Optimizing Thermoforming Process Windows Using Strain Hardening Rheology Metrics
Strain hardening rheology metrics define thermoforming process windows by predicting extensional melt strength to eliminate corner thinning and sheet sag.
Reclaim Regrind Ratio
Meaning
Proportion of recycled material added to virgin polymer resin in a manufacturing batch determines the physical and economic properties of the final product. This formulation balance, termed the reclaim regrind ratio, is a sensitive variable that must be monitored to prevent thermal degradation and part failure. Higher concentrations of recycled material lower the cost of the raw material but can reduce impact strength.
A balance is typically maintained to satisfy both budget and performance needs.
Mechanical Property
Repeated heat history during extrusion degrades the polymer chains, resulting in shorter molecules and lower tensile strength. If the reclaim regrind ratio is too high, the part will become brittle and fail quality tests. To prevent this degradation, the processor must limit the amount of regrind to a specific maximum percentage.
Economic Balance
Using recycled material significantly lowers the cost per unit, making the product more competitive. The ideal reclaim regrind ratio maximizes the use of scrap material without triggering an increase in part rejection rates. A higher rejection rate quickly cancels out the savings from cheaper raw materials.
Process Control
Automated gravimetric blenders are used to maintain a consistent mixture at the feed throat of the extruder. These blenders ensure that the reclaim regrind ratio remains stable throughout the production run. This prevents fluctuations in melt viscosity and part dimensions.