Determining Intrinsic Viscosity Loss in Polyethylene Terephthalate Processing
Intrinsic viscosity loss in PET processing is determined by measuring dilute solution flow time or capillary melt viscosity to quantify polymer chain cleavage.
PET Preforms
Meaning
Injection moulded blanks that serve as the foundation for bottle production. Most pet preforms resemble a small test tube with a threaded neck that is already in its final dimensions. This two stage process allows the moulding of the neck to occur under high pressure for precision, while the body remains thick and compact for easy transport.
Converting these blanks into bottles happens at a separate station using stretch blow moulding technology.
Material Geometry
Dimensions of the wall thickness and the overall length are designed to match the final expansion ratio of the container. A heavier pet preforms design is necessary for bottles that must withstand the internal pressure of carbonated beverages. If the preform is too light, the final wall of the bottle will be too thin to support the weight of the liquid or the stacking forces in a warehouse.
Engineers must balance the material weight with the structural requirements of the end use.
Sourcing Strategy
Procurement of these components often depends on the distance between the injection site and the blowing site. Because pet preforms are much smaller than the finished bottles, they are cheaper to ship and store in large quantities. A large bottling plant might purchase millions of units from a specialized manufacturer and blow them only when the filling lines are ready.
This approach reduces the logistics costs associated with moving air inside finished empty containers.
Production Lifecycle
Processing involves careful control of the thermal history of the resin to avoid crystallization. If the pet preforms are cooled too slowly during the initial injection phase, they become cloudy and brittle, making them impossible to blow into clear bottles. Modern systems use intensive cooling in the mould to freeze the polymer in its amorphous state.