scholarly journals Synthesis and Characterisation of Acrylic Resin-Al Powder Composites Suitable for Additive Manufacturing

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1642
Author(s):  
J. J. Relinque ◽  
Ismael Romero-Ocaña ◽  
Francisco J. Navas-Martos ◽  
F. J. Delgado ◽  
M. Domínguez ◽  
...  

Stereolithography is an additive manufacturing technology commonly used to build either prototypes or final parts. Nevertheless, the manufacture of structural parts has been ruled out owing to the poor mechanical properties of conventional UV-curable resins. Moreover, the inventory of available commercial resins is still limited and they exhibit low thermal and electrical conductivity values. In this work, some composite materials were designed using Al microparticles dispersed within an SLA commercial resin matrix. These composites overcame the difficulties caused by the light scattering effect during the photopolymerisation process in the SLA technology. Dispersion of the filler was characterised by means of SEM/EDX and AFM. The composites exhibited improved thermal and mechanical behaviour in comparison with the pristine resin. The simplicity of the synthesis method used to prepare the composites provides a convenient starting point to explore new ways of designing composites for SLA with improved mechanical and functional properties.

Author(s):  
Johanna Rokka ◽  
Eva Schlein ◽  
Jonas Eriksson

Abstract Introduction [11C]UCB-J is a tracer developed for PET (positron emission tomography) that has high affinity towards synaptic vesicle glycoprotein 2A (SV2A), a protein believed to participate in the regulation of neurotransmitter release in neurons and endocrine cells. The localisation of SV2A in the synaptic terminals makes it a viable target for in vivo imaging of synaptic density in the brain. Several SV2A targeting compounds have been evaluated as PET tracers, including [11C]UCB-J, with the aim to facilitate studies of synaptic density in neurological diseases. The original two-step synthesis method failed in our hands to produce sufficient amounts of [11C]UCB-J, but served as an excellent starting point for further optimizations towards a high yielding and simplified one-step method. [11C]Methyl iodide was trapped in a clear THF-water solution containing the trifluoroborate substituted precursor, potassium carbonate and palladium complex. The resulting reaction mixture was heated at 70 °C for 4 min to produce [11C]UCB-J. Results After semi-preparative HPLC purification and reformulation in 10% ethanol/phosphate buffered saline, the product was obtained in 39 ± 5% radiochemical yield based on [11C]methyl iodide, corresponding to 1.8 ± 0.5 GBq at EOS. The radiochemical purity was > 99% and the molar activity was 390 ± 180 GBq/μmol at EOS. The product solution contained < 2 ppb palladium. Conclusions A robust and high yielding production method has been developed for [11C]UCB-J, suitable for both preclinical and clinical PET applications.


Author(s):  
Filippo Simoni ◽  
Andrea Huxol ◽  
Franz-Josef Villmer

AbstractIn the last years, Additive Manufacturing, thanks to its capability of continuous improvements in performance and cost-efficiency, was able to partly replace and redefine well-established manufacturing processes. This research is based on the idea to achieve great cost and operational benefits especially in the field of tool making for injection molding by combining traditional and additive manufacturing in one process chain. Special attention is given to the surface quality in terms of surface roughness and its optimization directly in the Selective Laser Melting process. This article presents the possibility for a remelting process of the SLM parts as a way to optimize the surfaces of the produced parts. The influence of laser remelting on the surface roughness of the parts is analyzed while varying machine parameters like laser power and scan settings. Laser remelting with optimized parameter settings considerably improves the surface quality of SLM parts and is a great starting point for further post-processing techniques, which require a low initial value of surface roughness.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Emily Banwell ◽  
Neil Humphrey ◽  
Pamela Qualter

Abstract Background The increasing prevalence of mental health difficulties among children and young people (CYP) suggests that early intervention is vital. A comprehensive system of care and support requires the involvement of mental health professionals, including psychologists and psychiatrists, and allied professionals, including teachers, police, and youth workers. A critical starting point is the provision of effective training, in order that these professionals can better support the mental health needs of the CYP that they encounter. Objectives Given the primacy of training in the CYP mental health support system, understanding the factors that maximise potential gains and facilitate uptake is pertinent. The current review therefore located and explored qualitative research evidence, to identify the barriers and facilitators underpinning successful delivery and implementation of training focussed on the mental health of CYP, for both mental health and allied professionals. Methods A systematic review and qualitative meta-aggregation were conducted. Systematic searches were carried out using ASSIA, EMBASE, MEDLINE, NICE Evidence, PsycINFO, and Scopus databases, for papers published between 2000 and 2020. Twelve thousand four hundred forty-eight records were identified, of which 39 were eligible for review. The records were appraised for quality using the Joanna Briggs Institute Critical Appraisal Checklist for Qualitative Research, and synthesised using the qualitative meta-aggregation method. Results One hundred eighty-two raw findings were extracted from the 39 papers, which were condensed into 47 sub-categories, 19 categories, and finally 5 synthesis statements. These synthesis statements reflected the barriers and facilitators influencing the training delivery process (“support”; “content, design, and planning”), and the implementation of training into the workplace (“context”; “perceived value”; “organisational factors”). Conclusions The synthesis statements and underlying categories provide practical recommendations for those designing, delivering, or implementing CYP mental health training. Recommendations ranged from facilitating peer support during training, to the idea that training will be better implemented when perceived need is high. The review provides a robust evidence-based foundation to “common-sense” principles, drawing them into a coherent and organised framework using a synthesis method grounded in pragmatism. Protocol registration number PROSPERO reference ID: CRD42020162876.


Author(s):  
Dylan Bender ◽  
Ahmad Barari

This paper presents a methodology to find the optimum build orientation in the additive manufacturing of topologically optimized structural parts. The outlined methodology is based on applying a differential operator to the density distribution matrix of a topologically optimized design. The methodology is developed for 2D parts, where the profile of the geometry is constant. The 2D spatial difference operator effectively calculates the elemental density gradient vector, ultimately used to calculate the angles between i) overhanging surfaces of a topology optimized design, and ii) the build platform of a 3D printer. These angles, referred to as build angles, are used to estimate the relative amount of supporting structure required to print the design at a prescribed part orientation. This methodology can potentially be adopted to simulate the additive manufacturing surface quality of density based, structural topology optimization designs.


Author(s):  
Titik Ismiyati ◽  
Ananto Ali Alhasyimi

Background: A residual monomer might have impact on the quality of acrylic resin since its caused allergic reactions and inflammation. Chitosan is a biocompatible material and potential to reduce residual monomers and ameliorate the impact strength of acrylic resin Objective of the study: To examine the effect of an acrylic resin matrix mixed with chitosan together with 1% and 2% acrylic acid as denture base and orthodontic material on residual monomers and impact strength. Methodology: There were 30 samples for the test analysis. The impact strength test sample formed with a plate size of 55 × 10 × 10mm, whereas the residual monomer test sample was prepared into powder. The test samples were divided into 3 groups, of 10 samples. Group 1 acrylic resin only, group 2 acrylic resin matrix mixed with chitosan and 1% acrylic acid, group 3 is the same as group 2 but with a concentration of 2% acrylic acid. Gas chromatography was used for measuring the residual monomers. The impact strength was tested by the Charpy impact. The data was evaluated using the ANOVA and correlation test. Results: There were significant differences (p < 0.05) in acrylic resin without addition with the matrix of acrylic resin with chitosan and acrylic acid 1% and 2% to the number of monomers and impact strength. Conclusion: The mixture of acrylic resin with chitosan and acrylic acid 1% and 2% can reduce the amount of residual monomer and increase the impact strength.


2019 ◽  
Vol 54 (5) ◽  
pp. 647-657 ◽  
Author(s):  
Jose J Restrepo ◽  
Henry A Colorado

In this investigation, particulate composites materials made of epoxy resin matrix with magnetite particles were fabricated via additive manufacturing with the direct ink writing technique. Magnetite is an inexpensive material and the direct ink writing process is not only inexpensive but also easy to adapt to any material. A total of eight formulations were investigated, from which only four were feasible for the printing process: 32.6, 33.6, 35.4 and 41 wt.% of particles. The composites were characterized by scanning electron microscopy, compressive strength, particle size distribution, density, and ductility. Results showed that composites exhibit very competitive mechanical properties even though the process was not vacuum assisted, therefore enabling them to be used in large scale and in other structural applications. Composite can be used in electromagnetic shielding.


2019 ◽  
Vol 39 (13) ◽  
pp. 3797-3803 ◽  
Author(s):  
Mario Borlaf ◽  
Albert Serra-Capdevila ◽  
Carles Colominas ◽  
Thomas Graule

2010 ◽  
Vol 25 (3) ◽  
pp. 529-536 ◽  
Author(s):  
Yijun Wang ◽  
Isabel K. Lloyd

Nanoindentation and the viscous-elastic–plastic (VEP) model developed by Oyen and Cook for lightly filled thermoplastic polymer composites were used to characterize the elastic modulus, hardness, and viscoelastic response of a new high elastic modulus dental resin composite. The VEP model was used because loading rate studies indicated a viscous component in the loading/unloading response of our highly filled, thermosetting acrylic resin composites. Increasing the volume fraction of our high modulus filler increased the elastic modulus and hardness and decreased the viscous response in our composites. Coupling the filler and resin matrix with a commercial coupling agent like Metaltite or MPTMS (3-methacryloxypropyltrimethoxysilane) that ionically bonds to the filler and covalently bonds to the matrix decreases the viscous response and increases the hardness of the composite. The coupling agents did not affect the elastic modulus. The ability of the VEP model to predict load–displacement trajectories and the correlation of the elastic modulus and hardness values determined from the VEP model with those from the direct continuous stiffness measurement mode nanoindentation measurements indicate that the VEP model can be extended to highly filled, thermosetting systems. This is valuable since the potential to predict elastic, plastic, and viscous contributions to behavior should be valuable in the design and understanding of future highly filled resin composite systems.


2013 ◽  
Vol 864-867 ◽  
pp. 698-701
Author(s):  
Jian Yun He ◽  
Yong Liu ◽  
Li Chen He ◽  
Qiang Wang

In this study, waterborne UV-curable polyurethane acrylic resin was synthesized using polypropylene glycol, toluene diisocyanate, dimethylol propionic acid and hydroxyl ethyl acrylate, and modified by hyperbranched polyester acrylate. The influent factors on hydrophilic properties and UV curing speed of the resin were discussed, and the modified resin has compared with that of unmodified resin. Results showed that the overall performance and UV curing speed of the resin modified by hyperbranched polyester was greatly enhanced, the hydrophilic property of the resin was proportional to hydrophilic group content.


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