Rheological and Mechanical Gradient Properties of Polyurethane Elastomers for 3D-Printing with Reactive Additives

Abstract Polyurethane (PU) elastomers with their broad range of strength and elasticity are ideal materials for additive manufacturing of shapes with gradients of mechanical properties. By adjusting the mixing ratio of different polyurethane reactants during 3D-printing it is possible to change the mechanical properties. However, to guarantee intra- and inter-layer adhesion, it is essential to know the reaction kinetics of the polyurethane reaction, and to be able to influence the reaction speed in a wide range. In this study, the effect of adding three different catalysts and two inhibitors to the reaction of polyurethane elastomers were studied by comparing the time of crossover points between storage and loss modulus G′ and G′′ from time sweep tests of small amplitude oscillatory shear at 30°C. The time of crossover points is reduced with the increasing amount of catalysts, but only the reaction time with one inhibitor is significantly delayed. The reaction time of 90% NCO group conversion calculated from the FTIR-spectrum also demonstrates the kinetics of samples with different catalysts. In addition, the relation between the conversion as determined from FTIR spectroscopy and the mechanical properties of the materials was established. Based on these results, it is possible to select optimized catalysts and inhibitors for polyurethane 3D-printing of materials with gradients of mechanical properties.

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An Overview on the Rheology, Mechanical Properties, Durability, 3D Printing, and Microstructural Performance of Nanomaterials in Cementitious Composites

Materials ◽

10.3390/ma14112950 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2950

Author(s):

Hongwei Song ◽

Xinle Li

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Three Dimensional ◽

Cementitious Materials ◽

Research Area ◽

Cementitious Composites ◽

Split Tensile Strength ◽

Contour Crafting ◽

Wide Range ◽

Active Research

The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research.

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The Vulcanization of Elastomers. X. The Vulcanization of Natural Rubber with Thiuram Disulfides (V)

Rubber Chemistry and Technology ◽

10.5254/1.3542736 ◽

1957 ◽

Vol 30 (3) ◽

pp. 903-910

Author(s):

Otto Lorenz ◽

Walter Scheele ◽

Wolfgang Redetzky

Keyword(s):

Reaction Time ◽

Natural Rubber ◽

First Order ◽

Wide Range ◽

Identical Rate ◽

Tetraethylthiuram Disulfide ◽

Kinetics Of

Abstract The kinetics of crosslinking natural rubber during vulcanization with tetramethyl and tetraethylthiuram disulfide was investigated. The following results were derived: 1. The increase of crosslinking during vulcanization which was measured by the change of reciprocal swelling is first order over a wide range of reaction time and temperature. 2. During vulcanization, crosslinking and dithiocarbamate formation are reactions which proceed with identical rate. From this we had to conclude that the formation of dithiocarbamate is the immediate cause of the crosslink formation. 3. The concentration of the thiuram disulfide decreases much faster with respect to vulcanization time than crosslinking increases. In other words, the thiuram decrease can only be considered a reaction which precedes crosslinking.

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3D Printing of Thermoplastic Elastomers: Role of the Chemical Composition and Printing Parameters in the Production of Parts with Controlled Energy Absorption and Damping Capacity

Polymers ◽

10.3390/polym13203551 ◽

2021 ◽

Vol 13 (20) ◽

pp. 3551

Author(s):

Marina León-Calero ◽

Sara Catherine Reyburn Valés ◽

Ángel Marcos-Fernández ◽

Juan Rodríguez-Hernandez

Keyword(s):

Mechanical Properties ◽

Chemical Composition ◽

3D Printing ◽

Energy Absorption ◽

Thermoplastic Elastomers ◽

Damping Capacity ◽

Compression Tests ◽

Wide Range ◽

Printing Parameters

Additive manufacturing (AM) is a disruptive technology that enables one to manufacture complex structures reducing both time and manufacturing cost. Among the materials commonly used for AM, thermoplastic elastomers (TPE) are of high interest due to their energy absorption capacity, energy efficiency, cushion factor or damping capacity. Previous investigations have exclusively focused on the optimization of the printing parameters of commercial TPE filaments and the structures to analyse the mechanical properties of the 3D printed parts. In the present paper, the chemical, thermal and mechanical properties for a wide range of commercial thermoplastic polyurethanes (TPU) filaments were investigated. For this purpose, TGA, DSC, 1H-NMR and filament tensile strength experiments were carried out in order to determine the materials characteristics. In addition, compression tests have been carried out to tailor the mechanical properties depending on the 3D printing parameters such as: infill density (10, 20, 50, 80 and 100%) and infill pattern (gyroid, honeycomb and grid). The compression tests were also employed to calculate the specific energy absorption (SEA) and specific damping capacity (SDC) of the materials in order to establish the role of the chemical composition and the geometrical characteristics (infill density and type of infill pattern) on the final properties of the printed part. As a result, optimal SEA and SDC performances were obtained for a honeycomb pattern at a 50% of infill density.

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Study of Mechanical Properties of 3D Printed Material for Non-Pneumatic Tire Spoke

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.880.97 ◽

2021 ◽

Vol 880 ◽

pp. 97-102

Author(s):

Ravivat Rugsaj ◽

Chakrit Suvanjumrat

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Elastic Material ◽

Molding Process ◽

Breaking Strain ◽

Pneumatic Tire ◽

Wide Range ◽

Printing Technique ◽

3D Printed ◽

3D Printing Technique

The spokes of airless tire or non-pneumatic tire (NPT) are normally made with thermoplastic polyurethane (TPU), which is highly elastic material, to replace inflation pressure in conventional pneumatic tire. However there are limitation in designing of complex spoke geometries due to difficulty in manufacturing process, which normally involve molding process. Recently, the 3D printing technique has been improved and can be used to create highly complex geometries with wide range of materials. However the mechanical properties of printed spoke structure using 3D printing technique are still required to design and development of NPT. This research aim to study the mechanical properties of TPU while varying in printing conditions. The specimens were prepared from actual NPT spoke using waterjet cutting technique and 3D printing technique according to the testing standard ASTM D412 and D638, respectively. The tensile tests were performed on the specimens with corresponding crosshead speed. The testing speed of 3D printed specimen were also varied to 100 and 200 mm/min to study the effects of strain rate on mechanical properties. The stress-strain relationships were obtained from tensile testing and the important mechanical properties were then evaluated. The mechanical properties of specimens prepared from actual NPT spokes and 3D printed specimens were then compared. The ultimate stress of specimens prepared from actual NPT spokes in radial direction and 3D printed specimens with 100% infill were found to be 32.92 and 25.47 MPa, respectively, while the breaking strain were found to be 12.98 and 10.87, respectively. Thus, the information obtained from this research can be used to ensure the possibility in creating NPT spoke using 3D printing technique based on elastic material such as TPU.

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Microrheology of DNA hydrogels

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1722206115 ◽

2018 ◽

Vol 115 (32) ◽

pp. 8137-8142 ◽

Cited By ~ 21

Author(s):

Zhongyang Xing ◽

Alessio Caciagli ◽

Tianyang Cao ◽

Iliya Stoev ◽

Mykolas Zupkauskas ◽

...

Keyword(s):

Mechanical Properties ◽

Melting Temperature ◽

Loss Modulus ◽

Viscoelastic Behavior ◽

Building Blocks ◽

Diffusing Wave Spectroscopy ◽

Wide Range ◽

Transient Network ◽

Gel Transition ◽

Dna Hydrogels

A key objective in DNA-based material science is understanding and precisely controlling the mechanical properties of DNA hydrogels. We perform microrheology measurements using diffusing wave spectroscopy (DWS) to investigate the viscoelastic behavior of a hydrogel made of Y-shaped DNA (Y-DNA) nanostars over a wide range of frequencies and temperatures. We observe a clear liquid-to-gel transition across the melting temperature region for which the Y-DNA bind to each other. Our measurements reveal a cross-over between the elastic G′(ω) and loss modulus G″(ω) around the melting temperature Tm of the DNA building blocks, which coincides with the systems percolation transition. This transition can be easily shifted in temperature by changing the DNA bond length between the Y shapes. Using bulk rheology as well, we further show that, by reducing the flexibility between the Y-DNA bonds, we can go from a semiflexible transient network to a more energy-driven hydrogel with higher elasticity while keeping the microstructure the same. This level of control in mechanical properties will facilitate the design of more sensitive molecular sensing tools and controlled release systems.

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Printability assessment of psyllium husk (isabgol)/gelatin blends using rheological and mechanical properties

Journal of Biomaterials Applications ◽

10.1177/0885328220979473 ◽

2020 ◽

pp. 088532822097947

Author(s):

Piyush Sunil Agarwal ◽

Suruchi Poddar ◽

Neelima Varshney ◽

Ajay Kumar Sahi ◽

Kiran Yellappa Vajanthri ◽

...

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Storage Modulus ◽

Loss Tangent ◽

Loss Modulus ◽

Three Dimensional ◽

Elastic Behavior ◽

Flow Index ◽

Plastic Behavior ◽

Psyllium Husk

The primary goal of this study is to highlight the rheological and mechanical properties of a new blend composed of naturally-derived hydrogel materials- psyllium husk (PH) and gelatin (G) for its potential use in three-dimensional (3D) printing technology. The mixtures were prepared at various weight ratios of 100PH, 75PH + 25G and 50PH + 50G. A suitable selection of the printable ink was made based on the preliminary screening steps of manual filament drop test and layer stacking by 3D printing. Printing of the common features such as hexagon and square grids helped evaluating shape fidelity of the chosen ink. Although 50PH + 50G blend was found meeting most of the criteria for an ideal 3D printable ink, rheological and mechanical characterizations have been performed for all the ratios of polymeric blends. This study documents the correlation between various factors of rheology that should be taken into account while categorizing any biomaterial as a printable ink. Yield stress was measured as 18.59 ± 4.21 Pa, 268.74 ± 13.56 Pa and 109.16 ± 9.85 Pa for 50PH + 50G, 75PH + 25G and 100PH, respectively. Similarly, consistency index (K) and flow index (n) were calculated using the power law equation and found as 49.303 ± 4.17, 530.59 ± 10.92, 291.82 ± 10.53 and 0.275 ± 0.04, 0.05 ± 0.005, 0.284 ± 0.04 for 50PH + 50G, 75PH + 25G and 100PH, respectively. The loss modulus (G″) was observed dominating over storage modulus (G′) for 50PH + 50G, that depicts its liquid-like property; whereas storage modulus (G′) was found dominating in case of 75PH + 25G and 100PH, indicating their solid-like characteristics. In addition, the loss tangent value (tan δ) of 50PH + 50G was observed exceeding unity (1.05), supporting its plastic behavior, unlike 75PH + 25G (0.5) and 100PH (0.33) whose loss tangent values were estimated less than unity revealing their elastic behavior. Also, 50PH + 50G was found to have the highest mechanical strength amongst the three blends with a Young’s modulus of 9.170 ± 0.0881 kPa.

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Thermomechanical Properties of KevlarTM Reinforced Benzoxazine-Urethane Alloys

ASEAN Journal of Chemical Engineering ◽

10.22146/ajche.49720 ◽

2013 ◽

Vol 13 (1) ◽

pp. 11

Author(s):

Rimdusit S Rimdusit S ◽

Kasemsiri P. Kasemsiri P. ◽

Okhawilai M. Okhawilai M.

Keyword(s):

Mechanical Properties ◽

High Performance ◽

Loss Modulus ◽

Flexural Modulus ◽

Testing Machine ◽

Impact Resistance ◽

Mechanical Analysis ◽

Thermomechanical Properties ◽

Alloy Matrix ◽

Wide Range

Ballistic armor is one of an important application which required high performance of fiber-reinforced polymer due to its outstanding specific mechanical properties. Therefore, KevlarTM reinforced benzoxazine-urethane alloys as ballistic impact resistance composites were developed in this research. The polybenzoxazine alloy composites were fabricated by compression molding at 200ºC and 5 MPa by a compression molder. The amount of urethane fraction in the alloy matrix was ranging from 0-40wt% while the fiber content was kept constant at 80wt%. The mechanical properties of the matrix alloys and their KevlarTM fiber composites were characterized by dynamic mechanical analysis and universal testing machine. The results revealed that storage modulus at room temperature of the composites was reduced from 16.82 GPa when using the neat polybenzoxazine as a matrix to the value of 11.89 GPa at 40wt% of urethane content in the alloy matrix. Moreover, the more urethane in the alloy matrix resulted in lower flexural modulus of the KevlarTM composites i.e. 22 GPa when using the neat polybenzoxazine as a matrix to the value of 12 GPa when using 40wt% of urethane in the alloy matrix. Interestingly, glass transition temperature (Tg) obtained from the maximum peak of the loss modulus was observed to be in the range of 187-247ºC, which was significantly higher than those of the two parent polymers. Furthermore, the activation energy of the alloys was found to increase with increasing urethane content, which corresponded to the observed Tg value enhancement. The observed synergism in Tg of KevlarTM reinforced benzoxazine-urethane was an outstanding characteristic for a wide range of applications, which requires high thermal stability.

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A study of tensile and bending properties of 3D-printed biocompatible materials used in dental appliances

Journal of Materials Science ◽

10.1007/s10853-021-06811-3 ◽

2022 ◽

Author(s):

Marcos García Reyes ◽

Alex Bataller Torras ◽

Juan A. Cabrera Carrillo ◽

Juan M. Velasco García ◽

Juan J. Castillo Aguilar

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Biocompatible Materials ◽

Rupture Stress ◽

Bending Tests ◽

Wide Range ◽

3D Printers ◽

Materials Used ◽

Manufacturing Technologies ◽

Printing Direction

AbstractIn the last years, a large number of new biocompatible materials for 3D printers have emerged. Due to their recent appearance and rapid growth, there is little information about their mechanical properties. The design and manufacturing of oral appliances made with 3D printing technologies require knowledge of the mechanical properties of the biocompatible material used to achieve optimal performance for each application. This paper focuses on analysing the mechanical behaviour of a wide range of biocompatible materials using different additive manufacturing technologies. To this end, tensile and bending tests on different types of recent biocompatible materials used with 3D printers were conducted to evaluate the influence of the material, 3D printing technology, and printing orientation on the fragile/ductile behaviour of the manufactured devices. A test bench was used to perform tensile tests according to ASTM D638 and bending tests according to ISO 178. The specimens were manufactured with nine different materials and five manufacturing technologies. Furthermore, specimens were created with different printing technologies, biocompatible materials, and printing orientations. The maximum allowable stress, rupture stress, flexural modulus, and deformation in each of the tested specimens were recorded. Results suggest that specimens manufactured with Stereolithography (SLA) and milling (polymethyl methacrylate PMMA) achieved high maximum allowable and rupture stress values. It was also observed that Polyjet printing and Selective Laser Sintering technologies led to load–displacement curves with low maximum stress and high deformation values. Specimens manufactured with Digital Light Processing technology showed intermediate and homogeneous performance. Finally, it was observed that the printing direction significantly influences the mechanical properties of the manufactured specimens in some cases.

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Recent Advancements in Biomimetic 3D Printing Materials With Enhanced Mechanical Properties

Frontiers in Materials ◽

10.3389/fmats.2021.518886 ◽

2021 ◽

Vol 8 ◽

Author(s):

Xinxin Yan ◽

Brandon Bethers ◽

Hengxi Chen ◽

Siqi Xiao ◽

Shuang Lin ◽

...

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Smart Materials ◽

Waste Minimization ◽

Engineering Systems ◽

Balsa Wood ◽

Wide Range ◽

Future Challenges ◽

Printing Processes ◽

Design Freedom

Nature has developed a wide range of functional microstructures with optimized mechanical properties over millions of years of evolution. By learning from nature’s excellent models and principles, biomimicry provides a practicable strategy for designing and fabricating the next smart materials with enhanced properties. Nevertheless, the complicated micro-structural constructions in nature models are beyond the ability of conventional processes, hindering the developments of biomimetic research and its forthputting in engineering systems. Additive manufacturing (AM) or 3D printing processes have revolutionized manufacturing via their ability to manufacture complex micro/mesostructures, increase design freedom, provide mass customization, and waste minimization, as well as rapid prototyping. Here, a review of recent advances in biomimetic 3D printing materials with enhanced mechanical properties is provided. The design and fabrication were inspired by various natural structures, such as balsa wood, honeycomb, nacre, lobster claw, etc., which are presented and discussed. Finally, future challenges and perspectives are given.

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A Review on the Adaption of Alginate-Gelatin Hydrogels for 3D Cultures and Bioprinting

Materials ◽

10.3390/ma14040858 ◽

2021 ◽

Vol 14 (4) ◽

pp. 858

Author(s):

Magdalena B. Łabowska ◽

Karolina Cierluk ◽

Agnieszka M. Jankowska ◽

Julita Kulbacka ◽

Jerzy Detyna ◽

...

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Cell Cultures ◽

Polymeric Materials ◽

Optimal Growth ◽

Vital Functions ◽

Wide Range ◽

In Vitro Cell Cultures ◽

Living Tissues

Sustaining the vital functions of cells outside the organism requires strictly defined parameters. In order to ensure their optimal growth and development, it is necessary to provide a range of nutrients and regulators. Hydrogels are excellent materials for 3D in vitro cell cultures. Their ability to retain large amounts of liquid, as well as their biocompatibility, soft structures, and mechanical properties similar to these of living tissues, provide appropriate microenvironments that mimic extracellular matrix functions. The wide range of natural and synthetic polymeric materials, as well as the simplicity of their physico-chemical modification, allow the mechanical properties to be adjusted for different requirements. Sodium alginate-based hydrogel is a frequently used material for cell culture. The lack of cell-interactive properties makes this polysaccharide the most often applied in combination with other materials, including gelatin. The combination of both materials increases their biological activity and improves their material properties, making this combination a frequently used material in 3D printing technology. The use of hydrogels as inks in 3D printing allows the accurate manufacturing of scaffolds with complex shapes and geometries. The aim of this paper is to provide an overview of the materials used for 3D cell cultures, which are mainly alginate–gelatin hydrogels, including their properties and potential applications.

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