Chemical Recycling of PET Waste from Soft Drink Bottles to Produce a Thermosetting Polyester Resin Dayang Ratnasari Abu Bakar a , Ishak Ahmad a , Anita Ramli b a School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia. b Advanced Materials Centre SIRIM Berhad, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, Kulim 09000, Kedah, Malaysia.  Corresponding address: gading@pkrisc.cc.ukm.my Abstract : Poly(ethylene terephthalate) or PET waste from soft drink bottles was subjected to recycling by glycolysis. Characterization and identification were performed by the conventional method of hydroxyl and acid values, Differential Scanning Calorimetry (DSC) and Frourier Transform Infra Red (FTIR) techniques. It was found that the glycolysed product consists mainly of bis(hydroxyethyl) terephthalate (BHET) and its dimer. The glycolysed product was later polyesterified with maleic anhydride and then cross linked with styrene to produce a formulation for the resin. FTIR spectra also revealed the cross linking process between the polyester chain and styrene monomer, resulted in a final product with high densities of cross-linkages to form a network polymer. The cured resin exhibited thermal stability due to its fully curing. Keywords: Poly(ethylene terephthalate), polyester resin, glycolysis Received : 30.06.05; accepted : 25.04.06 Introduction Poly(ethylene terephthalate) (PET) is one of the most valuable versatile engineering plastics which is used especially in the manufacturing of soft drink bottles. With increasing application and decreasing prices, PET became the symbol of disposability in consumerism and hence a noxious material of concern in the relatively recent environmental protection issues, as it is highly resistance to atmospheric and biological agents. Therefore, the necessity of finding a simple economic route for the recycling of waste PET is an important practice for sustainable recycling and contributes to the conservation of raw petrochemical products and energy. Most of the past research concerned, focused on the production of products obtained by using glycolysis of PET such as unsaturated polyester resin, polyurethane foam, polymer concrete and polymer composites with reinforcement [1-4]. This paper reports on the possibility of the unsaturated polyester resin derived from PET soft drink bottles through chemical recycling. This preliminary study focuses on the characterization of products from the glycolysis reaction and to the formation of the resin by monitoring its average molecular weight as well as comparing it to a commercial UPR resin, the FTIR spectrum which can justify the synthesized resin as unsaturated polyester and finally an insight on the curing of the resin by FTIR spectrum and DSC scan. Experimental Materials Post consumer PET soft drink bottles were cut into small pieces (6 mm x 6 mm). For the glycolysis of PET, ethylene glycol and zinc acetate supplied by Ajax Chemicals Ltd and Riedel-de Haën respectively were used. In preparing the unsaturated polyester resin, maleic anhydride (Aldrich Co.), hidroquinon (Merck) was used to prevent premature curing and styrene monomer from Fluka Chemika as the cross- link agent. Methyl ethyl ketone peroxide (MEKP) and cobalt octoate supplied by Fluka AG, were used as initiator and accelerator, respectively, for curing the polyester resin. Glycolysis of PET soft drink bottles PET wastes and ethylene glycol (PET:EG = 1:4 w/w) together with 0.5% zinc acetate based on weight of PET as catalyst were charged to a four- necked round bottom flask of 500 ml capacity, connected to a reflux condenser, N 2 gas inlet, thermometer and stirrer. The reaction was carried out under reflux in nitrogen atmosphere at 180-190 C for 7 hr. Then, boiling water was slowly added to the Malaysian Journal of Chemistry, 2006, Vol. 8, No. 1, 022 - 026