The hot water flotation method of extraction enumerated by Warra [15] was adopted for the extraction. The sesame seeds were visually observed and cleaned to get rid of unwanted contaminants and ground to paste; The seeds were ground to paste and heated to 80˚C - 90˚C for 15 minutes with stirring, sufficient boiling water was added to suspend the ground sesame seeds and the mixture was boiled for another 15 minutes and allowed to cool. The upper layer was collected and dried by mild heating.

Different oil lengths formulation for the synthesis was calculated for the 40%, 50%, and 60% oil lengths alkyd resins respectively as shown in Tables 1-3 respectively. Calcium oxide served as the catalyst. A heating mantle, a 3-neck round-bottom flask, a mechanical stirrer, a nitrogen intake and a thermometer inlet were used to carry out the synthesis as shown in Figure 1. To get rid of any water that might have been formed during the trans-esterification reaction, xylene was also used as the azeotropic solvent. There were two stages to this process: alcoholysis-transesterification and poly-condensation.

In the alcoholysis-transesterification stage, a 500 ml three-neck round-bottom flask was filled with a measured amount of the sesame oil (120 g for the 40% oil length). It was followed by the addition of 0.3 g of calcium oxide alongside a measured amount of glycerol (71.09 g) and the temperature was raised gradually

to an elevated temperature of 200˚C and maintained for 2 hours, as the reaction progressed aliquots were constantly been taken at 30 minutes intervals to check for its solubility in 1 to 3 volumes of methanol which clearly indicated the formation of a monoglyceride upon giving a clear solution when observed. The system was then allowed to cool to about 120˚C to allow for onset introduction of the trans-esterification stage.

The poly-condensation stage was initiated when the temperature of the monoglyceride stage was brought down to about 120˚C and 108.91 g of phthalic anhydride was added to the reaction mixture, followed by the addition of xylene (10% of the total resin weight) to aid eliminate the water of esterification by producing an azeotrope [16] [17] . The temperature was extended to 230˚C - 250˚C while the reaction progresses. Aliquots were taken from the reaction blend at time periods of 30 minutes in other to determine the drop-in acid value and the volume of water removed was also recorded. The drop-in acid values were determined by titrating two aliquot portions of the mixture withdrawn against 0.1 M KOH solution, a measured amount of phenolphthalein dissolved in a mixture of ethanol and toluene (1:1) served as an indicator [18] . The reaction was halted when the acid value reached a value of less than 10 mg KOH/g. This process was repeated for the 50% and 60% alkyd resin oil lengths respectively. The pathway for the alkyd resin synthesis is shown in Figure 2(a) and Figure 2(b) respectively.

The analysis was performed on the 40% alkyd resin due to its remarkably low moisture absorption, degree of polymerization, extent of reaction and higher number-average molecular weight formation.

FTIR?8400S, Fourier Transform Infrared spectrophotometer to determine the functional groups present, the morphology of the alkyd resin sample was investigated using a scanning electron microscope (SEM). A JOEL JSM 5600 LV model scanning electron microscope with an accelerating voltage of 15 kilovolts was employed to observe the surface morphology of the alkyd, the resin was coated with gold before analysis to avoid any charge build-up by the electron absorbed by the resin [19] .

Thermo-gravimetric analysis (TGA) in an environment of argon at a heating rate of 10˚C /min from 30˚C to 950˚C using the PerkinElmer TGA model, the thermal characteristics of the resin sample were examined.

Using thermogravimetric analysis (TGA), variations in mass with respect to temperature are found. It is typically used to calculate the degradation temperatures, absorbency levels of materials, amounts of inorganic and organic components present in a material, and solvent residue analyses. The sample is hung in a furnace that has a temperature programmer under control using an electrical balance.

Differential scanning calorimetry was carried out using the STAR?SC/DTA F3 JUPITER instrument (NETZSTH, Germany) model within the temperature interval from 20˚C to 250˚C under nitrogen atmosphere. It is a method of thermal investigation that looks at how temperature affects a material’s heat capacity. When a known mass sample is heated or cooled, changes in the heat flow are seen as a result of differences in the sample’s heat capacity. This makes it

possible to see transitions like melt-to-glass transitions (Tg), melting point (Tm), and crystallization degree (Tc) [20] .

The graph below shows the result of the variation of acid value with reaction time of the various alkyd resin oil lengths; group [29] reported that acid values less than 15 are suitable for paint application which signifies a reasonable amount of conversion.

It was observed that there was a corresponding decrease in acid values at 40%, 50% and 60% oil lengths as the reaction progressed with time as seen in Figure 4(a), there is also a significant decrease in the acid values at the earlier stages and then followed by a gradual decrease which could be attributed to the variations in reactivities of the primary and secondary hydroxyl groups of the glycerol with the phthalic anhydride carboxyl group [12] .

It was reported by Nway and Mya [29] that the primary hydroxyl groups of the monoglyceride react faster than those of the secondary hydroxyl groups of the monoglyceride with the added phthalic anhydride which also accounts for the decrease in the acid values observed, and this is due to the increased concentration of these functional groups present in the glycerol and the phthalic anhydride at the first phase of the reaction which is characteristic of a step-growth polymerization [30] .

It was observed that as the oil length increased, the total volume of water evolved also increased, at the onset of the synthesis, the rate of water removal was high, and this trend is followed by a gradual removal rate at longer periods of reaction from 30 to 180 minutes till no water of esterification is observed. This reveals the formation of alkyd resin since all the available reactive species have reacted at this stage which can also be related to the acid value changes highlighted in Figure 4(b).

The extent or fraction of the reaction is defined as the fraction of the hydroxyl or carboxyl functional group that has taken part in the reaction at a given time [24] , Figure 4(c) shows that the extent of the reaction otherwise known as the esterification conversion percentage (%P_av) increased with increase in reaction. It can also be observed that this trend is faster in the 40% alkyd resin synthesis than in the 50% and 60% synthesis processes.

The average acid value decreases with an increase in the average degree of polymerization for the SISO alkyd resin samples as seen in Figure 4(d) which was expected owing to the formation of high molecular weight alkyd resin polymer.

The variation in degree of polymerization with reaction times is shown in Figure 5(a). There is a linear behavior at the onset of the reaction progress from 0 to 60 minutes before the deviation from linearity which marks the occurrence of branching along the polymer chain [31] , nevertheless a second order kinetics was observed at ≥ 9 D_p region, equivalent to >70% conversion, at this period,

a straight-line plot was obtained. This portion could also be used to mark changes in physical characteristics of the reaction process (such as changes in viscosities) [32] . It can also be observed that the 40% alkyd had the highest degree of polymerization followed by the 50% and 60% in that order and this corresponds to the reaction times of the primary and secondary hydroxyl groups which results in the yield of linear and three-dimensional molecules respectively [12] .

The average molecular weight (M_av) with respect to the acid value at different stages of the reaction is calculated using the equation:

M a v = W / ( k − P a v ) l A [18]

where W is the total weight of all the reactants; k is the ratio of the total moles of all reactants to the total equivalent of the acid (N_m/E_a); ℓA is the total equivalent of the acid and P_av is the extent of reaction.

It is deduced that no reasonable increase in the molecular size of the reaction mixture occurred during the early stages of the reaction. However, as shown in Figure 5(b), there is a significant increase as the reaction progresses. The low rate of polymerization is responsible for the low molecular weight observed at the start of the reaction. An increase in polymerization rate led to an increase in weight-average molecular weight.

This pattern continued until the gelation point, when structural changes in the polymer size of the molecule in solution begin. The weight-average molecular weight of the alkyd decreased as the length of the oil increases. This is in line with previous findings by Aigbodion and Oladipo [6] [12] .

It has also been suggested that increasing the oil length increases the fatty acids available for the reaction, resulting in a higher chance of chain growth termination, resulting in lower molecular weight polymers [33] and this can be seen evidently in the 40% alkyd resin having the highest weight-average molecular weight followed by the 50% and 60% alkyd with respect to their oil lengths.

The alkyd resin thermal degradation can be divided into three phases: drying, main pyrolysis and carbonization, the first phase, between 100˚C and 150˚C, results in a weight loss of around 4% which could be attributed to moisture vaporization and the possible emission of volatile organic compounds. The degradation begins around 300˚C and spreads across a wider temperature range. The second stage, between 300˚C and 500˚C, could be attributed to the removal of some chemical species that could have been identified using a combined TG-MS, and the third stage, above 500˚C, reflects total decomposition to char.

The results such as Initial decomposition temperature (T_i), final decomposition temperature (T_f), the temperature of 50% weight loss (T_50%), and percent residue at 500˚C is shown in Figure 6. The temperatures of 50% weight loss of the 40% alkyd resin as a standard indication for thermal stability of polymers was ≤440˚C which indicates they could meet temperature resistant requirements, which can be used in surface coating application. The percent weight residue of the 40% alkyd resin is 10% at 500˚C [34] .

The morphology of the alkyd resin sample was investigated using a scanning electron microscope (SEM). A JOEL JSM 5600 LV model scanning electron microscope with an accelerating voltage of 15 kV was employed to observe the surface morphology of the 40% alkyd resin sample at different magnifications as seen in Figure 7(a) and Figure 7(b), whilst Figure 8 displays a 3D interfacial plot of the polymer matrix of the 40% alkyd resin sample (Figure 7(c)).

The SEM micrograph highlighted regions that are homogenous and void of particles and regions that are reflective of particles unevenly distributed along the alkyd film, the magnification shows that the homogenous surface could be attributed to the formation of a polymer matrix that is strongly held forming the polymer backbone which can also be ascribed to the rigidity of the alkyd film, the SEM micrograph also revealed some areas of weakness in the form of an underlying crack which could be corrected if the alkyd was to be co-polymerized or blended.

The temperature at which the polymer changes from the glassy state to the rubbery state in the amorphous region as seen in Figure 8, indicates that the value of the glass transition (T_g) of the 40% alkyd resin is 34.99˚C and this value lies between the −93.5˚C to 226.85˚C range for most synthetic polymers [35] at temperatures above Tg, polymer molecules absorb energy to form ordered arrangements and undergo crystallization. This is an exothermic process and

requires that less heat is needed to maintain a constant heating rate of the sample with the reference and as a result, it is observed as the lowest point of the dip. At higher temperatures, crystallinity is distorted reaching the melting temperature (Tm), since melting is an endothermic process, the heat is increased to maintain the heating rate of the sample constant with the reference resulting in a discontinuity in the plot, and it is considered as the temperature at the peak.

FT-IR ? 8400S Fourier Transform Infrared spectrophotometer was used to detect the functional groups of the ester links present from the poly-condensation reaction between phthalic acid and glycerol modified with sesame seed oil.

It can be observed from Figure 9 that the weak broad peaks at 3454.21 suggest the presence of a carboxylic ?OH stretch present in the SISO modified alkyd resin samples. The medium peaks found at 2933.51 cm⁻¹ suggest the presence of an alkane C-H stretching in the SISO modified alkyd resin. The less intense peaks at 2682.59 cm⁻¹ infer the presence of an asymmetric stretch of the carbonyl groups present in the SISO modified alkyd resin. The peak at 2290.18 cm⁻¹ could be attributed to the C=O vibration of carboxylic and carbonyl compounds present. The medium peaks found at 1454.38 cm⁻¹ indicate the presence of a ?CH bending of the methyl groups. The medium peaks at 1742.55 cm⁻¹ show the presence of a carbonyl group which could be attributed to an aromatic ester C-O stretch present in the SISO modified alkyd resin.

The weak band at 1585.93 cm⁻¹ indicates the presence of a C=C stretching for aromatics and some in-plane and out-plane stretching vibrations were recorded at 726.15 cm⁻¹ which identifies the presence of the ?CH₂ rocking mode.