Rate dependent mechanical behavior of polymer network isomers with controlled topology

Thermosets are one important group of crosslinked polymers that are widely used in different applications including composites, adhesives, and coatings. In a novel processing technique, it was shown that toughness of these materials can be enhanced by incorporating crosslinked low-modulus domains and the level of enhancement can be controlled by tailoring the size of these domains. These domains are termed as Partially Reacted Substructures (PRS). In this work, the rate dependent mechanical behavior of these polymer network isomers were investigated. To do this, compression tests were performed on these polymer materials under quasi-static (∼ 0.05 1/s) and high strain (∼2000 1/s) rates. By looking at the small-strain mechanical properties of the system isomers under quasi-static strain rates, it was observed that the compressive modulus decreases with the increase of the PRS cure conversion. However, under high strain rates, the compressive modulus increases with the increase of the PRS cure conversion. This enhanced mechanical behavior under high strain rates would enable the modified systems to be applicable at extreme dynamic environments where durable composite materials are desired.