Polypropylene (PP) is emerging as a strong competitor to PET for many blow-molded bottle applications. Driving this trend are several advantages of PP. Compared to PET, for example, PP is less expensive, lighter in weight, more resistant to the high temperatures of hot filling, and less permeable to moisture. New clarified grades of PP have a clarity and gloss comparable to PET.
On the other hand, production cycles of PP bottles have generally been longer than those of PET bottles. PP also has a narrower range of processing temperatures than PET. Gas barrier properties of PP are not as high as those of PET, and PP also falls below PET in stiffness. But producers of PP resins and the additives that go into them are making important strides in overcoming these deficits.
Because of its relative permeability to carbon dioxide, PP has not displaced PET as a bottling material for carbonated beverages. Wide-mouth food containers are considered a particularly promising opportunity for future PP growth.