Recycling of PVC tarpaulin reinforced with PET through glycolysis using betaine, a bio-based catalyst

doi:10.1016/S1872-2067(25)64867-4

Abstract

Abstract:

Polyvinyl chloride (PVC) tarpaulins reinforced with poly(ethylene terephthalate) (PET) fibers are widely used in various industrial applications. However, the increasing demand for recycling PVC tarpaulin waste poses challenges because of the difficulty in separating the two different plastics. In this study, we investigated the possibility of recycling PVC and PET through the glycolysis of PET. The milled PVC tarpaulin underwent a glycolysis process, selectively depolymerizing the PET fibers into water-soluble bis(2-hydroxyethyl) terephthalate (BHET), while the PVC was removed by filtration. The PET fibers were selectively depolymerized by 77.6% after reacting at 190 °C for 2 h in the presence of 0.5% (w/w) betaine as a catalyst, quantitatively yielding BHET. During glycolysis, the physical appearance of the PVC changed because of leaching of the plasticizer, however, no dechlorination or shortening of the PVC polymer was observed. Interestingly, additives in PVC, such as CaCO₃ and CZ-stabilizer, act as catalysts for glycolysis, thereby enhancing PET depolymerization. The recovered PVC, when blended into a PVC formulation, maintained its mechanical properties and appearance up to 40 parts per hundred resins in roll-mill-processed sheets. In addition, ethylene glycol, which is used as a solvent in glycolysis, can be reused up to three times without the additional removal of BHET. This study demonstrated an industrially applicable method for simultaneously recycling PVC and PET from widely used tarpaulins.

Key words: Plastic recycling, Tarpaulin, Polyvinyl chloride, Poly(ethylene terephthalate), Glycolysis

Jae Kyun Kim, Yejin Won, Jeonghoon Yoon, Kyung Min Lee, Yeyoon Choi, Dong Hyun Kim, Kyoung Heon Kim. Recycling of PVC tarpaulin reinforced with PET through glycolysis using betaine, a bio-based catalyst[J]. Chinese Journal of Catalysis, 2026, 81: 366-379.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(25)64867-4

https://www.cjcatal.com/EN/Y2026/V81/I2/366

Figures/Tables 9

Scheme 1. Overall scheme of recycling of PVC tarpaulin fibered with PET by glycolysis using betaine, a bio-based catalyst.

Fig. 1. Glycolysis of PET fiber using betaine as a catalyst. (a) Comparison of the reaction profiles for the BHET production during the glycolysis reaction with the addition of betaine and without betaine. (b) Effect of the concentration of betaine on the conversion of PET based on weight loss after glycolysis reaction. Experimental data are expressed as mean ± SD from three independent experiments. (c) Linear regression between PET conversion and BHET yield based on the theoretical maximum of BHET from PET fiber.

Scheme 2. Proposed mechanism of PET glycolysis catalyzed by betaine, adapted with permission from Ref. [18]. Copyright 2021, American Chemical Society. (a) Optimized interaction structure showing all non-covalent interactions between betaine, ethylene glycol (EG), and the PET ester bond. (b) Schematic diagram of the stepwise mechanism, where the quaternary ammonium group of betaine activates the PET carbonyl oxygen and the carboxylate group enhances EG nucleophilicity, facilitating nucleophilic attack and ester bond cleavage leading to BHET formation.

Fig. 2. Glycolysis of PET fiber contained in tarpaulin. (a) Experimental scheme of glycolysis of PET contained in tarpaulin and recovery of PVC from tarpaulin glycolysate. Effect of betaine concentration (b) and tarpaulin loading (c) on BHET yield after glycolysis of PET fiber contained in tarpaulin. (d) Effect of addition of PVC on BHET yield after glycolysis of PET fiber. Experimental data are expressed as mean ± SD from two independent experiments.

Fig. 3. Glycolysis of PET fiber supplement with PVC components. Chemical glycolysis was performed in a flask reactor at 190 °C and 500 rpm with 0.3% (w/w) PET fiber loading, using PVC components as a catalyst. Control experiments were conducted without any catalyst, whereas experiments with the PVC components or betaine were conducted at a concentration of 100 mg/L. Experimental data were expressed as mean ± SD from three independent experiments. CZ, calcium-zinc stabilizer; CaCO3, calcium carbonate; PVC, PVC polymer; DINP, diisononyl phthalate; LPW, low-polymer PE wax; SA, stearic acid.

Fig. 4. SEM images of PVC recovered from tarpaulin and tarpaulin glycolysate. SEM images of PVC recovered from tarpaulin before glycolysis (a-d) and after glycolysis (e-h). Images of surface (a,b) and cross-section (c,d) of PVC recovered from milled tarpaulin. Images of surface (e,f) and cross-sectio (g,h)n of PVC recovered from tarpaulin glycolysate.

Fig. 5. Effect of amount of PET removal through glycolysis of PET contained in tarpaulin on recyclability of PVC recovered from tarpaulin glycolysate. Surface images of PVC sheets produced from: standard mixture (a), standard mixture supplemented with milled tarpaulin (b), standard mixture supplemented with solid obtained from tarpaulin glycolysate after removal of 50% of PET (c), and standard mixture supplemented with solid obtained from tarpaulin glycolysate after removal of 92.7% of PET (d). Effect of PET conversion of supplemented solids on Tensile strength (e) and Elongation (f) of PVC sheet. Experimental data are expressed as mean ± SD from five independent experiments.

Fig. 6. BHET yield from the four rounds of Glycolysis of PET contained in tarpaulin using re-used EG. Experimental data are expressed as mean ± SD from two independent experiments.

Table 1 Cost for manufacturing PVC and r-PVC.

Category	Virgin PVC	r-PVC
Material cost	1.01	PVC tarpaulin waste		use 1 kg
		betaine	$ 0.01/processing	use 5 g; $ 1.9 per kg betaine hydrochloride
		ethylene glycol	$ 0.54/processing	use 0.54 kg to supplement process loss; ^a$ 1.0/kg per kg EG
			$ 0.66 per production of 1 kg r-PVC
Processing cost	—	$ 0.80 ^c per production of 1 kg r-PVC
		heating (electricity)	$ 0.34-0.71/processing		based on 1 kg of tarpaulin with one run of glycolysis
		Milling	$ 0.05-0.10/processing
		solid-liquid separation	$ 0.01-0.02/processing
		washing	$ 0.03-0.06/processing
		drying	$ 0.03-0.1/processing
		processing subtotal ^b	$ 0.55-1.19 per production of 1kg r-PVC
Total cost	1.01	$ 1.46 per production of 1kg r-PVC

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