There are no direct QC test to determine quality of incoming sheet or means to determine the process conditions and thermoformability of new material. Yes, there are some indirect tests like MFR, sag resistance, melt tension, and hot tensile test. These tests do not reflect true nature of TF process. Actual trial often requires time consuming and expensive sheet extrusion trials -exspecially for new materials.
To address this need, we have developed a Thermoformability Analyzer which incorporates all three unit steps involved in TF process and produces quantitative information in matter of minue reflecting effect of temperature, speed, plug material, sheet thickness, sheet color, and heating rate under controlled conditions. We have applied this device to determine effect of regrind, moisutre, additves which bloom to surface, plug material, plug temperature, tie layer strength in coextruded stock, garin structure, post forming gloss retention, shirnkage etc.
The data is continuously captured as force required to form a part of specific shape at specific temperature to specific draw depth. We call it TFI or Thermoformability Index. We are now commercializing this "patent pending" equipment which was exhibited at TF conference in Milwaukee. I am proposing that ASTM adopt such a test to help TF industry in knwoing the characterstic of sheet stock.
Please send your comments to [email protected]