Synthesis of unsaturated polyester resins for large sized composites

Abstract

A series of unsaturated polyesters based on phthalic anhydride (PHA), maleic anhydride (MA), ethylene glycol (EG), diethylene glycol (DG), triethylene glycol (TG), propylene glycol (PG), styrene (Sty) and acrylonitrile (AN) were prepared. The molecular weights of the prepared polyesters were determined by end‐group analysis. The effect of the structure of the resin on its curing behavior has been investigated. On the basis of the experimental study, the following were concluded: (1) The maximum curing temperature (Tmax) is related to the molecular weight of the glycol incorporated in these castings. In this context the Tmax was found to decrease with increasing the molecular weight. Meanwhile the time to peak temperature tmax was increasing. (2) The higher the percentage of AN in the crosslinking monomer system, the slower a resin cures. (3) The values of Tmax were found to be influenced to a large extent by the percentage of AN.

Synthesis and characterization of some degradable polyesters

“…This in turn is reflected in T max and t max . It is well known that, as the number of curable double bond along the unsaturated polyester chain increases, the curing reaction becomes more exothermic and proceeds faster [27,28]. Mita and Kambe studied structural effects of unsaturated polyester resins on their curing behavior [29].…”

On the Heat Stabilization Efficiency of Polyester Plasticizers for Poly(vinyl chloride) (PVC)

“…[28] The constituents of these polyesters and their designations are given in Table 1. Once the various glycols and acids were weighed and charged into a kettle, they were constantly agitated.…”

“…After the completion of polyesterification reaction, the prepared polyesters were subjected to vacuum evaporation (100 mmHg at 180 8C) in order to increase the molecular weights of polyesters and lower the acid value to below 25.0 (mg KOH/g resin) and also to get rid of any unreacted materials. [28] The products were then purified by dissolving in acetone and precipitation in petroleum ether (60-80 8C). The acid numbers (A) and hydroxyl numbers (B) (mg KOH/g resin) of the purified samples were determined [29] and applied in the calculation of the number average molecular weights M n of the synthesized polyesters by substitution in Equation (1).…”

Modified unsaturated polyester resins synthesized from poly(ethylene terephthalate) waste, 1. Synthesis and curing characteristics

“…So, the net result of this variation is an increase of the number of curable double bonds along the unsaturated polyester chains. It is well known [25][26][27][28][29][30] that the curing reaction gets faster and more exothermic with increasing double bond intensity per each unsaturated polyester chain. Horie et al [27] studied the effect of the chemical structure of unsaturated polyester resins on their curing behavior and reported that the final degree of curing under isothermal conditions increases remarkably with increasing amount of fumarate/maleate unsaturations per polyester chain.…”

“…This effect of the varying MA concentration on the curing behavior of unsaturated polyester resins is consistent with our data obtained previously on unsaturated polyesters synthesized from virgin materials. [29,30] The effect of PHBA concentration…”