Assessment of Diffusion of an Antistatic Agent in One Side of EVA/LDPE Laminate Film Using Space Charge Measurement

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An antistatic agent is often used for avoiding electrification of polymer films. In some cases, the film has a double-layer structure to improve its adhesive property. As an example, an ethylene-vinylacetate copolymer (EVA) film in which an antistatic agent is mixed, corresponding to “EVA(ASA)”, is laminated with a low-density polyethylene (LDPE) film. In such a case, there is a possibility that the antistatic property of the EVA may be lost because of the diffusion of the antistatic agent into the LDPE side.A space charge study on the EVA(ASA)/LDPE laminate was carried out using the pulsed electroacoustic method under DC voltage. The space charge once formed at EVA(ASA)/LDPE interface decreased with time, and propagated into LDPE. A space charge profile at EVA (ASA)/LDPE interface was also calculated with difference of conductivities between LDPE and EVA(ASA). The space charge profile at EVA(ASA)/LDPE interface was qualitatively corresponded to that from space charge measurement. As a result, it was suggested that diffusion of the antistatic agent led to this space charge behavior. It was considered that measurements of space charge profiles would enable the assessment of diffusion of antistatic agent in multi-layer.