Soft polyurethane elastomers with adhesion properties based on palm olein and palm oil fatty acid methyl ester polyols

Author’s Accepted Manuscript SOFT POLYURETHANE ELASTOMERS WITH ADHESION PROPERTIES BASED ON PALM OLEIN AND PALM OIL FATTY ACID METHYL ESTER POLYOLS S. Mohd Norhisham, T.I. Tuan Noor Maznee, H. Nurul Ain, P.P. Kosheela Devi, A. Srihanum, M.N. Norhayati, S.K. Yeong, A.H. Hazimah, Christi M. Schiffman, Aisa Sendijarevic, Vahid Sendijarevic, Ibrahim Sendijarevic

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S0143-7496(16)30208-1 http://dx.doi.org/10.1016/j.ijadhadh.2016.10.012 JAAD1916

To appear in: International Journal of Adhesion and Adhesives Accepted date: 13 October 2016 Cite this article as: S. Mohd Norhisham, T.I. Tuan Noor Maznee, H. Nurul Ain, P.P. Kosheela Devi, A. Srihanum, M.N. Norhayati, S.K. Yeong, A.H. Hazimah, Christi M. Schiffman, Aisa Sendijarevic, Vahid Sendijarevic and Ibrahim Sendijarevic, SOFT POLYURETHANE ELASTOMERS WITH ADHESION PROPERTIES BASED ON PALM OLEIN AND PALM OIL FATTY ACID METHYL ESTER POLYOLS, International Journal of Adhesion and Adhesives, http://dx.doi.org/10.1016/j.ijadhadh.2016.10.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

SOFT POLYURETHANE ELASTOMERS WITH ADHESION PROPERTIES BASED ON PALM OLEIN AND PALM OIL FATTY ACID METHYL ESTER POLYOLS Mohd Norhisham, Sa; Tuan Noor Maznee, T.Ia; Nurul Ain, Ha; Kosheela Devi P.Pa; Srihanum Aa; Norhayati M.Na; Yeong S.Ka, Hazimah A.Ha, Christi M. Schiffmanb, Aisa Sendijarevicb, Vahid Sendijarevicb, Ibrahim Sendijarevicb* a

Synthesis and Products Development Unit, Advanced Oleochemical Technology Division,

Malaysian Palm Oil Board, No. 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia b

Troy Polymers, Inc., Troy, MI 48083, USA

*

CORRESPONDING AUTHORS: [email protected]

ABSTRACT Soft polyurethane (PU) elastomers with > 70% bio-based content and with properties characteristic of pressure sensitive adhesives were prepared from an equimolar ratio of a polyol derived from palm oil fatty acid methyl ester (PolyFAME-EG polyol) and palm olein polyols (Pioneer E-135 and Pioneer M-60) cured with 2,4’- and 4,4’- diphenylmethane diisocyanate isomeric mixture at isocyanate to hydroxyl equivalent weight ratio (Isocyanate Index) of 1.02 and 0.73. FTIR analyses of the resulting elastomers indicate high levels of free non-hydrogen bonded urethanes, indicating phase mixing of hard and soft segments, which explains the transparent nature of the elastomers. The physical properties of the elastomers were correlated with the cross-link density of the palm olein polyols and Isocyanate Index. Elastomers produced at an Isocyanate Index of 1.02 ranges in hardness from 21 to 67 Shore A which correlated with the average polyol functionality. However, at an Isocyanate Index of 0.72 the resulting elastomers were very soft with hardness ranging from 1 to 4 Shore A and with T-Ppeel adhesion to polypropylene in the range from 2.27 to 1.98 N/25mm. Based on these results, a polyurethane matrix with a high renewable content of palm oil polyols can be used as a platform for the development of transparent elastomers that can be used as soft energy-absorbing materials with potential use in pressure sensitive adhesives. KEYWORDS Polyurethane; pressure-sensitive; novel adhesives; structure property relations; renewable polymers

1.

INTRODUCTION

Polyurethanes are broadly defined as polymeric materials formed by the reaction of isocyanates with compounds containing active hydrogen. They are characterized with urethane groups, which are formed in the reaction of polyols and isocyanates [1-3].] Polyurethanes cover a broad spectrum of properties, from soft to hard, hydrophobic to hydrophilic, soft to hard, transparent to

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opaque, resilient to energy absorbing, and a broad range of applications such as rigid and flexible foams, elastomers, coatings, adhesives, sealants and binders [4]. The Pproperties of polyurethanes are controlled mainly by the structure and nature of the polyols used in their syntheseis. There are various types of polyols for polyurethanes that include polyols with polyether, polyester, polycarbonate, and hydrocarbon backbones. The polyols can be linear or branched, typically with two or more hydroxyls per chain, and their molecular weights can vary from small to large molecules of 10,000 daltons [5]. Due to environmental concerns, there has been significant development of polyols based on sustainable natural oils such as soybean oil, palm oil and canola oil [6,7, 8]. The natural oils consist of triglyceride molecules which are esters of glycerol with long chain fatty acids (4 to 22 carbon chains) with 0-3 unsaturated double bonds per fatty acid. The double bonds and ester groups are the main active sites that are used to introduce hydroxyl groups to convert natural oils to natural oil polyols (NOPs) [6,7,9]. Fatty acids esters isolated from triglycerides can also be used to produce polyols with natural content [6,7]. Palm oil-based polyols can be prepared by using different fractions and derivatives from palm oil [9-11]. Different synthetic routes are used in the syntheses of palm oil polyols but the most common route involves epoxidation of unsaturated double bonds in palm olein or palm oil derivatives followed by reaction of epoxides with polyhydric compounds to yield reactive hydroxyls [9, 10]. Other Another common route for polyol synthesis from palm oil is transesterification [11]. This paper is covering considers the synthesis and structure-propertiesy relationships of soft polyurethane elastomers with adhesion properties that are based on a combination of NOPs derived from palm olein fatty triglyceride and also from palm oil fatty acid methyl esters, which is a palm oil based biodiesel fuel [12-19]. Polyurethane elastomers are characterized, in general, with a segmented structure with polyols as “soft” and isocyanates as “hard” segments in the polyurethane matrix. The hardness and elasticity of polyurethanes are controlled by the nature of the polyol, isocyanate, and equivalent ratio of polyol and isocyanate used in their preparation [20-23]. Soft polyurethanes are of interest in many applications such as sealants, pressure sensitive adhesives, and various types of inserts for improved cushioning including furniture, athletic, wheel-chair, and medical applications. This is one of the first studies reporting the syntheses of NOPs from biodiesel fuel, which due to its low functionality, is uniquely suited for use in pressure sensitive adhesives. The palm oil derived polyols offer an opportunity to produce soft polyurethane elastomers with high sustainable content.

2.

MATERIALS AND METHODS

2.1

Materials

Unless otherwise noted, all materials, solvents, and reagents were purchased from commercial suppliers and were used as received.

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The Ssynthesis of PolyFAME-EG polyol (Figure 1) is described below. The Ssynthesis of palm olein polyols Pioneer E-135 (Figure 2) and Pioneer M-60 (Figure 3) are described in the following reference [13]. Mondur MLQ (2,4’-/4,4’-diphenylmethane diisocyanate, NCO 33.4%) was received from Covestro. Dabco T-12 (dibutyltin dilaurate) catalyst was received from Air Products. 2.1.1 Fatty Aacid Mmethyl Eester-based Ppolyol (PolyFAME-EG) Ssynthesis The synthesis of PolyFAME-EG involves two step reactions that include epoxidation and alcoholysis (Figure 1) [10]. Both reactions were carried out in a 10 L water jacketed glass reactor, equipped with an agitator, an addition funnel and a thermocouple. The hHeating and cooling was provided with a circulating water bath. Fatty acid methyl ester (FAME) with an iodine value of 92.7 g I2/100 g was supplied by Carotino Malaysia Sdn. Bhd. Formic acid (85-98% concentration) and hydrogen peroxide (50% concentration) were supplied by Kimia Cergas Sdn. Bhd. Boron trifluoride diethyl ether complex (50% BF3 in diethyl ether) was supplied by Merck Sdn. Bhd. Ethylene glycol (99.8% ethylene glycol) was supplied by Sigma Aldrich Malaysia Sdn. Bhd. Sodium chloride (NaCl) and sodium carbonate (Na2CO3) were supplied by Kong Long Huat (M) Sdn Bhd. All chemicals were used as received. Epoxidation Reaction: A total of 3.00 kg of FAME was placed in a reactor and preheated to 40 °C under agitation. A freshly prepared mixture of 0.34 mole of formic acid and 0.85 mole hydrogen peroxide was added slowly to the preheated fatty acid methyl ester. The addition of formic acid and hydrogen peroxide was stopped every time the reaction temperature increased to 50 – 65 °C at which point the reaction mixture was cooled until the temperature dropped to 40 °C. The total addition time for the formic acid and hydrogen peroxide mixture was within 2 h and 30 min. The aAgitation of the reaction mixture was continued at 50 to 65 °C until the epoxidation was completed (oxirane oxygen content reached about 95% of theoretical value). The reaction product was then decanted from the remaining acid. After that, the product was first washed with 1% NaCl solution, followed by 0.5% Na2CO3 solution until the pH of the product was between pH 6 to 8. The A final wash was with 1% NaCl solution was conducted to remove the residual carbonate solution. The final washed product had a pH value of 6 to 7. The neutralized epoxidized fatty acid methyl ester (epoxidized FAME) was dried under a vacuum of 17 mm Hg at 65 – 85 °C until the water content of the product was below 0.05%. The oxirane oxygen content of this product was 4.61% and the total weight of the final product was 2.65 kg (88.4% yield based on starting fatty acid methyl ester). Alcoholysis Reaction: A total of 2.65 kg of epoxidized FAME was placed in the a reactor and preheated to 50 -55 °C under agitation. A BF3/ethylene glycol mixture, which was prepared by blending 13 g of boron trifluoride diethyl ether complex with 474 g of ethylene glycol, was added slowly to the preheated epoxidized FAME. After the addition of BF3/ethylene glycol mixture was completed, mixing was continued for another 30 minutes while maintaining the reaction temperature at 50 – 55 °C. At that point, the alcoholysis was completed (oxirane oxygen content decreased to 0.02%).

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Subsequently, the product was neutralized and washed at 60 – 65 °C using a 10 liter water jacketed glass reactor. The product was washed with 1% NaCl solution, followed by 0.5% Na2CO3 solution until the pH of the product was about 6 to 8, which was measured using a pH paper. The final wash was with 1% NaCl solution to remove the residual carbonate solution. The pH of the final washed product was 6 to 7. The neutralized polyol product was dried under a vacuum of 17 mm Hg at 85 – 100 °C until the moisture content of the product reached less than 0.05%. The total weight of the final product was 2.35 kg (88.7% yield based on starting epoxidized FAME). 2.1.2 PolyFAME-EG Ppolyol Ccharacterization Oxirane oxygen content were measured by AOCS Cd 9-57, hydroxyl value by ASTM D4274-05, and acid value by ASTM D4662-08. Moisture content was measured on a Coulometric Karl Fischer Titrator, Model 275KF, Titration Controller Model 260 (Denver Instrument) based on ASTM D4672-00. The viscosities of polyols were measured using a Brookfield Viscometer, Model LVF according to ASTM D4878-08. Differential scanning calorimetry (DSC) analysis of polyols and epoxidized FAME was carried out using a differential scanning calorimeter, DSC, Q10, TA Instrument at the a heating rate of 10 °C/min. Molecular weight distributions were determined by using a gel permeation chromatograph (GPC) consisting of a Waters 515 HPLC Pump, Auto sampler (SIL-20A/20AC, Shimadzu), Waters 2410 Differential Refractometer (Waters, Milford, MA), On-line Degasser, Model JMDG-4 (JM Science, Grand Island, NY), a set of four Phenogel 5 μ (300 x 7.8 mm) 50 Ǻ; 102 Ǻ, 103 Ǻ, and 104 Ǻ GPC columns (all Phenomenex, Torrance, CA) covering a MW range of 102 -106, and a Guard column: 5 μ linear/mixed, 50 x 7.8 mm. The flow rate of tetrahydrofuran eluent was 1 mL/min. The columns and detector were thermostated at 40 °C. Primary and secondary hydroxyl content was determined via a titration method described in the following reference [13,24]. 2.2

Elastomers

Polyurethane elastomers were prepared via a one-shot method by reaction of Mondur MLQ diisocyanate with an equimolar blend of PolyFAME-EG and a selected polyol. Degassed polyols weighed into a 200 mL cup were mixed for 30 s at 2200 rpm via a multiaxial mixer (Speed Mixer, DAC 400 FV FlakTek Inc.) and then heated in an air circulating oven at 70 -100 °C. Liquid isocyanate conditioned at 70 °C was added via a syringe to the polyol mixture. All components of the PU system were mixed via a multiaxial mixer at 2200 rpm and then transferred into an aluminum mold covered with Teflon sheet that has had been preheated at 120 °C. At the gel time, determined as a short string formation time by touching the surface of the resin with a spatula, the mold was closed and the elastomer was cured for 2 h at 120 °C. After that, tThe samples were then post-cured for 20 h at 100 °C. Polyurethane samples were aged at room condition (23 oC) for seven days prior to the testing. Using this method, sheets (125 mm x 125 mm x 2.5 mm) and round button samples (28.5 mm in diameter and 13 mm thick) were prepared to test the physico-mechanical properties of the elastomers.

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2.2.1 Properties of Ppolyurethane Eelastomers Values of Hhardness (ASTM D-2240, Shore A), resilience (ASTM D-2632, Bashore rebound), compression set (ASTM D3574, Test D), and compressive strength (ASTM D575) were tested with respective methods assessed. Tensile properties (ASTM D 412) and tear strength (ASTM D624) were tested using a universal testing machine (Instron 5500R tester, model 1122). Tensile set was measured as a percent of unrecovered length of tensile specimen 10 min after the tensile test was performed. Thermal properties were measured via differential scanning calorimetry (DSC Q 10, TA Instruments) at a heating rate of 10 °C/min and via dynamic mechanical analysis at the a heating rate of 3 °C/min (DMA, 7E, Perkin Elmer). FT-IR spectra were recorded on a Perkin Elmer Spectrum Two with a Pike Miracle ATR Aattachment and deconvolution of the spectra was completed with PeakFit software using a Gaussian response function with a Fourier deconvolution fitting algorithm, and it assigns the relative % areas correlating to the identified peaks. 2.2.2 Adhesion Pproperties of Ffully Ccured Ppolyurethanes Thin PU sheets were prepared from polyurethane resins mixed as described above which was were coated onto Teflon sheets using a Dr. doctor Bblade and cured in an air circulated oven for 20 h at 100 °C. Afterwards, fFully cured thin polyurethane sheet (0.65 mm thick) was then applied between two polypropylene sheets and pressed for 10 min at room temperature (23 °C) in a Carver Press. TPeel tests was were performed on specimens of 25 mm x 94 mm according to ASTM D-1876 using the a pulling rate of 254 mm/min immediately after the sample was removed from the press.

3.

RESULTS AND DISCUSSION

3.1

PolyFAME-EG Ppolyol

The starting material in the synthesis of PolyFAME-EG polyol was FAME (biodiesel) derived from palm oil (Figure 1). The composition of FAME is listed in Table 1. FAME has the highest percentage of C18:1 fatty acid (72.7%) with one double bond, followed by 17.1% of C18:2 fatty acid with two double bonds. The Rremaining 10.2% are saturated fatty acids. FAME was epoxidized in the reaction with performic acid which formed epoxidized FAME. Epoxidized FAME was then reacted with ethylene glycol in the a reaction catalyzed with BF3/diethyl ether in which epoxide groups were opened forming two hydroxyl groups (Figure 1). The properties of PolyFAME-EG polyol are shown in Table 2. The oxirane oxygen content decreased from 4.88% in epoxidized FAME to 0.02% in PolyFAME-EG polyol indicating that the epoxide groups were consumed in the reaction (Table 2).

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In the GPC analyses, Eepoxidized FAME exhibited one strong peak indicating that the bulk of the product was mono-fatty acid methyl ester (Figure 4). However, multiple peaks were recorded in PolyFAME-EG polyol, indicating intermolecular opening of epoxide groups and the presence of di- and tri-fatty acid methyl esters. Epoxidized FAME had a polydispersity (Mw/Mn) of 1.02 and PolyFAME-EG 1.44 (Table 2). PolyFAME-EG polyols also contains have 40.2 percent primary hydroxyl content (Table 2), which is somewhat lower than the theoretical 50%. This discrepancy could be explained by that fact that some primary hydroxyls, generated from opening of epoxies with ethylene glycol, consequently participate in the intermolecular opening of epoxies. DSC analyses of Epoxidized FAME shows a glass transition at -38.5 °C and a significant melt transition at 4.2 °C (Figure 5). PolyFAME-EG polyol showed a glass transition at -65 °C, however, the melt transition was significantly attenuated compared to Epoxidized FAME. Therefore, opening of epoxy rings of Epoxidized FAME with ethylene glycol appears to have significantly reduced the molecular ordering and crystallinity.

3.2

Polyurethane Eelastomers

PolyFAME-EG polyol’s low degree of crystallinity could be beneficial in creating soft polyurethane networks at room conditions. PolyFAME-EG has a unique structure with pendant hydroxyl groups attached to the backbone of a hydrocarbon chain with the ester group at the terminal end (Figure 1). The Ppendant position of hydroxyl groups should contribute to lower symmetry and hardness of the PU network, while the presence of terminal polar ester groups should promote adhesion to various substrates. In addition, a fraction of non-functional saturated fatty acid methyl esters in PolyFAME-EG polyol are effectively a plasticizer, which can potentially contribute to the tackiness of the elastomer. These characteristics combined could contribute to enhance the pressure-sensitive adhesion of polyurethane elastomers. However, Poly-FAME-EG polyol has a low functionality of 1.2 (equation 1 and 2) and it is expected that in a reaction with di-isocyanate there would be insufficient functionality to form a polymer chain. Therefore, it came as little surprise that the polyurethane prepared from PolyFAME-EG reacted with Mondur MLQ (2,4-/4,4’-MDI isomer mixture) at 1.02 isocyanate index was a viscous liquid at room temperature (Table 3). For this reason, in order to maintain a high sustainable content and to take advantage of the unique molecular structure of PolyFAME-EG, polyurethane elastomers were produced from equimolar blends of PolyFAMEEG with higher functionality natural oil polyols. (1) (2) where Hydroxyl Number is expressed as mg KOH g-1 and 56100 is the equivalent weight of KOH in mg [5].

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Pioneer M-60 and Pioneer E-135 are palm olein-based polyols which are prepared by the epoxidation of palm olein and their subsequent reaction with short-chain hydroxyl-functional reactants (Figures 2 and 3) [13]. The properties of these palm olein based polyols are listed in Table 2. Pioneer M-60 polyol is characterized with high a content of secondary hydroxyl groups, a functionality of 2.8, and hydroxyl equivalent weight of 722. Pioneer E-135 polyol contains both primary and secondary hydroxyl groups. The functionality of Pioneer E-135 polyol is 5.2 and its hydroxyl equivalent weight is 420. The equimolar polyol blends of Poly-FAME-EG with Pioneer M-60 and Poly-FAME-EG with Pioneer E-135 were reacted with Mondur MLQ at 1.02 and 0.73 isocyanate index to form a polyurethane elastomer. Since the Pioneer E-135 NOP has a higher primary hydroxyl content and functionality than Pioneer M-60, less dibutyltin dilaurate (Dabco T12) catalyst was required in the syntheses for elastomers based on Pioneer M-E-135. In all instances, the completion of the polymerization reaction was confirmed via FTIR by the absence of the peak at 2270-2280 cm-1 attributed to isocyanate. Properties of the resulting elastomers are presented in Table 3. The elastomer based on Poly-FAME-EG / Pioneer E-135 blend at 1.02 isocyanate index showed significantly highest higher hardness and compression strength values than the elastomers based on Poly-FAME-EG / Pioneer M-60 polyol. These results are supported by higher functionality of Pioneer E-135 polyol compared to Pioneer M-60, which would directly impact the cross-link density of the elastomers and thus their hardness. The tensile strength, tear strength, and compressive strength were higher for elastomers based on Poly-FAME-EG / Pioneer E-135 polyol with higher functionality. In addition, Pioneer E-135 has a lower equivalent weight than Pioneer M-60, so elastomers based on the equimolar Poly-FAME-EG / Pioneer E-135 blends have a higher hard segment concentration at the same isocyanate index than the elastomers based on blends elastomers based on Poly-FAME-EG / Pioneer M-60 blends. In general, the hardness of PU elastomers increases with increasing hard segment concentration [18]. Therefore, the elastomers produced at an isocyanate index of 0.73 with lower overall hard segment concentration were significantly softer with Shore A hardness ranging from Shore A 1 to 4 than the corresponding elastomers produced at an isocyanate index of 1.02. The resulting soft polyurethane elastomers prepared at 0.73 isocyanate index exhibited adhesion properties potentially suitable for pressure sensitive adhesives. A T-peel adhesion test to a nonpolar polypropylene substrate showed the a peel adhesion of 2.27 and 1.98 N for elastomer prepared from Poly-FAME-EG / Pioneer M-60 and Poly-FAME-EG / Pioneer E-135 polyol blends, respectively (Table 3). At an isocyanate index of 1.02, the elastomer based on PolyFAME-EG / Pioneer E-135 polyol had no pressure adhesion strength, however, the elastomer based on Poly-FAME-EG / Pioneer M-60 polyol blend still produced 0.92 N peel strength. These values fall in the range of 1 to 5 N/inch for commercial pressure sensitive adhesives, and for reference peel strength of Scotch Magic Tape from 3M is about 1 N/inch [25, 26]. In all elastomers prepared at a 1.02 isocyanate index, the recovery in the tensile strength measurement was 100% (0% tensile set) and the recovery after constant deflection compression set was closed to 100% (Table 3). These results therefore indicate excellent recovery of the

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elastomers and potentially excellent durability. This could be attributed to the non-polar nature of polyols and relatively low hydrogen bonding in the polyurethane network. Elastomers prepared at a 0.73 isocyanate index did not have sufficient mechanical integrity to complete the mechanical or dynamic testing. All produced elastomers regardless of the polyol combinations were transparent at room temperature indicating an amorphous polymer structure (Figure 6). The morphology of the elastomers was also analyzed with by DMA (Figure 7 and 8). In the glassy state, storage modulus of elastomers based on Poly-FAME-EG / Pioneer E-135 polyols was were equal to the elastomers based on Poly-FAME-EG / Pioneer M-60 polyols, however, in the rubbery region the storage modulus was higher for the elastomers based on Poly-FAME-EG / Pioneer E-135 polyols which correlates with a higher polyol functionality (Figure 7). However, the tangent delta curves show a higher peak for elastomers based on Poly-FAME-EG / Pioneer M-60 polyols, which could be correlated with more defined separation of hard and soft segments in agreement with the FTIR analyses. Therefore, it appears that the higher functionality of the Poly-FAME-EG / Pioneer E-135 polyol blend can decrease the ordering of hard and soft segments in the elastomer. DSC analyses show that the elastomers based on Poly-FAME-EG/Pioneer E-135 polyols have a glass transitions and no melt transition (Figure 9). On the other hand, the elastomers based on Poly-FAME-EG/Pioneer M-60 have a glass transition temperature at -25oC and also a pronounced melt transition at about 7oC (Figure 9). Pioneer E-135 polyol and Pioneer M60 polyols both exhibit crystalline domains with respective melt transitions at 15 oC and 13oC respectively. Therefore, it appears that the higher functionality of Poly-FAME-EG/Pioneer E-135 polyols results in higher phase mixing in polyurethane elastomers and less defined separation and ordering of the hard and soft segments, which is in agreement with the DMA data. On the other hand, the elastomers based on Poly-FAME-EG/Pioneer M-60 appear to have well defined hard and soft segments, evident by the preservation of the crystalline domain of the polyol melt transition. The elastomers were also analyzed via FTIR to determine the impact of composition on the separation between hard and soft segments (Figure 10). The FTIR absorption peak at 1600 cm-1 corresponds to carbon-carbon bond stretching of aromatic rings, and the relative measured intensities of this peak correlate with the concentration of MDI in the respective elastomers. The FTIR absorption peaks in the range of 1640 to 1732 cm-1 are of the most interest, where signals relate to bonded and free urethane and urea segments [20, 21]. The elastomers evaluated in this study only contain urethane bonds and no urea bonds, so the ratio of non-bonded and bonded urethane is a good indicator of the hard and soft segments separation. The relative ratio of the areas of the deconvoluted FTIR absorption peaks associated with free and bonded urethane are presented in Table 4. The free to bonded urethane ratio of 12.2 was determined for the elastomer produced at 1.02 isocyanate index based on Poly-FAME-EG/Pioneer E-135 equimolar polyol blends, which was significantly higher than the 3.1 determined for the elastomer based on Poly-FAME-EG / Pioneer M-60 polyols. It should be noted that Pioneer E-135 polyol has the higher functionality, which could create a higher degree of steric hindrance to alignment of the isocyanates into separate hard domains, resulting in the higher free-urethane content and overall less ordered hard and soft segment separation, which is in agreement with the DMA and DSC analyses.

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4.0

CONCLUSIONS

A novel polyol was produced from palm oil based methyl ester (biodiesel). The resulting biodiesel based polyol was blended in equimolar rations with natural oil polyols produced from palm olein which were reacted with aromatic diisocyanate to produce elastomers at 1.02 and 0.73 isocyanate index. Overall the resulting polyurethane elastomers contained high renewable content greater than 70%. Despite the fact that the palm olein based polyols contained exhibited a melt transition, the resulting elastomers were transparent at room temperature. It was determined that the hard and soft segment separation of the elastomer matrix correlates with the polyol functionality, with higher functionality polyols yielding higher degrees of phase mixing. As expected, it was determined that the elastomer hardness, tensile strength, compressive modulus, and tear strength correlate with the functionality of the polyols. The soft polyurethane elastomers based on the biodiesel polyols and prepared at an isocyanate index of 0.73 were found to exhibit adhesion properties potentially suitable for pressure sensitive adhesives. A T-peel adhesion test to a non-polar polypropylene substrate showed the peel adhesion in the range from 1.98 to 2.27 N/inch for elastomer prepared from biodiesel/palm olein polyols. These values fall in the range of 1 to 5 N/inch for commercial pressure sensitive adhesives. Even at a 1.02 isocyanate index, the elastomer based on a low functionality biodiesel/palm olein polyol blend had 0.92 N/inch peel strength. Therefore, the polyols produced from biodiesel, with their unique structure that contains methyl ester and hydroxyl reactive groups, could potentially be used to develop a new generation of polyurethane pressure sensitive adhesives with high renewable content.

5.0

ACKNOWLEDGEMENTS

The authors would like to thank Malaysian Palm Oil Board (MPOB) and the Director General of MPOB for providing the financial support for this research work. We would also like to thank our colleagues at Advanced Oleochemical Technology Division and Troy Polymers, Inc. for their invaluable contributions to this work.

6.0

REFERENCES

1. Saunders JH, Frisch KC. Polyurethanes Chemistry and Technology, Part I. Chemistry. New York: Interscience Publishers; 1962. 2. Oertel G. Polyurethane Handbook. Munich: Carl Hanser Verlag; 1985. 3. Herrington R, Hock K. Flexible polyurethane foams. Midland: Dow Chemical Company; 1997. 4. 2012 End-Use Market Survey for Polyurethanes Industry in the United States, Canada and Mexico. Washington: American Chemistry Council; 2013. 9 Submission to International Journal of Adhesion and Adhesives

5. Ionescu M. Chemistry and Technology of Polyols for Polyurethanes. Shawbury: Rapra Technology Limited; 2005. 6. Lligadas G, Ronda JC, Galia M, Cadiz V. Plant Oils as Platform Chemicals for Polyurethane Synthesis: Current State-of-the-Art. Biomacromolecules 2010; 11: 2825-2835. 7. Petrović ZS. Polyurethanes from Vegetable Oils. Polym Rev 2008; 48(1): 109-155. 8. Li Y, Luo X, Hu S. Polyols and Polyurethanes from Vegetable Oils and Their Derivatives. In Bio-based Polyols and Polyurethanes. Springer International Publishing; 2015. 9. Saurabh T, Patnaik M, Bhagt SL, Renge V. Epoxidation of vegetable oils: a review. Int J Adv Eng Technol 2011; II(IV): 491-501. 10. Hassan HA, Ismail TN, Sattar MN, Hoong SS, Ooi TL, Ahmad S, Cheong MY. Process to produce polyols. US 7,932,409; 2011. 11. Arniza MZ, Hoong SS, Idris Z, Yeong SK, Hassan HA, Din AK, Choo YM. Synthesis of Transesterified Palm Olein-Based Polyol and Rigid Polyurethanes from this Polyol. J Am Oil Chem Soc 2015; 92(2): 243-55. 12. Hepburn C. Polyurethane Elastomers, England: Applied Science Publishers; 1982. 13. Tuan Ismail TN, Palam P, Devi K, Bakar A, Bin Z, Soi HS, Kian YS, Abu Hassan H, Schiffman C, Sendijarevic A, Sendijarevic V, Sendijarevic I. Urethane‐forming reaction kinetics and catalysis of model palm olein polyols: Quantified impact of primary and secondary hydroxyls. J App Polym Sci 2016; 133(5): 42955. 14. Chongkhong S, Tongurai C, Chetpattananondh P, Bunyakan C. Biodiesel production by esterification of palm fatty acid distillate. Biomass and Bioenergy 2007; 31(8): 563-8. 15. Crabbe E, Nolasco-Hipolito C, Kobayashi G, Sonomoto K, Ishizaki A. Biodiesel production from crude palm oil and evaluation of butanol extraction and fuel properties. Proc Biochem 2001; 37(1): 65-71. 16. Smith CP, Reisch JW, O’Connor JM. Thermoplastic Polyurethane Elastomers Made from High Molecular Weight POLY-L™ Polyols. Proceedings of Polyurethane World Congress, Niece France 1991; 313-318. 17. Lay DG, Cranley P, Chorghade M. 2,4' MDI Based Prepolymers: A Viable Alternative to TDI Prepolymers in Polyurethane Sealants. Proceedings of Polyurethane World Congress, Niece France 1991; 319-324. 18. Vlajic M, Torlic E, Sendijarevic A, Sendijarevic V. Chemical Structure and Properties of Polyurethane Elastomers I. The Effects of the Chemical Structure of the Flexible Segment on the Properties of Thermoplastic Elastomers.Polimeri 1989; 10(3): 62. 19. Sendijarevic V. Natural Oil Polyols in Polyurethane Industry - Design for Performance. Int Palm Oil Cong – Oleo and Spec Chem Conf 2011; OS-3: 59-71. 20. Sharma C, Kumar S, Unni A, Aswal VK, Rath SK, Harikrishnan G. Foam stability and polymer phase morphology of flexible polyurethane foams synthesized from castor oil. J Applied Polym Sci 2014; 131(17): 40668. 21. Zhang L, Jeon HK, Malsam J, Herrington R, Macosko CW. Substituting soybean oil-based polyol into polyurethane flexible foams. Polymer 2007; 48(22): 6656-67. 22. Saunders JH, Frisch KC. Polyurethanes Chemistry and Technology, Part II. Technology. New York: Interscience Publishers; 1962. 23. Petrovic Z, Guo A, Javni I. Process for the preparation of vegetable oil-based polyols and electroinsulating casting compounds created from vegetable oil-based polyols. US 6,573,354; 2003.

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24. Fijolka P. Eine Methode zur quantitativen differenzierten Bestimmung von primaren und sekundaren Hydroxylendgruppen. PlasteKautsch 1971; 18: 431-432. 25. Ahn BK, Kraft S, Wang D, Sun XS. Thermally stable, transparent, pressure-sensitive adhesives from epoxidized and dihydroxyl soybean oil. Biomacromolecules 2011; 12(5): 1839-43. 26. Yonghui Li, Byung-Jun Kollbe Ahn, Xiuzhi Susan Sun. Kansas State University, PressureSensitive Adhesives from Soybean Oils, https://www.adhesionsociety.org/wpcontent/uploads/2013-Annual-Meeting-Abstracts/Li_Pressure-Sensitive_2013.pdf.; 2013 [accessed 28.2.2016].

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Table 1. Chemical composition of fatty acids in FAME (composition supplied by Carotino Malaysia Sdn Bhd) C12:0

0.1 %

C14:0

0.6 %

C16:0

5.7 %

C18:0

3.6 %

C18:1

72.7 %

C18:2

17.1 %

Table 2. Properties of palm olein polyols Pioneer M-60 and Pioneer E-135 [13] Designation Properties Hydroxyl Value, mg KOH/g Acid Value, mg KOH/g Moisture Content, % Oxirane Oxygen Content, % Viscosity at 25oC, cP Tm , °C GPC Data Mn, Daltons Mw, Daltons Mw/Mn Equivalent weight (Eq. Wt.)a Primary OH content Secondary OH content Hydroxyl Functionalityb a

Pioneer M-60

Pioneer E-135

PolyFAME-EG

77.64 0.66 0.17 0.03 2,000 13.29

133.98 0.70 0.15 0.03 4,400 14.75

166.5 0.74 0.098 0.02 200 -0.5 to 7.8

1995 4125 2.07 722.57 5.6 94.6 2.8

2175 5530 2.54 420.60 39.5 60.5 5.2

410 579 1.44 337 40.2 59.8 1.22

Calculated from Hydroxyl Value. b Ratio of Mn to Eq.Wt.

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Table 3. Elastomers based on PolyFAME-EG polyol and Palm Olein NOPs

FAME-EG

FAME-EG

FAME-EG

FAME-EG

II=1.02

M60 II=1.02

E135 II=1.02

M60 II=0.73

E135 II=0.73

Pioneer E-135

-

-

33.3

-

33.48

Pioneer M-60

-

41.0

-

30.79

-

PolyFAME-EG

60

19.0

26.7

12.21

26.90

Mondur MLQ

22.8

14.5

20.3

7.26

14.56

Dabco T-12

0.6

0.6

0.05

0.6

0.05

Hard segment concentration, %

27.5

19.5

25.3

14.4

19.4

Isocyanate index

1.02

1.02

1.02

0.73

0.73

72

74

80

50

75

Viscous liquid

Solid, tacky

Solid

Solid, tacky

Solid, tacky

Hardness @ RT, Shore A

N/A

21 ± 1.9

67 ± 1.9

1±1

4±1

Resilience, %

N/A

2

16

N/A

N/A

Tensile strength at break at RT, psi

N/A

77 ± 11

403 ± 39

N/A

N/A

Elongation at break at RT, %

N/A

166 ± 18

131 ± 6

N/A

N/A

Tensile set, %

N/A

0

0

N/A

N/A

Tear strength – Die C, N/cm

N/A

9.5 ± 1

58 ± 6

N/A

N/A

Compressive strength, psi

N/A

36 ± 1

170 ± 3

N/A

N/A

Constant Deflection Compression set, % (Method A) Method B, CB

N/A

0.09 ± 0.34

3.83 ± 0.54

N/A

N/A

DSC Thermal Transitions, oC*

N/A

-25 (glass) 7 (melting)

1.5 (glass) -

N/A

N/A

DMA, Tan Delta Maximum, oC DMA, Loss Modulus Max., °C

N/A

18 -1

37 21

N/A

N/A

T-Peel Test, Polypropylene Substrate (ASTM D1876), N/in

N/A

0.92 ± 0.16

-

2.27 ± 0.17

1.98 ± 0.70

Elastomer designations

FAME-EG

Formulation (pbw)

Sustainable content, % Elastomer Properties Appearance

Table 4. IR band assignment in carbonyl region and relative ratio of assigned peaks in the elastomers Chemical Bond

Wavenumber (cm-1)

FAME-EG E135

FAME-EG

II=1.02

M60 II=1.02

Free urethane

1732

0.61

0.55

H-bonded urethane Free-/H-Bonded urethane ratio

1695

0.05

0.18

-

12.2

3.1

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Figure 1. Synthesis of PolyFAME-EG polyol from FAME (biodiesel).

Figure 2. Idealized chemical structure of Pioneer E-135 palm-based polyols with primary and secondary hydroxyl groups.

Figure 3. Idealized chemical structure of Pioneer M-60 palm-based polyols with secondary hydroxyl groups.

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Epoxidized FAME

PolyFAME-EG

Figure 4. GPC chromatograms of Epoxidized FAME and PolyFAME-EG polyol.

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Figure 5. DSC thermal measurements of Epoxidized FAME and PolyFAME-EG polyol.

Figure 6. Picture of elastomers prepared from Poly-FAME-EG/Pioneer M-60 equimolar polyol blend and Poly-FAME-EG/Pioneer E-135 equimolar polyol blend reacted respectively with Mondur MLQ diisocyanate at 1.02 Isocyanate Index.

1.0E+10

Storage Modulus (Pa)

1.0E+09

1.0E+08

1.0E+07

1.0E+06 -100

-50

0 Temperature (°C)

50

100

Figure 7. Storage modulus of polyurethane elastomers produced from the Poly-FAME-EG/Pioneer M-60 equimolar polyol blend (dotted line) and Poly-FAME-EG/Pioneer E-135 equimolar polyol blend (solid line) reacted respectively with Mondur MLQ diisocyanate at 1.02 (Table 4).

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1.8 1.6 1.4

[X VALUE] °C [X VALUE] °C

Tan d

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -100

-50

0 Temperature (°C)

50

100

Figure 8. Tangent delta of polyurethane elastomers produced from the Poly-FAME-EG/Pioneer M-60 equimolar polyol blend (dotted line) and Poly-FAME-EG/Pioneer E-135 equimolar polyol blend (solid line) reacted respectively with Mondur MLQ diisocyanate at 1.02 (Table 4).

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Figure 9. Overlay of DSC thermograms of polyurethane elastomers produced from reaction of Mondur MLQ with Poly-FAME-EG/Pioneer E-135 at (top) and with Poly-FAME-EG/Pioneer M-60 at (bottom) at 1.02 isocyanate index.

Free

PolyFAME-EG/E135 II=1.02

Intensity (a.u.)

PolyFAME-EG/M60 II=1.02

1850

H-bonded Urethane

1800

1750

1700

1650

Wavelength (cm-1)

1600

1550

1500

Figure 10. Deconvoluted FTIR spectra of elastomers produced from the Poly-FAME-EG/Pioneer M-60 equimolar polyol blend and Poly-FAME-EG/Pioneer E-135 equimolar polyol blend reacted respectively with Mondur MLQ diisocyanate at 1.02 Isocyanate Index (II).

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