Abstract
A series of shape memory blends of natural Eucommia ulmoides gum (EUG) and low-density polyethylene (LDPE) with a bicontinuous cross-linked structure were prepared by a physical blending method, which could be used in the field of thermal response with two different temperatures. We report the shape memory properties of these blended materials with two response temperatures for the first time. The mechanical, curing, thermal and shape memory properties of the blends were studied in this manuscript. Schematic diagrams are proposed to illustrate the dual shape memory behaviors of the EUG/LDPE blends. Our study focused on observing the relationship between the shape memory behavior and the microscopic crystalline phase states in the blends. In the blends, both the cross-linked network and the LDPE crystalline regions could act as fixed domains, while the crystalline regions of LDPE or EUG could act as the reversible domain. The shape memory properties were mainly determined by the components of the fixed and reversible domains. We focused on the shape memory behavior of blends at 60 °C and 130 °C in this manuscript. The results showed that when the peroxide dicumyl peroxide (DCP) dosage was 1.0 phr, the blends exhibited acceptable shape behavior at 60 °C (R1f = 74.8%, R1r = 63.3%). At the same time, when DCP dosage was 0.4 phr, the shape memory behavior of the blends at 130 °C was good and much better than that at 60 °C (R2f = 91.1%, R2r = 89.4%).
Highlights
Shape memory polymers (SMPs) are novel smart materials which possess the capacity to maintain temporary shapes and recover their permanent shape under an external stimulus [1], such as temperature [2,3], pH [4,5], light [6,7,8] and an electromagnetic field [9,10]
When the cross-linked network and crystalline regions of low-density polyethylene (LDPE) acted as the fixed domain, the sample was first maintained isothermally at 60 ◦ C for 5 min to completely melt the crystalline domain of Eucommia ulmoides gum (EUG)
When only the cross-linked network acted as the fixed domain, the sample was first maintained isothermally at 130 ◦ C for 5 min to completely melt the crystalline domain of the EUG/LDPE blend
Summary
Shape memory polymers (SMPs) are novel smart materials which possess the capacity to maintain temporary shapes and recover their permanent shape under an external stimulus [1], such as temperature [2,3], pH [4,5], light [6,7,8] and an electromagnetic field [9,10]. With the merits of being lightweight, structurally versatile and having large recovery ability [11], SMPs exhibit tremendous advantages over shape memory alloys (SMAs) and shape memory ceramics (SMCs) [12,13] These advantages provide SMPs with potential applications in aerospace [14], self-healing materials [15,16,17,18], intelligent textiles [19,20] and biomedical devices [21,22,23]. Schematic diagrams are proposed to explain the effects of the fixed domains on the shape memory behavior of the blends These blends could be prepared and potentially used in the field of thermal sealing and shape memory annular tubes with two different response temperatures
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