Polymers | Intrinsic Viscosity Measurements for Quality Control of PET
PET is one of the most important polymers for packaging materials. Different grades of PET are classified using intrinsic viscosity, a parameter to calculate the polymer’s molar mass. Lovis microviscometer with its built-in polymer software measures and calculates polymer parameters automatically.
This report presents intrinsic viscosity measurements of PET (Polyethylene terephthalate) used for bottle manufacturing of soft drinks.
PET is a linear thermoplastic with a wide range of use including fibers, textiles, and of course packaging material. The main indicator for the quality and the most important characteristic of PET is the value of its intrinsic viscosity. This parameter is related to the polymer’s molar mass and therefore reflects the material’s melting point, crystallinity, and tensile strength. The intrinsic viscosity depends on the length of the polymer chains. The longer the polymer chains are, the more entanglements occur between the chains, and therefore the viscosity value is higher. The desired intrinsic viscosity of PET depends on its application and is classified into different grades
PET grade | Intrinsic Viscosity [dL/g] |
---|---|
Fiber grade | 0.40 to 0.70 |
Film grade | 0.70 to 1.00 |
Bottle grade | 0.70 to 0.78 |
Water and soft drink bottle grade | 0.78 to 0.85 |
Table 1: Typical intrinsic viscosity values of different PET grades.
The demand for reliable intrinsic viscosity measurements is high as PET has to be characterized in various fields:
- Research and development, where new polymers are synthesized and characterized
- PET suppliers, who want to control the quality of their products
- Process plants, where conditions need to be to optimized for constant production
- Recycling facilities, that need to control the properties of recycled PET
Get the document
To receive this document please enter your email below.