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Thermoforming is a plastic conversion process to shape a heated sheet via application of force, vacuum or both. It is most suitable for parts with large area/ weight ratio where injection molding or compression molding is either too expensive or not practical. Unlike other conversion processes, the thermoforming process starts with extruded sheet and not resin pellets. So thermal history, thickness, and thickness uniformity are critical.
Thermoforming involves preheating of a sheet, stretching preheated sheet into shape, cooling part, removing the part, and trimming excess. This is done in high speed continuous (thin gauge roll fed) or in a stepwise batch process (thick cut sheet).
Thermoplastic material’s ability to thermoform depends on its molecular structure (Mw, MWD, content of long chain branches). Molecular order (crystallinity, orientation, residual stresses), ability to retain and remove heat (density, specific heat, thermal conductivity), geometry (thickness), and hot modulus (melt strength and sag resistance). Materials with extended rubbery plateau thermoform well. Thus amorphous materials like ABS, PMMA, PC and PMMA thermoform relatively easily while semi-crystalline materials like PP, PE, Polyamide, and PET thermoforms with difficulty. Any additive or reactive modification which leads to long chain branches or reduction in crystallinity facilitates forming. Some other key variables which influence thermoformability are sheet thickness variations, variable frozen in orientation, presence of volatiles, recycled content, density or area weight, and friction between the hot sheet and tool surface.
The industry currently uses indirect methods to assess thermoformability. Several different tests are required. Many of these methods such as MFR, Hot tensile test, sag test, DMA and melt rheology tests provide valuable insight, but results do not readily account for overall thermoforming process or thermoformability.
Nearly sixty plus paid experimental studies are conducted using Technoform on a wide range of materials ranging from PE to PEEK. Results have shown to be useful in establishing processing range, determining maximum draw ratio, determining effects of orientation, % regrind, volatile additives, inorganic fillers, co-monomers, long chain branching, tool material on thermoformability.
After twelve years of development and interest from major global players in Thermoforming industry, we are now ready to introduce Technoform to Industry. Technoform is most cost-effective tool for QC, QA, material development, and process optimization.
Contact us for more information, no cost test-trial, or for price and availability. Please visit New Product page on this website for presentation slides or contact Amit Dharia at (972)-915-0516 or email to [email protected].