The permeation resistance of polyethylene, polyethylene/polyamide and polyethylene/modified polyamide blown tubes against unleaded gasoline

The barrier resistance of polyethylene (PE), polyethylene/polyamide (PE/PA) and polyethylene/modified polyamide (PE/MPA) blown tubes against gasoline permeation is reported. The blown tubes prepared from pure PE exhibited much poorer gasoline permeation resistance than PE/PA and PE/MPA blown tubes. About 93% of the filled gasoline permeated out of PE blown tubes in 14 days at 40°C. In contrast, the gasoline permeation resistance of the blown tubes improved significantly by blending MPA (or PA) before tube blowing. PE/MPA blown tubes exhibited significantly better gasoline permeation resistance than PE/PA blown tubes of the same PE contents. The order of gasoline permeation resistance of PE/MPA blown tubes is the same as the order of the barrier resistance of MPA resins against gasoline permeation before blending with PE. In fact, by using proper compositions and carefully controlling the MPA morphology, the gasoline permeation resistance of the PE/MPA blown tubes can reach about 360 times better than that of pure PE blown tubes at 25°C. These interesting phenomena were investigated in terms of the morphology, thermal and rheological properties of the base resins and/or blown tubes of PE/PA and PE/MPA blends.