Preparation and properties of bidirectional reversible shape memory ethylene vinyl acetate copolymer

doi:10.19491/j.issn.1001-9278.2022.12.002

Abstract

Abstract:

A type of cross⁃linked ethylene⁃vinyl acetate copolymer （EVA）⁃based bidirectional shape memory polymer （SMP） was prepared using EVA as a raw material and tert⁃butyl peroxy⁃2⁃ethylhexanoate （TBPE） as a cross⁃linking agent， and the effect of TBPE content on the performance of the resultant products was investigated. The results indicated that the T_m and T_c of the EVA⁃based SMPs decreased with an increase in the content of TBPE， and their driving temperature could be adjusted by the content of the cross⁃linking agent. The EVA⁃based SMPs obtained both one⁃way and two⁃way shape memory functions. The shape fixation rate presented a downward trend with an increase in the content of TBPE， reaching the lowest value of 88.83 % and a shape recovery rate of over 99 %. The EVA⁃based SMPs also exhibited two⁃way memory performance， and their R_a，_2W decreases with an increase in the content of TBPE content， but their R_r，_2W presented an opposite trend. The content of cross⁃linking agent showed a great influence on the performance of the EVA⁃based SMPs.

Key words: cross?linked ethylene?vinyl acetate copolymer, tert?butylperoxy 2?ethylhexyl carbonate, shape memory polymer, two?way memory function

CLC Number:

TQ 325.1⁺2

ZHANG RUI, YAO Jiabin, LI Xuan, HE Xuelian. Preparation and properties of bidirectional reversible shape memory ethylene vinyl acetate copolymer[J]. China Plastics, 2022, 36(12): 6-15.

Figures/Tables 17

Fig.1. Second heating（a） and cooling （b） DSC curves of cross⁃linked EVA samples

Fig.2. The storage modulus⁃temperature （a） and tan delta⁃temperature curves （b） of cross⁃linked EVA with different TBEC contents

Fig.3. Stress⁃strain curves of cross⁃linked EVA with different TBEC contents

样品	拉伸强度/MPa	断裂伸长率/%
EVA0	6.34	1 104.25
EVA1.0	19.50	867.58
EVA1.5	22.69	841.46
EVA2.0	22.73	761.32
EVA3.0	17.84	687.29
EVA4.0	16.07	507.95

Tab.1. Tensile properties of cross⁃linked EVA

Fig.4. Swelling degree of cross⁃linked EVA with different TBEC contents

Fig.5. XRD patterns of cross⁃linked EVA with different TBEC contents

Fig.6. Shape programming and recovery process of the cross⁃linked EVA

Fig.7. One⁃way shape memory cycles under a constant stress of 0.1 MPa for EVA1.0 （a）， EVA1.5 （b） and EVA2.0 （c）

Fig.8. One⁃way shape memory cycles under constant stress of 0.1 MPa for EVA1.0 （a）， EVA1.5 （b） and EVA2.0 （c）， respectively

Fig.9. The shape fixing ratios and shape recovery ratios of cross⁃linked EVA under a constant stress of 0.1 MPa with different TBPE contents

Fig.10. One⁃way shape memory cycles under a constant stress of 0.2 MPa for EVA1.5 （a）， EVA2.0 （b）， EVA3.0 （c） and EVA4.0 （d）

Fig.11. One⁃way shape memory cycles under a constant stress of 0.2 MPa for EVA1.5 （a）， EVA2.0 （b）， EVA3.0 （c） and EVA4.0 （d）

Fig.12. The shape fixing ratios and shape recovery ratios of cross⁃linked EVA under a constant stress of 0.2 MPa with different TBPE contents

Fig.13. Two⁃way shape memory cycles under a constant external stress of 0.1 MPa for EVA1.0 （a）， EVA1.5 （b）， EVA2.0 （c）， EVA3.0 （d） and EVA4.0 （d）

Fig.14. Temperature⁃strain cycle curves of EVA1.0 （a）， EVA1.5 （b）， EVA2.0 （c）， EVA3.0 （d） and EVA4.0 （e）

Fig.5. Actuation magnitude （a） and recovery magnitude （b） of cross⁃linked EVA under a constant stress of 0.1 MPa with different TBPE contents

Fig.16. Strain recovery rate vs temperature for cross⁃linked EVA under different stress conditions.

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