The ternary blends of high‐density polyethylene (PE), EPDM terpolymer and polypropylene (PP) have been used as a model low interfacial tension system to study encapsulation dynamics in ternary blends and their relation to the blends' mechanical properties. It was found that the modulus, tensile strength and impact resistance can be improved by PE addition if the PE is localized within the EPDM phase. A range of blend morphology was found depending on the PE viscosity and polymer incorporation sequence in the twin‐screw extruder. In the most favorable sequence, PE and EPDM were mixed together prior to their dispersion in the PP matrix. This practice resulted in a 50% increase in impact resistance when compared to mixing the three components in a single‐step. 相似文献
This paper reports on how the blend ratio and morphology influence the mechanical, thermal, thermomechanical, and rheological properties of poly(propylene) (PP)/low density polyethylene (LDPE) blends. The blend morphology is composed of the major matrix phase and the minor phase, with subinclusions of the major matrix existing within the minor phase. Blends containing low amounts (<20 wt%) of either phase exhibit partial miscibility but the phases are immiscible at higher contents. Partial miscibility of the blends is revealed by scanning electron microscopy studies showing fibril‐like structures and confirmed by rheology. The tensile modulus of the blends decreases with increasing amounts of LDPE, but low LDPE contents exhibit positive deviation from the mixing rule of mixture due to partial compatibility. The crystallinity of PP is affected less than that of LDPE in the blends. Thermomechanical and rheological properties of neat polymers are significantly influenced by blending. The blend ratio and morphology influence impact strength and elongation at break, and the result demonstrates that the 80/20 PP/LDPE blend offers a balance among the mechanical and material properties that are essential for flexible packaging applications.
Summary: Metallocene‐catalysed linear low density polyethylenes (mLLDPEs) of different molecular weights are mixed with a base mLLDPE to obtain a pre‐determined grade and a suitable extrusion processability. Complex viscosity results are revealed as a very suitable tool to tailor the properties of the prepared binary and ternary blends. The investigated blends show symptoms of miscibility like time‐temperature superposition and observance of Cox‐Merz rule. This allows to evaluate the molecular weight distribution, supplying also practical data related to the polyethylene grade and ‘sharkskin’ instability. The complex viscosity curve of a model sample that would have both, a suitable grade and processability, is created; blends are prepared to match the model curve. The blend with a low molecular weight mLLDPE shows a parallel shift of the complex viscosity to lower values (molecular weight distribution is not broadened), postponing sharkskin, but changing the polymer grade. Satisfactory results are neither obtained with blends of a high molecular weight mLLDPE. Best results are obtained with ternary blends, which combine the modifications provided by low and high molecular weight mLLDPEs, approaching the complex viscosity and molecular weight distribution of the model.
Complex viscosity results of PR‐207 (– —), PR‐209 (···) and PR‐210 (– –) ternary blends, as compared with those of base samples PR‐201 (symbols) and the model (line). 相似文献
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