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In this work, a facial approach was proposed to improve the thermal and electrical conductivity of poly(vinylidene fluoride) (PVDF) by constructing a segregated graphene nanoplatelets (GNP) network structure. PVDF/GNP composites with segregated filler network were fabricated by coating GNP on the surface of PVDF powders using ball milling treatment, followed by compression molding technique. PVDF powders of different particle size (e.g., 100 and 400 μm) were employed to elucidate the influence of matrix particle size on the properties of PVDF/GNP composites. Results showed that the formation of segregated GNP network contributed to a concurrent enhancement of both thermal and electrical conductivity of corresponding composites. A thermal conductivity as high as 2.23 W/mK coupling with an electrical conductivity of about 0.2 S/m was achieved for segregated PVDF100/GNP 6 wt% composite, which demonstrates potential applications in the areas that require both high electric and heat dissipations. [ABSTRACT FROM AUTHOR]

A high-performance interpenetrating polymer network (IPN) system was synthesized from vinyl-terminated polysiloxane (VS) and siliconized epoxy resin (ES) via one‐step preparation method. The compatibility between polysiloxane and epoxy was improved due to the IPN structure, as confirmed by dynamical mechanical analysis and scanning electron microscopy. Both the mechanical and adhesive properties of modified polydimethylsiloxane (PDMS) were significantly enhanced when the weight ratio of VS: ES is 100:20 (i.e. 20p-IPN). For example, the tensile strength and elongation at break for 20p-IPN were 205% and 119.9%, which were higher than that of pure PDMS. The shear strength of 20p-IPN was also doubled when compared with that of pure PDMS counterpart. Thermogravimetric analysis showed that although the degradation temperatures were slightly reduced due to the addition of modified epoxy, the residue at 800 oC was still maintained at a very high level (56.3%) in terms of 10p-IPN. These results showed that the properties of PDMS can be markedly improved by our proposed method, which demonstrated a promising aspect for high performance engineering applications. [ABSTRACT FROM AUTHOR]

In this study, the morphological, thermal and electrical properties of microinjection-molded multi-walled carbon nanotubes (CNT)-filled poly(lactic acid) (PLA) and PLA/poly[(butylene succinate)-co-adipate] (PLA/PBSA) immiscible blends were studied systematically. The PLA/PBSA/CNT immiscible blends were prepared by melt blending of PLA, PBSA and CNT in a batch mixer. Four different types of compounding procedure were employed to investigate the influence of compounding sequence of various components on the electrical conductivity of subsequent micromoldings. Results revealed that despite the compounding sequence, the electrical conductivity of PLA/PBSA/CNT microparts is invariably higher than that of CNT-filled mono-PLA counterparts and the selective localization of CNT in PBSA is thought to be the contributing factor. Furthermore, the prevailing high shearing conditions in microinjection molding (µIM) could lead to the coalescence of CNT-enriched PBSA domains, favoring the formation of conductive pathways in the melt flow direction, as confirmed by morphology observations. The crystallinity of PLA/PBSA immiscible blends is higher than that of mono-PLA system and a further increase in crystallinity after µIM suggested flow-induced crystallization. Moreover, thermal stability analysis indicated that the prevailing high shear rates in µIM might have a chain scission effect on PLA and PBSA. [ABSTRACT FROM AUTHOR]

This paper highlighted the morphological effect of aramid, i.e. fibers and particles, on friction and wear properties of polyoxymethylene (POM)/aramid composites under dry frictional conditions. Meanwhile, the mechanical, rheological and crystalline properties were also studied as a function of filler content. Results showed that addition of aramid short fibers (ASF) and particles (AP) affected the frictional behavior of POM in two different ways due to distinguished packing structure in composites. The mechanical performance of aramid short fibers filled POM composite outweighed that of POM/AP composite because of quite well length retention of aramid fibers, however this kind of morphology appeared not helpful to the enhancement of wear resistance. Dynamic rheology analysis confirmed the existence of network structure of POM filled with aramid short fiber, which was consistent with SEM observation of the worn scar surfaces. Compared with aramid particles, the entanglement and overlap of aramid fibers made it hard to deform under the same frictional conditions and could not to protect the matrix effectively, thus led to poor wear resistance. [ABSTRACT FROM AUTHOR]

In this work, high electrically conductive Polymethylmethacrylate/graphite (PMMA/G) composites with a specific core-shell structure were synthesized via Pickering emulsion (solid-stabilized emulsion) route. The electrical conductivity of the core-shell composites was measured by a four-point probe resistivity determiner and a very high value of 9.8 × 10 S/cm (10 times higher than virgin PMMA) was obtained at 30 wt% graphite. However, the electrical conductivity of the PMMA/G composites gained through traditional blend process was relatively lower and the value only reached 9.4 × 10 S/cm at same graphite loading fraction. Contact angle measurement was applied to determine the surface free energy of the modified graphite which was cladded by Al(OH). The morphology of the core-shell composites was observed by SEM and optical microscopy. Dynamic rheology analysis was employed to study the structural change by the interconnection of the graphite flakes and the formation of the networks in the composites. The interconnected networks of the core-shell composites were more easily constructed when compared with the composites obtained by the traditional blending process. [ABSTRACT FROM AUTHOR]

Withdrawal from prescribed opioids results in increased pain sensitivity, which prolongs the treatment. This pain sensitivity is attributed to neuroplastic changes that converge at the spinal cord dorsal horn. We have recently reported that repeated morphine administration triggers an insertion of GluA2-lacking (Ca2+-permeable) α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPAR) in the hippocampus. This finding together with the reported involvement of AMPAR in the mechanisms underlying inflammatory pain led us to hypothesize a role for spinal AMPAR in opioid-induced pain behavior. Mice treated with escalating doses of morphine showed hypersensitivity to mechanical stimulation. Intrathecal administration of a Ca2+-permeable AMPAR selective blocker disrupted morphine-induced mechanical sensitivity. Analysis of the expression and phosphorylation levels of AMPAR subunits (GluA1/2/3/4) in homogenates and in postsynaptic density fractions from spinal cord dorsal horns showed an increase in GluA4 expression and phosphorylation in the postsynaptic density after morphine. Co-immunoprecipitation analyses suggested an increase in GluA4 homomers (Ca2+-permeable AMPAR) and immunohistochemical staining localized the increase in GluA4 levels in laminae III-V. The excitatory postsynaptic currents (EPSCs) recorded in laminae III-V showed enhanced sensitivity to Ca2+-permeable AMPAR blockers in morphine-treated mice. Furthermore, current-voltage relationships of AMPAR-mediated EPSCs showed that rectification index (an indicator of Ca2+-permeable AMPAR contribution) is increased in morphine-treated but not in saline-treated mice. These effects could be reversed by infusion of GluA4 antibody through patch pipette. This is the first direct evidence for a role of GluA4-containing AMPAR in morphine-induced pain and highlights spinal GluA4-containing AMPAR as targets to prevent the morphine-induced pain sensitivity. [ABSTRACT FROM AUTHOR]

HDPE/UHMWPE and LDPE/UHMWPE blends were prepared and the environmental stress cracking resistance (ESCR) was compared using the Bell-telephone test. The time to failure in the ESCR test improved with increasing UHMWPE content, and considerable improvements were both produced when an UHMWPE weight fraction of 0.4 was used. Whereas LDPE/UHMWPE blend yield a higher improvement in stress cracking resistance compared to that of HDPE/UHMWPE blend. Thermal, morphological and mechanical studies were conducted and a relationship between morphological features and composition was established. Furthermore, the failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism for ESCR samples. [ABSTRACT FROM AUTHOR]