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Improved Mechanical Properties (improved + mechanical_property)
Selected AbstractsConjugated Polymers: Enhanced Charge Transportation in Semiconducting Polymer/Insulating Polymer Composites: The Role of an Interpenetrating Bulk Interface (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Mater. By taking advantage of two-phase interface engineering in three dimensions, X. Yang and co-workers demonstrate on page 1714 the substantially improved (instead of decreased) electrical properties of conjugated polymer/insulating polymer composites. This novel approach paves the way for preparing high-performance semiconducting polymer composites with reduced cost, improved mechanical properties, and environmental stability. [source] Development of an extrusion system for producing fine-celled HDPE/wood-fiber composite foams using CO2 as a blowing agentADVANCES IN POLYMER TECHNOLOGY, Issue 4 2004H. Zhang Abstract This paper presents an innovative design of a tandem extrusion system for fine-celled foaming of plastic/wood-fiber composites using a physical blowing agent (PBA). The plastic/wood-fiber composites utilize wood-fibers (WF) as a reinforcing filler in the plastic matrix and are known to be advantageous over the neat plastics in terms of the materials cost and some improved mechanical properties such as stiffness and strength. However, these improvements are usually accompanied by sacrifices in the ductility and impact resistance. These shortcomings can be reduced by inducing fine-celled or microcellular foaming in these composites, thereby creating a new class of materials with unique properties. An innovative tandem extrusion system with continuous on-line moisture removal and PBA injection was successfully developed. The foamed composites, produced on the tandem extrusion system, were compared with those produced on a single extruder system, and demonstrated significant improvement in cell morphology, resulting from uniform mixing and effective moisture removal. The effects of WF and coupling agent (CA) on the cell morphology were studied. An increase in the WF content had an adverse affect. The cell morphology and foam structures were improved when an appropriate CA was added. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 263,276, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20016 [source] Fabrication of Aligned Poly(L -lactide) Fibers by Electrospinning and DrawingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2009Amalina M. Afifi Abstract A new target collector was designed for taking up aligned nanofibers by electrospinning. The collector consists of a rotor around which several fins were attached for winding electrospun filaments continuously in large amounts. The alignment of the nanofibers wound on the collector was affected by the electrospinning conditions, such as the needle-to-collector distance and the applied voltage, but not by the rotation speed of the collector. At a voltage of 0.5,kV,·,cm,1, about 60% of the fibers were found to be aligned within an angle of,±,5° relative to the rotational direction of the collector. The fiber alignment was improved to 90% by drawing the fiber bundle 2,3 times at 110,°C. The drawing was also effective for crystal orientation of the fibers as revealed by WAXD. The drawn fibers show improved mechanical properties. [source] Functionalized polypropylenes in the compatibilization and dispersion of clay nanocompositesPOLYMER COMPOSITES, Issue 4 2006C. Varela The preparation of polypropylene (PP) nanocomposites was studied using clay and three types of modified PP (m-PP) as compatibilizers: diethyl maleate grafted PP (PP- g -DEM), maleic anhydride grafted PP (PP- g -MA), and PP grafted with carbamyl maleamic acid (PP- g -UMA). The clay was made organophylic by an acid treatment with octadecylamine. PP functionalization and blending were carried out in an internal mixer. Blends of PP containing 20 and 40 wt% each of the modified PP and 5 wt% of organophilic clay (IMt), in each case, were prepared. Samples were characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical microscopy, and mechanical testing. The presence of tactoid, intercalated and exfoliated structures was observed by TEM in all the samples containing clay and modified PP, which also showed improved mechanical properties with tensile modulus as much as three times that of PP. Melting temperature did not vary significantly with the addition of clay. However, because of the clay's nucleating effect, an increase in the crystallization temperature was observed, accompanied by a slight decrease in the degree of crystallinity. The best results were obtained when PP- g -MA was used as the compatibilizer; intermediate results were obtained with the use of PP- g -UMA, followed by the results obtained when PP- g -DEM was used. Property enhancements were obtained when a higher percentage of modified PP was employed. POLYM. COMPOS., 27:451,460, 2006. © 2006 Society of Plastics Engineers [source] Biodegradable polyester layered silicate nanocomposites based on poly(,-caprolactone)POLYMER ENGINEERING & SCIENCE, Issue 9 2002Nadège Pantoustier Nanocomposites based on biodegradable poly(,-caprolactone) (PCL) and layered silicates (montmorillonite, MMT) were prepared either by melt interaction with PCL or by in situ ring-opening polymerization of ,-caprolactone as promoted by the so-called coordination-insertion mechanism. Both non-modified clays (Na+ -MMT) and silicates modified by various alkylammonium cations were studied. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. Even at a filler content as low as 3 wt% of inorganic layered silicate, the PCL-layered silicate nanocomposites exhibited improved mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as a result of a charring effect. It was shown that the formation of PCL-based nanocomposites depended not only on the nature of the ammonium cation and related functionality but also on the selected synthetic route, melt intercalation vs. in situ intercalative polymerization. Interestingly enough, when the intercalative polymerization of ,-caprolactone was carried out in the presence of MMT organo-modified with ammonium cations bearing hydroxyl functions, nanocomposites with much improved mechanical properties were recovered. Those hybrid polyester layered silicate nanocomposites were characterized by a covalent bonding between the polyester chains and the clay organo-surface as a result of the polymerization mechanism, which was actually initiated from the surface hydroxyl functions adequately activated by selected tin (II) or tin (IV) catalysts. [source] Influence of clay modification on the reinforcement of vinyl-terminated polydimethylsiloxane networksPOLYMER INTERNATIONAL, Issue 4 2010Eung Soo Kim Abstract A novel method was attempted to reinforce a vinyl-terminated polydimethylsiloxane (PDMS) with two commercially available clays, sodium montmorillonite and Cloisite® 25A. The two clays were functionalized with bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) to prepare Na+MMTS4 and C25AS4, respectively. Incorporation of the tetrasulfide group-containing clays, especially Na+MMTS4, was found to be effective for the enhancement of the interfacial interaction between PDMS and the clays by way of a plausible chemical reaction between the tetrasulfide groups (TSS) and the vinyl-terminated PDMS. Compounding of PDMS with the TESPT-modified clays improved the mechanical properties significantly. In particular, the elongation at break of PDMS/Na+MMTS4 composite was almost twice as high as that of neat PDMS, even if the silicate layers were not fully exfoliated in the PDMS matrix. The tear strength of PDMS was also improved greatly as a result of the incorporation of Na+MMTS4. According to toluene swelling test results, the crosslinking density of the composites was lower than that of neat PDMS, indicating that the improved mechanical properties of the composites arise from enhanced compatibility between the constituents and not from increased crosslinking density. 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