Thermally formed thermoplastic articles can be protected from stress
cracking in the presence of stress cracking promoting compounds by forming
a shaped article comprising a thermoplastic and a liquid hydrocarbon oil
composition. We have found that the liquid hydrocarbon oil composition
prevents the stress cracking promoting materials from interacting with the
polymeric structure of the stressed container to prevent or inhibit stress
cracking in such materials. The methods and compositions of the invention
are particularly useful in preventing stress cracking in polyethylene
terephthalate beverage containers during bottling operations during which
the bottle in contacted with aqueous and non-aqueous materials such as
cleaners and lubricants that can interact with the polyester to cause
stress cracking particularly in the container base. A process for
lubricating a container, such as a beverage container, or a conveyor for
containers, by applying to the container or conveyor, a thin continuous,
substantially non-dripping layer of a liquid lubricant. The process
provides many advantages compared to the use of a conventional dilute
aqueous lubricant.
