A comparison of the thermoformability of a PPE/PP blend with thermoformable ABS. Part I: Small deformation methods

Abstract

Different factors important in ascertaining the thermoformability of polymeric materials are identified and defined. These include resistance to sag, ease of flow, mold replication, deep draw capability, sensitivity to thermoforming temperature and speed, uniformity of thickness distribution, and post‐forming shrinkage and dimensional stability. Methods to study these properties can be classified into small deformation and large deformation methods. The small deformation methods, which are the subject of this paper, include dynamic temperature sweep tests, dynamic frequency sweep tests, stress relaxation time, and creep recovery tests. These tests were used to compare the thermoformabilities of a blend of polyphenylene ether (PPE) and polypropylene (PP) and thermoformable acrylonitrile butadiene styrene (ABS) resin. The dynamic temperature and frequency tests showed that the PPE/PP blend generally has a better viscoelastic balance than ABS implying a better balance between resistance to sag and ease of flow. Creep recovery tests suggested that the PPE/PP blend may offer better mold replication during thermoforming. Studies based on the stress relaxation time showed a lower residual stress build‐up in thermoformed PPE/PP blend than ABS implying better dimensional stability and a higher in‐service temperature window for the thermoformed PPE/PP blend than ABS. POLYM. ENG. SCI., 45:1369–1376, 2005. © 2005 Society of Plastics Engineers

Studies on the stretching behaviour of medium gauge high impact polystyrene sheets during positive thermoforming

“…No significant difference in product quality is observed at different sheet heating temperatures of 130 C and 140 C. This can be attributed to the amorphous nature of HIPS. 16 Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.…”

Micro-deformation mechanisms in thermoformed alumina trihydrate reinforced poly(methyl methacrylate)

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“…Thermoformability which depends on thermo-mechanical and rheological properties of polymeric material is the main restriction on implementation of the procedure. Morye [3] defined different aspects of thermoformability as resistance to sag, ease of flow, mold replication, deep draw capability, sensitivity to thermoforming temperature and speed, uniformity of thickness distribution, and post-forming shrinkage and dimensional stability. Reliable estimation of thermoformability of materials and optimum thermoforming conditions are essential for the procedure.…”

Deformation Phenomena of Thermoplastic Materials in the Solid and Semifluid States

“…Thus, hot compaction can been used for instance to consolidate ultra‐light ultra‐high‐molecular‐weight polyethylene panels for the fabrication of fully thermoplastic composites, where the material is able to retain its high molecular orientation and tensile behavior . Properties of particular relevance when operating in the semifluid state include high melt strength to increase the drawing capability, along with high plastic strain and short characteristic stress relaxation time which provide dimensional stability .…”

“…The processing of polymer pellets as described above requires temperatures greatly in excess of the melting temperature (T m ), in the order of T m + 80 C to T m + 100 C. Alternatively, if the starting material is a semifinished product such as polymer blanks or sheets, processing techniques like thermoforming or hot compaction are employed, which can be operated at temperatures in the order of T m + 20 C to T m + 40 C. This kind of processing only induces a semifluid state in the material, where the viscoelastic behavior of the polymer greatly influences its processability [5,6]. Thus, hot compaction can been used for instance to consolidate ultra-light ultra-high-molecular-weight polyethylene panels for the fabrication of fully thermoplastic composites, where the material is able to retain its high molecular orientation and tensile behavior [7].…”