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A new technique to show good electroconductivity was proposed using carbon nanotube (CNT) localization in cocontinuous immiscible polymer blends comprising ultrahigh-molecular-weight polyethylene (UHMWPE) and polycarbonate (PC). When UHMWPE was added to PC/CNT in the molten state in an internal mixer, CNTs started moving to the UHMWPE phase. However, CNTs require a long time to diffuse into the UHMWPE phase owing to a low diffusion constant. Consequently, they remain at the interface between PC and UHMWPE. When the blends have cocontinuous structure, the localized CNTs at the phase boundary act as a conductive path, leading to a good electroconductivity. Although a similar morphology is obtained by adjusting the balance of interfacial tensions among polymers and CNT, it is difficult to find a system showing appropriate interfacial tensions. As the present method is applicable to various polymer blends, it will be an important technique to prepare a conductive nanocomposite.

Adding polyethylene greatly affects the rheological response of isotactic polypropylene (PP) under uniaxial elongational flow. Though strain hardening in the transient elongational viscosity barely appeared in pure PP, we induced strain hardening by adding low-density polyethylene (LDPE) to PP, even though the blends showed a phase-separated structure. During elongational flow, LDPE droplets dispersed in the PP were deformed in the flow direction. Because LDPE shows marked strain hardening in the elongational viscosity, the deformed LDPE droplets behaved as rigid fibers as the strain increased. Consequently, the PP between the fibrous LDPE droplets experienced excess localized deformation, which increased the apparent elongational viscosity. Furthermore, adding the high-density polyethylene (HDPE) increased the drawdown force—defined as the force required for uniaxial stretching of a molten polymer in the nonisothermal condition. This behavior comes from the rapid crystallization of HDPE, which causes the deformed HDPE particles to act as rigid fibers in the molten PP and enhances the PP crystallization, which increases the elongational stress.

We investigated the structure and properties of strands of high‐density polyethylene (HDPE), containing multi‐walled carbon nanotubes (MWCNTs) extruded from a capillary rheometer. Surprisingly, we found that the MWCNTs enhanced the chain orientation of HDPE, and that in the absence of MWCNTs, orientation relaxation occurred in the HDPE immediately after passing through the die. Conventional differential scanning calorimetry measurements indicated that MWCNT acts as a nucleating agent and raises the crystallization temperature 2–4 °C under quiescent condition. In the flow field, oriented MWCNTs behave like polymeric chain extended crystals “shish” and greatly accelerate the flow‐induced crystallization of the HDPE “kebab.” Consequently, the modulus was significantly increased in the flow direction. These findings demonstrate that the addition of MWCNTs is an effective method of enhancing the rigidity of HDPE. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48010.

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