Non-isothermal crystallization and melting of ethylene-vinyl acetate copolymers with different vinyl acetate contents

Abstract

Abstract. Non-isothermal crystallization and subsequent melting of three grades of ethylene-vinyl acetate copolymer were investigated by differential scanning calorimetry (DSC) technique. The DSC crystallization curves show that vinyl acetate (VAc) content has the same effect on the onset, peak and final crystallization temperatures, and these copolymers have almost the same spacing of thermal windows under identical crystallization condition. Subsequent melting DSC results suggest that EVA14 (14 wt% VAc) has the narrowest distribution of lamellar thickness and the most perfect crystals. Though the instantaneous nucleation was preferred, non-isothermal crystallization kinetics shows that EVA14 could form tridimensional crystallites, whereas EVA18 (18 wt% VAc) and EVA28 (28 wt% VAc) are prone to crystallize two-dimensionally, as a result of more noncrystallizable VAc co-monomers introduced in the crystallizable ethylene segments. The growth rate falls on the following sequence: EVA14>EVA18>EVA28. Moreover, the kinetic crystallizability G also well characterizes the variation of the non-isothermal crystallization of these EVA materials, in the view of structural impediment caused by the VAc content.

Structural and Thermal Analysis of Carbon Nano-Particles/Polypyrrole/Poly (Ethylene – Co – Vinyl Acetate) Composites

“…DSC and TGA techniques are widely used to measure the thermal properties and the blending polymers and embedding them with filler [1]. Homo-polymers, copolymers and also polymer blends can be characterized by a significant parameter known as glass transition temperature (T g ) obtained by DSC measurements [2].…”

Specific Chromatographic Retentions on Polymer Pore Surface of Macroporous Spongy Monoliths

“…Our thermal analysis result supported that polymer-chain orientation on EVA decreases with respect to vinyl acetate content. 8 The results suggested that polymer-chain orientation is stronger in pure polyethylene. In other words, vinyl acetate units are roughly oriented compared to polyethylene.…”

Influence of polymer melting point and Melt Flow Index on the performance of ethylene-vinyl-acetate modified bitumen for reduced-temperature application

“…As can be observed in Figure 3a, they all display a broad shoulder followed by a unique endothermic event, which appears at temperature ranges typically found for this type of polyolefins [26]. It has been considered that the width of EVA melting peak can reflect the distribution of the lamellar thickness of its crystalline fraction [27][28]. Therefore, EVA-VA7 has the narrowest size distribution of crystallites (and highest melting temperature), followed by EVA-VA18, EVA-VA28 and EVA-VA33.…”