Study of mechanical and rheological behaviors of linear and branched polycarbonates blends

Abstract

A study of the mechanical and rheological properties of linear and branched polycarbonates blends is presented. Phase separations of the blends were checked through DSC and SEM, and, subsequently, mechanical and rheological properties were investigated. Phase separations were not observed in the blends. The mechanical properties were examined through tensile, flexural, and impact tests. All the mechanical properties of the blends were relatively independent of the compositions. For study of the rheological properties, melt viscosity, storage and loss moduli, and melt tension of the blends with various compositions were examined at various temperatures. The dependence of the viscosity on the molecular weight was also studied. As the content of branched polycarbonate increases, the dependence of the viscosity on the molecular weight and the shear thinning behavior became more marked. Melt tensions were also increased as the branched polycarbonate content increased in the blends for all tested temperatures. In this study, the blend systems which have same mechanical properties but different rheological properties can be obtained through blending of linear and branched polycarbonates.

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

“…The glass transition temperature of the low molecular weight linear prepolymer (PRE‐0) is 132.8°C but the T g increases with reaction time as both the polymer molecular weight and the insoluble fraction increase. After 180 min of reaction time (SSPM‐180), T g becomes constant at around 159°C which is higher than the reported T g values of commercial linear BPAPC (e.g., 146°C (31,000 g mol −1 ), 153°C (43,000 g mol −1 )) . The presence of partially crosslinked polymer chains copresent with linear BPAPC chains is believed to increase the T g because they would hinder the rotation of chain segments.…”

“…It has been reported that molecular weight, molecular structure, and polymer relaxation rate affect the degree of shear thinning . Decreased polymer chain relaxation or diffusion rate for high molecular weight nonlinear polycarbonates with branching and partial crosslinking give rise to higher shear thinning effect . Linear viscoelastic behaviors were observed for the SSPM‐180 and SSPM‐420 which contain about 5 and 49% insoluble gel, respectively.…”

“…For instance, while high molecular weight linear polycarbonate melt is not easy to process, long‐chain branched PCs are relatively easier to process for injection molding. The higher mobility of polymer chains in long‐chain branched polycarbonates compared to that of linear polycarbonates was reported through dielectric relaxation analysis . Higher melt elasticity and shear rate sensitivity were also observed while mechanical properties were not changed much for a wide range of compositions (0–100 wt % of branched BPAPC) of linear and branched BPAPC blends in commercially available long‐chain branched polycarbonates …”

“…Because SSP m PCs have branched and partially crosslinked chemical structures, the flow properties enable us to further understand the microstructural characteristics of the polymer. In general, higher molecular weight polymers have lower flow property . However, flowability of nonlinearly structured polymers such as branched and crosslinked polymers depends not only on the molecular weight but also on the degree of branching and crosslinking .…”

“…For the SSPM‐180 and SSPM‐420, the Newtonian behavior is not observed in the frequency range of 0.01–100 rad s −1 . It has been reported that molecular weight, molecular structure, and polymer relaxation rate affect the degree of shear thinning . Decreased polymer chain relaxation or diffusion rate for high molecular weight nonlinear polycarbonates with branching and partial crosslinking give rise to higher shear thinning effect .…”