Relationship on structure and properties of polyurethane modified Diels–Alder addition polymer

ABSTRACT A series of linear and crosslinked polyurethane modified materials were prepared by Diels–Alder cycloaddition reaction. Based on raw materials, some novel equations were designed and effects of equation parameters on the mechanical properties of modified material were explored. It was demonstrated that tensile strength of modified materials and elongation at break were changed from 3.68 to 18.71 MPa, 200 to 866%, respectively. In addition, the optimal reaction temperature of retro‐Diels–Alder (r‐DA) reaction was determined by differential scanning calorimeter (DSC). Gel permeation chromatography (GPC) and tensile experiments were used to characterize the properties of repolymerized material after degradation. The results indicated the optimal temperature of r‐DA for linear and crosslinked polyurethane modified materials is 127 and 150 °C. Moreover, after decomposed, the product was slowly repolymerized at 60 °C, and can more effectively restore material strength under the action of the solvent to achieve self‐healing effect. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47355. D‐A adducts have characteristics that polymerizing in low temperature and depolymerizing in slightly high temperature. To explore whether the material has reversible self‐healing properties, GPC were used to characterize the properties of polymerization‐depolymerization‐repolymerization material. The GPC of L‐DAPU‐8 was measured and the experimental results are as follows. It can be seen that the relative molecular weight decreases rapidly after 40 minutes of depolymerization, and the relative average molecular weight of the r‐DA products gradually increase after 16 hours of repolymerization, which indicates that D‐A products undergo depolymerization‐repolymerization and have self‐healing properties.