Chemical recycling of all-polyester vehicle interior solutions
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Materials chemistry (MPMCN), MSc
Publicerad
2023
Författare
Nilsson, Karin
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Increased circularity in the plastic industry is key to decrease oil-dependence and find
more sustainable solutions. In addition to the most widely used method, mechanical
recycling, others are possible which could enable more complex material streams to
be recycled. One such route is chemical recycling where depolymerisation yields
monomers of virgin quality, which can be used to synthesise new polymer chains.
Typical vehicle flooring solutions results in waste consisting of various different
polymeric fibres and foams adhered together, resulting in low recyclability and the
waste is either incinerated or sent to landfills. In response to the low recyclability
of conventional soulutions, new solutions based on polyester and comonomers have
been developed, as the most commonly used polyester, poly(ethylene terephthalate)
(PET), has good recyclability. However, the recyclability of an all-polyester solution,
containing different polyesters and comonomers has not been investigated and
that will therefor be done in this project. In the project, PET, poly(butylene
terephthalate) (PBT), polyester based components for vehicle flooring, and a
complete all-polyester vehicle flooring solution were depolymerised by glycolysis.
Analyses showed that the components in the polyester based vehicle flooring
consisted mainly of either PET or PBT. Glycolysis of neat PBT gave a crystallised
yield of 38 mol% of bis(2-hydroxyethyl)terephthalate (BHET), PET monomer,
compared to 79 mol% from neat PET. Several of the components yielded similar
amounts as neat PET, whilst lower yields were obtained from components which
consisted mainly of PBT, where co-polyester glue appeared most challenging. The
glycolysis of the full vehicle flooring solution yielded white crystalline BHET with a
purity above 97 % and a crystallised yield of 60 mol% confirming that the product
is recyclable.
The origin of the low yield of BHET crystals from PBT, compared to PET, was
further studied using HPLC. It was shown that the yields of BHET in the reaction
solution was significantly higher compared to the crystallised yield after workup.
This indicates that for the flooring, and other PBT containing mixes, the separation
process needs adjusting as compared to that used for neat PET, likely due to
additional byproducts forming. The results showed that the polyester based vehicle
flooring solution, and PET and PBT blends, can be chemically recycled by glycolysis
to BHET which could help close the material loop as a more circular solution.
Beskrivning
Ämne/nyckelord
chemical recycling , depolymerisation , glycolysis , polyester , PET , PBT , BHET , vehicle interior