A systematic study on the effects of types and contents of compatibilizer precursors (CPs) on degrees of crystallinity (W c ), melt shear viscosities ( h s ), and permeation barrier properties of modified polyamides (MPAs) and on their corresponding morphology and barrier properties of bottles blow-molded from polyethylene (PE)/MPA blends is reported. Two alkylcarboxyl-substituted polyolefins were selected as CPs to modify PA and to improve its permeation resistance to xylene by the ''reactive extrusion'' process. The barrier improvements of MPAs prepared in this study depend significantly on the type and content of CP present in the MPA. A maximum improvement in barrier properties of each MPA series samples were found as the contents of CP reached an ''optimum'' value. On the other hand, it is interesting to note that bottles blow-molded from PE/MPA series samples exhibited better barrier properties because the MPAs used were associated with better permeation resistance to xylene. The melt shear viscosities of MPAs were found to depend on the type of CP used and increase with increasing CP contents. In contrast, the W c of MPAs decreased with increasing CP contents. Further analysis of the fracture surfaces of bottles blow-molded from PE/ MPA blends also indicated that the morphology of MPA laminas depended on the type of CP present in the MPA, and these MPA laminar structures became clearer as the contents of CPs increased. Possible mechanisms accounting for the interesting behaviors described above are discussed.

A critical concentration was found for different compositions of UHMWPEBBPE solutions, at which the concentration dependence of the reduced viscosity changes from low to high power. The critical concentration (C,) is shifted to a higher value with increasing amount of SBPE in the UHMWPElSBPE gel. The birefringence of the drawn films suggests that the degree of orientation of UHMWPE molecules along the drawing direction increases with the draw ratio. The increased orientation of UHMWPE improves the tensile strength and moduli of the drawn films. The draw ratios of gel films prepared from each blend of UHMWPE and SBPE exhibits a maximum value when the samples were prepared at concentrations close to their critical concentration. On the other hand, the maximum draw ratio obtained for gel films prepared near their C, decreases significantly at higher weight ratios of SBPE to UHMWPE. In contrast, the gel films with less than 2 wt.-% of SBPE in UHMWPE yield a higher maximum draw ratio than the sample prepared from pure UHMWPE gel. Possible mechanisms accounting for this behavior are proposed.

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A systematic investigation of the effects of melt indices of polyamides (PAs) on the morphology, barrier, and impact properties of blow‐molded polyethylene—polyamide and polyethylene‐modified polyamide (PE—MPA) containers is reported. An appropriate alkyl carboxyl‐substituted polyolefin was chosen as a compatibilizer precursor to modify PAs of varying melt indexes in a twin‐screw extruder by the “reactive extrusion” process. The melt shear viscosities (ϵs) of MPAs increased with decreasing melt indices of their corresponding PAs and were higher than those of their corresponding PAs, respectively. The barrier properties of MPAs were better than those of their corresponding PAs, and the level of barrier improvement of PAs and MPAs increased consistently with decreasing melt indices of their corresponding PAs. The values of total impact energy (Et) of PAs and MPAs also improved with decreasing melt indices of PAs; however, MPAs exhibited lower values of Et than their corresponding PAs. The barrier properties of PE—MPA bottles were much better than those of PE—PA bottles. The order of barrier improvement 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 exhibiting the best barrier improvement in all MPAs, a significantly smaller barrier improvement of PE—MPA5 bottles was observed when the viscosity ratio of MPA to PE was significantly greater than one. Finally, it is interesting to note that PE—MPA sheets exhibited significantly higher Et than their corresponding PE—PA sheets, although each PA was associated with a higher Et than their corresponding MPAs. Possible mechanisms accounting for the interesting behaviors noted above are suggested in this study. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2517–2527, 1997

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