Reaction to fire of recycled poly(ethylene terephthalate)/polycarbonate blends

On the role of flame retardants in mechanical recycling of solid plastic waste

Flame retardants are used in a wide range of plastics to extend the time-of-escape from fires. By definition, they are designed to perform this task only in case of a fire, which is then automatically the end of the plastic's lifetime. However, not all flame retardant plastic products are eventually set on fire, which is why they are abundant in plastic waste, potentially interfering with the mechanical recycling systems in place. To date, there has been little information on the influence of flame retardant additives during the mechanical recycling of solid (thermo)plastic waste. This contribution provides a comprehensive overview of the state of the art concerning the mechanical recycling of flame retardants containing polymers and plastics. In a first part, this review discusses the effect of mechanical melt reprocessing on the flame retardant properties of different recycled thermoplastic polymers, addressing questions whether the flame retardant additives are still present and effective after recycling and whether they interfere with the mechanical recycling itself. Special attention is paid to Waste from Electrical and Electronic Equipment containing flame retardants. A second part of the review lists several upgrading strategies for common polymeric waste streams that consist of adding virgin flame retardants to recycled plastics with the purpose of bringing an additional value to the compound.

Thermal characterization of reactive blending of 70PC/30PET mixtures prepared in the presence/absence of samarium acetylacetonate as a transesterification catalyst

Poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends were prepared in the presence and absence of samarium (III) acetylacetonate hydrate [Sm(acac)3] used as an ester-ester exchange reaction catalyst. Differential scanning calorimetry (DSC) and thermogravimetric analysis/differential thermogravimetry (TGA/DTG) were used to study the variations in the thermal properties of blends before and after reactive blending. Solubility measurements in methylene chloride (CH2Cl2) and infrared spectroscopy were also employed to highlight the structural changes that occurred during mixing in the presence of Sm(acac)3. The DSC results showed two distinct transition temperatures (Tg) for all the compositions. Also, the Tg values of components were shifted compared to the parent polymers in both the blends prepared with and without catalyst. Further, the Tg of the PET-rich phase was displaced to higher temperatures and that of the PC-rich phase showed a tendency to diminish as the catalyst’s concentration increased. At the same time, the melting temperature (Tm) of the PET-rich phase was shifted to lower temperatures. The evaluation of the compositions of the PC- and PET-rich phases using Wood’s equation showed a strong dependence on the catalyst concentration. Furthermore, the thermogravimetric thermograms showed that the thermal stability of the blends was between those of the homopolymers, and evidenced a net improvement relatively to the neat PET. The obtained results confirmed the aptitude of Sm(acac)3 to promote exchange reactions between PC and PET, and to achieve their compatibilization through an interfacial copolymer synthesis process.