Synthesis and Characterization of Urethane Modified Polyestreamide

Introduction

In recent years synthesis of the polymers from renewable resources has attracted considerable attention of the research scientists and academia through out the world, because of the continuous hike in price of petroleum and high rate of depletion of natural mineral resources 1-7. Furthermore, it has also been forecasted that petroleum stocks moving of the point of exhaustion by the late of 21st century 8-10 consequently much attention is focused in the development of materials from forest product which could be grown again and again. This has inspired investigation of the natural renewable sources as an alternative for the polymer industry1, 3, 11-13. These polymers are having great application in different areas such as in adhesive, varnishes, coatings materials, encapsulating materials and surgical equipments etc 5, 6, 14-16.

India possess vast forest resources and  crowned with various herbs, plant and farm land, yielding variety of oil bearing seeds such as castor17-18, linseed19,vernonia 20 anona  squamossa21, pungamia glabra 22, soybean 23-24,  cocos25,  sunflower25-26,  tung oil27-28  safflower 29-30, canola 30etc . The advantage of these polymeric starting materials include their low cost, ready availability and annual renew ability of resultant polymer material after the targeted use 4-5, 31.

Jatropha tree yielded non edible seeds which contain about 48% oil into appropriate percentage of fatty acid. Although the Jatropha oil is of significant importance, but very little work has been reported in the literature regarding its utility in synthesizing polymers30, 34. Keeping the fact that Jatropha curcus will be going to one of the most abundant oil bearing plant. In present work we have utilized the seed oil of the Jatropha curcas in making urethane modified polyesteramide resin with the objective of using a precursor obtained from of a non-conventional seed oil in making polymeric materials cured at room temperature and reduce the pressure on utilization of petrochemicals.

Experimental

Materials: Oil was extracted from crushed seed of Jatropha curcas through soxhlet apparatus, petroleum ether (b.p 60-80⁰C) was used as solvent. The fatty acids composition of the oil is given in Table-1. Phthalic acid, oxalic acid, acetic acid glacial, pyridine, methanol, carbon tetrachloride, sodium hydroxide, were used of analytical grade (Merck India). Diethanolamine of analytical grade (S.d.Fine chemicals) was distilled under redused pressure before use. Toluene 2,4 diisocynate was obtained from s.d.Fine Chemicals.

SYNTHESIS OF N.N-BIS (2-HYDROXY ETHYL) JATROPHA CURCAS OIL FATTY AMIDE (HEJCA)

Diethanolamine 0.32 mol and sodium methoxide 0.007 mol were taken in four necked round bottom flask fitted with an electrical stirrer, thermometer, dropping funnel and condenser. The reaction mixture was heated to 140±5⁰C. The Jatropha curcas oil (0.1 mole) was added drop wise into the reaction mixture over a period of one hour. The progress of reaction was monitored by TLC .The reactant was further heated for 2-21/2 hour to ensure the conversion of oil into HEJCA. After the completion of reaction the product was dissolved in diethyl ether and washed with dilute aqueous sodium chloride solution. The ethereal solution was filtered and evaporated in a rotatory vacuum evaporator to obtain HEJCA.

SYNTHESIS OF JATROPHA CURCAS POLYESTERAMIDE (JCPEA)

HEJCA, phthalic acid in equal molar ratio and xylene as a solvent were placed in four necked round bottom flask fitted with a Dean Stark Trap, thermometer and mechanical stirrer. Reaction mixture was heated up to 160^o C. The progress of reaction was monitored by taking acid value at regular intervals. After the completion of reaction, the product was taken out from the reaction flask and xylene was removed under reduced pressure to obtain JCPEA.

SYNTHESIS OF POLYESTERAMIDE URETHANE (PEAU)

Polyesteramide of Jatropha curcas seed oil dissolved in xylene, and treated with varying amount of toluene-2, 4 diisocyanate (TDI) monomer in three necked round bottom flask fitted with mechanical stirrer and thermometer. The extent of loading of toluene-2, 4 diisocyanate (TDI) is given in Table-2. The reaction mixtures were heated at 130±5⁰C under continuous stirring. The progress of reaction was monitored by thin layer chromatography (TLC) and also by determination of the hydroxyl value and acid value. The drying time continuously decreases on increasing the amount of TDI upto 6 wt% no signified reduction in time was noticed after this wt%. In addition to this resins losses fluidity and form lumpy aggregates.

Characterization

HEJCA, JCPEA, , and PEAU were characterized by FTIR, ¹HNMR and ¹³CNMR spectroscopies. FTIR spectra of these resins were taken on a Perkin Elmer 1750 FTIR spectro photometer  (Perkin Elmer Cetus instrument Norwalk, CT, USA) using NaCl cell. ¹HNMR and ¹³CNMR spectra were recorded on JEOL GSX 300MHZ FX 1000 spectrometer using deutrated chloroform as a solvent and tetramethylsilane as an internal standard.

The various physico-chemical characterizations like specific gravity, refractive index, inherent viscosity, iodine value, hydroxyl value, acid value and saponification value of the same were determined as per standard laboratory methods and summarized in Table 1and 2.

Table 1:   Characterization of JCSO, HEJCA and JCPEA

Characteristic	JCSO	HEJCA	JCPEA
Oil content	40%	–	–
Gardener color no.	4.0	5	8
Specific gravity	0.927	0.938	0.948
Refractive indexIodine value Acid value Saponification value Yield Fatty acid composition Myristic Palmitic Stearic Arachidic Oleic Linoleic	1.475 96 7 9 0.5 12-17 5-6 0.3 37-63 19-40	-30 4 144 80.68	-24 10.6 132                                                                                                                85.16%

 

Table 2: Physico-chemical characterization of polyesteramide urethane resins.

Resin	Wt % of             TDI	Acid value( mg KOH)	Hydroxyl value (%)	Saponification value	Iodine value	Specific gravity	Refractive index	Viscosity      ( dl/g)
PEAU	2	7.42	7.82	132	32.0	0.948	1.512	0.652
PEAU	4	7.26	7.74	124	30.0	0.952	1.515	0.664
PEAU	6	7.22	7.66	118	28.2	0.955	1.517	0.674
PEAU	8	7.06	7.52	113	27.8	0.957	1.518	0.728

 

SPECTRAL ANALYSIS

N.N-BIS (2-HYDROXYL ETHYL) JATROPHA CURCAS OIL FATTY AMIDE (HEJCA):

The  IR  spectra of  the  HEJCA  shows the band of  alcoholic  group  at 3376 cm^-1 (broad band of a primary alcohol), CH₂ asymmetric and symmetric stretching peak at 2927 and 2855 cm^-1 respectively. The band  for amide carbonyl was observed at 1622 cm^-1 confirm the formation of amide linkages, while CH₂ bending  appears at 1463 cm^-1 and CN stretching peak  ( C-N group ) at 1368 cm^-1.

The ¹HNMR spectrum of HEJCA shows the peak at δ = 0.862-0.89 ppm for terminal methyl group. A broad peak of chain CH₂ group appears at 1.26 – 1.60 ppm ,  CH₂  attached to amide nitrogen appears  at  δ = 3.46  ppm  as a triplet. CH₂ attached to –OH group appears at 4.20 ppm, the alcoholic group appears at 5.3 ppm, the chain -CH=CH- appears at 5.282-5.35 ppm as a multiplet. These spectral datas are characteristic of structure of HEJCAFig.1 (a).

¹³CNMR spectra shows the characteristic signal of amide –CO group at 175.22 other signal such as terminal –CH₃ group appears at 13.9 ppm, the different CH₂ group of the fatty acid chain appears at 22-34 ppm. The CH₂ of adjacent to carbonyl group appears at 32.9, the CH₂ adjacent to –OH appears at 65.52, and CH₂ adjacent to amide appears at 50.75 ppm. The olefinic double bonded carbon of fatty acid chain appears at 127 and 129 ppm, respectively.

JATROPHA CURCAS POLYESTERAMIDE (JCPEA)

The IR spectra of the JCPEA    shows the band of alcoholic group at 3378 cm^-1 (broad band of a primary alcohol), CH₂ asymmetric and symmetric stretching band at 2921 and 2856 cm^-1 respectively. The band for amide carbonyl and carbonyl group of ester are observed at 1634 and 1735 cm^-1. The CN stretching band ( C-N group ) at 1463 cm^-1; The C-O-C symmetric and  asymmetric band are observed at 1275 and 1383 cm^-1.The band at 769.4 a characteristic of disubstituted benzene of a phthalic acid. The ¹HNMR spectrum of JCPEA shows the peak at δ=0.86-0.89 ppm for terminal methyl group. A broad peak of chain CH₂ group appears at 1.26-1.30 ppm , CH₂ attached to amide nitrogen appears at δ=1.60-1.61 ppm . The sharp peak of CH₂ adjacent to the ester group is observed at δ=2.02- 2.06 ppm, alcohol i.e proton at δ=4.33 ppm, -CH=CH- at δ = 5.29-5.36 ppm, and aromatic protons are observed at δ=7.30-7.48 ppm, supporting the structure of JCPEA as shown in Fig.1 (b).

¹³C-NMR spectra shows the characteristic signal of carbonyl of ester at 177 ppm confirm the formation of ester linkages. The additional signal such as –CO of amide appears at 173 ppm . Various ring carbon of benzene ring appears at 133, 132, 129, 127, 123 ppm. The peak for different CH₂ groups of the fatty acid chain appears at 34-24 ppm the peak for double bonded carbon of a fatty acid chain appears at 127.8 and 127.2 ppm respectively . Terminal methyl group of fatty acid chain appears at 14 ppm.

POLYESTERAMIDEURETHANE (PEAU)

The IR spectra of PEAU are more spread than PEA in the range of 3500-3150 cm^-1 indicates the overlap of OH and NH groups. These characteristic bands indicate the introduction of NH group in addition to OH group. In case of PEA the peak is suppressed and appears as a solder 3378 cm^-1. In PEAU the NH deformation mode appears at 1560 cm^-1, CH₂ asymmetric and symmetric stretching peak appears at 2925.3 and at 2863 cm^-1       respectively. The –CH=CH- appears at 3022.6 cm^-1 where as aromatic double bond appears at 2963.3 cm^-1. The peak for amide carbonyl and carbonyl group of ester are observed at 1607 and 1727 cm^-1. The CN stretching peak (C-N group) appears at 1494 cm^-1. The C-O-C symmetric and asymmetric peaks are observed at 1378 and 1456 cm^-1. The band at 1456, 1378, 1229, 1038 are characteristic of disubstituted benzene of a phthalic acid.      

The ¹HNMR spectrum of PEAU shows the peak at δ=0.86-0.88 ppm for terminal methyl group.  The peak at δ=2.02-2.07 ppm for methyl group of TDI. A broad peak of chain CH₂ group appears at 2.23-2.37 ppm , CH₂ attached to amide nitrogen appears at δ=2.56-2.66 ppm . The new peak for –NH of urethane at 7-8.8 ppm. The different characteristic peaks for aromatic protons are observed at δ=6.93-7.28 ppm. These observations broadly confirm the proposed   structure of PEAU as shown in Fig.1(c).

¹³CNMR spectra show the characteristic signal of carbonyl of ester at 178 ppm and signal for carbonyl of amide at 174 ppm. Various ring carbon of benzene ring appears at 137, 136, 134, ppm. The peak for different CH₂ groups of the fatty acid chain appears at 22-19 ppm. The peaks for methyl group of TDI appear at 15- 14 ppm.

Conclusion

In this work Jatropha curcas seed oil a renewable resource used as a starting material for the synthesis of PEAU, cured at room temperature which reduce the consumption of petrochemical in making polymeric resins. The color of PEAU very low which provide avenue for utilization in paint industries. The broad spectral feature of the HEJCA, JCPEA and PEAU was confirmed by IR, ¹HNMR, ¹³CNMR spectroscopies. The various physico-chemical properties were also investigated. These informations can be used in making high performance coatings and paints.

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