ARTICLE IN PRESS D.R PeuL LM.Robeson/Polymer xx(00)1-18 Intercalated Exfoliate 公 之轻是多 Fig 3.Illustration of different states of dispersion of organoclays in polymers with corresponding WAXS and TEM results. of thepolyamide a larger number of alkyls decrease the possible frequency of th lkyl-polyami olar poly quency of more f n this c .increa the number kyls on the surfactant im- ersion of the organoclay in the polyolefin matrix since very good and far sheaegctehetbd prganecgyartck Shear Platelets peel apart by combined diffusion/shear process Fig 4.Mechanism of organoclay dispersion and exfoliation during melt processing 841 Reproduced with permission of Elsevier Ltd. Please cite this article in pressas:Paul DR Robeson LM,Polymer (0)do:.17 access of the polyamide chains from the silicate surface diminishing these favorable interactions while increasing the very unfavorable alkyl–polyamide interaction. On the other hand, non-polar poly￾olefin segments have no attraction to the polar silicate surface, and in this case, increasing the number of alkyls on the surfactant im￾proves dispersion of the organoclay in the polyolefin matrix since a larger number of alkyls decrease the possible frequency of the unfavorable polyolefin–silicate interaction and increases the fre￾quency of more favorable polyolefin–alkyl contacts [96,100,105]. Even under the best of circumstances exfoliation of organoclays in neat polyolefins like polypropylene, PP, or polyethylene, PE, is not very good and far less than that observed in polyamides, 200 nm 200 nm 100 nm Intensity Intensity Intensity Immiscible Intercalated Exfoliated pure organoclay Immiscible nanocomposite pure organoclay pure organoclay exfoliated nanocomposite Intercalated nanocomposite 2θ 2θ 2θ Fig. 3. Illustration of different states of dispersion of organoclays in polymers with corresponding WAXS and TEM results. Platelets peel apart by combined diffusion/shear process Shear Organoclay particle (~ 8 µm) Stacks of silicate platelets or tactoids Shearing of platelet stacks leads to smaller tactoids Shear Diffusion Shear Stress = ηγ Fig. 4. Mechanism of organoclay dispersion and exfoliation during melt processing [84]. Reproduced with permission of Elsevier Ltd. D.R. Paul, L.M. Robeson / Polymer xxx (2008) 1–18 5 ARTICLE IN PRESS Please cite this article in press as: Paul DR, Robeson LM, Polymer (2008), doi:10.1016/j.polymer.2008.04.017