Impact of compression molding conditions on the thermal and mechanical properties of polyethylene

Abstract

Compression molding is a current technique in polymer processing. Despite numerous studies, effect of molding pressure on physical properties has surprisingly not been fully investigated. In this study, the thermal and mechanical behavior of the compression-molded polyethylene were thus explored to better grasp the relationship between processing parameters and ensuing properties. The effect of the molding temperature, pressure, cooling rate, and temperature profile on the tensile and flexural moduli as well as melting point of polyethylene was studied. We conclude that higher tensile and flexural moduli are obtained by increasing pressure and molding temperature, as well as decreasing the cooling rate. Our results were corroborated by X-ray diffraction and differential scanning calorimetry measurements. Moreover, the use of a temperature gradient with different temperatures for the upper and bottom plates of the mold leads to asymmetric samples whose tensile and flexural moduli are improved. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46176.

Injection Molding of Low-Density Polyethylene (LDPE) as a Model Polymer: Effect of Molding Parameters on the Microstructure and Crystallinity

“…Because of its semicrystalline nature, the microstructure presents ordered regions of polymer chains known as spherulites, which are conformed of fold back chains or lamellae growing out from nucleation points, interconnected by disordered polymer chains or amorphous regions [ 6 ]. The ratio of the crystalline to amorphous regions influences the different physical properties, such as mechanical, thermal, surface, and hardness [ 13 , 14 ]. Consequently, several works have qualitatively related this ratio with the final measured properties [ 10 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

A method based on the time–temperature superposition principle to predict pressurization time in compression molding

“…8 A few key process parameters, such as the rate of temperature rise, holding temperature, holding time, pressurization time, and compression pressure, affect the quality of the final product. [9][10][11][12][13][14][15][16] Among them, the pressurization time is considered a key parameter in manufacturing of thermosetting composites because it is related to the curing process, during which the thermosetting polymer crosslinks, resulting in the consolidation of the composites. When pressurization takes place ahead of time, resin-starved areas develop inside the composites as lowviscosity resin is squeezed out of the mold.…”