THE BARRIER, IMPACT, MORPHOLOGY, AND RHEOLOGICAL PROPERTIES OF MODIFIED POLYAMIDES AND THEIR CORRESPONDING POLYETHYLENE-MODIFIED POLYAMIDE BLENDS

A systematic investigation of the effects of melt indices of polyamide s (PAs) on the morphology, barrier, and impact properties of blow-mold ed polyethylene-polyamide and polyethylene-modified polyamide (PE-MPA) containers is reported. An appropriate alkyl carboxyl-substituted pol yolefin was chosen as a compatibilizer precursor to modify PAs of vary ing melt indexes in a twin-screw extruder by the ''reactive extrusion' ' process. The melt shear viscosities (eta s) of MIPAs increased with decreasing melt indices of their corresponding PAs and were higher tha n those of their corresponding PAs, respectively. The barrier properti es of MPAs were better than those of their corresponding PAs, and the level of barrier improvement of PAs and MPAs increased consistently wi th decreasing melt indices of their corresponding PAs. The values of t otal impact energy (E-t) of PAs and MPAs also improved with decreasing melt indices of PAs; however, MPAs exhibited lower values off, than t heir corresponding PAs. The barrier properties of PE-MPA bottles were much better than those of PE-PA bottles. The order of barrier improvem ent of these PE-MPA bottles corresponded approximately to the order of barrier improvement of pure MPA when the viscosity ratio of MPA to PE was about equal to or less than one. However, regardless of exhibitin g the best barrier improvement in all MPAs, a significantly smaller ba rrier improvement of PE-MPA5 bottles was observed when the viscosity r atio of MPA to PE was significantly greater than one. Finally, it is i nteresting to note that PE-MPA sheets exhibited significantly higher E -t than their corresponding PE-PA sheets, although each PA was associa ted with a higher E-t than their corresponding MPAs. Possible mechanis ms accounting for the interesting behaviors noted above are suggested in this study. (C) 1997 John Wiley & Sons, Inc.