Studies on maleate/fumarate isomerisation in unsaturated polyesters by infrared spectroscopy

Abstract

For study of maleate/fumarate isomerisation in unsaturated polyesters infrared technique was used without using model compounds. This was done by solving the following equation for two different polyesters or one polyester with two concentrations for the molar extinction coefficients at 675 crn-1 for maleate and 980 cm-1 for fumarate.Percentages of maleate and fumarate are given by following equations :The out of plane vibration of CH for maleate appeared a t slightly lower frequency, i.e. at 675 cm-1 due to steric hindrance. It was noted that the increase of the ratio of maleate to saturated acid in the polyester enhances the conversion from maleate to fumarate due to coiling tendency of the chain and causing steric compression. This tendency was also shown by phthalic anhydride based polyesters due to ortho carboxylic group compared with adipic acid and isophthalic acid. It is evident from more conversion from maleate to fumarate in case of phthalic anhydride based polyesters than that of isophthalic acid and adipic acid based polyesters. I n case of bisphenol-A based polyesters, low conversion from maleate to fumarate took place, because of less coiling of between the two segments of the chain which are phenyl groups associated through carboxyl group of maleate. Conversion was more pronounced in polyesters based on 2.2-di-(4-hydroxy-3.5-dibromophenyl) propane and 2.2-di-(4-*) At present a

Modeling of unsaturated polyester prepolymer structures. I. Chain branches and overall chain end numbers

“…Unfortunately, due to and branching chains caused by the Ordelt reaction, (14) it is clear that the number-average molar masses measured by both methods, M n ,index and M n ,SEC , Consequently, one has are not the real number-average molar mass, M n , in eq. (12) …”

“…The isomerization extent depends on reaction conditions 11 and naAt high temperature, the polyesterification reacture of the acids, 12,13 diols, 13,14 and catalysts. 15 tion in Scheme 3 is often accompanied by transesterification, which is, in fact, an alcoholysis or an acidolysis of the polyester chains by hydroxyl or carDouble-bond Saturation (Ordelt Reaction) boxyl groups of monomers and/or macromolecules.…”

Unsaturated Polyesters

“…6o, [63][64][65][66] At the beginning of the reaction, non-catalyzed isomerization exhibits second-order kinetics,60,63,67 indicating an autocatalytic effect of the protons of maleic acid on isomerization Some isomerization catalysts have been described, including acids, amines, 68 -71 alkali metal halides 72 and sulfides."? the acidity of the system, and the nature of the reactants and catalysts.60 The rate of maleate to fumarate conversion depends on the nature of the «-diol used: the longer the chain of the diol, the lower the isomerization rate.…”

DSC curing study of catalytically synthesized maleic‐acid‐based unsaturated polyesters

“…The curing of unsaturated polyesters includes varyious concentrations of initiator19 or accelerator,15 the use of different accelerators,22, 23 the influence of styrene concentration,18 the use of a vinylic comonomer other than styrene,16 the effect of the molar mass of the pre‐cured resin14 as well as the influence of additives or fillers 20. 24–29 The cis–trans isomerization during polyesterification of maleic acid has been investigated extensively,30–34 as well as the effect of isomerization on the curing reaction,14 but the effect of polyester composition on the isomerization reaction and especially on the curing reaction have not been studied properly.…”