Processing Technologies International (PTi), a leading global manufacturer of high-performance sheet extrusion machinery, has launched a real-time intrinsic viscosity (IV) monitoring system which delivers greater quality assurance and potentially lower costs for PET sheet production.The unique system, developed in cooperation with Plastic Technologies Inc., Holland, Ohio, allows for the material formulation (recycled, virgin, or post-consumer) to be adjusted online in order to maximize product performance.
“Our approach to IV monitoring is unique because it offers an instant IV measurement so we can readjust the formulation to potentially reduce costs,” explained James Johnson, PTi’s Senior Vice President of Applications and Technology. “Basically, we can provide quality assurance for the entire shipment and ensure that off-spec IV material will no longer be discovered during the forming process.”
Intrinsic viscosity is a measurement of the molecular weight distribution of PET. The performance characteristics of PET (impact, clarity, and strength) are greater at higher IV and reduced at lower IV. The real-time monitoring system is an invaluable process tool because it allows for the identification of online process deviations along with corrective action to maintain consistent and efficient production, according to Johnson. For example, material formulations containing virgin and recycled materials (industrial scrap and post-consumer recycle) can be adjusted and optimally balanced to maximize performance. More virgin can be added if the IV is off-spec while more recycled material can be added if the IV is un-necessarily too high.
PTi’s real-time IV monitoring system is based on a precise measurement of melt temperature and capillary piping pressures. These results are benchmarked against the ASTM D4603-86 standard test method for measuring IV and possess an accuracy of +/- 0.02 decaliters/g. The data is fully integrated into PTi’s TITAN Plus control system for real time and historical trending analysis. This real-time system offers distinct advantages over offline Solution Test methods which are time-consuming and have delayed results.
The real-time IV monitoring system – initially targeted for twin-screw PET sheet extrusion systems – is also being quoted on single-screw systems.
