Band 37, Heft 6

The demand for contactless and wear-free sensor systems for the measurement of different physical values, such as angle, position, or speed has increased over the past years and opened up new application areas for magnetically sensitive sensors. Polymer bonded magnets can be used as signal transmitters in these sensor applications. In general, a high precision and good repeatability of the magnetic field is required, whereas in particular, a high peak flux density and accurate pole length of each pole is demanded for precise measurement. These polymer bonded magnets can be produced economically using the injection molding process with an integrated magnetization of the particles, such that a second magnetization step is unnecessary. This article addresses the influences of the gating system on the magnetic properties of multipolar bonded rings. Further, the particle orientation as well as filler content at different locations, and along the pathway are investigated. It was evaluated that the gating system significantly influences the pole length accuracy, as well as the peak flux density. However, differences in the filler orientation and content cannot be analyzed quantitatively.

In this paper, the combined effect of different weight percentages of silicon carbide (SiC) and graphite (Gr) reinforcement on the mechanical properties of polyamide (PA6) composite is studied. Test specimens of pure PA6, 85 wt% PA6+10 wt% SiC+5 wt% Gr and 85 wt% PA6+5 wt% SiC+10 wt% Gr are prepared using an injection molding machine. The tensile, impact, hardness, morphology and thermal properties of the injection molded composites were investigated. The obtained results showed that mechanical properties, such as tensile and impact strength and modulus of the PA6 composites, were significantly higher than the pure PA6, and hybridization with silicon carbide and graphite further enhanced the performance properties, as well as the thermal resistance of the composites. The tensile fracture morphology and the characterization of PA6 polymer composites were observed by scanning electron microscope (SEM) and Fourier transform infrared spectroscopic methods. SEM observation of the fracture surfaces showed the fine dispersion of SiC and Gr for strong interfacial adhesion between fibers and matrix. The individual and combined reinforcing effects of silicon carbide and graphite on the mechanical properties of PA6 hybrid composites were compared and interpreted in this study. Improved mechanical properties were observed by the addition of small amount of SiC and Gr concurrently reinforced with the pure PA6. Finally, thermogravimetric analysis showed that the heat resistance of the composites tended to increase with increasing silicon carbide and graphite content simultaneously.

In this study, two different surface-modified silica nanoparticles, amino-functionalized nanosilica (ATS) and methyl-functionalized nanosilica (HDS), were separately used as nanofillers to fabricate PA66-based nanocomposites by melt blending. The morphology and interface characteristics of the two nanofillers in the composite system and their influence on the mechanical properties, thermal decomposition behavior, and crystallization behavior of PA66 were investigated. The Avrami and Mo methods were applied to study the non-isothermal crystallization kinetics of the nanocomposites. The results revealed that different surface modifications of silica nanoparticles can produce different influences on the mechanical properties and thermal decomposition behavior of the final nanocomposites. The addition of ATS helps increase the strength and stiffness of PA66/ATS nanocomposites, and in the meantime enhances the thermal stability of PA66. The case of HDS is opposite to that of ATS; however, its incorporation can improve the toughness of the material. In addition, the results also indicate that ATS possesses strong heterogeneous nucleation capability, the introduction of which can accelerate the crystallization rate and increase the crystallization temperature, as well as the degree of crystallinity of PA66, while HDS displays an obvious blocking effect on the crystallization process of PA66.

Poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends were prepared in the presence and absence of samarium (III) acetylacetonate hydrate [Sm(acac) 3 ] used as an ester-ester exchange reaction catalyst. Differential scanning calorimetry (DSC) and thermogravimetric analysis/differential thermogravimetry (TGA/DTG) were used to study the variations in the thermal properties of blends before and after reactive blending. Solubility measurements in methylene chloride (CH 2 Cl 2 ) and infrared spectroscopy were also employed to highlight the structural changes that occurred during mixing in the presence of Sm(acac) 3 . The DSC results showed two distinct transition temperatures ( T g ) for all the compositions. Also, the T g values of components were shifted compared to the parent polymers in both the blends prepared with and without catalyst. Further, the T g of the PET-rich phase was displaced to higher temperatures and that of the PC-rich phase showed a tendency to diminish as the catalyst’s concentration increased. At the same time, the melting temperature ( T m ) of the PET-rich phase was shifted to lower temperatures. The evaluation of the compositions of the PC- and PET-rich phases using Wood’s equation showed a strong dependence on the catalyst concentration. Furthermore, the thermogravimetric thermograms showed that the thermal stability of the blends was between those of the homopolymers, and evidenced a net improvement relatively to the neat PET. The obtained results confirmed the aptitude of Sm(acac) 3 to promote exchange reactions between PC and PET, and to achieve their compatibilization through an interfacial copolymer synthesis process.

Toner is a fine powder composed of a resin and a coloring agent, which has been massively used in digital printing. The successfulness of digital printing can be measured in terms of the degree to which the properties of toner are finely controlled. In this work, we applied response surface methodology (RSM) to synthesize printing toners with appropriate physical and color properties. Based on a systematic experimental pattern proposed by RSM, styrene and butyl acrylate monomers are copolymerized through suspension polymerization to determine the individual and interactive effects of foregoing material parameters on the particle size, particle size distribution, and thermal and color properties of the resulting toner composites. Different analyses are carried out through which the optimum criterion for manufacturing well-controlled toner particles is established. Particularly, the results show that fine-tuning of toner properties depends on the careful regulation of material parameters, which we have learned from interactive effect identification.

Electroconducting structural polymer-based nanocomposites were prepared by incorporating carbon nanotubes (CNTs) into commercially available Polybond (PB) using the melt compounding technique. The structural, morphological, electrical, thermal, mechanical, and chemical properties of the nanocomposites were investigated via Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis, high resistance meter, a Universal Testing Machine (UTM), and chemical resistivity measurements, respectively. FTIR spectra showed the successful grafting of CNT functional groups onto polymer chains. SEM analysis confirmed that the optimum state of dispersion was made for the nanocomposites. Electrical conductivity, melting transition temperatures, mechanical properties, and chemical resistance were improved by incorporating CNTs into PB.

A comb-like copolymer poly (styrene-co-maleic anhydride)-graft-poly (ε-caprolacton) (SMA-g-PCL, SP) with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was used as an effective dispersant for CaCO 3 in the polypropylene (PP) matrix. The effects of CaCO 3 concentration on crystallization behaviors, mechanical properties, and thermal stabilities were studied systematically. The results revealed that the dispersion of CaCO 3 in the PP matrix was markedly improved owing to the steric hindrance effect caused by PCL, and the SP-coated CaCO 3 was a very effective nucleating agent for PP. Proper CaCO 3 concentration corresponded to the improvement of crystallization temperature, crystallinity, and crystallization rate of PP. There was only a slight improvement in yield stress but great improvement in Young’s modulus, flexural modulus, and impact strength. However, the excessive CaCO 3 filler deteriorated the mechanical properties. The good dispersion of SP-coated CaCO 3 in the PP matrix also accounted for the improvement of thermal stability. The initial decomposition temperature of the PP/CaCO 3 composite with 7.4 wt.% CaCO 3 increased 35°C compared with neat PP.

lithium ion conducting polymer electrolyte is one of the essential components of modern rechargeable lithium batteries because of its good interfacial contact with electrodes and effective mechanical properties. A solid lithium ion conducting polymer blend electrolyte is prepared using poly (vinyl acetate) (PVAc) and poly (methyl methacrylate) (PMMA) polymers with different molecular weight percentages (wt%) of lithium chloride (LiCl) by the solution casting technique with tetrahydrofuran as a solvent. The polymer electrolytes were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), Thermogravimetry (TG), AC impedance spectroscopy and ionic transport measurements. XRD and FTIR studies confirm the amorphous nature of the polymer electrolyte and the complexation of salt with polymer. The thermal behavior of polymer electrolytes has been studied from DSC and TG. The highest conductivity obtained using AC impedance spectroscopy is 1.03×10 −5 Scm −1 at 303 K for 70 wt%PVAc:30 wt%PMMA:0.8 wt% of LiCl polymer-salt complex. The plasticizer ethylene carbonate (EC) and nanofiller titania (TiO 2 ) were added to the optimized high conducting blend polymer electrolyte. An enhancement in conductivity by one order of magnitude was observed for the plasticized 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl polymer electrolyte at ambient temperature. The ionic conductivity value obtained using AC impedance spectroscopy for the plasticized 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl polymer electrolyte was 1.03×10 −4 Scm −1 . The highest conductivity obtained for 70 wt%PVAc-30 wt%PMMA-0.8% LiCl-6 mg TiO 2 was 4.45×10 −4 Scm −1 . Dielectric properties of polymer films are studied and discussed. The electrochemical stability of 1.69 V and 2.69 V was obtained for 70 wt%PVAc-30 wt%PMMA-0.8% LiCl and 70 wt%PVAc-30 wt%PMMA-0.8% LiCl-6 mg TiO 2 polymer electrolytes, respectively, using linear sweep voltammetry. The value of Li + ion transference number was estimated by the DC polarization method and was found to be 0.99 for the highest conducting 70 wt%PVAc-30 wt%PMMA-0.8 wt% LiCl-6 mg TiO 2 nanocomposite polymer electrolyte.

Hygrothermic aging of epoxy and carbon nanotube (CNT)/epoxy composites (0.5, 0.75, and 1 wt.%) was studied for their application suitability in seawater environments. The specimens were emerged in seawater and kept at constant temperature of 30°C for a maximum duration of 180 days. The specimens were periodically weighed for water absorption study and tested for mechanical as well as thermal properties. All aged samples were showing some amount of degradation owing to their moisture-absorption rates. CNT composites absorbed less moisture than pure epoxy because of the presence of nanofillers. C 0.75 was found to be hygrothermally more stable reflecting minimum reduction in flexural properties and glass transition temperature value, which was due to least moisture/water absorption. Deterioration of properties was significant in C 1 , though it was better than pure epoxy. Fractographic analysis by scanning electron microscopy (SEM) revealed interfacial debonding as the dominant failure mechanism, resulting in pull out of nanotubes.