Polymer Blends

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

We study the formation and growth of equilibrium clusters in a suspension of weakly-charged colloidal particles and small non-adsorbing polymers. The effective potential is characterised by a short-range attraction and a long-range repulsion. The size, shape and local structure of the clusters are studied using three-dimensional particle microscopy. We observe a rapid growth in the mean cluster size and the average number of nearest neighbours approaching the gel boundary.

A unique approach was adopted to drive the multiwall carbon nanotubes (MWNTs) to the interface of immiscible PVDF–ABS blends by wrapping the nanotubes with a mutually miscible homopolymer (PMMA). A tailor made interface with an improved stress transfer was achieved in the blends with PMMA wrapped MWNTs. This manifested in an impressive 108% increment in the tensile strength and 48% increment in the Young's modulus with 3 wt% PMMA wrapped MWNTs in striking contrast to the neat blends. As the PMMA wrapped MWNTs localized at the interface of PVDF–ABS blends, the electrical conductivity could be tuned with respect to only MWNTs, which were selectively localized in the PVDF phase, driven by thermodynamics. The electromagnetic shielding properties were assessed using a vector network analyser in a broad range of frequency, X-band (8–12 GHz) and K u-band (12–18 GHz). Interestingly, enhanced EM shielding was achieved by this unique approach. The blends with only MWNTs shielded the EM waves mostly by reflection however, the blends with PMMA wrapped MWNTs (3 wt%) shielded mostly by absorption (62%). This study opens new avenues in designing materials, which show simultaneous improvement in mechanical, electrical conductivity and EM shielding properties.

In this research the variation of mechanical and rheological properties of the composite as a function of different processing parameters and ethylene propylene diene monomer (EPDM) rubber content was studied. The optimum amount of dicumyl peroxide (DCP) to achieve the highest percentage of grafting of maleic anhydride to EPDM was obtained by Fourier transform infrared (FTIR) spectroscopy. In general, immiscibility between nylon 66 and EPDM, and their high interfacial tension makes their blending difficult. Maleic anhydride was grafted to EPDM to reduce interfacial tension between two phases. Also the blends were prepared at highest possible speed of mixing (screw speed in extrusion) and lowest temperature to reach a well mixed sample which can be seen in scanning electron microscopy (SEM) images and impact strength results. Dynamic mechanical thermal analysis (DMTA) tests were conducted to evaluate the miscibility of the components and to measure the glass transition temperature of...

Silver conductive ink is widely used to form conductive electrode in printed electronics applications. However, rapid rise in silver price is driving the need for alternative conductive ink that is significantly more cost-effective [1]. Copper based conductive ink is a promising alternative due to inherently lower material cost compared with silver conductive ink. In addition, copper conductive ink will provide solderable printed interconnects unlike those using silver conductive ink [2]. A key limitation of copper based conductive ink is inherently higher electrical resistivity compared with silver conductive ink. This study focuses on large area screen printing, low temperature ink curing and electrical characterization. The selected copper conductive ink has a metal loading of 65wt.%, and viscosity range of 25,000 to 35,000 cps. Two test vehicles on Polyethylene Terephthalate (PET) substrate were used for performance characterization: 1) printed conductive circuit 2) printed frequency selective electromagnetic interference (EMI) shield. By optimising key screen printing parameters including screen mesh size, printing speed and squeegee pressure, a minimum printed line width of 100 μm was achieved for a printed area of 500 mm × 500 mm. A low curing temperature of 60°C was achieved by optimising air-flow rate and curing profile. Good printing uniformity was achieved, translating to a 10% tolerance for measured electrical resistance in printed conductive circuit. High-frequency characterization was also performed on printed frequency selective EMI shield. A shielding effectiveness of 24 dB was achieved at the tuned rejection frequency of 1.8 GHz for a narrow band topology. The shielding performance is comparable with that of printed frequency selective EMI shield using silver conductive ink.

Ultrasonic investigations of molecular interactions of polymer blends of chitosan (Ch)/ polyvinyl pyrrolidone (PVP), in a buffer solution (0.1 M acetic acid + 0.2 M sodium acetate) have been reported within the temperature range 303.15 K-323.15 K. Several acoustic parameters such as acoustic impedance, isothermal compressibility, adiabatic compressibility, internal pressure have been determined. Various thermo-dynamical parameters viz; pseudo-Gruneisen parameter and surface tension have been evaluated. Some thermo-elastic parameters such as bulk modulus, shear modulus and Young's modulus are also computed. The non-ideal behaviour of the blend, in the buffer solution has been explained in terms of its composition and temperature variation of acoustical and thermo-dynamical parameters. The reliability model for polymer blends of chitosan (Ch)/ polyvinyl pyrrolidone (PVP) has also been proposed.

Mercapto-modified ethylene-vinyl acetate (EVASH) has been employed as a reactive compatibilizing agent for nitrile-butadiene rubber (NBR)/ethylene-propylene-diene monomer (EPDM) blends vulcanized with a sulfur/2,2′-dithiobisbenzothiazole (MBTS) single accelerator system and a (sulfur/MBTS/tetramethylthiuram disulfide (TMTD) binary accelerator system. The addition of 5.0 phr EVASH resulted in a significant improvement in the tensile properties of blends vulcanized with the sulfur/MBTS system. In addition to better mechanical performance, these functionalized copolymers gave rise to a more homogeneous morphology and, in some cases, better aging resistance. The compatibilization was not efficient in blends vulcanized with the S/MBTS/TMTD binary system, probably because of the faster vulcanization process occurring in this system. The good performance of these EVASH samples as compatibilizing agents for NBR/EPDM blends is attributed to the higher polarity of these components that is associated with their lower viscosity. Dynamic mechanical analysis also suggested a good interaction between the phases in the presence of EVASH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1404–1412, 2004

Small amounts of fluorinated polyethers, and in particular a nonionic fluorinated polyether, can upgrade considerably the cold-water swelling and internal bond strength of wood particleboard bonded with urea–formaldehyde (UF) resins. The effect is maximized at an additive concentration of about 0.1 wt % with respect to the adhesive resin solid content. The effect of the fluorinated polyether appears to be greater with older UF resins, which have a more pronounced colloidal state. The mechanism appears to be somewhat related to the reduction of the interfacial tension of the resins, with improved substrate wetting leading to better adhesion. The addition of a fluorinated polyether well in advance of resin use further enhances the improvement. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

The immiscible bio-plastic blend of poly(lactic acid) (PLA) and polyamide11 (PA11 or Nylon11) was compatibilized, using a catalyzed the ester-amide interchange chemical reaction during reactive extru-sion. The effects of screw configuration on mixing and reaction optimization were explored. It was found that effective mixing and minimized degradation were achieved when kneading elements were installed only near the die end of the extruder rather than near the beginning of the melt section. However, significant degradation of PLA could not be avoided during processing, which led to a decrease in mechanical strength of blend. To prevent the molecular weight reduction, tris(nonylphenyl) phosphite (TNPP) stabilizer was introduced to improve the thermal stability of PLA matrix. Improvement to both tensile strength and elongation were achieved in the resulting PLA/PA11/TsOH/TNPP blend.

This article studies the mechanical properties of short fiber reinforced polymer blends comprised of a soft thermoplastic matrix (polyethylene, PE), a rigid dispersed thermoplastic phase (polyamide-6, PA6) and glass fiber reinforcement. These ternary composites are designed as a model system to investigate the impact of the mutual interactions of the three phases on the composite mechanical properties. For this purpose

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH and eCO 2 H functional groups on the surface of the peels and rough morphologies were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy investigations, respectively. Corn fibers and luffa peels showed maximum extraction effi-ciencies within the pH range of 4e10 and adsorption reached a steady state within 2e3 h. Prewashed corn fibers and luffa peals extracted 159 mg g À1 and 90 mg g À1 of alcian blue, 70 mg g À1 and 124 mg g À1 of methylene blue, 50 mg g À1 and 108 mg g À1 of neutral red as well as 35 mg g À1 and 40 mg g À1 of coomassie brilliant blue from water, respectively. Both materials did not show significant extraction affinity towards heavy metal ions such as Pb 2þ (1 mg g À1), Ni 2þ (4 mg g À1 for corn fiber and 12 mg g À1 for luffa peels), and chromate (3 mg g À1 for corn fibers and 6 mg g À1 for luffa peels) ions from water. The Langmuir and Freundlich isotherms were used to understand the adsorption process on the surface of the adsorbents. Langmuir isotherm model yielded the best fit for the data obtained in the study, indicating a monolayer adsorption of pollutants on the adsorbent surface. Both adsorbents can be regenerated at acidic pH and could be reused for up to five cycles without significant loss of efficiency. Our experimental results suggest that both natural materials are effective towards removing dissolved dyes from water.