Wankai bottle-grade PET: which grades suit preform lines
How to choose bottle-grade PET for your product and equipment: how the grades for water, carbonated drinks and hot-fill differ, and what information we need to select one.
A preform producer chooses resin not by its name but by how it will behave on a specific line and in a specific bottle. Here is what determines the choice of a bottle-grade PET and what to prepare so that grade selection takes as little time as possible.
Three Wankai bottle grades
The representative office's catalogue includes three bottle grades. They differ primarily in intrinsic viscosity (IV), a parameter that reflects the length of the polymer chains and the strength of the future bottle.
- PET for water — for still drinking water. The focus is on clarity, neutral taste and stable processing of lightweight preforms.
- PET for carbonated soft drinks — higher viscosity: the bottle withstands carbon dioxide pressure and the wall retains the gas better.
- PET for hot-fill — for juices, tea and isotonic drinks that are filled hot. The grade is intended for heat-set blowing.
What drives the choice
Product. Water, a carbonated drink or hot-fill sets the baseline viscosity range — this is where selection starts.
Preform and bottle. Preform weight, neck finish, bottle volume and shape determine how far the material is stretched during blowing and how much strength margin is needed.
Equipment. The same grade can behave differently on single-stage and two-stage lines and on injection moulding machines from different manufacturers. Output, the number of mould cavities and dryer capacity all matter.
Appearance requirements. Clarity, tint and the use of colourants or additives are also taken into account.
Preparing the resin
Whatever grade you choose, PET must be dried before injection moulding: moisture in the melt lowers the viscosity, and preforms come out with deviations in strength and appearance. Drying and processing conditions are given in each grade's TDS. The more consistent the resin viscosity from lot to lot, the less often the line has to be re-tuned.
How we select a grade
- You send a description of the product, preform parameters, the equipment model and the grade you currently use.
- We propose a grade and send the TDS.
- We send a sample for a trial run.
- After the trial we prepare a quotation including delivery to your warehouse.
Send a grade selection request stating your application and monthly volume.