Study of shape memory mechanism and performance of shape memory polyurethane prepared based on tetrahydrofuran

Abstract

A series of shape memory polyurethane (SMPU) substrates were fabricated utilizing polyether polyol (PPG) with varying molecular weights, 4,4′-diphenylmethane diisocyanate (MDI), and4,4′-methylene-bis-(2-chloroaniline) (MOCA) as primary raw materials. Tetrahydrofuran (THF) served as the solvent. The investigation focused on the effects of different soft segment molecular weights and additional THF content on the properties of SMPU. The study aimed to explore the impact of varying soft segment molecular weights and THF additions on the shape memory properties of polyurethane, as well as the mechanism behind THF's influence. The findings demonstrated that the introduction of THF significantly enhanced the phase separation degree and ordered hydrogen bonding of polyurethane, leading to the acquisition of shape memory properties. Compared to specimens without THF addition, when PPG had a molecular weight of 500, hydrogen bonding increased by 50 %. Furthermore, at THF addition of 9 mL, the specimen exhibited the highest shape recovery degree, with a phase separation temperature of 28.21 °C, a degree of carbonyl-ordered hydrogen bonding of 49.08 %, a bending strength of 43.81 MPa, and an impact toughness of 38.19 KJ/m2. The shape memory performance of the specimens was evaluated at various temperatures, revealing that the models both achieved 100 % shape fixation at different temperatures. Additionally, the degree and rate of retraction increase with the increase in temperature. The shape memory performance of the prepared specimens was shown to be good by the DMA shape memory cycling test.