Characterization of Rigidpolyurethane Foam Preparedfrom Recycling Of
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PP Periodica Polytechnica Characterization of Rigid Chemical Engineering Polyurethane Foam Prepared from Recycling of PET Waste 59(4), pp. 296-305, 2015 DOI: 10.3311/PPch.7801 Abolfazl Ghaderian1, Amir Hossein Haghighi2*, Creative Commons Attribution b Faramarz Afshar Taromi3, Zizi Abdeen4**, Ali Boroomand2,5, Seyyed Mohammad-Reza Taheri6 research article Received 08 November 2014; accepted after revision 26 May 2015 Abstract 1 Introduction Poly (ethylene terephthalate) (PET) waste bottles were recy- Poly (ethylene terephthalate) (PET) is a thermoplastic poly- cled to prepare RPUFs (rigid polyurethane foams) by using ester widely used in manufacturing of high-strength fibers, propylene glycol (PG) in different glycol/polymer molar photographic films and soft drink bottles [1]. With increasing ratios. The glycolysis products were characterized, after PET consumption as packaging material, the effective utiliza- that, they reacted with poly methylene diphenyl diisocyanate tion of PET waste has received wide attention for the preserva- (PMDI) in the presence of blowing, co-blowing and second tion of resources and protection of the environment [2]. Since blowing agents to produce the RPUFs. The prepared foams PET waste does not create hazards to the environment, its vol- were characterized and compared to foam that is produced ume and cost of landfilling are very high. However, several by original polyol. It was found that the glycolysis products methods have been proposed for recycling waste PET [3-7]. have possibility for the fabrication of RPUFs with proper Generally, different methods for the chemical recycling of PET properties depending on the blowing agent type and density, could be categorized in five main branches including: 1) gly- also they have similar thermal stability compared to that one colysis, 2) methanolysis, 3) hydrolysis, 4) ammonolysis and 5) produced by original polyol. This may provide an advantage aminolysis [8]. It is suggested that the most attractive method in the future planning for recycling of PET bottles to enhance is chemical glycolysis into the corresponding monomers or raw the mechanical and thermal properties of PU. chemicals that could be reused for the production of plastics or other advanced materials [9]. The glycolysis method makes Keywords it possible to employ very low amounts of reactants as well Recycling, poly (ethylene terephthalate) waste, rigid polyure- as application of lower temperatures and pressures in contrast thane foams, glycolysis, polyester polyols with other methods such as supercritical methanol and thermal degradation [3-7], while hydrolysis under acidic or basic con- ditions may cause corrosion and pollution problems [10, 11]. Glycolysis involves the insertion of olefin-glycol within PET chains to synthesis bis (2-hydroxyolefin) terephthalate, which is a substrate for PET synthesis. The glycols usually used for PET glycolysis are ethylene glycol (EG), diethylene glycol 1 Young Researchers and Elite Club, Shiraz Branch, Islamic Azad University, Shiraz, Iran (DEG), propylene glycol (PG) and dipropylene glycol (DPG). However, EG has been reported as the most reactive olefin- 2 Department of Polymer Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran glycol for PET glycolysis [12, 13]. The glycolysis product can 3 Department of Polymer Engineering, Amir Kabir university of Technology, be used in the synthesis of unsaturated polyester resins, ure- Tehran, Iran thane oils [14], dimethacrylated oligoesters, epoxy resins [15], 4 Petrochemical Department, Egyptian Petroleum Research Institute, Nasr City, polymer concretes [16, 17] and rigid polyurethane foams [18]. Cairo, Egypt RPUFs are commonly available heat insulation materials with 5 Department of Chemical Engineering,University of Tehran, Kish International the lowest thermal conductivity among foamed polymers used Campus, Kish, Iran commercially [1, 19]. These foams are used for example for 6 Physics Department, Institute for Advanced Studies in Basic Sciences outer wall insulation of apartment houses, factory shops, office (IASBS), Zanjan, Iran rooms, cold stores and pipelines [20]. The broad application * First corresponding author, e-mail: [email protected] is the result of their very good heat insulation properties, low ** Second corresponding author, e-mail: [email protected] density and relative ease of specific properties modification 296 Period. Polytech. Chem. Eng. A. Ghaderian et al. Table 1 List of PET glycolysis products Glycol Glycol/PET Glycol/PET Catalyst/PET Product code Catalyst Temperature (°C) type molar ratio weight ratio weight ratio PG2.52m PG 2.52 1 Zn(O2CCH3)2 0.5 200-210 PG2m PG 2 0.79 Zn(O2CCH3)2 0.5 200-210 PG1m PG 1 0.396 Zn(O2CCH3)2 0.5 200-210 depending on the use as well as on adjusting technology of pro- 220W are used as polyols, respectively that include additives. duction and application in the place of use. Isocyanates, poly- PMDI is used with an amount of 32% NCO. ols, foaming and auxiliary agents are the main components for polyurethane foams synthesis. Polyester polyols are an impor- 2.2 Method tant raw material for the production of insulation panels [21]. 2.2.1Glycolysis of PET wastes These foams derive their excellent flammability performance PET wastes were initially immersed in 1% (w/v) sodium from the high content of aromatic groups which results from hydroxide solution for 1 h to remove surface impurities and high aromaticity polyester polyols. In some regions, polyester subsequently rinsed with water and dried in an oven at 80ºC. polyols’ applications are increasing for the same reason as well The pre-washed PET and the propylene glycol PG, at different as for their relatively low cost. The latter is ultimately con- molar ratios of PG/PET, as, 1/1, 2/1 and 2.52/1 respectively, in nected to the origin of aromatic polyester polyols which are the presence of 0.5% (w/w) zinc acetate were glycolysed. The produced from recycled PET bottles, fibers, and x-ray film glycolysis reactions were conducted in a 1 liter three-necked sheets, or DMT process waste. Azim et al. glycolyzed PET reactor equipped with a reflux condenser, a thermometer and wastes using trimethylol propane and pentaerytheriol to pro- a mechanical steel stirrer in an oil bath in nitrogen gas atmos- duce hydroxyoligomers to producing RPUFs with a density of phere for 15 min. in initial time of the reaction, at 200-210 range 55-65 kg/m3. They made separation and purification for °C for about 4 hours. Upon completion of the reaction, the solvent and glycolysis agent by using a very expensive pro- glycolysed products were allowed to cool down to the room cedure that consume a lot of time [22]. This work, primarily temperature under nitrogen atmosphere, Table 1. A schematic discusses a potential use of the recycled PET products in prepa- of used procedure for the glycolysis of waste PET is depicted ration of RPUFs without separation and purification of solvent in Scheme 1. and glycolysis agent. The amount ratio of glycols/ PET on PET glycolysis process was studied. The glycolysis products are characterized using GPC, FTIR and viscometry analysis meth- ods. The characteristics of RPUFs were examined by FTIR, SEM, TGA, thermal conductivity coefficient and compressive strength, moreover, their density. The properties of foams were compared with that foam made with original polyol. 2 Experimental 2.1 Materials Post consumer PET beverage bottles were crushed to small pieces after washing them with acetone and methanol to removing an adhesive and other materials. PG and zinc acetate Scheme 1 Schematic of Waste PET glycolysis process using PG as glycols. were obtained from Panreac Co. The required material to pro- duce RPUFs such as, PMDI, activators and surfactant agent were commercial grades and were used as received. But with 2.2.2 Preparation of RPUFs respect to cyclopentane, dichloroethane, and all materials used RPUFs were produced in a two steps. First, the prepared for analysis, were purchased from Merck Co., and were used polyol was mixed with triethyl amine (TEA) and dibutyltin as received. FMHC and FMR11 foams that were produced by dilaurate (DBTDL) as catalysts as well as silicone surfactant Urethane Co (Iran). are commercial and a very common. They and the blowing agent. The prepared mixture was allowed were used for comparison with prepared samples in this work. to mix for about one minute at a stirring rate of 2000 rpm to FMHC and FMR11, have HCFC-141B and R11 as blowing obtain a homogenous resin. Afterward, PMDI was added to agents, respectively. Also, URONOLE 210R, and URONOLE the prepared polyol mixture and was allowed to stir with a Recycling of PET Waste 2015 59 4 297 constant stirring rate of 2000 rpm for about 10 seconds. Sub- 1100, which included a Refractometer Index Detector (RID) sequently, the prepared mixture was discharged into an open and a set of three high resolution PL gel 10μm Agillent col- mold (15×15×7 cm3) for free-rise foams preparation process. umns (500,103,104Å). THF was used as the solvent with a flow The foams were removed after 30 min and allowed to condition rate of 1ml/min, while monodisperse polystyrene was used as at room temperature for 16 h before further characterization. the reference. Also, the density of the RPUFs was measured About 10 weight% of PMDI more than Stoichiometries ratio according to ASTM D-1622. The size of the specimen used for was used for the completion of the reaction. The basic formu- density calculations was 30 × 30 × 30 mm3. To normalize the lation used for the synthesis of RPUF is presented in Table 2. density results, the density of five specimens per each of the And, simultaneous with expanding the reaction time and after foam was calculated and the results were averaged. The mor- two weeks the core density of foams was determined. phology of the RPUF samples was studied with AIS 2100 SEM that was made by Seron.