Percorrer por autor "Ariati, Ronaldo"
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- Composite material of PDMS with interchangeable transmittance: study of optical, mechanical properties and wettabilityPublication . Sales, Flaminio; Souza, Andrews; Ariati, Ronaldo; Noronha, Verônica Teixeira; Giovanetti, Elder Gulick; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is a polymer that has attracted the attention of researchers due to its unique properties such as transparency, biocompatibility, high flexibility, and physical and chemical stability. In addition, PDMS modification and combination with other materials can expand its range of applications. For instance, the ability to perform superhydrophobic coating allows for the manufacture of lenses. However, many of these processes are complex and expensive. One of the most promising modifications, which consists of the development of an interchangeable coating, capable of changing its optical characteristics according to some stimuli, has been underexplored. Thus, we report an experimental study of the mechanical and optical properties and wettability of pure PDMS and of two PDMS composites with the addition of 1% paraffin or beeswax using a gravity casting process. The composites’ tensile strength and hardness were lower when compared with pure PDMS. However, the contact angle was increased, reaching the highest values when using the paraffin additive. Additionally, these composites have shown interesting results for the spectrophotometry tests, i.e., the material changed its optical characteristics when heated, going from opaque at room temperature to transparent, with transmittance around 75%, at 70 °C. As a result, these materials have great potential for use in smart devices, such as sensors, due to its ability to change its transparency at high temperatures.
- Low-cost multifunctional vacuum chamber for manufacturing PDMS based compositesPublication . Ariati, Ronaldo; Sales, Flaminio C.P.; Noronha, Verônica Teixeira; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is one of the best known elastomers and has been used in several areas of activity, due to its excellent characteristics and properties, such as biocompatibility, flexibility, optical transparency and chemical stability. Furthermore, PDMS modified with other materials promotes the desired changes to broaden its range of applications in various fields of science. However, the heating, mixing and degassing steps of the manufacturing process have not received much attention in recent years when it comes to blending with solid materials. For instance, PDMS has been extensively studied in combination with waxes, which are frequently in a solid state at room temperature and as a result the interaction and manufacturing process are extremely complex and can compromise the desired material. Thus, in this work it is proposed a multifunctional vacuum chamber (MVC) with the aim to improve and accelerate the manufacturing process of PDMS composites combined with additives, blends and different kinds of solid materials. The MVC developed in this work allows to control the mixing speed parameters, temperature control and internal pressure. In addition, it is a low cost equipment and can be used for other possible modifications with different materials and processes with the ability to control those parameters. As a result, samples fabricated by using the MVC can achieve a time improvement over 133% at the heating and mixing step and approximately 200% at the last degassing step. Regarding the complete manufacturing process, it is possible to achieve an improvement over 150%, when compared with the conventional manufacturing process. When compared to maximum tensile strength, specimens manufactured using the MVC have shown a 39% and 65% improvement in maximum strain. The samples have also shown a 9% improvement in transparency at room temperature and 12% at a temperature of about 75 C. It should be noted that the proposed MVC can be used for other blends and manufacturing processes where it is desirable to control the temperature, agitation speed and pressure.
- Manufacture and development of a 3D printing handle for laparoscopic applicationPublication . Ariati, Ronaldo; Rocha, Catarina; Ribeiro, J.E.; Rocha, JoãoLaparoscopy is a minimally invasive surgery (MIS) technique that began to be developed approximately a century ago and due to its advantages, such as the rapid recovery of patients, it has become the focus of several studies for the improvement of the equipment and the technique. However, the equipment has a serious ergonomic problem in its configuration, which causes several musculoskeletal problems for surgeons causing, for example, muscle pain, temporary paresthesia, and fatigue, among other long-term pathologies. The study and development of new handle models and the reduction of the forces required for their manipulation are of fundamental importance in the field of laparoscopy. In this sense, this work presents the integration of the product development method of Pahl and Beitz (2007) and the DSR (Design Science Research) method for the development of a laparoscopic instrument, to be applied in tweezers and scissors, that meets the ergonomic requirements presented in the literature.
- Manufacture wing models to analyze air fluid flow in wind tunnel using a 3D printerPublication . Ariati, Ronaldo; Rocha, João; Ribeiro, J.E.Aerodynamics is a field that is very present in our daily lives, but we are unaware of it. One of the best examples of this is our car, which was not designed at random. This study of aerodynamics has been very important in recent years in several areas, namely motor racing and aeronautics, which is so useful for us when we want to travel. This study consists of developing prototypes of aircraft wings for wind tunnel simulation and numerical simulations due to the high demand to be able to better develop cars, aircraft, and all means involving aerodynamics. The prototypes were created using the SolidWorks CAD software, and additive printing was done in a 3D printer using PLA filament.
- Mechanical and optical properties assessment of an innovative PDMS/beeswax composite for a wide range of applicationsPublication . Ariati, Ronaldo; Souza, Andrews; Souza, Maria S.; Zille, Andrea; Soares, Delfim; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is an elastomer that has received primary attention from researchers due to its excellent physical, chemical, and thermal properties, together with biocompatibility and high flexibility properties. Another material that has been receiving attention is beeswax because it is a natural raw material, extremely ductile, and biodegradable, with peculiar hydrophobic properties. These materials are applied in hydrophobic coatings, clear films for foods, and films with controllable transparency. However, there is no study with a wide range of mechanical, optical, and wettability tests, and with various proportions of beeswax reported to date. Thus, we report an experimental study of these properties of pure PDMS with the addition of beeswax and manufactured in a multifunctional vacuum chamber. In this study, we report in a tensile test a 37% increase in deformation of a sample containing 1% beeswax (BW1%) when compared to pure PDMS (BW0%). The Shore A hardness test revealed a 27% increase in the BW8% sample compared to BW0%. In the optical test, the samples were subjected to a temperature of 80 ◦C and the BW1% sample increased 30% in transmittance when compared to room temperature making it as transparent as BW0% in the visible region. The thermogravimetric analysis showed thermal stability of the BW8% composite up to a temperature of 200 ◦C. The dynamic mechanical analysis test revealed a 100% increase in the storage modulus of the BW8% composite. Finally, in the wettability test, the composite BW8% presented a contact angle with water of 145◦. As a result of this wide range of tests, it is possible to increase the hydrophobic properties of PDMS with beeswax and the composite has great potential for application in smart devices, food and medicines packaging films, and films with controllable transparency, water-repellent surfaces, and anti-corrosive coatings.
- Mechanical characterization of PDMS with different mixing ratiosPublication . Sales, Flaminio C.P.; Ariati, Ronaldo; Noronha, Verônica Teixeira; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is a transparent, biocompatible, flexible, simple processing, chemically and thermally stable polymer that has been attracting attention due to its wide range of applications in mechanical, civil and electronic engineering and biomedical field. In order to improve PDMS’ properties, many studies have been investigating the effect of the mixing ratios of its components (base polymer and curing agent) on the mechanical properties, once they affect the number of interactions between the polymer chains of the material. With the aim to make a comparison of the mechanical response of pure PDMS (SYLGARD 184) with different ratios of the base elastomer and the curing agent, tensile and hardness tests were performed. The tested mixing ratios were 10:1, 10:2 and 10:3 (base: curing agent). Tensile tests were executed in a universal tester machine, set up with a velocity of 500 mm/min and pre-load of 1 N. An analogical portable durometer type Shore A was used to carry out the hardness test, according to ASTM D2240. The results for the tensile test showed that an increase in the amount of cure agent reduced the tensile strength. The hardness values obtained were 41.7±0.95, 43.2±1.03 and 37.2±1.14 Shore A for pure PDMS with ratios equal to 10:1, 10:2 and 10:3, respectively.
- Mechanical characterization of specimens manufactured in 3D printingPublication . Ariati, Ronaldo; Rocha, Catarina; Ribeiro, J.E.The use of additive manufacturing (3D printers) in the direct fabrication of commercial items is widespread, owing to the advancements and popularization of computer design programs (CAD) and 3D printers, particularly in the previous 10 years. Shimadzu Autograph AGS - X series universal testing machine was used for both tests. PLA+ can withstand larger stresses than ABS, with 44.2% and 25.73% higher tensile and yield strains, respectively. The modulus of elasticity of PLA+ is shown to be 61.99% greater than that of ABS. The goal of this study is to describe the most often used materials and procedures in 3D printing, as well as to characterize ABS and PLA polymers through tensile testing.
- Polydimethylsiloxane composites characterization and its applications: a reviewPublication . Ariati, Ronaldo; Sales, Flaminio; Souza, Andrews Victor Almeida; Lima, Rui A.; Ribeiro, J.E.Polydimethylsiloxane (PDMS) is one of the most promising elastomers due its remarkable pro-prieties such as good thermal stability, biocompatibility corrosion resistance, flexibility, low cost, ease of use, chemically inertia, hyperplastic characteristics, and gas permeability. Thus, it can be used in areas like microfluidic systems, biomedical devices, electronic components, membranes for filtering and pervaporation, sensors and coatings. Although pure PDMS has low mechanical properties, such as low modulus of elasticity and strength, it can be improved by mixing the PDMS with other polymers and by adding particles or reinforcements. Fiber-reinforced PDMS has proved to be a good alternative to manufacture flexible displays, batteries, wearable devices, tac-tile sensors, and energy harvesting systems. PDMS and particulates are often used in the sepa-ration of liquids from wastewater by means of porosity followed by hydrophobicity. Waxes as beeswax and paraffin have proved to be materials capable of improving properties such as hy-drophobic, corrosion resistance, thermal and optical properties of PDMS. Finally, blended with polymers such as poly (vinyl chloride-co-vinyl acetate), PDMS became a highly efficient alterna-tive for separation membrane applications. However, to the best of our knowledge there are few works dedicated to the review and comparison of different PDMS composites. Hence, this review will be focused in PDMS composites, their respective applications, and properties. Generally, it will be discussed the combination of elastomer with fibers, particles, waxes, polymers, and others; aiming to be a review able to demonstrate the wide applications of this material and how tailored characteristics can be reached for custom applications.
- Properties characterization of PDMS/Beeswax compositePublication . Ariati, Ronaldo; Ribeiro, J.E.; Gomes, Maria Nalu Verona
- PU tensile tests: conventional and digital image correlation analysisPublication . Sales, Flaminio C.P.; Ariati, Ronaldo; Noronha, Verônica Teixeira; Costa, Romeu R.C. da; Ribeiro, J.E.Polyurethane (PU) is a polymer, used as coating, paint, foam, adhesive, and even in biomedical devices. To furthermore expand its applications, it can be combined with additives such as Calcium Carbonate (CaCO3), an inexpensive material, widely available in nature, or with fibers, such as glass fibers explored in several sectors, likewise the aerospace and automobile industries. To determine the mechanical properties of these materials, the tensile test is the most used due to its great ease of application and flexibility. However, conventional processes, such as the use of strain gauges or crosshead displacement data, may not provide detailed information about the strain field, or cannot be able to evaluate the Poisson's ratio and the true stresses for the entire stressstrain curve. Thus, digital image correlation (DIC) methods are a promising alternative, consisting of strain field measurement without contact with the surface of the structure. In this context, this study carried out the tensile characterization of two main polyurethane samples: one petrochemical, distributed by Sika (R), reinforced with type E glass fiber: and the other, natural, manufactured by Kehl (R) from castor oils, and combined with CaCO3 particles. During the tests, DIC was applied to evaluate the Poisson's ratio and, subsequently, Scanning Electron Microscopy (SEM) analyses were performed, revealing a higher number of bubbles on Sika's polymer, which contributes to the reduction of the maximum supported stresses, since these pores, with dimensions of up to 25 hm, were regions where the cracks started and headed the breakage. Poisson's ratios were all around 0.4 and the highest tensile strength values were obtained from E-glass reinforced samples (TS015), around 117.24 +/- 13.20MPa. CaCO3 particles also acted as reinforced, increasing maximum stress reached from 20MPa to values between 29 and 37MPa.