Kinetic modeling of nanoclay‐reinforced unsaturated polyester resin

Abstract

Curing behavior of an unsaturated polyester (UP) resin containing 1 wt% organically modified clay (OMC) catalyzed with methyl ethyl ketone peroxide (MEKP) initiator and promoted by cobalt naphthenate accelerator was investigated by dynamic differential scanning calorimetry (DSC) at five different heating rates of 5, 10, 15, 20, and 25°C/min. X‐ray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/OMC composites. Results showed a mixture of intercalated and exfoliated morphology. The dynamic DSC curing curves showed a bimodal exothermic peak; therefore, two independent reactions, namely, redox and thermal copolymerizations were assumed. Kinetic parameters were calculated by using autocatalytic model and using Down hill simplex method and Runge–Kutta algorithm for each reaction. The addition of nanoclay resulted in decrease of the activation energy of the redox reaction compared to that of the neat UP resin. Also, the pre‐exponential factor of the first reaction for UP/OMC was less than that of the neat UP. Two factors including decreasing the activation energy and decreasing the number ofcollisions of reactionary components finally resulted in increasing the reaction rate of the first reaction out of the whole reaction in the system containing nanoclay compared to the neat UP resin. It is interesting that nanoclay has no effect on the thermal decomposition reaction. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

Cure kinetic study of organoclay‐unsaturated polyester resin nanocomposites by using advanced isoconversional approach

“…, the activation energy of neat UP system at 0 ≤ α ≤ 0.4 is about 53 kJ mol −1 which are attributed to the redox decomposition of peroxide. This value is in accordance with the results reported by others . For a reduction–oxidation type of initiation, peroxide can be decomposed rapidly by metal ions at ambient temperature, generating free radicals as follows : where ROOH is the initiator, Co 2+ (Co 3+ ) is the promoter, RO • and ROO • are the free radicals, and L is the octoate or naphthenate ligand.…”

“…Comparison of activation energy curves of neat UP and UP/30B systems versus the degree of conversion reveal that the curves follow the same trend except that for α ≤ 0.8, the activation energy of redox reaction for UP/30B system is less than that of the neat UP. The decrease in the activation energy of redox reaction of peroxide may be due to the co‐catalytic effect of nanoclay surfactant which forms complex ligands with cobalt . The decrease is not observed at α ≥ 0.8.…”

Unsaturated Polyesters and Vinyl Esters

“…Curing rate modification is believed to be the result of two concurring events taking place in the presence of nanoclay: (1) the activation energy for the curing of UPR has been shown to decrease in the presence of nanoclay (which is in favor of accelerated cure), and (2) the number of collisions during cure is reduced (which is in favor of decelerated cure) [84]. Typically, the decrease in activation energy outweighs the latter so that often the presence of nanoclay enhances the UPR cross-linking.…”

“…The curing reaction of UPRs is typically modified by organoclay additives [80,83,84]. Curing rate modification is believed to be the result of two concurring events taking place in the presence of nanoclay: (1) the activation energy for the curing of UPR has been shown to decrease in the presence of nanoclay (which is in favor of accelerated cure), and (2) the number of collisions during cure is reduced (which is in favor of decelerated cure) [84].…”

Impact of titanium and silica/titanium fumed oxide nanofillers on the elastic properties and thermal decomposition of a polyester resin

“…6,[12][13][14][15] The unsaturated polyester resin (UPR), which belongs to thermosetting polymers, demonstrates a good combination of mechanical and electric parameters and resistivity to chemically aggressive environments, and it is a good matrix for preparing composite materials with improved functional parameters. [16][17][18][19][20][21][22][23][24][25] In addition, because of the relatively low cost of the polyester resin, its composites are promising it's the manufacture of construction components in both domestic and industrial applications. 26 It is known that concentration effects of inorganic oxide nanoparticles of a high surface-active site number on the physical parameters of polymer composites have an unmonotonic character.…”