Novel shape memory polymers (SMPs) were prepared from benzoxazine-modified epoxy resin. Specimens consisting of aromatic epoxy (E), aliphatic epoxy (N), Jeffamine D230 (D) and BA-a benzoxazine monomer (B) were evaluated. The mole ratio of D/B was used as a mixed curing agent for an epoxy system with a fixed E/N. The effects of BA-a content on the thermal, mechanical and shape memory properties of epoxy-based shape memory polymers (SMPs) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), flexural test and shape recovery test. The results revealed that the obtained SMPs exhibited a higher flexural strength and flexural modulus than those of the unmodified epoxy-based SMP at room temperature and at 20?? C above glass transition temperature (Tg). The presence of 1?mol BA-a as a curing agent provided the specimen with the highest Tg, i.e. about 72?? C higher than that of epoxy-based SMP cured by Jeffamine D230. All SMP samples needed only a few minutes to fully recover to their original shape. The samples exhibited high shape fixity (98?99%) and shape recovery ratio (90?100%). In addition, the recovery stress values increased with increasing BA-a mole ratio from 20 to 38?kPa, when BA-a up to 1?mol ratio was added. All of the SMP samples exhibited only minimum change in their flexural strength at the end of a 100 recovery cycles test.
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Rimdusit et al. (2013) studied this question.
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