Making Industrial Processes More Cost Efficient

Polymer Processing

Advanced nonlinear models help plastics processors in many ways

New technology, new possibilities
Nonlinear modeling has been around for over ten years. It has been successfully utilized by various industries for a variety of purposes from quality control, product development and process guidance to software sensors and fault detection.

This new technology benefits you in several ways. Besides higher level process control of injection moulding and extrusion whereby the final properties of the extruded or moulded products are controlled by adjusting the process variables based on nonlinear models, even your raw material production benefits from them, as a consequence of which, you can now demand more from your polymer suppliers. Many companies around the world produce and supply polypropylene and its heterophasic copolymers of various kinds. Ask them if and when they can provide you the material with specified narrow ranges of mechanical properties, and specified constraints on MFR and crystallinity, and then you can start to see the difference between the producers. Ask them the maximum tensile modulus they can provide you while keeping impact strength and other variables within narrowly specified limits, and the difference between them becomes more pronounced. Thanks to the new technology, this task is now much easier. Engineers can calculate the polymer structure variables and polymerisation conditions that will lead to the desired properties in a matter of seconds, while you are still on the phone, and if it is not possible, they can tell you the closest they can get.

Currently polypropylene (PP) is the fastest growing bulk polymer, with a consumption today of around 30 million tonnes globally and an estimated consumption of 40 million tonnes in 2005. PP is the most versatile polymer and has the advantages of having light weight and a broad range of properties. Impact PP materials are used for wide range of applications. High modulus and thin walled pipes, packaging items, packaging films and automotive parts are the important end products.

The reason for the development of PP heterophasic copolymers is the improvement in the low-temperature impact strength. This is achieved with a polymer structure where an elastomeric phase, usually ethylene-propylene copolymer rubber, is dispersed uniformly within the PP homopolymer matrix.

The present trend in the market is to enhance the rigidity of the material while retaining the impact properties. This translates to thinner walled extruded and moulded products, resulting in raw material savings to the plastics processors. The stiffness of heterophasic PP copolymers varies from high modulus PP of 2000 MPa to soft PP of 200 MPa . Another trend among plastic converters is reduced cycle times in processing which is obtained by nucleation seen as fast crystallisation of the material.

The fast growth and the need to find economical ways to design new and improved properties required new approaches in development work. In line with Borealis’ policy of using the best available technology, nonlinear modeling was introduced in this development activity. Combined knowledge of PP structure property relationship and experimental data by nonlinear modeling permits us to investigate the final properties by fewer experiments, and lesser development costs. It helps to gain the quantitative knowledge necessary for quick tailormaking of polypropylene to suit the requirements of plastics processors.