The Future Quality Control of Modern Factory Mixing Process.
Polymer to Finished compound characterisation using dynamic mechanical analysis as unique source of data
Henri Burhin - Alpha Technologies UK
Polymer manufacturing process is inherently variable, principally due to the variability of the major raw material components, synthetic and natural rubber and polymers, and to a lesser extent, other key raw materials (filler, accelerators etc.).
The equipment used in factory mixing also contributes its share of variables, caused by the type of equipment used (age, efficiency, size) and in control (temperature, power, time). A given formulation with a mixing and processing schedule set to achieve optimum throughput and performance, may not process successfully in different production sites or even in different lines at the same site.
Dynamic mechanical analysis is an excellent tool to monitor incoming polymers, masterbatches and uncured fully mixed compound quality. It provides reliable results correlating closely to compound processing characteristics, such as extrudate swell and extruder output enabling detailed characterisation and selection of polymer sources, grades and batches.
In the thermoplastic area, compounding and mixing have shown an increasing importance to offer material with optimum properties for used processing tools. Dynamic testing has largely supplemented traditional testing techniques to assure product consistency and processing quality assurance.
Optimum mixing and processing conditions can thus be established and mixed compound characteristics verified, thus reducing variability, process down time and eventual scrap.
Conventional testing by Mooney and rheometer is neither capable nor sensitive enough for fully detailed characterisation, particularly for polymer microstructure, and with masterbatches, to ensure optimum throughput of high quality compounds.
Dynamic mechanical analysis can now be fully automated. This technique has the potential for real, online quality control. This capability has been demonstrated at a tyre manufacturer during extended testing of production masterbatches, final mixes and raw polymers. Large compound property variations were found. These variations may be due to variations in the polymers but also to variations in the mixing process. Variations in mixing behaviour were successfully correlated to key polymer properties.
Dynamic mechanical testing provides in a single test, the key parameters that relate to compound properties on the factory floor thus ensuring the control necessary to achieve high quality and efficient production.