Improvement of the Long‐Term Performance of Impact‐Modified Polycarbonate by Selected Heat Treatments

Abstract

Next to the intended increase of the impact toughness, impact modification of polycarbonate generally results in an unwanted decrease in yield stress and time‐to‐failure under constant stress. It is demonstrated that this loss in strength can be fully compensated for by an annealing treatment, or by increasing the mold temperature. The influence of impact modification on the short‐ and long‐term strengths of glassy polymers is predicted by the extension of existing models with a scaling rule based on the filler volume percentage. Introduction of this scaling rule in the evolution of yield stress during physical aging even allows for the direct prediction of yield stress on the basis of processing conditions.magnified image

Role of processing history on the mechanical and electrical behavior of melt‐compounded polycarbonate‐multiwalled carbon nanotube nanocomposites

“…All nanocomposite specimens failed by brittle fracture while the stress was still rising, regardless of T c or forming method, as shown in the representative stress–strain curves in Figure . This is in sharp contrast to the unfilled PC, which deforms in a ductile fashion with a yield followed by strain softening and subsequent hardening and failure at large strains . The micrographs in Figure and those published by one of the authors on identical PC‐MWCNT (3 wt %) suggest that significant agglomeration is present in these materials.…”

“…In IM specimens, the additional increase relative to CM specimens could be attributed to (1) the frozen‐in orientation of the polymer chains, (2) the orientation of the CNTs, and (3) a different macrodispersion index D . We rule out polymer chain orientation, as its effects on IM PC are small …”

The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer

“…Moreover, the annealing process changes the failure mode from ductile to brittle. Engels et al . described a method of predicting the yield stress distribution of injection molded polycarbonate.…”

Temperature dependent two-body abrasive wear of polycarbonate surfaces

“…The material used in this study is Lexan 141R, a high molecular weight injection moulding grade polycarbonate (Sabic Innovative Plastics, Bergen op Zoom, The Netherlands). Samples of dimensions 20×20×1 mm 3 were cut from the centre of injection moulded plates, produced in a mould of 90 • C. The experimental protocol used to prepare these plates is given in more detail elsewhere [33]. After being stored at room temperature for over a year, the samples are dried for three days in a vacuum oven at 80 • C before being annealed for two weeks at a temperature of 120 • C. Subsequently the samples are air-cooled to room temperature under ambient conditions.…”