Sustainable shape memory polymers based on epoxidized natural rubber cured by zinc ferulate via oxa-Michael reaction

Figures & data

Table 1. Compositions of ENR and ENR/HNT composites cured by ZDF.

Sample	EFeZn5	EFeZn10	EFeZn15	EFeZn25	EFeZn40	EFeZn25H10	EFeZn25H20	EFeZn25H40	EFeZn25H60
ENR	100	100	100	100	100	100	100	100	100
FA	5	10	15	25	40	25	25	25	25
ZnO	1.05	2.10	3.15	5.25	8.40	5.25	5.25	5.25	5.25
HNTs						10	20	40	60

Figure 1. Typical curing curve for rubber compound.

Figure 2. XRD patterns of FeA, ZnO, FeA/ZnO/SBR compound (SFeZn25-0 min) and heat treated FeA/ZnO/SBR compounds with different curing time (SFeZn25-10 min, SFeZn25-20 min, SFeZn25-30 min).

Figure 3. SEM image (left) and EDS spectrum of zinc element (right) for EFeZn40.

Scheme 1. Formula of the crosslinking reaction of ENR cured by ZDF.

Figure 4. Tan δ of ENR cured by ZDF with variable ZDF content.

Figure 5. Thermomechanical cycles of EFeZn15 (a) and EFeZn25 (b) to characterize the shape memory behaviors. The red points indicate the starting point of the test.

Figure 6. Histogram of R_f (a) and R_r (b) of EFeZn15 and EFeZn25.

Figure 7. Curing curves of ENR and ENR/HNT nanocomposites cured by ZDF.

Figure 8. SEM images of ZDF-cured ENR/HNT composites: EFeZn25H10 (a, c) and EFeZn25H40 (b, d).

Figure 9. Stress-strain curves of ENR/HNT nanocomposites cured by ZDF at room temperature (a) and at 70 °C (b). The black asterisk is used to illustrate that the sample is not fractured but the test is stopped due to reaching the elongation limit of DMA instruments.

Figure 10. Storage modulus (a) and tan δ (b) of neat ENR and ENR/HNT composites as a function of temperature.

Figure 11. Thermomechanical cycles of ENR and ENR/HNT composites.

Figure 12. R_f (a) and R_r (b) of ENR and ENR/HNT composites.

Figure 13. Evolution of (a) EFeZn25 at 45 °C, (b) EFeZn25H40 at 45 °C and (c) EFeZn25H40 at 60 °C from a temporary spiral to permanent linear shape.