Abstract
Bisphenol A diglycidyl ether (DGEBA) was blended with polyetherimide (PEI) as a thermoplastic toughener for thermal stability and mechanical properties as a function of PEI contents. The thermal stability and mechanical properties were investigated using a thermogravimetric analyzer (TGA) and a universal test machine, respectively. The TGA results indicate that PEI addition enhanced the thermal stability of the epoxy resins in terms of the integral procedural decomposition temperature (IPDT) and pyrolysis activation energy (Et). The IPDT and Et values of the DGEBA/PEI blends containing 2 wt% of PEI increased by 2% and 22%, respectively, compared to those of neat DGEBA. Moreover, the critical stress intensity factor and critical strain energy release rate for the DGEBA/PEI blends containing 2 wt% of PEI increased by 83% and 194%, respectively, compared to those of neat DGEBA. These results demonstrate that PEI plays a key role in enhancing the flexural strength and fracture toughness of epoxy blends. This can be attributed to the newly formed semi-interpenetrating polymer networks (semi-IPNs) composed of the epoxy network and linear PEI.
Highlights
Epoxy is extensively used as a typical thermosetting resin
The peaks of the epoxide group for the cured DGEBA and DGEBA/PEI blends significantly decreased after the curing reaction
The polymer decomposition temperature (PDT) and integral procedural decomposition temperature (IPDT) values of the blends slightly increased with the PEI content
Summary
Epoxy is extensively used as a typical thermosetting resin. Epoxy resin is widely used as adhesives, high-performance coatings, packaging, and lamination materials because it exhibits excellent chemical stability, low shrinkage, good adhesion to various metals, good thermal stability, and good mechanical properties [1,2,3,4,5,6]. From the perspective of high-performance engineering applications, pure epoxy resin possesses some limitations, including poor crack resistance and inherent brittleness with the high cross-linking density for curing. To overcome these problems, several methodologies, including the integration of a second phase (e.g., thermoplastics and inorganic nonparties), have been explored to improve the fracture toughness and strength in modified epoxy systems. IPN are special blends defined as mixtures of two or more cross-linked polymer networks with intermolecular interlocking, rather than chemical bonds. The network interlocking occurs during the curing process and affects the physical properties of the blends
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