Synthesis of a New Hyperbranched Polyaminoester and Its Use as a Reactive Modifier in Anionic Curing of DGEBA Thermosets

Abstract

The synthesis and characterization of a new hyperbranched PAE with a flexible structure and terminal hydroxyl groups is reported. The influence of PAE in the anionic curing of DGEBA with 1‐methylimidazole was studied. The curing reaction was investigated by DSC and FT‐IR. The covalent incorporation of the modifier in the matrix was proven. The addition of PAE to the formulation reduced the contraction on curing. The modified materials were more thermally degradable than neat DGEBA thermosets, which is advantageous from the point of view of their reworkability. Their Tgs were reduced by the flexibility introduced by the aliphatic structure of PAE. SEM microscopy on the fractured surface of cured samples revealed a homogeneous morphology and a possible effect of PAE as a toughness enhancer.

Synthesis of a new multiarm star polymer based on hyperbranched poly(styrene) core and poly(ε‐caprolactone) arms and its use as reactive modifier of epoxy thermosets

“…In previous work on anionic curing of epoxy resins, we observed an acceleration of the curing process and an increase of the final conversion of epoxide groups on increasing the proportion of hydroxyl groups in the curing mixture 4, 27. However, on adding the star polymer, the concentration of epoxy groups decreases and this fact can explain the observed deceleration.…”

“…The main one involves the use of flexible linear or dendritic polymers capable to plasticize the epoxy matrix increasing the ductility. This fact, despite of improving this property, usually worsen the thermomechanical characteristics of the modified materials 3–5…”

Structural analysis of the curing of epoxy thermosets crosslinked with hyperbranched poly(ethyleneimine)s

“…For that reason, they have a more disperse, less perfect structure than perfect dendrimers, but they have the advantage that no intermediate purification steps are required in their synthesis, leading to a good compromise between affordable cost and properties. In the field of thermosetting polymers, one of their most relevant applications is as toughening agents that phase-separate during curing [2][3][4][5][6][7][8][9][10], but it is also of interest their role as reagents that get incorporated into the network structure [11][12][13][14][15][16][17].…”

Improved epoxy thermosets by the use of poly(ethyleneimine) derivatives

“…Other HBPs as poly(ester-amide) and poly(amino-ester) have been used as modifiers for epoxy resins, leading to improvements in shrinkage, degradability or mechanical properties [52,101]- [103]. The effect of molecular weight of different hyperbranched poly(ester-amide)s before shrinkage was investigated and a progressive decrease of global shrinkage was observed on increasing the proportion of HBP and in the higher molecular weight [101].…”

“…In order to overcome these limitations, HBPs have been proposed as reactive modifiers, leading to a significant improvement of this property without negatively affecting the thermomechanical characteristics [151]. The modification of different epoxy systems using commercially available HBPs has been reported [52,103,152,153]. An increase in impact strength was achieved without sacrificing the thermal and thermomechanical properties.…”