Macromol. Chem. Phys. 7/2010

Abstract

Front Cover: Co‐continuous nanostructured semi‐crystalline blends, in which long graft chains are incorporated, are obtained by reactive blending of functional polyethylene and bi‐modal molecular weight polyamides. The short chains react more readily to form graft copolymers that facilitate both grafting of long chains and formation of nanostructures. Further details can be found in the article by L. Gani, S. Tencé‐Girault,* M. Milléquant, S. Bizet, and L. Leibler .

The Influence of Blend Morphology (Co‐Continuous or Sub‐Micrometer Droplets Dispersions) on the Nucleation and Crystallization Kinetics of Double Crystalline Polyethylene/Polyamide Blends Prepared by Reactive Extrusion

“…In the case of the MC blend, a much higher content of graft copolymer was extracted. As reported, [5] blend MC contains 38 wt.-% of copolymer, 53 wt.-% of free PE-3 chains, and 9 wt.-% of free PA 6 chains. The amount of graft copolymer is 38 wt.-% (with a composition of 27 wt.-% PE-3 and 11 wt.-% PA 6 chains) and that of unreacted PA 6 is 9 wt.-%, therefore, the sum of unreacted and grafted PA 6 is 20 wt.-%.…”

“…The formed materials contained graft copolymers as well as unreacted PA and PE chains. Using a combination of selective extraction, already described in a previous study, [5] we have evaluated the blends composition. For the MA and MB blend a content of 5 wt.-% graft copolymer was obtained.…”

“…This difference in the supercooling needed for crystallization and the lower crystallinity developed during cooling from the melt reflect the topological confinement experienced by the PA 6 chains when they are forming part of the compatibilized blend. It should be noted that this blend also contains a large amount of grafted copolymer [5] (i.e., 38 wt.-%). Therefore, a very large difference in crystallization rate under isothermal conditions can be envisaged between bulk PA 6 and the sub-micrometer confined but percolated (i.e., co-continuous) PA 6 minor phase within blend MC (see the isothermal crystallization section below).…”

“…[17,20,26] In this case, the T g values for Nylon 6 are in the order of 40-60 8C depending on the molecular weight and measuring method. [50] Therefore, since the lowest crystallization temperatures reported by us are still far from the T g value of Nylon 6 (by at least 40-60 8C) and during the preparation of our blends by reactive extrusion an active interphase has been developed that includes a graft copolymer, [5] we believe that the heterogeneity free cPA 6 droplets are probably being nucleated at the interphase or in other words by superficial nucleation.…”

“…[1][2][3][4] Binary blends of semicrystalline polyethylene (PE) and polyamide (PA) have already been prepared by reactive blending. [3,5] By an appropriate choice of the molecular parameters of the two functionalized polymers, it is possible to control the grafting reaction at the interface thus the amount of graft copolymer. Therefore, various morphologies can be obtained from sub-micrometer dispersion for a low content of graft copolymer to co-continuous nanostructured morphology for a high content of graft copolymer.…”