PRODUCTION OF FLEXIBLE POLYURETHANE FOAM FROM COMMERCIALLY SOYBASED PRECURSOR

Transcription

1 MATERIALS SCIENCE and TECHNOLOGY Edited by Evvy Kartini et.al. PRODUCTION OF FLEXIBLE POLYURETHANE FOAM FROM COMMERCIALLY SOYBASED PRECURSOR Flora E. Firdaus Department of Chemical Engineering, Jayabaya University, Jl. Pulomas Selatan Kav. 23, Jakarta 13210, Indonesia. ABSTRACT Flexible polyurethane foam has been prepared from soy oil-derived polyol. The polyol as precursor was synthesized by hydroxylation reaction of epoxide and peracetic acid using respectively methanol and ethylene glycol. The obtained soy oil based polyol was blended to synthetic polyol to be reacted with TDI:MDI (80:20), and water. The effects of the amount of methanol and ethylene glycol on foam properties (i.e. density, curing time, water absorbency and average pore diameter) were studied. Keywords : polyurethane, soy, polyol, foam characteristics INTRODUCTION Utilization of renewable natural resources to replace petroleum for a variety of current applications tends to increase. This was triggered by a variety of considerations such as environment, availability, and lower prices.[1]-[2] Soybean and its products, being renewable and readily biodegradable, are the alternative feed stocks for the production of soy-based polyol for polyurethane products which have been used in many commercial applications; as thermosetting plastics, plasticizers, and additives in lubricants.[3]-[5] A wide range of polymer is available, however currently most of the commercial polyols are petroleum based. The structure, molecular weights and functional groups of polyols play vital roles in determining the properties of the final urethane polymers; which are degree of crosslinking has achieved in the polymer formed in the reaction with isocyanate. For flexible foam a lesser degree of crosslinking is needed.[6] Polyurethanes are the result of exothermic reaction of isocyanates with polyol, which unwanted byproducts are given off because the raw materials reacts completely. Within a short time interval, a liquid mixture of relatively low molecular is transformed into solid polymer. The process involves a rapid exotherm, change in density, and sudden stiffening due to urea microphase separation.[7] It has a range of physical properties of a very wide, from soft semi-flexible, flexible to rigid, then its use is also a variety of applications.[8] The mechanical properties displayed by flexible polyurethane foam which possesses a cellular structure that is created by the expansion of a blowing agent depend essentially on the structure and morphology of the cells.[9]-[10]

2 Materials Science and Technology EXPERIMENTAL METHOD Materials Soybean oil of RBD (Refined, Bleached, Deodorized) was obtained from PT Variatama Jakarta with Iodine value 53,89 gram Iod/100 gr sample, viscosity 65,5278 cps, acid value 0,024 mgr KOH/ gr sample, hydrogen peroxide from PT Brataco Chemika, acetic acid from Merck Germany, and sulphuric acid from Tedia Company, Inc. All materials were used as received without further purification. Soy polyols was synthesized in laboratory by using epoxidation routes with peracetic solvent in situ method. The production of polyurethane was using several ingredients; soypolyol, isocyanate; the mixture of TDI;MDI (80:20), water, surfactant. The formula was summarized in table 1. Preparation of Soy based Polyol Hydroxyl groups have been introduced through two-step synthesis involving epoxidation of the unsaturated sites with acetic acid and hydrogen peroxide, followed by epoxy ring opening with methanol and ethylene glycol, both reactants taking role as a chain extender/ crosslinker. The experiments were carried out in a 500 ml three necked round bottom flask which were equipped with a thermometer, mechanical stirrer. The whole apparatus was placed in a water-bath to maintain the temperature at range 110 ± 0,5 0 C which was measured inside the flask, and also inside the water bath. The obtained product was allowed to cool to room temperature. 242 Table 1: Formulation of Synthesizing Polyurethane Formulation Polyol Distilled water TDI:MDI Silicone Preparation of Flexible PU Foam The procedure for the preparation of a flexible polyurethane foam involves ongoing process at the interfacial level as well as within bulk. The foam formulation were polyols; a hydroxylation of soy epoxide to methanol and ethylene glycol using homogeneous catalyst; which respectively blend to petroleum polyol with ratio 1:5. Polyols were synthesized in a three neck 500 ml flask equipped with reflux condenser which has been prepared into two internmediate products: 1) polyol was synthesized by hydroxylation of epoxide by using methanol named as (P1) and 2) ethylene glycol as (P2). Each (P1) and (P2) should be in optimized conditions before manufactured to polyurethane. The best conditions in synthesizing polyurethane were 1% v/v acid catalyst, with temperature of C. The foam were prepared by mixing blending TDI (2,4):MDI (4,4 ) (80:20) to surfactant, and distilled water. The mixtures were vigorously mixed (stirring at 1000 rpm using high speed mixer for 1 min), then were poured into an open glass mold. RESULTS AND DISCUSSION a. Polyurethane Polyol which has been optimized is ready for use as a reagent manufacture of polyurethane, which were previously synthesized using methanol and ethylene glycol as

3 Production of Flexible Polyurethane Foam chain extender to hydroxylation reaction. The role of chain extender is a source of OH, so the polyols have more hands to tie the isocyanate ion (SCN - ). Polyol product that is formed will result oxirane number on reducing numbers, and increasing the active site to be the synthesis of polyurethane Oxirane Number (%) hours 1 hour 1:00 1:01 1:03 1:04 1:06 1:07 epoxide/methanol Figure 1: Soy polyol synthesized by methanol chain extender Optimal conditions of manufacture polyols was at ratio methanol/epoxide 1:6 (mol/mol) with oxirane number 0.14,%; as it illustrated in figure 1. For ethylene glycol/epoxide was at 1:3 (mol/mol) where the oxirane number was 0.079% shown in figure 2. Both were at 2 (two) hours reaction Oxirane Number (%) hour hours 2 hours 1:00 1:01 1:03 1:04 1:06 1:07 1:09 1:10 epoxide/ethylene glycol Figure 2: Soy polyol, synthesized by ethylene glycol chain extender b. Curing Time Polyurethane curing time, a phase which polyurethane is perfectly expanded, were still need time to completely dry and safe to be lifted from the molding. At table 2 it can be seen the differences of curing time of polyol (P1) to (P2) which were not significant. This gives an indication that the active site prepared by ethylene glycol-based polyols (P2) is greater than methanol-based polyol (P1) which does not provide significant differences. Table 2: Curing of Polyurethane Sample Average Curing Time PUR (minutes) PUR

4 Materials Science and Technology c. Characterization of Polyurethane Products Characterization was performed on polyurethane, such as water absorbency, foam density, and average pore diameter as shown in table 2. These observations used synthetic polyurethane as control. It was found that the synthetic polyurethane absorb less water compare to polyurethane soy-based. It is visually approved that the polyurethane soy-based has much hollow space dispersed at the surface as well as in the bulk. Composition of unsaturated fatty acids contained in soybean triglycerides influence the elasticity and foam deployment process. Table 3: Characterization of Flexible Polyurethane Foam Observation Polyurethane PUR 1 PUR 2 Synthetic Water Absorbency (% wt) 86,76 98,46 14,54 Density (gr/cm3) 0,0992 0,1156 0,1295 Pore Diameter (ml) 7,8 5,0 0,2 Notes: (PUR1) methanol based, (PUR2) ethylene glycol based d. Cell Morphology SEM micrograph were used to take images of cured solid polyurethane foams polyurethane (PUR 2) which polyol was synthesized using ethylene glycol, has slightly imperfect form of cell morphology compared to foams polyurethane (PUR 1). (a) (b) (c) (d) Figure 3: Cell Morphology of polyurethane; a. (PUR 2);40x 500µm b. (PUR 2): 170x 100 µm c. (PUR 1): 40x 500 µm and d. (PUR1): 170x 100µm e. Photos of Surface polyurethane Polyurethane surface characterization had performed using Light Microscope with magnification of 3 (three) times. Visible cavities (voids) generated by the surface of polyurethane (PUR 2) is more larger compared to polyurethane (PUR 1). There is still needs further characterization of the cell. 244

5 Production of Flexible Polyurethane Foam a b Figure 4: Sectional surface of polyurethane of a. (PUR1) b. (PUR2) CONCLUSION The effect of chain extender methanol and ethylene glycol in the polyol synthesis, to the cells pore diameter of polyurethane flexible foam were not significantly different. The foam aquadest absorbency for (PUF 1) and (PUF 2) is very high, which gain weight to more than 85%, but clearly comparative to synthetic polyurethane. This can be concluded the foam is not recommended to be used in the wet area. ACKNOWLEDGMENT The authors gratefully acknowledge the support of the Indonesia Department of higher education as funding the research. REFERENCES [1]. Zlatanic, Petovick, and Dusek, Structure and Properties of Triolein Based Polyurethane networks. Biomacromolecules 3: (2002) [2]. Guidotti et.al. Hetergeneous Catalytic Epoxidation of Fatty Acid and Methyl Esters on Titanium Grafted Silicas. Green Chem; 5; (2003) [3]. Hanson and Larock, Soybean Oil divinylbenzene Thermosetting Polymers: Synthesis, Structure, Properties and Their Relationships. Polymer 42 (2001): [4]. Okiemen and Bakare. Studies on The Epoxidation of Rubber Seed Oil. Ind Crops Products 15 (2003): [5]. Rangarajan et.al. Kinetic Parameters of a Two Phase Model for in situ Epoxidation of Soybean Oil. J Am Oil Chem Soc 72: [6]. Lye et. al., An overview of R&D in Palm Oil-Based Polyols and Polyurethanes in MPOB [7]. Singh and Bhattacharya, Viscoelastic Changes and Cell Opening of Reacting Polyurethane Foams from Soy Oil. Polymer Engineering and Science, 44 (2004) no 10 [8]. Yerrakondreddygary, Kiran. Polyols Made From Vegetable Oil and Their Applications. Thesis. Univ. of Columbia [9]. Comstock, MJ. Urethane chemistry and applications. ACS symposium series 172; American Chemical Society: Washington DC, 1981 [10]. Javni et.al. Effect of Nano and Micro Silica Fillers on Polyurethane Properties. J. of Cellular Plastics 38, (2002)