Synthesis of polyurethane resin from chemical recycling of PET [polyethylene terephtalate] waste bottle

The feasibility of synthesizing polymer from the chemical recycling of waste polyethylene terephthalate (PET) bottles for the production of wood finishing material was investigated. The waste PET was subjected to a two-stage reaction. Initially, the cleaned PET pellets were reacted with amino propanol under reflux at three different ratios: 1:3, 1:4 and 1:5 PET to amine ratio in the presence of sodium acetate as catalyst. After the four-hour reaction, a yellowish to brownish homogenous solution was formed as end-product. This product turned creamy white at room temperature. The product was then subjected to the second reaction stage where it was reacted with E-caprolactone at 1:20 ratio, with dibutyltindilaurate (DBTDL) as catalyst. The process was done through refluxing for three hours in the presence of nitrogen. This yielded an orangebrown homogenous product at room temperature. FT-IR analysis was then done to characterize the products from the two-stage reaction. The FT-IR spectra of the synthesized first-stage product showed the presence of alcohol, amines/amide and aromatic ring functional groups characteristic of bis (3-hydroxy propyl) terephthalamide (BHPTA). On the other hand, the FT-IR spectrum of the synthesized second stage product showed the presence of asymmetric and symmetric CH2 groups, ester, amide, carbonyl and aromatic ring functional groups characteristic of polyol. A test was done to determine the product's suitability as wood finish. The synthesized polyol was mixed with a catalyst of two-component commercial finishes: polyurethane (PU) and acrylic urethane (AU) at 1:1 (w/w) ratio and thinned with xylene. The finish was then applied on wood samples via brushing, then allowed to cure for 24 hours. The gloss and thickness of applied formulated finishes were then recorded. The applied formulation showed a film-forming finish similar to the two commercial PU and AU. Film thickness ranged from 61.80 to 76.40 micron and gloss ranged of 28.4 to 94.6 GU at 60 deg incidence angle. Further, synthesized polyol was formulated into polyurethane finish by mixing with isophorone diisocyanate, DBTDL and xylene showed similar result. Formulated finish applied on Gmelina arborea Roxb showed comparable color, lower gloss, better adhesion and lower gouge and scratch resistance than commercial PU.