Rheological characterization of ethylene vinyl acetate copolymers

Abstract

A series of ethylene vinyl acetate (EVA) copolymers was studied by dynamic mechanical spectroscopy to understand the relative influence of composition, structure, and molecular weight distribution on their rheological behavior in the melt. The examination of their viscoelastic properties in a large temperature range showed that the glass transition temperature is nearly independent on their composition because of the statistical nature of the copolymers, though some long sequence of polyethylene homopolymer may exist at low vinyl acetate (VA) content. The successful use of the time temperature superposition for oscillatory experiments in the melt confirmed the previous remarks, because the application of the Williams Landel Ferry (WLF) equation leads to a unique set of WLF coefficient, whatever the composition of the EVA. This enables the comparison of the rheological behavior in the melt at the same temperature, in the same free volume condition, and at last it was shown that in the terminal zone, the molecular weight distribution is more influent on the behavior of EVA copolymers than their composition.

Modulated Crosslinking of Polyolefins through Radical Processes in the Melt

“…The DSC of EVA 15 samples between 50 and 100 8C showed a broad peak deriving from the melting of the crystalline phase of polyethylene segments present in the copolymer. [27] It seemed that the introduction of crosslinking points did not influence the melting temperature (T m ) and also the crystallinity appeared to have not changed significantly with respect to the polymer not treated in the melt with the peroxide ( Table 5). The preservation of the crystallinity is probably a consequence of the crosslinking process occurring at the vinyl acetate units present preferentially in the amorphous phase.…”

Effects of crystallinity and crosslinking on the thermal and rheological properties of ethylene vinyl acetate copolymer

“…Many researches have been studied the crystallinity of the EVA. For example, Brogly et al [1] and Arsac et al [2] have investigated the effects of crystallinity on the thermal properties of the EVA with VA content.…”

“…The EVA shows various properties with varying the VA content. The properties of the EVA are caused by the crystallinity of the EVA [1][2][3][4] which can be controlled by the VA content. The crystallinity of the EVA with the VA content is very important to understand the thermal and rheological properties of the EVA.…”

Dielectric relaxation behaviour of ethylene-vinyl acetate–exfoliated graphene nanoplatelets (xGnP) composites

“…The elastomer ethylene vinyl acetate (EVA) is proved to be very compatible for carbon-based fillers. The crystallinity of the EVA majorly depends upon the amount of VA content which shows different behaviour of the EVA matrix itself [17][18][19][20]. Researchers have studied the effect of carbonbased fillers on different properties of EVA elastomers having low VA content (25-32 %) by melt mixing process [21][22][23][24].…”