Investigating the degradation of PET utilizing NHC‐based catalysts and effective reuse of the degradation product as an additive with polyurethane adhesive material

Abstract

Herein we have reported the effective use of palladium‐based systems which contain modified N‐Heterocyclic carbene (NHC) tagged with poly(N‐isopropylacrylamide) (PNIPAM) moiety as an organometallic catalyst. This report involves a comparative study between two catalysts, PNIPAM‐NHC‐Pd (II) complex (catalyst A) and PNIPAM‐NHC‐Pd (0) nanoparticles (catalyst B), to participate in the degradation of poly(ethylene terephthalate) (PET) into its monomer, bis(2‐hydroxyethyl terephthalate) (BHET) through glycolysis with ethylene glycol (EG). Glycolysis of the PET was carried out at different temperatures (170, 175, 180, 185, and 190°C) and times (6 and 24 h) where optimum results were obtained while glycolysis was performed at 180°C for 24 h using catalyst B. The investigation of the glycolysis product through NMR, ATR‐IR, TGA, and DSC proved the formation of BHET as the main product. To ensure the effective recycling of the PET and further value additions, the obtained glycolysis product, BHET was further transformed into its dibenzoylated derivative, bis(2‐([4‐Butoxy benzoyl]oxy)ethyl) terephthalate (BBET) by successive benzoylation using 4‐butoxybenzoyl chloride. The obtained BBET was used as an additive along with the commercial polyurethane‐based adhesive (CPU), and its effect on the properties of CPU was investigated using differential scanning calorimetry (DSC) studies.

Synthesis of new sustainable polyester‐type hydrogels from chemical recycled poly(ethylene terephthalate) products applied on the removal of indigo carmine dye

“…In the region of 4 to 5 ppm there is the presence of peaks corresponding to the protons of hydroxyl originating from the glycerol moieties inserted in the BDHPT. Similar results are presented by Mohammadi et al, for the glycolysis of PET with EG 16,17,24–26 . As the product was not purified, there is a mixture of derivatives of the PET chain, EG and unreacted glycerol, which makes it difficult to integrate the signals and accurately elucidate the structures forms in the depolymerization of wPET 23 …”

“…Similar results are presented by Mohammadi et al, for the glycolysis of PET with EG. 16,17,[24][25][26] As the product was not purified, there is a mixture of derivatives of the PET chain, EG and unreacted glycerol, which makes it difficult to integrate the signals and accurately elucidate the structures forms in the depolymerization of wPET. 23 The products of all reaction times were analyzed through ATR-FTIR spectroscopy (Figure 3).…”

Envisioning a BHET Economy: Adding Value to PET Waste

“…The addition of 1% BBET in a commercial PU adhesive quickly nucleated the crystallization. Higher incorporations failed to nucleate as rapidly, making 1% the best nucleating ratio [156]. The authors compared PUs with BHET to those with bis(2-hydroxyethyl) terephthalamide (BHETA).…”

“…The addition of 1% BBET in a commercial PU adhesive quickly nucleated the crystallization. Higher incorporations failed to nucleate as rapidly, making 1% the best nucleating ratio [156]. He et al modified graphene oxide (GO) with BHET to act as a functional crosslinker in composite WPUs with high conductivity.…”

Transparent Superhydrophobic Coatings of Silica Nanoparticles Using Functionalized Polyurethanes

“…[20] As reported in this paper, we have synthesized the linear polyurethane clicked with a single phenyl moiety on both ends of a linear chain via click chemistry. Furthermore, the effect of an additive as plasticizer on those polyurethanes has been studied [21] using DSC. Since effective adhesions involve noncovalent interactions, a study on the specific interaction of silica nanoparticles and synthesized polyurethanes is required to understand their usability.…”