Abstract
The electrically conductive poly (lactic acid) (PLA)/recycled high-density polyethylene (HDPE)/carbon black (CB) composites with a fine co-continuous micro structure and selective localization of CB in the HDPE component were fabricated by one-step melt processing via a twin-screw extruder. Micromorphology analysis, electrical conductivity, thermal properties, thermal stability, and mechanical properties were investigated. Scanning electron microscope (SEM) images indicate that a co-continuous morphology is formed, and CB is selectively distributed in the HDPE component. With the introduction of CB, the phase size of the PLA component and the HDPE component in PLA/HDPE blends is reduced. In addition, differential scanning calorimetry (DSC) and thermos gravimetric analysis (TGA) results show that the introduction of CB promotes the crystallization behavior of the PLA and HDPE components, respectively, and improves the thermal stability of PLA70/30HDPE/CB composites. The electrically conductive percolation threshold of the PLA70/30HDPE/CB composites is around 5.0 wt %, and the electrical conductivity of PLA70/30HDPE/CB composites reaches 1.0 s/cm and 15 s/cm just at the 10 wt % and 15 wt % CB loading, respectively. Further, the tensile and impact tests show that the PLA70/30HDPE/CB composites have good mechanical properties. The excellent electrical conductivity and good mechanical properties offer the potential to broaden the application of PLA/HDPE/CB composites.
Highlights
Compared with synthesizing a new polymer, the blending of various thermoplastic polymers is an important and efficient technique to developing high performance polymeric materials [1,2]
The microscopic phase morphology plays a decisive role in the macroscopic properties [27]
In order to better observe the co-continuous microscopic phase morphology of the PLA/high-density polyethylene (HDPE) binary blends (50/50, 60/40, 70/30), the PLA component of the PLA/HDPE binary blends was etched by chloroform, and the Scanning electron microscope (SEM) images are shown in Figure 1a’–c’, respectively
Summary
Compared with synthesizing a new polymer, the blending of various thermoplastic polymers is an important and efficient technique to developing high performance polymeric materials [1,2]. Most polymer blends are immiscible and tend to separate into two or more distinct phases during the processing. For two-phase blends, “sea-island” and co-continuous micro structure are the two major phase morphologies [3,4,5]. Polymer blends with a co-continuous structure have many interesting applications and excellent performance, such as electrical conductivity, thermal conductivity, heat resistance, and so on [5,9]. Electrical conductive polymer composites (ECPCs) have aroused enormous attention in various high value-added applications, such as anti-static packaging materials, Polymers 2019, 11, 1583; doi:10.3390/polym11101583 www.mdpi.com/journal/polymers
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