Influence of miscibility of PEG-B-PPG-B-PEG/EPOXY systems on thermal, mechanical and fracture properties

Abstract

Epoxy matrix blends with poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) triblock copolymer (PEG-b-PPG-b-PEG) with 30% PEG blocks were elaborated and investigated. The systems were prepared by the casting method with cure at 100 °C, with different amounts of copolymer in the epoxy matrix, and with the aim of evaluating the influence of the modifier on the properties of the blends. By DSC it was verified that the glass transition temperature relating to the matrix phase decreased in systems with copolymer in relation to neat epoxy, thus the blends formed partially miscible systems. On the other hand, phases separation or microdomains of the block copolymer within the epoxy matrix were not discernible by scanning electron microscopy. In general, the addition of the block copolymer impaired the mechanical properties evaluated in the tensile test. However, the fracture mechanisms observed on the fracture surface of the blends indicate that an improvement in the toughness of the systems may have occurred due to the crack pinning and crack deflection mechanisms.