Fabrication of sintered porous polymeric materials: effect of chain interdiffusion time on mechanical properties

In this study, sintered porous polymeric materials made of high density polyethylene (HDPE) were fabricated through controlling the chain interdiffusion time at the transition temperature of semicrystalline and melt states. At this intermediate state, where both crystalline and amorphous phases coexist, the interfacial welding of HDPE particles is facilitated thanks to interdiffusion caused by chain relaxation phenomena. Then, by assuming a spherical shape and a cubic packing configuration of particles, a geometrical model was developed to predict porosity variations as sintering progresses. Moreover, the HDPE used, as a broad molecular weight distributed polymer, has different family chains with different specific molecular weight ranges. Accordingly, the melt coalescence rate of the particles was tracked using an optical microscope equipped with a hot stage, in order to determine the diffusion characteristic times for each family. During the characterization stage, SEM images proved the presence of porous structures in the sintered samples. In addition, mechanical properties were assessed through the shear punch test. It was shown that the mechanical properties are governed by the interdiffusion of long chains which occurs at relatively long sintering times. The results also demonstrated the role of reptation motion of long chains in the interfacial welding of polymeric particles. They revealed the compatibility of macroscopic properties of the samples and chain motions at microscopic levels. © 2017 Society of Chemical Industry