Hierarchy structure in injection molded polypropylene/ethylene–octane copolymer blends

Abstract

In this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene-octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin-core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing.

Influence of injection rate on crystallization of injection-molded β-nucleated isotactic polypropylene

“…We were surprised to find that the temperature in each layer did not vary much with different injection rates, as shown from Figure . Li et al proposed that the high injection rate may induce a great amount of heat because of the friction toward the mold wall. For the sample in our study is 4.0 mm in thickness and the changes among the injection rates are relatively small, the increasing heat from changing the injection rate is not high enough to influence the temperature.…”

Microscopic mechanical properties and injection molding‐induced morphology on polypropylene rubber blend

“…During the injection process, EPR particles were subject to deformation, breakup, and coalescence 6. Same morphological changes were also observed with a blends of PP and EOR 7. From the comparison of the EPR microstructure between a titanium (Ti) and a vanadium (V) based catalytic system, crystallinity and lamellar thickness of PP in the blends were reduced by adding 40 wt % of Ti‐EPR 8, 9.…”

“…A lot of previous studies deal with morphology of TPO 6–9. There are two types of the PP blends for commercial TPO.…”

Greatly improved toughness of isotactic polypropylene blends with traces of carbon nanotubes

“…Generally, blending iPP with elastomers or rubbers, such as ethylene–propylene diene terpolymers (EPDMs) , butadiene–styrene block copolymers , and ethylene‐octene copolymer (POE) , is an efficient way to increase the impact strength of iPP. However, the tensile properties are often sacrificed, along with the interfacial problem .…”