluted concentrations below the typical FR contents in PET.Multiple extrusion cycles are used to assess the repeated processing behavior of the compounds,and the mechanical properties and fire behavior of melt-spun fibers are compared before and after recycling.The results reveal that DP can maintain the mechanical performance of recycled PET/FR fibers,even if it is mixed(contaminated)with AF.
