Method for blow molding plastic articles

A method of making a clear blown bottle of polyethylene terephthalate which is essentially free of any haze caused by stress whitening and which is biaxially oriented, comprising the steps of:

• closing the sections of a blow mold around a blowable plastic shape consisting essentially of polyethylene terephthalate;
• axially stretching the blowable shape while the polyethylene terephthalate material is at a temperature conducive to molecular orientation in the range of from about 165.degree. F. to about 200.degree. F.;
• injecting blow fluid under pressure into the stretched blowable shape while said material is still at a temperature conducive to molecular orientation in said temperature range, the blow fluid being at a pressure of between about 400 and about 500 psi and at a temperature between about 150.degree. F. and about 400.degree. F. when injected into the blowable shape prior to any adiabatic expansion;
• during the streching and blowing steps, molecularly orienting the polyethylene material without developing a haze of stress whitening;
• and
• removing the blown article from the blow mold as a biaxially oriented, clear article.