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Thermoplastic composites of polylactic acid (PLA)-hydroxyapatite (HAp)-chitosan (CS) (in 91-8-1% weight proportion) is one of the acceptable composition/proportions for preparation of biomedical scaffolds (printed by fused deposition modeling (FDM)) in tissue engineering applications. But hitherto, little has been reported on the repair of PLA-HAp-CS based orthopedic scaffolds, especially in case of minor surface cracks observed post-surgery (maybe because of residual stresses/accident, etc.) from mechanical, thermal, in-vitro, in-vivo, and morphological analysis viewpoint. In this study, the 3D printed scaffolding structures of PLA-HAp-CS (3D printed on FDM) were further joined by friction stir spot welding (FSSW) process for minor repairs (such as surface cracks). The joints formed by the FSSW process were subjected to mechanical, thermal, cytotoxicity (by in-vitro, in-vivo analysis) and morphological analysis. The study results suggest that joints prepared using the consumable tool in FSSW have good mechanical, thermal stability, a good range of biocompatibility, and suitable tissue engineering applications. For FSSW of 3D printed scaffolding structures of PLA-HAp-CS, 1000 rpm tool rotational speed, 4 mm consumable plunge depth, and 40 s stirring time are the optimized set of process parameters. The results are also supported by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. [ABSTRACT FROM AUTHOR]

Highlights • Solution for compatibility issues between two dissimilar thermoplastic materials. • MFI of ABS and PA 6 was modeled by reinforcement of Al metal powder. • Reinforcement of 15% Al in ABS and 50% Al in PA6 resulted in thermally compatibility. • Suggested settings are 1200 rpm, 40 mm/min transverse speed and 8 mm pin diameter. Abstract This study demonstrates the solution for compatibility issues between two dissimilar thermoplastic materials for friction stir welding (FSW) applications. The joints of similar thermoplastic materials possesses good mechanical strength and uniform morphological characteristics but dissimilar thermoplastic are difficult to join as they are having large variation in molecular weight, carbon chain length, melt flow index (MFI) and melting point etc. In the present study, MFI of dissimilar thermoplastics namely: acrylonitrile butadiene styrene (ABS) and polyamide (PA)6 was modeled by reinforcement of Al metal powder for enhancing the material compatibility. Reinforcement of 15% Al metal powder (by weight) to ABS (as ABS-15Al) and 50% to PA6 (as PA-50Al) resulted in the similar MFI range of 11.57 g/10 min and 11.97 g/10 (with similar melting point range) confirmed the enhanced material compatibility with possibilities of sound FSW joints. Twin screw extrusion (TSE) and fused deposition modeling (FDM) were used to prepare the specimens of ABS-15Al and PA6-50Al and FSW was performed on conventional vertical milling setup. Further multi response optimization has been performed for establishing best settings of input process parameters. [ABSTRACT FROM AUTHOR]

In the present paper a meticulous study for controlling the process parameters of twin screw extruder has been highlighted for in-house preparation of reinforced PA6-TiO 2 hybrid feed stock filament (HFSF) of fused deposition modelling (FDM) for applications in several engineering fields. The experimental study has been reported for field engineers, to understand the influence of twin screw extrusion (TSE) process parameters on mechanical and metallurgical properties of Nylon-TiO 2 HFSF for printing of functional prototypes by FDM, with special focus on the additive manufacturing of innovative composite materials and structures with arbitrary geometry at different scales. These properties were statistically compared to verify the suitability of the screw extrusion process. The study suggested the long-term performance level of the TSE process after it has been brought under statistical control. The provided data from the experimentation highlights the ability of the TSE process to produce a product that will consistently meet the design requirements and the customer expectation. [ABSTRACT FROM AUTHOR]

Friction welding is one of the solid state welding techniques, for which the two pieces of thermoplastic materials must be compatible to each other. Friction welding of the two similar thermoplastic is an easy exercise but joining two dissimilar thermoplastic is difficult because of large differences in viscosity, specific density, molecular weight, melting point, crystalline vs. amorphous nature, surface behavior and dynamic-mechanical properties. In last three decades, studies have been reported to perform the friction and friction stir welding of thermoplastics but still the reason for compatibility of thermoplastic is not understood properly. In the present study attempts have been made to perform the compatibility analysis of two dissimilar polymers namely; acrylonitrile butadiene styrene (ABS) and polyamide 6 (PA6) by establishing their melt flow properties after Aluminum (Al) metal powder reinforcement. Twin screw extrusion (TSE) and fused deposition modeling (FDM) technologies were used to fabricate the welding specimen for potential application in maintenance engineering. [ABSTRACT FROM AUTHOR]

Polymer composites have certain advantages over metals in terms of mechanical as well as metallurgical properties. These can be joined with similar as well as dissimilar polymer composites (subject to certain conditions like glass transition temperature, rheological properties etc.). In last 20-25 years number of techniques and concepts has been developed to offer the possibility of joining of polymeric materials which have similar or dissimilar characteristics. In present scenario mechanical fastening and adhesive bonding is replaced by applying welding concepts like: laser transmission welding, friction stir welding (FSW), ultrasonic welding, hot fusion resistance welding etc. The FSW is one of the most acceptable welding techniques for production of structural/industrial components. In this present work, requirements of FSW and its process capability has been highlighted for joining of similar/dissimilar polymeric materials for future prospective. [ABSTRACT FROM AUTHOR]

Nano graphene (Gr) particles are of abundant methodical and scientific interest as having the astonishing prospective to usage as the sensors element in the miniaturized and biomedical sensor device. The nano Gr particles have been appeared on the life science and health platform due to their interesting material performance like; excellent biocompatibility, conductivity, super para magnetism, thermal, chemical, mechanical and metallurgical properties to use as a sensor component. In recent years, Gr as nanoparticles has acquired powerful technological and scientific attention and having potential applications like; for fabrication of super-capacitors, batteries, solar or fuel cells, miniaturized and biomedical sensors. Gr is one of the most influential nano composites with endowment of use in the sensing mechanism like; bio-sensing, bio-imaging and diagnostic of diseases due to stimulating material behavior like; biocompatibility, cell growing properties, excellent surface behavior thermally and chemically etc. The present discussion explores the state of art review and prospective of the Gr in the miniaturized and biomedical sensors. The sensing mechanism for each of the sensors has been discussed for betters understanding of the functionality and prospective of the Gr in the sensors. [ABSTRACT FROM AUTHOR]

Previous studies have highlighted the potential application of Polyamide 6 (PA6) as excellent recyclable polymeric material, which is well suited to form carbon-fiber-reinforced, graphene-nanoplatelets-reinforced or metal-porous-polymer composite structures. The conventional screw extrusion process is one of the established melt processing techniques, having potential of enhancing mechanical, thermal and morphological properties of polymeric materials. PA6 is an important engineering material which exhibits excellent mechanical properties, chemical resistance, wear resistance, dimensional stability, and low coefficient of friction. In the present study attempts have been made to explore the behavior and characteristics of the recycled PA6 polymer through twin screw extrusion process towards increase in recyclability (as primary recycling process). The mechanical properties (tensile strength, Young’s modulus, peak load), metallurgical properties (porosity, wear and material loss) supported with optical microscopy were investigated to ensure the recyclability of PA6 as a properties enhancing extrusion process. It has been observed in the present study that, melt processing by screw extrusion at best settings of input process parameters enhances the material properties for applications in sustainable civil engineering. [ABSTRACT FROM AUTHOR]

In the present work PA6 matrix reinforced with metal powder (Fe) has been joined by friction welding with ABS matrix reinforced with Fe powder for structural applications (like: joining of pavement sheets, assembly of pipe lines etc.). The melt flow index (MFI) of PA6+Fe powder was put approximately equivalent to MFI of ABS + Fe powder by varying the proportion of Fe powder in PA6 and ABS matrix. After fixing proportion of Fe powder in PA6 and ABS material, these materials were used for preparation of feed stock filament of fused deposition modelling filament (FDM) by screw extrusion process. Finally two FDM filaments of PA6+Fe powder and ABS + Fe powder were fed into FDM machine independently. The functional prototypes of circular cross-section were prepared on FDM machine (one with filament of PA6+ Fe powder and second with ABS + Fe powder). These geometrical shapes of two dissimilar plastic/polymer materials were used on friction welding setup. Finally under best parametric conditions of feed, rpm etc. these reinforced polymer materials were successfully joined. This study provides a response surface methodology (RSM) based statistical model for enhancing the weldability of dissimilar polymer materials (as an alternative method) with improved mechanical/metallurgical properties. [ABSTRACT FROM AUTHOR]

Friction welding is one of the established processes for joining of similar as well as dissimilar polymer/plastics and metals. In past 20 years numbers of application in different areas using this process have been highlighted, but very limited contributions have been reported on properties of friction welded joints of dissimilar polymer/plastic materials after reinforcement with metal powder. In the present work an attempt has been made to perform friction welding of dissimilar plastic based materials by controlling the melt flow index (MFI) after reinforcement with metal powders. The present studies of friction welding for dissimilar plastic were performed on Lathe by considering three input parameters (namely: rotational speed, feed rate, and time taken to perform welding). Investigations were made to check the influence of process parameters on mechanical and metallurgical properties (like: tensile strength, Shore D hardness and porosity at joint). The process parameters were optimized using Minitab software based on Taguchi L9 orthogonal array and results are supported by photomicrographs. [ABSTRACT FROM AUTHOR]

Abstract: Novel functionalized polymeric flocculants based on polyacrylamide grafted carboxymethylstarch (CMS-g-PAM) have been successfully synthesized via conventional method (using ceric ammonium nitrate as free radical initiator, in an inert atmosphere) as well as by using microwave irradiation (‘microwave initiated’ synthesis). Under optimal grafting conditions, 50% grafting has been observed in case of the microwave irradiation based method and 47% grafting has been observed in case of the conventional process. The synthesized graft copolymers have been characterized by elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, molecular weight determination, 13C NMR spectroscopy and scanning electron micrograph (SEM); taking carboxymethylstarch (CMS) as reference. The effects of reaction parameters onto the percentage of grafting have been studied. Further, the applicability of these grafted polymers as flocculants for the treatment of municipal sewage wastewater has also been investigated. [Copyright &y& Elsevier]

The friction stir welding (FSW) or friction stir spot welding (FSSW) with non-consumable tool is one of the established processes for joining of thermoplastics/low melting point metals/alloys. But hitherto little has been reported on joining of similar/dissimilar thermoplastics with FSSW especially with use of semi-consumable/consumable tool. The present study deals with thermo-mechanical investigations for FSSW of thermoplastics with fully/semi-consumable tool as a novel method. The FSSW was performed on 3D printed functional prototypes of acrylonitrile butadiene styrene (ABS) reinforced with 15% Al powder (by weight) as ABS-15Al, with polyamide (PA)6 reinforced with 50%Al powder (by weight) as PA6-50Al. The online monitoring by thermal imaging camera and axial force measurements was performed to investigate variations in tensile, thermal and morphological properties. The influence of input process variables (namely: rotational speed, plunge depth and stirring time) of FSSW joints has been explored. The results of study suggest that for joining of ABS-15Al substrates with PA6-50Al, rotational speed 1400 rpm, plunge depth 2 mm and stirring time 15 s are the best settings from multifactor optimization view point. Further the tensile properties of ABS-15Al joints prepared by FSSW are comparable to virgin ABS thus made it suitable for maintenance and repair applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal-organic frameworks (MOFs) are proven heterogeneous recoverable catalysts in a number of organic transformations. However, their role in the reaction of amines with dialkyl carbonates has only been partially investigated. In this paper, the catalytic potential of Ce-Zr UiO-66 MOF towards the N- alkylation of secondary amines with dimethyl carbonate has been investigated. The desired MOF catalyst was prepared by the solvothermal method and its morphology, texture, porosity, functionality, and crystallinity were examined before its catalytic investigation. The MOF consisted of sphere-like particles with a surface area of 272 m2/g and an average pore size of 3.4 nm. Under the optimized conditions, the aromatic and heterocyclic amines yielded the N -methylated derivatives as the sole or the major product in the presence of Ce-Zr UiO-66 MOF. The maximum methylation percentage achieved was 100%. The reaction followed the pseudo-first-order rate kinetics and the heterogeneous bimetallic Ce-Zr UiO-66 MOF was reused four times without any significant activity loss. Thus, the Ce-Zr UiO-66 MOF serves as an efficient, selective, and reusable heterogeneous catalyst in N -methylation reactions. [ABSTRACT FROM AUTHOR]