Abstract
In this study, we enhanced the toughness of epoxy resin by blending it with the diblock copolymer poly(ethylene oxide–b–ε-caprolactone) (PEO-b-PCL) with a benzoxazine monomer (PA-OH) as the thermal curing agent. After thermal curing, Fourier transform infrared spectroscopy revealed that intermolecular hydrogen bonding existed between the OH units of the epoxy–benzoxazine copolymer and the C–O–C (C=O) units of the PEO (PCL) segment. Differential scanning calorimetry and dynamic mechanical analysis revealed that the glass transition temperature and storage modulus of the epoxy–benzoxazine matrix decreased significantly upon increasing the concentration of PEO-b-PCL. The Kwei equation predicted a positive value of q, consistent with intermolecular hydrogen bonding in this epoxy–benzoxazine/PEO-b-PCL blend system. Scanning electron microscopy revealed a wormlike structure with a high aspect ratio for PEO-b-PCL as the dispersed phase in the epoxy–benzoxazine matrix; this structure was responsible for the improved toughness.
Highlights
Because epoxy resins possess excellent thermal and mechanical properties, good chemical resistance, ready processability, and excellent adhesion to many substrates, they have many applications in composites—for example, as encapsulates for semiconductor materials, surface coatings, adhesives, and painting materials [1,2,3]
Most epoxies and polybenzoxazines usually but there is a drawback in that intermolecular hydrogen bonding can occur with other polymers form immiscible or phase‐separated blends with homopolymers
°C under a N2 atmosphere rate: were 20 °Cfirst min nonisothermal crystallization experiments, the epoxy–benzoxazine resins with various amounts of PEO‐b‐PCL were first annealed at 240 °C for 5 min, and the crystallization exotherm was at 240 ◦ C for 5 min, and the crystallization exotherm was obtained at temperatures down to obtained at temperatures down to –90 °C
Summary
Because epoxy resins possess excellent thermal and mechanical properties, good chemical resistance, ready processability, and excellent adhesion to many substrates, they have many applications in composites—for example, as encapsulates for semiconductor materials, surface coatings, adhesives, and painting materials [1,2,3]. -miscible block segments; for example, PCL and PEO segments have been added obtain, through hydrogen bonding, nanostructures within epoxy resins [25,26,27]. Most epoxies and polybenzoxazines usually but there is a drawback in that intermolecular hydrogen bonding can occur with other polymers form immiscible or phase‐separated blends with homopolymers (e.g., PCLusually or PEOform [38,39]), and formor after thermal curing. Most epoxies and polybenzoxazines immiscible miscible blends only with poly(N‐vinylpyrrolidone) (PVP) as a result of strong hydrogen bonding phase-separated blends with homopolymers (e.g., PCL or PEO [38,39]), and form miscible blends only [40].
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