Poly(ethylene terephthalate) (PET) waste from soft drink bottles was incorporated into palm olein alkyd to produce new polyol for use in polyurethane resins as surface protection on metal surfaces.
Alkyd was prepared from palm olein, glycerol and phthalic anhydride. PET underwent simultaneous glycolysis and transesterification reactions with the alkyd. Varying the amount of PET has led to polyols with different viscosities. Polyurethane resins were produced by reacting the polyols with toluene diisocyanate. The resins were coated on mild steel panels and cured. Performances of the cured films were tested.
The polyurethanes (PU) resin cured to a harder film with better thermal stability. Films showed excellent adhesion properties, while higher content of PET exhibited higher pencil hardness, better water, salt, acid and alkali resistance.
Other vegetable oils could also be used. The alkyd structure could be changed by formulation to have different functionality and the ability to incorporate higher amount of PET waste. Rate of glycolysis of PET could be increased by higher amount of ethylene glycol.
This method has managed to use waste PET in producing new polyol and PU resins. The cured films exhibit good mechanical and chemical properties, as well as excellent adhesion and thermal stability.
The non-biodegradable PET has created environmental pollution problems connected to littering and illegal landfilling. It has become necessary to pay greater attention to recycling PET bottles for obtaining valuable products.
This approach is different from the earlier reports, where PET was recycled to recover the raw materials.
Conflicts of interest: There is no conflict of interest to declare.
The authors appreciate the University of Malaya for monetary funding (PG311-2016A) and Impact-Oriented Interdisciplinary Research Grant (IIRG006A-19IISS).
Adamu, A.A., Muhamad Sarih, N. and Gan, S.N. (2021), "Polyurethane resin derived from polyol of palm olein and recycled poly(ethylene terephthalate)", Pigment & Resin Technology, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/PRT-06-2020-0056
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