scholarly journals Study of mechanical behavior of additive manufacturing bioresorbable polymeric stents models

2020 ◽  
pp. 38-51
Author(s):  
Adriana DM Del Monaco ◽  
MI Del Monaco ◽  
Aron JP Andrade ◽  
Sonia Maria Malmonge
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Additive Manufacturing ◽  
Aortic Coarctation ◽  
Polymeric Materials ◽  
Memory Allocation ◽  
Interesting Point ◽  
Allocation Process ◽  
Artery Disease ◽  
Mechanical Performances

Stents are devices with important applications in cardiology. They can be used in different cases, as coronary artery disease, peripheral interventions, such as the iliac and carotid arteries, and in very specific applications, as congenital heart disease in aortic coarctation. Studies point to biodegradability of stents as one of the main properties of future generations of these devices. The development of stents made from fully bioresorbable polymeric materials, with appropriate mechanical properties for different applications, is considered an interesting point to be studied. Thus, the objective of this project was to study models of bioabsorbable stents of poly (-L-lactic acid) (PLLA), poly (-LD lactic acid) (PLDLA) produced by additive manufacturing. The mechanical performances were evaluated by stress and tensile strain tests of different blends compositions of these materials. A heatshock shape memory allocation process and a flexible tube model for simulating implant conditions were developed. PLLA has higher mechanical strength and hardness, while PLDLA is more elastic. Thus, it was possible to study the adequacy of the composition and mechanical properties of the prototypes for each different situation studied (coronary, peripheral and Aortic coarctation implants).

Location Depending Textures of the Human Dental Enamel

2010 ◽  
Vol 160 ◽  
pp. 281-286 ◽  
Author(s):  
Lars Raue ◽  
Helmut Klein
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Dental Enamel ◽  
Polymeric Materials ◽  
Incisor Tooth ◽  
Worst Case ◽  
Dental Fillings ◽  
Anisotropic Mechanical Properties ◽  
Different Types ◽  
Materials Used

Dental enamel is the most highly mineralised and hardest biological tissue in human body [1]. Dental enamel is made of hydroxylapatite (HAP) - Ca5(PO4)3(OH), which is hexagonal (6/m). The lattice parameters are a = b = 0.9418 nm und c = 0.6875 nm [1]. Although HAP is a very hard mineral, it can be dissolved easily in a process which is known as enamel demineralization by lactic acid produced by bacteria. Also the direct consumption of acid (e.g. citric, lactic or phosphoric acid in soft drinks) can harm the dental enamel in a similar way. These processes can damage the dental enamel. It will be dissolved completely and a cavity occurs. The cavity must then be cleaned and filled. It exists a lot of dental fillings, like gold, amalgam, ceramics or polymeric materials. After filling other dangers can occur: The mechanical properties of the materials used to fill cavities can differ strongly from the ones of the dental enamel itself. In the worst case, the filling of a tooth can damage the enamel of the opposite tooth by chewing if the interaction of enamel and filling is not equivalent, so that the harder fillings can abrade the softer enamel of the healthy tooth at the opposite side. This could be avoided if the anisotropic mechanical properties of dental enamel would be known in detail, hence then another filling could be searched or fabricated as an equivalent opponent for the dental enamel with equal properties. To find such a material, one has to characterise the properties of dental enamel first in detail for the different types of teeth (incisor, canine, premolar and molar). This is here exemplary done for a human incisor tooth by texture analysis with the program MAUD from 2D synchrotron transmission images [2,3,4].

scholarly journals Processing of Sr2+ Containing Poly L-Lactic Acid-Based Hybrid Composites for Additive Manufacturing of Bone Scaffolds

2020 ◽  
Vol 7 ◽  
Author(s):  
Priscila Melo ◽  
Raasti Naseem ◽  
Ilaria Corvaglia ◽  
Giorgia Montalbano ◽  
Carlotta Pontremoli ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Additive Manufacturing ◽  
Hybrid Composites ◽  
Homogeneous Distribution ◽  
Fused Filament Fabrication ◽  
Rheological Characterization ◽  
Biodegradable Composite ◽  
Manufacturing Technologies

Biodegradable composite materials represent one of the major areas of investigation for bone tissue engineering due to their tuneable compositional and mechanical properties, which can potentially mimic those of bone and potentially avoid the removal of implants, mitigating the risks for the patient and reducing the overall clinical costs. In addition, the introduction of additive manufacturing technologies enables a strict control over the final morphological features of the scaffolds. In this scenario, the optimisation of 3D printable resorbable composites, made of biocompatible polymers and osteoinductive inorganic phases, offers the potential to produce a chemically and structurally biomimetic implant, which will resorb over time. The present work focuses on the development and process optimisation of two hybrid composite filaments, to be used as feedstock for the fused filament fabrication 3D printing process. A Poly L-lactic acid matrix was blended with either rod-like nano-hydroxyapatite (nano-HA) or nanoparticles of mesoporous bioactive glasses, both partially substituted with strontium (Sr2+), due to the well-known pro-osteogenic effect of this ion. Both inorganic phases were incorporated into Poly L-lactic acid using an innovative combination of processes, obtaining a homogeneous distribution throughout the polymer whilst preserving their ability to release Sr2+. The filament mechanical properties were not hindered after the incorporation of the inorganic phases, resulting in tensile strengths and moduli within the range of cancellous bone, 50 ± 10 MPa and 3 ± 1 GPa. Finally, the rheological characterization of the hybrid composites indicated a shear thinning behaviour, ideal for the processing with fused filament fabrication, proving the potential of these materials to be processed into 3D structures aiming bone regeneration.

Influence of Nucleating Agent on PLLA Crystalline and Mechanical Properties

2012 ◽  
Vol 624 ◽  
pp. 269-273 ◽  
Author(s):  
Gang Yang ◽  
Qun Gao ◽  
Chun Fa Ouyang ◽  
Kang Sheng Zheng ◽  
Yun Guo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Lactic Acid ◽  
Tensile Test ◽  
Nucleating Agent ◽  
Nucleating Agents ◽  
Maximum Value ◽  
Crystalline Property ◽  
Mechanical Performances ◽  
Sem Investigation

This paper mainly concerned the effect of nucleating agents CAV101 on PLLA crystalline property. CAV101 was mixed with poly (L-lactic acid) (PLLA) to make PLLA/CAV101 blends, with CAV101 contents of 0, 0.1%, 0.3%, 0.5%, 0.7%, respectively. Mechanical performances, morphology and crystalline properties were investigated by tensile test, WAXD, SEM. The results demonstrated that the tensile strength and elongation of PLLA increased with the increase of CAV101 content and the maximum value at CAV101 of 0.3% and 0.5%, respectively. The crystallinity of PLLA blends CAV101 of 0.1%, 0.3%, 0.5%, 0.7% were 86.58%, 82.43%, 49.01%, 64.00% respectively.The SEM investigation found that the agglomeration of PLLA with the increasing of nucleating agents CAV101 content.

scholarly journals Direct Digital Manufacturing of Nanocomposites

2019 ◽  
Vol 890 ◽  
pp. 92-97
Author(s):  
Saeed D. Mohan ◽  
Meruyert Nazhipkyzy ◽  
Pedro Carreira ◽  
Cyril Santos ◽  
Fred J. Davis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Additive Manufacturing ◽  
Digital Manufacturing ◽  
Polymer Devices ◽  
Automated Process ◽  
Mechanical Performances ◽  
Direct Digital Manufacturing

Additive manufacturing has surged in popularity as a route to designing and preparing functional parts. Depending on the parts function, certain attributes such as high mechanical performances may be desired. We develop a route for improving the mechanical properties of polymer devices, fabricated through additive manufacturing by combining electrospinning and stereo-lithography into one automated process. This process utilises the impressive mechanical properties of carbon nanotubes by encapsulating and aligning them in electrospun fibres. Composite fibres will be incorporated into polymer resins prepared with stereo-lithography, thereby providing resins that benefit from the composite fibres properties, enhancing their overall mechanical properties.

scholarly journals Incorporating isosorbide as the chain extender improves mechanical properties of linear biodegradable polyurethanes as potential bone regeneration materials

RSC Advances ◽  
2017 ◽  
Vol 7 (23) ◽  
pp. 13886-13895 ◽  
Author(s):  
Yufei Ma ◽  
Juan Liu ◽  
Min Luo ◽  
Juan Xing ◽  
Jinchuan Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Lactic Acid ◽  
Bone Regeneration ◽  
High Molecular Weight ◽  
Chain Extender ◽  
Soft Segments ◽  
Scaffold Materials ◽  
Mechanical Performances

Novel linear biodegradable polyurethanes based on poly (d,l-lactic acid) as soft segments and isosorbide as chain extender were exhibited with high molecular weight and appropriate mechanical performances, promising as the scaffold materials for bone regeneration.

scholarly journals Structural, mechanical and morphological analysis of self assembled bionanocomposites

2020 ◽  
Author(s):  
◽  
Ajay Vasudeo Rane ◽  
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Carbon Nanomaterials ◽  
Degradation Products ◽  
High Stress ◽  
Polymeric Materials ◽  
Strength Properties ◽  
Electrical Performance ◽  
Poly Lactic Acid ◽  
Deformation Properties

The wide usage of polymeric materials in engineering is largely due to their valuable mechanical properties. Fracture is a rupture of the bonds between elements of a body (atoms, molecules or ions) resulting in breakage or cleavage of the specimen into parts. The resistance of a material to fracture is called strength or mechanical strength. Since the mechanical properties of polymers largely depend on their structure, it is necessary to create a structure ensuring an optimal set of mechanical properties which do not vary with time. The structure of the polymer is established during processing. Processing not only imparts certain shape to the material but also plays an important role in the creation and determination of its structure, i.e. microstructures. Structures are often conceived in the melts or solutions from which the polymers are fabricated. An interesting method of structure control is by introducing artificial nuclei into the polymer melt, which then becomes crystallization centers. Growing attention in PLA is because of some distinctiveness that is deficient in other polymers, specifically concerning renewability, biocompatibility, processability, and energy saving. PLA is derivative from renewable and biodegradable resources, and its degradation products are non-pollutant and non-toxic. Therefore, PLA may be a substitute for petrochemical plastics. Furthermore, PLA has several bio applications, such as biodegradable matrix for surgical implants, and in drug delivery systems. On the other hand, for structural use, it is required that some of its properties be improved, namely in terms of thermo-mechanical and electrical performance. To rise above these limitations, approaches, like blending with other polymers, functionalization, and adding of fillers, are practiced. Adding up of nanofillers is an appealing approach, as with small quantity of filler, it is achievable to improve desired features, keeping key properties of PLA unharmed. The most reported nanofillers are clays, silica’s, and carbon nanomaterials as incorporating nanofillers is a common approach to attain this goal. Exceptional properties of carbon-based nanomaterials have increased research works dealing with PLA composites. To discuss in brief, poly (lactic acid) originally is a brittle material with low impact strength and its elongation at break is similar to other brittle polymer such as polystyrene. On the contrary, its tensile strength and modulus are comparable to poly (ethylene terephthalate). The inability of poly (lactic acid) to plastically deform at high-stress levels limits its application; hence several modifying techniques have been used to enhance its deformation properties, as discussed above. From the available literature, has been confirmed that crystallinity is an important characteristic affecting the strength properties of poly (lactic acid) and its composites.

Effects of vacuum exposure on mechanical properties of thermoplastic materials

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Tiago Rodrigues Dos Santos ◽  
Isla Kalleny Marques Brandão ◽  
Mateus Silva Sant'Ana ◽  
Pedro Henrique dos Santos Alves ◽  
Rana Mayeli Piêgas Taborda ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Polymeric Materials ◽  
Acrylonitrile Butadiene Styrene ◽  
Pressure Oscillation ◽  
Bending Test ◽  
Poly Lactic Acid ◽  
Fused Deposition Modelling ◽  
Space Applications ◽  
Fused Deposition

The present paper proposes the study of the behavior of three thermoplastic materials: acrylonitrile butadiene styrene (ABS), poly(lactic acid) (PLA), and polyethylene glycol terephthalate (PETG), processed by additive manufacturing type fused deposition modelling (FDM) when exposed to low vacuum. The experiment was composed of three moments consisting of tridimensional modeling and manufacturing of the specimens, drying process and vacuum exposure for 24 hours, according to American Society for Testing and Materials (ASTM) D6653/D6653M standards, and bending test for the determination of mechanical properties, based on ASTM D790 standards. The vacuum chamber tests exposed oscillations in the pressure indicating gases releasing from the specimen, but none of the samples showed visible deformations. Subjecting the materials exposed to low vacuum to bending tests and comparing them to the unexposed material, we observed a significant increase in the calculated modulus of elasticity and a change in the slope of graphic force versus deflection in all materials. This behavior demonstrates that it is possible to submit polymeric materials to vacuum, and low vacuum exposure can be a treatment for thermoplastic materials. In the future, a study using a spectrometer will be necessary to verify which gases are present during pressure oscillation in the chamber, thus making it possible to understand which factor has increased the mechanical properties of the materials. In sequence, experiments will be necessary to validate the vacuum exposure as a form of treatment of materials and to verify the possibility of applying thermoplastics commonly used in additive manufacturing for low-impact space applications.

scholarly journals Methods for the Characterization of Polyetherimide Based Materials Processed by Fused Deposition Modelling

2020 ◽  
Vol 10 (9) ◽  
pp. 3195 ◽  
Author(s):  
Claudio Tosto ◽  
Lorena Saitta ◽  
Eugenio Pergolizzi ◽  
Ignazio Blanco ◽  
Giovanni Celano ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Mechanical Tests ◽  
Fused Deposition Modelling ◽  
Specific Test ◽  
Test Standards ◽  
Fused Deposition ◽  
Structural Applications ◽  
Mechanical Performances ◽  
Manufacturing Technologies

Fused deposition modelling (FDM™) is one of the most promising additive manufacturing technologies and its application in industrial practice is increasingly spreading. Among its successful applications, FDM™ is used in structural applications thanks to the mechanical performances guaranteed by the printed parts. Currently, a shared international standard specifically developed for the testing of FDM™ printed parts is not available. To overcome this limit, we have considered three different tests aimed at characterizing the mechanical properties of technological materials: tensile test (ASTM D638), flexural test (ISO 178) and short-beam shear test (ASTM D2344M). Two aerospace qualified ULTEMTM 9085 resins (i.e., tan and black grades) have been used for printing all specimens by means of an industrial printer (Fortus 400mc). The aim of this research was to improve the understanding of the efficiency of different mechanical tests to characterize materials used for FDM™. For each type of test, the influence on the mechanical properties of the specimen’s materials and geometry was studied using experimental designs. For each test, 22 screening factorial designs were considered and analyzed. The obtained results demonstrated that the use of statistical analysis is recommended to ascertain the real pivotal effects and that specific test standards for FDM™ components are needed to support the development of materials in the additive manufacturing field.

Possibilities of using biodegradable polymeric materials in the agricultural sector

2020 ◽  
Vol 67 (2) ◽  
pp. 115-120
Author(s):  
Raisa A. Alekhina ◽  
Victoriya E. Slavkina ◽  
Yuliya A. Lopatina
Keyword(s):  
Mechanical Properties ◽  
Biodegradable Polymers ◽  
Biodegradable Polymer ◽  
Agricultural Sector ◽  
Polymeric Materials ◽  
Polymer Materials ◽  
Limiting Factors ◽  
Research Purpose ◽  
Biodegradable Materials ◽  
Advantages And Disadvantages

The article presents options for recycling polymers. The use of biodegradable materials is promising. This is a special class of polymers that can decompose under aerobic or anaerobic conditions under the action of microorganisms or enzymes forming natural products such as carbon dioxide, nitrogen, water, biomass, and inorganic salts. (Research purpose) The research purpose is in reviewing biodegradable materials that can be used for the manufacture of products used in agriculture. (Materials and methods) The study are based on open information sources containing information about biodegradable materials. Research methods are collecting, studying and comparative analysis of information. (Results and discussion) The article presents the advantages and disadvantages of biodegradable materials, mechanical properties of the main groups of biodegradable polymers. The article provides a summary list of agricultural products that can be made from biodegradable polymer materials. It was found that products from the general group are widely used in agriculture. Authors have found that products from a special group can only be made from biodegradable polymers with a controlled decomposition period in the soil, their use contributes to increasing the productivity of crops. (Conclusions) It was found that biodegradable polymer materials, along with environmental safety, have mechanical properties that allow them producing products that do not carry significant loads during operation. We have shown that the creation of responsible products (machine parts) from biodegradable polymers requires an increase in their strength properties, which is achievable by creating composites based on them. It was found that the technological complexity of their manufacture and high cost are the limiting factors for the widespread use of biodegradable polymers at this stage.

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