The Thermal and Mechanical Properties of Poly(ethylene-co-vinyl acetate) Random Copolymers (PEVA) and its Covalently Crosslinked Analogues (cPEVA).

Ke Wang,Qibo Deng

doi:10.3390/polym11061055

Abstract

The thermal and mechanical properties of poly(ethylene-co-vinyl acetate) random copolymers (PEVA) and its covalently crosslinked analogues (cPEVA) were controlled by the overall crystallinity of the polymer networks. The cPEVAs with different VA-content were synthesized by thermally-induced crosslinking of linear PEVA with dicumyl peroxide (DCP). This work was mainly concerned with the effect of vinyl acetate (VA) content on the crosslinking density, thermal and mechanical properties of PEVAs and cPEVAs, respectively. The chemical composition was analyzed by thermogravimetric analysis and 1H-NMR. The thermal and mechanical properties of PEVAs and cPEVAs have been studied through a series of conventional analytical methods, including gel content determination, different scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis and traditional mechanical measurements. The experimental results show that the thermal and mechanical properties of PEVAs and cPEVAs increase with decreasing the VA-content. A broad melting transition with a ΔTm in the range from 78 °C to 95 °C was observed for all polymer networks.

Highlights

Shape memory polymers (SMP) are materials which can be deformed and fixed in a temporary shape, from which they recover their original, permanent shape when being exposed to a certain external stimulus, such as heat, light, electricity or magnetic field [1,2,3,4]
The chemical composition of in this work was nominated poly(ethylene-co-vinyl acetate) random copolymers (PEVA) and cPEVAs was investigated by thermogravimetric (TG) and derivative thermogravimetric (DTG), and 1 H-NMR spectroscopy
Summary and Outlook cPEVAs were synthesized by introducing the crosslinks into the linear random poly(ethylene-co-vinyl acetate) copolymers (PEVA)

Summary

Introduction

Shape memory polymers (SMP) are materials which can be deformed and fixed in a temporary shape, from which they recover their original, permanent shape when being exposed to a certain external stimulus, such as heat, light, electricity or magnetic field [1,2,3,4]. The emerging field of SMP has attracted tremendous interest due to its various potential applications covering smart packaging [5], heat-shrink tubing, deployable structures and microdevices [6], intelligent drug releasing systems and medical devices for minimally invasive surgery [7,8,9,10,11,12,13], etc. Shape-memory semi-crystalline polymers with covalent crosslinking, e.g., degradable SMPs containing poly(ε-caprolactone) (PCL) switching segments [12,14,15] or covalent crosslinked poly(ethylene-co-vinyl acetate) (cPEVA) using polyethylene (PE) switching segments [16], have been widely studied and become popular in biomedical application. Poly(ethylene-co-vinyl acetate) [17] is a random copolymer consisting of semi-crystalline polyethylene (PE) segments and amorphous poly(vinyl acetate) (PVA) segments.

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Results

Conclusion