Relationship between the Morphology of Nanostructured Unsaturated Polyesters Modified with PEO-b-PPO-b-PEO Triblock Copolymer and Their Optical and Mechanical Properties

Abstract

Nanostructured thermosets were achieved by mixing an unsaturated polyester (UP) resin with an amphiphilic poly[(ethylene oxide)b-(propylene oxide)-b-(ethylene oxide)] block copolymer (EPE). Differential scanning calorimetry and dynamic light scattering were used to study the miscibility and molecular dynamics of nonreactive mixtures. Obtained results indicated that the formation of the nanostructured thermosets followed a self-assembly mechanism. Atomic force microscopy was used to study the morphology of the thermosets. It was found that mixtures cured at 25 °C nanostructured with smaller domains had higher transparency if compared to the mixtures cured at 35 °C. The mechanical properties of nanostructured thermosets showed that UP resin was significantly toughened by addition of the EPE. Results indicated that, for an EPE content of 15 wt %, the critical stress intensity factor, K Ic , of the mixture increased ca. 40%, if compared to the neat UP thermoset.

Epoxy matrix toughness improvement via reactive bio-resin alloying

“…As mentioned before, the compatibility of the blend components and improved adhering between PFA and the epoxy matrix is originated from the formation of intermolecular hydrogen bonds between the hydroxyl groups of epoxy and PFA, as well as the nitrogen groups of DETA. 55 The SEM micrograph of PFA-modified epoxy fracture surfaces, unlike neat epoxy, is extensively rough, indicative of a ductile nature of fracture. As seen in the SEM micrographs of the samples S5, S10 and S15, the roughness of the surfaces is enhanced with increasing amount of PFA.…”

Effect of carboxylated poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymer on nanostructured unsaturated polyester resin

“…As published by us, 11 EPE has the ability to form selfassembled structures when mixed with UP resin. In order to study the changes in the dynamics of chemically modied EPE and UP resin mixtures, DLS measurements of nonreactive 5% EPES and 5%EPEM mixtures were carried out.…”

“…Under measurement conditions, the UP cured systems with 5 and 15 wt% BCPs did not exhibit any crystallization transition neither during cooling nor heating scans, which implies that chemically modied PEO blocks could remain amorphous in cured systems as was also observed for the 5%EPE and 15%EPE cured systems. 11,13 The T g-BCP s of the investigated cured systems shied aer curing to values almost equal to the T g s of neat BCPs. This effect is related to the phase separation in the designed thermosetting systems and the homopolymerization of styrene inside micelles.…”

“…Detailed description of the employed procedure and this application of DLS technique were given in our previous work. 11 Dynamic mechanical analysis (DMA). Dynamic mechanical analysis was done using a GABO Eplexor 100 N, with a threepoint bending device having a span length of 20 mm.…”

“…In our previous works [11][12][13] it was proved that poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymers (EPE) can be employed as a nanostructuration agent for developing toughened thermosetting materials based on UP. This capability of the EPE is ascribed, on the one hand, to the fact that the initially miscible block copolymer (BCP) microphase separates during the curing process following the Reaction Induced Phase Separation (RIPS) and, on the other hand, to the fact that BCP can form self-assembled micelles before curing which remain in the nal cured system.…”