Large strain, high rate semi‐solid deformation of high density polyethylene at elevated temperatures

Abstract

High density polyethylene (HDPE) is predominately processed from the molten state. However, there is the potential to enhance the mechanical properties by forming below the melt temperature, in the semi-solid phase. To further investigate this enhancement, HDPE sheets were deformed under constant width, simultaneous equalbiaxial (EB), and sequential biaxial deformation. The samples were deformed at strain-rates, from 4 to 16 s 21 , up to nominal strains of 3.0 at temperatures below 1308C. The strain-rate and high-strain level applied were chosen so that the data was comparable to the thermoforming process. It was discovered that in order for the HDPE sheet to deform at the high-rate and high strains the processing temperature must be between 1268C and 1308C. This resulted in a processing window that was particularly small, 58C, and that within this window a temperature change of 18C had a significant impact on the stress-strain response. The samples were analyzed post deformation, where the elastic modulus was found to increase by a factor of 2.08 in the machine direction, when deformed via EB at 1298C. The results showed that HDPE can be deformed to strain levels comparable to the thermoforming process. POLYM. ENG. SCI., 00:000-000, 2017. FIG. 9. The effect of forming temperature (A) and strain-rate (B) on the Young's modulus of the sample post deformation at 1288C and strain-rate 4 s 21 , determined via tensile testing at room temperature.

Local process-dependent structural and mechanical properties of extrusion blow molded high-density polyethylene hollow parts

“…The anisotropy of the properties is determined by the molecular orientation, which is generally induced during processing and is related to thermo-mechanical behavior of the material. Orientation of polymers might even enhance these properties [1,5].…”

Mechanical Testing of Recycled HDPE Extruded Hollow Section

“…Using a material with a high flexural strength can allow the manufacturer to potentially reduce the wall thickness of the extruded article while maintaining the same stiffness. Bearing in mind that the high strength materials are difficult to form, it is of utmost importance to carefully select the material with the desired properties (McKelvey, Menary, Martin, & Yan, 2017).…”

Thermomechanical Modeling of Material Flow and Weld Quality in the Friction Stir Welding of High-Density Polyethylene

“…This is mainly due to the lack of sufficient experimentally generated thermomechanical material properties of the polymer. Several researchers [26][27][28][29][30] have presented the experimentally generated stress flows for various variants of HDPE at various strain rates and temperatures. Since there is no extensive strain-rate-and temperature-dependent material data for HDPE available in the literature, the need for an analytical model is critical to simulate the behavior of the material during the FSW process.…”