228 research outputs found

    The exploitation of polymer based nanocomposites for additive manufacturing: a prospective review

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    Additive manufacturing (AM) is a well-known technology for making real three dimensional objects, based on metal, ceramic and plastic material used for various applications. The aim of this review is to explore and offer an insight in to the state of the art polymer based nanocomposites in to additive manufacturing applications. In context to this, the developing efforts and trends in nanocomposites development particularly for additive manufacturing processes were studied and summed up. The scope and limitations of nanocomposites into Stereolithography, selective laser sintering and fused deposition modeling was explored and highlighted. The review highlights widely accepted nanoparticles for range of applications including mechanical, electrical, flame retardance and crossing over into more biological with the use of polymer matrices. Acquisition of functional parts with limitations in regard to printing is highlighted. Overall, the review highlights successes, limitations and opportunities that the union of AM and polymer based nanocomposites can bring to science and technology

    Processing of Bio-Polymer Based Nanocomposite for Fused Filament Fabrication

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    Polylactic acid (PLA) is perhaps one of the best known polymers produced from renewable raw materials such as sugar cane and corn starch. Several studies have focused on improving the properties of PLA by incorporating nanofillers in polymer matrix. Cellulose nanocrystals (CNC) is a nanofiller from natural sources (typically wood pulp) that is used to reinforce and modify the mechanical properties and biodegradability of PLA. In this work, cellulose nanocrystals (CNC) reinforced polylactic acid composite was produced in 1, 2, 5 and 10 wt % CNC content by a single-screw extruder in filament form. The effect of cellulose content on the thermal properties of the bio-composite were studied. Differential scanning calorimetry results showed shift in the glass transition temperature and a change in the melting temperatures, where 10% CNC content showed highest reduction in melting temperature. Cellulose proved to increase the crystallinity of the matrix compared to the neat PLA, 1% cellulose exhibited the highest cold crystallization peak. Precision filament (1.75 mm in diameter) was made for fused deposition modeling (3D printing) in order to study the mechanical properties of the bio-composites. The tensile modulus increased in 1% cellulose composites (4.55 GPa) compared to neat PLA (3.03 GPa) for the printed samples. However, the elongation at break reduced when comparing neat PLA (8.7%) while in 1% cellulose was (2.9%)

    Lignin: A Biopolymer from Forestry Biomass for Biocomposites and 3D Printing

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    Biopolymers from forestry biomass are promising for the sustainable development of new biobased materials. As such, lignin and fiber-based biocomposites are plausible renewable alternatives to petrochemical-based products. In this study, we have obtained lignin from Spruce biomass through a soda pulping process. The lignin was used for manufacturing biocomposite filaments containing 20% and 40% lignin and using polylactic acid (PLA) as matrix material. Dogbones for mechanical testing were 3D printed by fused deposition modelling. The lignin and the corresponding biocomposites were characterized in detail, including thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction analysis (XRD), antioxidant capacity, mechanical properties, and scanning electron microscopy (SEM). Although lignin led to a reduction of the tensile strength and modulus, the reduction could be counteracted to some extent by adjusting the 3D printing temperature. The results showed that lignin acted as a nucleating agent and thus led to further crystallization of PLA. The radical scavenging activity of the biocomposites increased to roughly 50% antioxidant potential/cm2, for the biocomposite containing 40 wt % lignin. The results demonstrate the potential of lignin as a component in biocomposite materials, which we show are adequate for 3D printing operations

    Nanostructured polymers for additive manufacturing

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    Fused filament fabrication (FFF) is one of the most widely employed techniques of additive manufacturing, which produces three dimensional (3D) printed objects by the layering of melt-extruded thermoplastic-based filaments. Despite its ease of use and environmentally friendly nature, FFF has so far only provided a narrow range of potential applications due to the limited number of materials (mostly thermoplastic-based composites, with metal or ceramic fillers) compatible with this technique. Another obstacle for the wider application of 3D printed parts is their inferior mechanical performance compared to that of their conventionally-manufactured counterparts. A strategy for overcoming this deficiency is by merging polymer/clay nanocomposites with 3D printing. However, the incorporation of clays in the nanocomposite feedstock filament usually incurs several processing challenges, including clay agglomeration to the detriment of the formation of the printed part. This research aims to provide a systematic investigation and understanding of the influence of clay fillers and additives (coupling agents) on the mechanical properties and morphology of 3D printed nanocomposites. A series of polylactide (PLA)/clay nanostructured composite filaments were developed and successfully printed by an open-source 3D printer based on FFF. The effect of filament composition on the mechanical properties and morphology was investigated and correlated with the extent of intercalation of different clay types. The mechanical behaviour of the printed composite samples was influenced significantly by the clay type and content. For example, the samples containing organoclay with the same clay content exhibited a higher modulus of elasticity and strength than those with natural clay. In addition, the Halpin-Tsai model was found to be successful in predicting the moduli of the PLA/clay systems. Based on the experimental results, the mechanical properties of the PLA/clay composite systems were shown to be correlated to the extent of clay intercalation. An implication from the model is that clay intercalation was more effective as a reinforcement technique than raising the total clay content. Upon the introduction of Garamite clay in the polymer matrix, the flowability of the melt was improved followed by a decrease in the die swell ratio of the composite samples. As a consequence, the composite feedstock filaments provided an enhanced print resolution compared to neat PLA and resulted to a printed part with a more compact mesostructure. The research showed that the dispersibility of the nanophase was a general difficulty affecting nanocomposite performance. As a result, grafted PLA was added to act as a compatibiliser to the Garamite and Cloisite composite systems, in order to promote the dispersion of clays in the polymer matrix. It was found that the mechanism underlying the mechanical performance of the grafted PLA/PLA/clay composites was dependent on the clay morphology. Upon the addition of grafted PLA in the PLA/Cloisite composite, the mechanical properties were improved due to the increased interfacial interaction and wetting between PLA and Cloisite platelets. In the case of the PLA/Garamite system, however, the addition of various concentrations of grafted PLA did not substantially improve the mechanical properties. These findings could act as a guideline in the design and development of feedstock filaments for 3D printing

    The Use of Cellulose Nanofibers in Polymer Matrix Composites via 3D Printing

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    Filament fused fabrication (FFF) is an extrusion-based 3D printing technology for manufacturing thermoplastic polymers. A major obstacle of 3D printed thermoplastic is the limited crystallinity resulting from a fast quench while material leaving the hot nozzle and solidifying quickly at the low-temperature platform. As a result, the mechanical performances of 3D printed thermoplastic is normally inadequate in comparison with conventionally manufactured ones (e.g., from injection molding). In this work, we developed two strategies for reinforcing and functionalizing 3D printed thermoplastic composites using cellulose nanofibers (CNFs) as nanofillers. Firstly, L-lactide monomers were grafted onto CNFs via ring-opening polymerization. The synthesized poly(lactic acid) grafted cellulose nanofibers (PLA-g-CNFs) compounded with Poly(lactic acid) (PLA) pellets improved storage modulus of the composite in both glassy state (low temperature) and rubbery state (high temperature). Dynamic mechanical analysis, including temperature ramp, frequency sweep, and creep-recovery, confirmed the enhancement of annealed composites to viscoelastic factors. Secondly, we converted CNFs into carbonized CNFs (CCNFs) through pyrolysis. When integrated with carbon black (CB) and polycaprolactone (PCL) matrix, the CCNF-CB-PCL conductive composites found applications for reinforcing, conducting, electromagnetic interference shielding, and deformation sensing. CCNFs also have superior dielectric properties. When irradiating CCNF-PLA composites with microwave, high dielectric loss CCNFs selectively absorbed microwave energy and generated localized heat in the surrounding regions. Such heat transferred to the adjacent PLA, triggering PLA chains to repack and form crystallites, and as a result, enhancing crystallinity as well as mechanical

    Flame Retardant Polymer Nanocomposites and Interfaces

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    The flame retardant efficiency of polymer nanocomposites is highly dependent on the dispersion of the nano-fillers within the polymer matrix. In order to control the filler dispersion, it is very essential to explore the interfacial compatibility between fillers and matrices, which provides a guide for the flame retardant nanocomposites compounding. In this short review, we mainly focus on the thermoplastic polymers and their interactions with the surfaces of the flame retardant fillers. Other physical properties of those nanocomposites such as mechanical properties, gas permeability, rheological performance and thermal conductivity are also briefly reviewed along with the flame retardancy, since they are all dispersion related

    “Study of Electro-thermal Effects on PLA Materials Fed with AC Currents”

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    Given the rise in the emergence of new composite materials, their multifunctional properties, and possible applications in simple and complex structural components, there has been a need to unravel the characterization of these materials. The possibility of printing these conductive composite materials has opened a new area in the design of structural components which can conduct, transmit, and modulate electric signals with no limitation from complex geometry. Although several works have researched the behaviour of polymeric composites due to the immediate growth, however, the electrothermal behaviour of the material when subjected to varying AC applied voltage (Joule’s effect) has not been thoroughly researched. This study presents the characterization of the electrothermal behaviour of conductive composites of a polylactic acid matrix reinforced with conductive carbon black particles (CB-PLA). An understanding of this behaviour would contribute to the improved work in additive manufacturing of functional electro-mechanical conductive materials with potential application in energy systems, bioelectronics, etc. In this study, the electrothermal interplay is monitored under applied AC voltage, varying lengths, and filament printing orientations (longitudinal, oblique, and transverse). Each sample was printed using the fused deposition modeling technique such that each specimen has three different lengths (1L, 2L, 2.75L). To this end, deductions were made on properties that affect composite’s efficiency and life expectancy. The result of this study shows a great influence of printing orientation on material properties of 3D printed conductive composites of CB-PLA. The result also identifies the contribution of AC applied voltage to composites' stabilization time. This knowledge is important to provide experimental background for components' electrothermal interplay, estimate possible degradation and operating limits of composite structures when used in applications

    Clay Minerals as Bioink Ingredients for 3D Printing and 3D Bioprinting: Application in Tissue Engineering and Regenerative Medicine

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    The adaptation and progress of 3D printing technology toward 3D bioprinting (specifically adapted to biomedical purposes) has opened the door to a world of new opportunities and possibilities in tissue engineering and regenerative medicine. In this regard, 3D bioprinting allows for the production of tailor-made constructs and organs as well as the production of custom implants and medical devices. As it is a growing field of study, currently, the attention is heeded on the optimization and improvement of the mechanical and biological properties of the so-called bioinks/biomaterial inks. One of the strategies proposed is the use of inorganic ingredients (clays, hydroxyapatite, graphene, carbon nanotubes and other silicate nanoparticles). Clays have proven to be useful as rheological and mechanical reinforcement in a wide range of fields, from the building industry to pharmacy. Moreover, they are naturally occurring materials with recognized biocompatibility and bioactivity, revealing them as optimal candidates for this cutting-edge technology. This review deals with the use of clays (both natural and synthetic) for tissue engineering and regenerative medicine through 3D printing and bioprinting. Despite the limited number of studies, it is possible to conclude that clays play a fundamental role in the formulation and optimization of bioinks and biomaterial inks since they are able to improve their rheology and mechanical properties, thus improving printability and construct resistance. Additionally, they have also proven to be exceptionally functional ingredients (enhancing cellular proliferation, adhesion, differentiation and alignment), controlling biodegradation and carrying/releasing actives with tissue regeneration therapeutic activities.This research was funded by the BASQUE COUNTRY GOVERNMENT/EUSKO JAURLARITZA (Department of Education, University and Research, Consolidated Groups IT907-16). Authors S.R.-A. and M.S.-R. thank the BASQUE COUNTRY GOVERNMENT for the granted fellowship (PRE_2020_2_0143) and the UNIVERSITY OF THE BASQUE COUNTRY/EUSKAL HERRIKO UNIBERTSITATEA (UPV/EHU) for the granted pre-doctoral fellowship (PIF17/79), respectively

    Fused deposition modeling: process, materials, parameters, properties, and applications

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    In recent years, 3D printing technology has played an essential role in fabricating customized products at a low cost and faster in numerous industrial sectors. Fused deposition modeling (FDM) is one of the most efficient and economical 3D printing techniques. Various materials have been developed and studied, and their properties, such as mechanical, thermal, and electrical, have been reported. Numerous attempts to improve FDM products’ properties for applications in various sectors have also been reported. Still, their applications are limited due to the materials’ availability and properties compared to traditional fabrication methods. In 3D printing, the process parameters are crucial factors for improving the product's properties and reducing the machining time and cost. Researchers have recently investigated many approaches for expanding the range of materials and optimizing the FDM process parameters to extend the FDM process’s possibility into various industrial sectors. This paper reviews and explains various techniques used in 3D printing and the various polymers and polymer composites used in the FDM process. The list of mechanical investigations carried out for different materials, process parameters, properties, and the FDM process's potential application was discussed. This review is expected to indicate the materials and their optimized parameters to achieve enhanced properties and applications. Also, the article is highly anticipated to provide the research gaps to sustenance future research in the area of FDM technologies
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