Does co-combustion of PVC and other plastics lead to enhanced formation of PCDD/F?

Co-combustion of PVC together with further common plastics were performed in a gramme scale micro combustion apparatus to investigate whether PCDD/F-formation is influenced hereby. Materials applied were polyethylene (PE), polystyrene (PS), polyurethane (PUR), epoxy- and phenol/formaldehyde resin (Epox and Ph). These co-combustion experiments yielded mainly PCDF in the high μg/kg range. Correlation between structural features of co-combusted plastics and PCDD/F formation could be obtained for PE and PS, with PS showing higher values due to its aromatic sidegroups. More detailed investigations on the combustion kinetics revealed that HCl and hydrocarbons are not formed at the same time during burning process even in the case of PVC. Therefore, combustion experiments were also performed in the presence of additional HCl usually yielding higher amounts of PCDD/F. Further experiments showed that PCDD/F formation does not depend on the distance between the co-combusted materials indicating that PCDD/F-formation takes place in a gas phase reaction exclusively.