Nanocomposites of ethylene-vinyl acetate copolymer (EVA) and organoclay prepared by twin-screw melt extrusion

Preparation of nanocomposites based on ethylene-vinyl acetate copolymer (EVA) and organoclay by melt intercalation is described in this paper. Effects of VA content, melt flow index (MFI) and maleation of EVA on melt intercalation were investigated by X-ray diffraction. The level of intercalation into the organoclay increases greatly as VA content increases from 6 to 12 wt%, but shows minimal change from 12 to 28 wt%. For 28 wt% VA content polymers with MFI from 3 to 150, interlayer expansion exhibited a maximum at MFI = 6. Exfoliated nanocomposites were not obtained for a range of unfunctionalized EVA's of different VA content: and MFI. Use of maleated EVA (MEVA) had an obvious improvement on exfoliation of the silicate layers probably due to chemical interaction between the MEVA matrix and silicate layers. FTIR results showed that the MA functionality reacts during processing. Lower clay content favored formation of an exfoliated nanocomposite structure. Exfoliated nanocomposites from MEVA exhibited higher Young's modulus and tensile strength than either pure EVA or intercalated nanocomposites from non-maleated EVA. (C) 2004 Society of Plastics Engineers.