Abstract
Epoxy vitrimers with reprocessability, recyclability, and a self-healing performance have attracted increasingly attention, but are usually fabricated through static curing procedures with a low production efficiency. Herein, we report a new approach to fabricate an epoxy vitrimer by dynamic crosslinking in a torque rheometer, using diglycidyl ether of bisphenol A and sebacic acid as the epoxy resin and curing agent, respectively, in the presence of zinc acetylacetonate as the transesterification catalyst. The optimal condition for fabricating the epoxy vitrimer (EVD) was dynamic crosslinking at 180 °C for ~11 min. A control epoxy vitrimer (EVS) was prepared by static curing at 180 °C for ~11 min. The structure, properties, and stress relaxation of the EVD and EVS were comparatively investigated in detail. The EVS did not cure completely during static curing, as evidenced by the continuously increasing gel fraction when subjected to compression molding. The gel fraction of the EVD did not change with compression molding at the same condition. The physical, mechanical, and stress relaxation properties of the EVD prepared by dynamic crosslinking were comparable to those of the EVS fabricated by static curing, despite small differences in the specific property parameters. This study demonstrated that dynamic crosslinking provides a new technique to efficiently fabricate an epoxy vitrimer.
Highlights
Crosslinked structures confer thermosets with many superior advantages, including excellent mechanical properties, chemical and thermal resistance, and dimensional stability, which makes them irreplaceable in various applications such as encapsulants [1], coatings [2], adhesives [3], electronics [4], and high performance composites [5,6,7]
We evaluated the possibility of using dynamic crosslinking to curing glass reactors
To gain insight differences in the dynamic mechanical properties of the two samples, we meas gel fraction of the samples after compression molding at 180 °C under 20 MPa fo and found that the gel fraction of epoxy vitrimers prepared by static curing (EVS) increased from 84.4% to 90.6%, while tha remained almost unchanged with a value of 85.9% before and after compression
Summary
Crosslinked structures confer thermosets with many superior advantages, including excellent mechanical properties, chemical and thermal resistance, and dimensional stability, which makes them irreplaceable in various applications such as encapsulants [1], coatings [2], adhesives [3], electronics [4], and high performance composites [5,6,7]. We reported that highly crosslinked castor oil-based poly(ester amide) networks containing disulfide bonds could be synthesized by condensation polymerization directly, and could be thermally processed into final products [38]. Extensive investigations have been conducted in order to develop epoxy vitrimers through the incorporation of various dynamic covalent bonds Most of these investigations focused on the structure design [41], malleability [42,43], and recyclability [44,45] of the vitrimers. No investigations have been conducted on fabricating epoxy vitrimers through dynamic crosslinking procedures in traditional polymer processing machines, such as internal mixers or extruders. The structure and properties of the epoxy vitrimer prepared by dynamic curing were comparatively investigated with the counterpart synthesized by static curing in a flask
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