Influence of compositions of modified blends of polyamide/poly(vinyl alcohol) on the methanol/gasoline fuel barrier properties of polyethylene/modifiedblends of polyamide/poly(vinylalcohol) bottles

Abstract

Polyamide (PA), poly(vinyl alcohol) (PVA) and the blends of PA and PVA were modified by a compatibilizer (CP) to make modified polyamide (MPA), modified PVA (MPVA) and modified PA/PVA (MPAPVA) blends through reactive extrusion. The MPVA and MPA hot-pressed sheets exhibit the best and worst methanol/gasoline fuel permeation resistance among these modified resins, which show much better methanol/gasoline fuel permeation resistance than pure PE resin. It is worth noting that the methanol/gasoline fuel permeation resistance of MPAPVA sheets improves consistently with their PVA contents. Similarly, after blending these barrier resins with PE, the methanol/gasoline fuel permeation resistance of the blended bottles improves to become significantly better than that of pure PE bottles. Further investigations found that the hydrocarbon components with 5 to 10 main-chain carbon atoms present in methanol/gasoline fuels were successfully blocked during the permeation tests. However, the order of barrier improvement of PE/MPA, PE/MPAPVA and PE/MPVA bottles does not completely correspond to the order of the barrier improvement of the base barrier resins before blending and blow-molding with PE. For instance, the PE/MPVA and PE/MPAPVA bottle series with a PVA/PA weight ratio of 4 : 1 exhibit poorer methanol/gasoline fuel permeation resistance than all the other PE/MPAPVA bottles, although the base MPVA and MPAPVA with a 4 : 1 PVA/PA weight ratio are associated with better permeation resistance than the other MPAPVA resins prepared in this study. These interesting phenomena were investigated in terms of the melt shear viscosities, chemical structure and morphology of the barrier resins present in their corresponding bottles.