Evaluation of the fracture behavior of multilayered polypropylene sheets obtained by coextrusion

Abstract

The mechanical and fracture behavior of multilayered sheets (up to three layers) is presented. The sheets were processed by plane coextrusion-calendering using two polypropylene-based materials, isotactic polypropylene homopolymer (H0), and an ethylene-propylene block copolymer (C1) with 5.5% ethylene content in weight. Combining these materials five different sheets were produced, (H0, C1, H0-C1, H0-C1-H0, and C1-H0-C1), with an overall thickness of 0.5 mm. The processing variables (temperature, extrusion rate, calendering speed, etc.) were set constant among the different structures to facilitate the evaluation of the results. The structure of the sheets was characterized with wide angle X-ray scattering (WAXS). The mechanical behavior was determined from dumbbell tensile specimens in the melt flow (MD) and transverse to the melt flow (TD) directions. The fracture parameters were determined by the essential work of fracture (EWF) technique in mode I in both MD and TD directions. The results show variations on the induced orientation of the sheets, with remarkable differences on the fracture properties. The poor fracture resistance of the homopolymer (H0) film in TD is improved through coextrusion with C1, obtaining the best results for toughness in the case of the three-layered sheets. POLYM. ENG.

Evaluation of the fracture behaviors of multilayered propylene–ethylene copolymer/polypropylene homopolymer composites with the essential work of fracture

“…Similar fracture behaviors were observed for all of the extrusion sheets. The fracture behaviors were strongly dependent on the testing direction …”

“…Compared with common structure, the layered structure has better mechanical properties. Simulation results obtained by some theoretical models, such as the equivalent box, have indicated that the mechanical properties, including the modulus, yield strength, and tensile strength, of layered structure are higher than those of a dispersed, cocontinuous structure . Kolarik ascribed this enhancement in the mechanical properties of a layered morphology to its best phase continuity in the direction of the acting force.…”

“…Gámez‐Pérez et al investigated the fracture behavior of coextruded polypropylene sheets using the EWF method. The results show that coextrusion with an ethylene–propylene copolymer could improve the fracture behavior of the polypropylene extruded sheets.…”

Puncture characterization of multilayered polypropylene homopolymer/ethylene 1-octene copolymer sheets

“…Due to best phase continuity of multilayered structure, the mechanical properties, including the modulus, yield strength, and tensile strength, of multilayered structure are higher than those of conventional structure. [31][32][33] Consequently, the puncture strength, which seriously depends on the modulus, yield strength, and tensile strength, for multilayered structure were higher than that for blend sample. 27 And the puncture strengths of multilayered and blend samples were both decreased with the volume fraction of POE increasing, indicating a lower deformation resistance of puncture.…”