A combination of high-pressure compression molding plus saltleaching was first proposed to prepare porous graphene/polystyrene composites. The specific shielding effectiveness of the lightweight composite was as high as 64.4 dB cm 3 g À1 , the highest value ever reported for polymer based EMI shielding materials at such a low thickness (2.5 mm).

No abstract

It is widely believed that the trigonal β-form is favorable and effective for toughening isotactic polypropylene (iPP). Therefore, β-form content should be achieved as high as possible to realize excellent toughness in iPP. However, in this study, we demonstrate that the connection between crystallites might mainly determine the toughness of iPP instead of the β-crystal content. A new rare earth nucleator (WBG) was used to generate the rich β-crystalline structure in the compression-molded bars that were fabricated upon different molten temperatures (T f ). Interestingly, the increase in tensile elongation can be as large as 8 times for increased T f . The polymorphic composition and overall crystallinity of β-nucleated iPP are almost independent of T f . Nevertheless, the β-nucleated crystalline morphology has completely changed. Three types of β-crystalline morphology, namely, β-spherulite, β-transcrystalline entity, and "flower"-like agglomerate of β-crystallites, are sequentially obtained with increasing T f . From the morphological point of view, the connection between the crystallites in "flower"-like agglomerate is significantly better than that for the crystallites generated under lower T f . Therefore, it is concluded that the formation of β-nucleated iPP provides very good toughness only with sufficient connection between the crystallites. The result of this study clearly verifies the importance of crystal morphology on tuning the toughness of iPP. It provides important information for potential industrial applications.

Boron nitride nanosheet (BNNS) films receive wide attention in both academia and industry because of their high thermal conductivity (TC) and good electrical insulation capability. However, the brittleness and low strength of the BNNS film largely limit its application. Herein, functionalized BNNSs (f-BNNSs) with a well-maintained in-plane crystalline structure were first prepared utilizing urea in the aqueous solution via ball-milling for the purpose of improving their stability in water and enhancing the interaction with the polymer matrix. Then, a biodegradable and highly thermally conductive film with an orderly oriented structure based on cellulose nanofibers (CNFs) and f-BNNSs was prepared just by simple vacuum-assisted filtration. The modification of the BNNS and the introduction of the CNF result in a better orientation of the f-BNNS, sufficient connection between f-BNNS themselves, and strong interaction between f-BNNS and CNF, which not only make the prepared composite film strong and tough but also possess higher in-plane TC. An increase of 70% in-plane TC, 63.2% tensile strength, and 77.8% elongation could be achieved for CNF/f-BNNS films, compared with that for CNF/BNNS films at the filler content of 70%. Although at such a high f-BNNS content, this composite film can be bended and folded. It is even more interesting to find that the in-plane TC could be greatly enhanced with the decrease of the thickness of the film, and a value of 30.25 W/m K can be achieved at the thickness of ∼30 μm for the film containing 70 wt % f-BNNS. We believe that this highly thermally conductive film with good strength and toughness could have potential applications in next-generation highly powerful and collapsible electronic devices.

There is a growing shift from liquid electrolytes toward solid polymer electrolytes, in energy storage devices, due to the many advantages of the latter such as enhanced safety, flexibility, and manufacturability. The main issue with polymer electrolytes is their lower ionic conductivity compared to that of liquid electrolytes. Nanoscale fillers such as silica and alumina nanoparticles are known to enhance the ionic conductivity of polymer electrolytes. Although carbon nanotubes have been used as fillers for polymers in various applications, they have not yet been used in polymer electrolytes as they are conductive and can pose the risk of electrical shorting. In this study, we show that nanotubes can be packaged within insulating clay layers to form effective 3D nanofillers. We show that such hybrid nanofillers increase the lithium ion conductivity of PEO electrolyte by almost 2 orders of magnitude. Furthermore, significant improvement in mechanical properties were observed where only 5 wt % addition of the filler led to 160% increase in the tensile strength of the polymer. This new approach of embedding conducting-insulating hybrid nanofillers could lead to the development of a new generation of polymer nanocomposite electrolytes with high ion conductivity and improved mechanical properties.