Preparation of renewable polyol as natural stuff for polyurethane ( PU ) rosin is become more of import presents.
In this research, polyol was prepared from epoxidized soya bean oil ( ESO ) and applied as PU coatings on wood. Additional nucleophilic onslaught method with glycerin and ethene ethanediol ( EG ) was performed to supply hydroxyls functionality in fatty acerb anchors. By responding the modified polyol with Isophorone diisocyanate ( IPDI ) adduct, where different ratios of NCO/OH were used, PU of assorted composings had been obtained. The samples of polyols and PU obtained were characterized by Fourier Transform Infrared ( FTIR ) spectrometry. Types of polyols prepared with assorted ratio of NCO/OH in each type of alteration had been studied for surfacing belongingss ( hardness, tensile and adhesion strength onto wood substrate ) .
The consequence showed that the hardness and tensile strength of PU dependant on the ratio of NCO/OH. Polyol from glycerin provide higher tensile strength and adhesion on merantin wood substrate.Keywords – Polyols ; Polyurethane ; Isophorone diisocyanate ; soya bean oils ; coatingsIntroductionIn recent old ages, polymeric stuffs prepared from natural and renewable resources have attracted the attending of many research workers due to their possible to replace petrochemical derived functions [ 1 ] . Presently, involvement in inexpensive biodegradable polymeric stuffs has late encouraged the development of such stuffs from readily available, renewable, cheap natural beginnings such as amylum, polyose and comestible oils [ 2 ] .Oils and fats of veggies and carnal beginnings make up the greatest proportion of the current ingestion of renewable stuff in chemical industry.
They offer a big figure of possibilities in chemical science that can be seldom met by petrochemical [ 3 ] . Vegetable oils contain unsaturated side on fatty acids bond, which have potency in polymerisation of biopolymers [ 4-5 ] . Numerous fatty acids are now available in pureness and that make itself more attractive for synthesis and natural stuff for industrial usage particularly in oil-base polymer.In this research, polyol from ESO were synthesized for two constituents ( 2K ) PU and applied as surfacing rosin. Hydroxylation of ESO with ethylene ethanediol ( EG ) and glycerol has been done to supply the primary hydroxyl onto fatty acerb anchors in triglyceride. On the other manus, the use of glycerol in this reaction provides primary and secondary hydroxyl on the fatty acid anchors.
It is an attempt to hold more hydroxyl functionality but at difference responsiveness to the isocyanate.
Epoxidize soya bean oil ( ESO ) supplied by Cognis and used without extra purification. Glycerine, ethene ethanediol ( EG ) , hydrogen bromide, phosphorous acid, glacial acetic acid, K phthalate, butyl intoxicant, Na sulfate anhydrous, N-methylpirrolydon ( NMP ) , dibutyltin dilaurate ( DBTL ) ( Sigma Aldrich, Germany ) , acetic anhydride, diethyl quintessence, ethanolic K hydrated oxide ( R & A ; M Marketing Essex, UK ) analytical class was used. Isophorone diisocyanate ( IPDI ) prepolymer ( Desmodur 4470 ) from Bayer, Germany was used as received.
2.2 Synthesis of Triglyceride Polyol
ESO was modified with glycerol and EG to organize two type of polyols. All Polyols were synthesized through hydroxylation procedure at Polymer Laboratory, UiTM Shah Alam.
Hydroxylation was done with surplus of two moles EG or glycerols to the epoxies functionality. Phosphoric acid was used as accelerator ( 0.05 % w/w ) .500-ml multi-neck reaction flask equipped with a mechanical scaremonger, a thermometer, a H2O cooled capacitor and a dropping funnel, EG or glycerol, phosphorous acid in a specified proportion, was charged.
The mixture was brought to the reflux status by heating at a slow rate under mechanical stirring. The temperature of the reaction mixture was in 120 AA°C. ESO was dissolved in a part of reaction dissolver and added bead wise into the flask over a period of 45 proceedingss. After add-on of the ESO solution was complete, warming was continued and the reaction sample was sporadically tested for the acid value and the per centum of the oxirane contents. Chemical reaction was stopped after 6 hours or when the oxirane contents was found to be.The outputs from the reaction were dissolved in diethyl quintessence and washed utilizing deionise H2O for 4 times in separation funnel until the pH was 7 to take extra glycerol or EG. Oxirane pealing trial was done harmonizing to the AOCS Cd.9-57, reapproved 1997 to mensurate the decreasing of epoxies functionality.
The reaction was ended when the per centum of oxirane rings is about to zero. Hydroxyl value trial was done harmonizing to AOCS Cd. 4-40 to mensurate the per centum of hydroxylation from the epoxidize oil.
Samples were dried utilizing Na sulfate anhydrous and it was filtered out after 2 hours. Diethyl quintessence was evaporated from the samples utilizing rotational evaporator at 55 AA°C in vacum status. Samples were assorted with IPDI at specified proportion and 0.05 % ( w/w ) DBTL used as accelerator.Viscosities of polyols were measured utilizing Brookfield viscosimeter. Molecular weights were obtained from Gel Permeation Chromatography ( GPC ) . FTIR was used to qualify the reaction between isocyanate and polyols during formation of polyurethane coatings.Synthesized rosin was applied as surfacing on meranti wood as depicts in figure 1 with different ration of IPDI and Polyol.
NMP was used as movie formation dissolver and DBTL is a accelerator.Figure 1: Preparation of PU coatings
2.3 Physical Testing
Physical belongingss of PU movies were tested on their hardness ( Pencil Hardness Test, ASTM D3363 ) , Adhesion ( Defelsco, Pull off Adhesion trial, ASTM D4541 ) and Tensile trial ( ASTM D882 ) . Gel content was done by soxhlet extraction utilizing tolune as dissolver.
3.0 Result & A ; Discussion
Synthesis of Polyol
The readying of polyol from ESO and glycerol or EG are basically a nucleophilic permutation reaction affecting the nucleophilic onslaught of hydroxyl on an electrophilic protonation of oxirane O by an acerb accelerator. The nucleophilic onslaught with acerb accelerator in epoxidize fatty acid is described in conventional figure as below:Figure 2: Addition intoxicant constituent to epoxidize fatty acerb [ 6 ] .
Figure 3: The reduction of Epoxy groups during hydroxylation procedureGlycerolFigure 4: Molecular weight of PolyolHarmonizing to the consequence in table 1, most of the epoxy functionality in ESO reacted during hydroxylation procedure. The reduction of epoxy in soya bean fatty acid was monitored by per centum of O content ( % OOC ) ( Figure 3 ) and hydroxyl value at the terminal of the reaction. The opening reaction of epoxy rings with hydroxyl shows the proportionate tendencies with hydroxyl value. The hydroxyl value increased at the terminal merchandise due to the increasement of hydroxyl from glycerol and EG. These phenomenon is shown during hydroxylation procedure in figure 3.
The high hydroxyl value justifies the fact that inordinate oxirane groups are non lost in oligomerization. It is of import to observe that under the conditions of all the reactions, no appreciable glyceryl ester hydrolysis has occurred, as indicated by reasonably narrow polydispersity index ( Mw/Mn ) for all the samples.However, from the output of reaction, 89.
2 % ( Polyol-EG ) and 83.7 % ( Polyol-Glycerin ) were converted to the OH group from the epoxy group. More than 10 % of epoxy was suspected to organize an ether linkage and organize the dimers when glyceryn was used in the reaction. The present of dimers can be shown in figure 4. Higher molecular weight and interaction of hydroxyls in polyol increased the viscousness belongingss and it could be seen in Polyol-Glycerine.Phosphoric acid was used as a reactant every bit good as a accelerator.
Phosphoric acid, a polybasic acid has three dissociation invariables associated with each of its protons, giving rise to anions holding significantly changing nucleophilicity. The used of phosphorous acid in the reaction produced a dark output of polyol and it is disadvantage to the polyol for farther preparation with isocyanate.Table 1: Properties of modified PolyolPolyol/ EthylenePoyol/ GlycerinePercentage of oxirane rings ( % OOC )0.30.4Hydroxyl Number ( mgKOH/g )207268Acid Number ( mgKOH/g )4.22.
5Average weight of Molecular Weight ( Mw )9021021Number of Average Molecular Weight ( Mn )13181869Polydispersity ( Mw/Mn )1.461.83Viscosity ( CPs )15201823
3.2 Effectss of different Polyols at 40 % IPDI ( w/w )
FTIR spectrum in figure 3 depicts the reaction between isocyanate and hydroxyl group in IPDI and Polyol during the formation of PU at 40 % IPDI content. The cut downing extremum at 2260 cm-1 ( isocyanate ) and 3200 cm-1 ( hydroxyl ) during the hardening procedure at 60A°C shows the reaction was occurred to organize urethane linkage. After 12 hours, all the isocyanate had been reacted and staying hydroxyl ( harmonizing to theoretical computation ) is still in PU system.Pencil Hardness, pull of adhesion and tensile strength were tested on coatings movie. The consequence depicts that the hardness, tensile and adhesion strength are higher in Polyol-Glycerine than Polyol aa‚¬ ” EG at the same per centum of IPDI.
Higher functionality of hydroxyls in Polyol Glycerines provides random crosslink denseness and could impute to the higher hardness and tensile strength. The adhesion of two battalion PU ( isocyanate and polyols ) on wood substrate provide the possibility of chemical bonding between isocyanate and hydroxyl in wood fibres. On the other manus, the staying hydroxyls in Polyol-Glycerine will advance the interaction between hydroxyl in wood and rosin.
Appropriate viscousness below than 2000CPs could supply an surface assimilation and mechanical engagement between wood and rosin.2260 cm-13 hours12 hourswavelenght cm-16 hours3200 cm-1Figure 5: FTIR spectrum of PU base on Polyol-EG ( 40 % IPDI )Table 2: Physical belongingss of coatingsType of PolyolPencil HardnessPull off Test Adhesion ( MPa )Tensile Strength ( MPa )Polyol- EG2B4.68.2Polyol- GlycerineHemoglobin6.
Effectss of different per centum of IPDI to the
hydroxyl functionality on coatings belongingss
Assorted ratios of IPDI was used to the polyol to look into the belongingss of polyurethane belongingss. The sum of IPDI in polyurethane system could lend higher denseness of crosslink when higher isocyanate is reacted to the hydroxyl in polyol. Table 3 illustrates the consequence of IPDI in PU at assorted composing.Table 3: Physical belongingss of coatings movie with different per centum of IPDI to the hydroxyl functionality.Type of PolyolPencil HardnessPull off Adhesion ( MPa )( SD )Tensile Strength ( MPa )( SD )Gel Content ( % )Polyol-EG( 20 % )TackyTackyTacky45.
3Polyol-EG( 40 % )6b1.0 ( 0.2 )
73.1Polyol-EG ( 70 % )5B2.3 ( 0.41 )2.
5 ( 0.82 )95.0Polyol-EG( 90 % )2B4.6 ( 1.06 )8.2 ( 2.
3 )99.2Polyol- Glycerine ( 20 % )TackyTackyTacky56.5Polyol- Glycerine ( 40 % )6B1.3 ( 0.5 )2.2 ( 2.
1 )92.2Polyol- Glycerine ( 70 % )5B2.6 ( 1.0 )3.3 ( 1.
3 )98.9Polyol- Glycerine ( 90 % )Hemoglobin6.3 ( 2.2 )8.7 ( 3.
7 )98.5SD=Standard DeviationFrom the consequence, two type of samples which is tacky or healed sample were produced when adding IPDI to the polyol. Tacky sample is a low or inediquate of crosslink denseness due to the low isocyanate content. Density of crosslink was measured utilizing gel content trial and the consequence depicts the increasing tendency when higher per centum of IPDI was used.Consequently, when the composing of IPDI was increased, the tensile and hardness of PU movie besides increased.
The same tendency showed in pull off adhesion. In pull off adhesion, adhesion of sample to the substrate and the tensile strenght of the sample is the chief factor to the value of adhesion.
Hydroxylation procedure utilizing EG and glycerols have high potency as renewable coatings rosin due to the higher hardness, adhesion and tensile strength to the wood substrate. Higher functionality of hydroxyl in Polyol-Glycerine provide more active side for isocyanate and more polar rosin to the polar substrate.