Evaluation of UV post-curing depth for homogenous cross-linking of stereolithography parts

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tristan Schlotthauer ◽  
Jan Nitsche ◽  
Peter Middendorf
Keyword(s):  
Mechanical Properties ◽  
Mechanical Load ◽  
Uv Light ◽  
Load Capacity ◽  
Tensile Tests ◽  
Exposure Dose ◽  
Cross Linking ◽  
Urethane Acrylate ◽  
Post Processing ◽  
Content Type

Purpose During post-processing of stereolithography photopolymers, the limited penetration depth of ultraviolet (UV) light can lead to inhomogeneous cross-linking. This is a major problem in part design for industrial applications as this creates uncertainty regarding the mechanical load capacity. Therefore, this paper aims to present an experimental method to measure the post-curing depth in stereolithography photopolymers. Design/methodology/approach Printed specimens made from urethane acrylate photopolymers are placed in a protective housing and are exposed on one side to UV light during post-processing. A depth profile of the hardness according to ASTM D2240 Shore D is determined alongside the specimens. UVA,-B and -C spectra are investigated and the dependence on exposure dose and pigmentation is studied. The results are directly linked to the mechanical properties via tensile tests and validated on an automotive trim part. Findings Exposure with a 405 nm light-emitting diode provides the deepest homogenous post-curing depth of 10.5 mm, which depends on the overall exposure dose and pigmentation. If the initially transparent photopolymer is colored with black pigments, post-curing depth is significantly reduced and no homogenous post-curing can be achieved. To obtain comparable mechanical properties by tensile tests, complete cross-linking of the specimen cross-section has to be ensured. Research limitations/implications The spatial resolution of the presented measurement method depends on the indenter size and sample hardness. As a result, the resolution of the used setup is limited in the area close to the edges of the specimen. Originality/value This paper shows that the spatially resolved hardness measurement provides more information on the post-curing influence than the evaluation of global mechanical properties. The presented method can be used to ensure homogenous cross-linking of stereolithography parts.

Effect of extrusion temperature on fused filament fabrication parts orthotropic behaviour

2019 ◽  
Vol 26 (4) ◽  
pp. 639-647
Author(s):  
Michele Angelo Attolico ◽  
Caterina Casavola ◽  
Alberto Cazzato ◽  
Vincenzo Moramarco ◽  
Gilda Renna
Keyword(s):  
Mechanical Properties ◽  
Morphological Characteristics ◽  
Single Layer ◽  
Acrylonitrile Butadiene Styrene ◽  
Surface Characteristics ◽  
Tensile Tests ◽  
Extrusion Temperature ◽  
Fused Filament Fabrication ◽  
Bonding Quality ◽  
Content Type

Purpose The purpose of this paper is to verify the effects of extrusion temperature on orthotropic behaviour of the mechanical properties of parts obtained by fused filament fabrication (FFF) under quasi-static tensile loads. Design/methodology/approach Tensile tests were performed on single layer specimens fabricated in polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) to evaluate the mechanical properties at different extrusion temperatures and raster orientations (0°, 45° and 90°). Furthermore, a detailed study of morphological characteristics of the single layer samples cross-section and of the bonding quality among adjacent deposited filaments was performed by scanning electron microscopy to correlate the morphology of materials with mechanical behaviour. Findings The results show that the orthotropic behaviour of FFF-printed parts tends to reduce, while the mechanical properties improved with increase in extrusion temperature. Furthermore, the increase in extrusion temperature led to an improvement in inter-raster bonding quality and in the compactness and homogeneity of the parts. Originality/value The relation between the extrusion temperature, orthotropic behaviour and morphological surface characteristics of the single layer specimen obtained by FFF has not been previously reported.

Cellular Cross-linking of Peptide Modified Hydrogels

2004 ◽  
Vol 127 (2) ◽  
pp. 220-228 ◽  
Author(s):  
Jeanie L. Drury ◽  
Tanyarut Boontheekul ◽  
David J. Mooney
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Cell Density ◽  
Tensile Tests ◽  
Cross Linking ◽  
Engineering Applications ◽  
C2c12 Myoblasts ◽  
Polymer Systems ◽  
Peptide Modification ◽  
Adhesive Interactions

Peptide modification of hydrogel-forming materials is being widely explored as a means to regulate the phenotype of cells immobilized within the gels. Alternatively, we hypothesized that the adhesive interactions between cells and peptides coupled to the gel-forming materials would also enhance the overall mechanical properties of the gels. To test this hypothesis, alginate polymers were modified with RGDSP-containing peptides and the resultant polymer was used to encapsulate C2C12 myoblasts. The mechanical properties of these gels were then assessed as a function of both peptide and cell density using compression and tensile tests. Overall, it was found that above a critical peptide and cell density, encapsulated myoblasts were able to provide additional mechanical integrity to hydrogels composed of peptide-modified alginate. This occurred presumably by means of cell-peptide cross-linking of the alginate polymers, in addition to the usual Ca++ cross-linking. These results are potentially applicable to other polymer systems and important for a range of tissue engineering applications.

scholarly journals Relationship Between Mechanical Properties and Bone Mineral Density of Human Femoral Bone Retrieved from Patients with Osteoarthritis

2012 ◽  
Vol 6 (1) ◽  
pp. 458-463 ◽  
Author(s):  
Yvonne Haba ◽  
Tobias Lindner ◽  
Andreas Fritsche ◽  
Ann-Kristin Schiebenhöfer ◽  
Robert Souffrant ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Mineral Density ◽  
Bone Density ◽  
Bone Mineral ◽  
Mechanical Load ◽  
Load Capacity ◽  
Quantitative Computed Tomography ◽  
Hip Osteoarthritis ◽  
Femoral Bone ◽  
Mineral Density

The objective of this study was to analyse retrieved human femoral bone samples using three different test methods, to elucidate the relationship between bone mineral density and mechanical properties. Human femoral heads were retrieved from 22 donors undergoing primary total hip replacement due to hip osteoarthritis and stored for a maximum of 24 hours postoperatively at + 6 °C to 8 °C. Analysis revealed an average structural modulus of 232±130 N/mm2 and ultimate compression strength of 6.1±3.3 N/mm2 with high standard deviations. Bone mineral densities of 385±133 mg/cm2 and 353±172 mg/cm3 were measured using thedual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), respectively. Ashing resulted in a bone mineral density of 323±97 mg/cm3. In particular, significant linear correlations were found between DXA and ashing with r = 0.89 (p < 0.01, n = 22) and between structural modulus and ashing with r = 0.76 (p < 0.01, n = 22). Thus, we demonstrated a significant relationship between mechanical properties and bone density. The correlations found can help to determine the mechanical load capacity of individual patients undergoing surgical treatments by means of noninvasive bone density measurements.

Using statistically designed experiment to optimize vacuum-assisted post-processing of binder jetted specimens

2019 ◽  
Vol 25 (3) ◽  
pp. 653-663 ◽  
Author(s):  
Dejan Movrin ◽  
Ognjan Luzanin ◽  
Vera Guduric
Keyword(s):  
Tensile Strength ◽  
Design Of Experiment ◽  
Complex Geometry ◽  
Load Capacity ◽  
Vacuum Impregnation ◽  
Post Processing ◽  
Technological Parameters ◽  
Content Type ◽  
Stage Of Development ◽  
Infiltration Method

PurposeThis paper aims to propose a vacuum-assisted post-processing method for use in binder jetted technology. The method is based on six key technological parameters and uses standard, commercially available consumables to achieve improvement in tensile strength, as well as the microstructure and porosity of the infiltrated matrix.Design/methodology/approachSix key technological parameters were systematically varied as factors on three levels, using design of experiment, i.e. definitive screening design. Surface response methodology was used to optimize the process and yield optimal tensile strength for the given range of input factors. Thus obtained, the optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. To confirm improvement in microstructure of the infiltrated matrix, SEM analysis was performed, while the reduction of porosity was analyzed using mercury porosimetry.FindingsThe obtained results indicate that, compared to its conventional counterpart, the proposed, optimized infiltration method yields improvement in tensile strength which is significant from both the statistical and engineering point of view, while reducing porosity by 3.5 times, using only standard consumables. Scanning electron microscopy examination of fractured specimens’ micrographs also revealed significant morphological differences between the conventional and proposed method of post-processing. This primarily reflects in higher surface area under hardened epoxy infiltrate, which contributes to increased load capacity of specimen cross-section.Research limitations/implicationsAt the present stage of development, the most important limitation of the proposed method is the overall size of models which can be accommodated in standard vacuum impregnation units. Although, in this study, the infiltration method did not prove statistically significant, further investigation is required with models of complex geometry, various sizes and mass arrangements, where infiltration would be more challenging and could possibly result in different findings.Practical implicationsThe most important practical implication of this study is the experimentally verified result of optimization, which showed that tensile strength and matrix microstructure can be significantly improved, using just standard consumables.Social implicationsImproved strength contributes to reduction of material consumption, which, in a longer run, can be beneficial for environment protection and sustainable development.Originality/valueBased on literature review, there have been no previous investigations which studied the tensile strength of infiltrated specimens through design of experiment, which involved specimen preheating temperature, level and duration of vacuum treatment of infiltrate mixture and infiltrated specimens and infiltration method.

Effect of Al on the microstructure, corrosion behavior and mechanical properties of Mg-4Li

2020 ◽  
Vol 67 (1) ◽  
pp. 31-37
Author(s):  
Cheng Zhang ◽  
Liang Wu ◽  
Zilong Zhao ◽  
Guangsheng Huang ◽  
Bin Jiang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Behavior ◽  
Design Methodology ◽  
Electron Backscatter Diffraction ◽  
Tensile Tests ◽  
Content Type ◽  
Solid Solution Strengthening ◽  
Corrosion Behaviors ◽  
Solution Strengthening ◽  
Backscatter Diffraction

Purpose This paper aims to investigate microstructure, corrosion behavior and mechanical properties of Mg-4Li and Mg-4Li-3Al. Design/methodology/approach The microstructure was characterized by using scanning electron microscopy and electron backscatter diffraction. The corrosion behaviors were measured by hydrogen evolution and potentiodynamic polarization tests. The mechanical properties were evaluated by tensile tests. Findings The addition of Al results in the precipitation of some Mg-Al phase and Al3Li phase particles, and the formation of some fine recrystallized grains. Originality/value Mg-4Li-3Al showed a higher corrosion rate than that of Mg-4Li, attributed to the precipitate particles in Mg-4Li-3Al causing microgalvanic corrosion and the change of grain orientation. The addition of 3 Wt. per cent Al increased the tensile strength by solid solution strengthening, precipitation strengthening, refinement strengthening and texture strengthening, whilst the elongation decreased by almost half.

UV curable urethane acrylate coatings formulation: experimental design approach

2014 ◽  
Vol 43 (2) ◽  
pp. 61-68 ◽  
Author(s):  
Ghodsieh Mashouf ◽  
Morteza Ebrahimi ◽  
Saeed Bastani
Keyword(s):  
Mechanical Properties ◽  
Experimental Design ◽  
Physical And Mechanical Properties ◽  
Scratch Resistance ◽  
Urethane Acrylate ◽  
Uv Curable ◽  
Content Type ◽  
Mathematical Equations ◽  
Acrylate Monomers ◽  
Mixture Experimental Design

Purpose – The purpose of this work was to perform a systematic study on the effect of formulation on the physical and mechanical properties of ultaviolet (UV) curable urethane acrylate resins. In addition, the authors wanted to derive mathematical formula for the prediction of physical and mechanical properties for the aforementioned system. Design/methodology/approach – The experiments were carried out based on mixture experimental design to determine the effect of different multifunctional acrylates (i.e. 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), trimethyolpropane triactylate (TMPTA)) concentration on the physical and mechanical properties of a UV curable polyurethane acrylate system. The urethane oligomer was synthesized and characterized by the research team. Microhardness, adhesion strength and scratch resistance of the cured films were evaluated as the physical and mechanical properties. Findings – The results revealed that the resin and TMPTA concentrations had the most significant effects on the microhardness property. Adhesion strength of the films showed a linear trend with respect to all variables. Moreover, all components also had a significant and complex influence on the scratch resistance of the cured systems. In addition, mathematical equations proposed by mixture experimental design were derived for all the mentioned properties. Research limitations/implications – Other multifunctional acrylate monomers (i.e. more than three functional) can be used in the formulations. The kinetics of the curing can affect on the network formation and consequently on the properties of the cured films. Practical implications – The obtained results can be used by the researchers who are active in the field of structure-property relationship of polymers and surface coatings. The reported data and the mathematical equations can also be used for the formulating of an appropriate formulation based on a specific application. Originality/value – A systematic and statistical-based approach, i.e. mixture experimental design, was used to evaluate the effect of formulation on some of the properties of a UV curable polyurethane acrylate system. A urethane oligomer and three different multifunctional acrylate monomers as reactive diluents were used in the formulations. Noteworthy to mention that several mathematical models were derived by using analysis of variance for the prediction of the properties studied in this system.

Development of CNTs-filled photopolymer for projection stereolithography

2017 ◽  
Vol 23 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Hengky Eng ◽  
Saeed Maleksaeedi ◽  
Suzhu Yu ◽  
Yu Ying Clarrisa Choong ◽  
Florencia Edith Wiria ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Exchange Process ◽  
High Strength ◽  
Thermal Curing ◽  
Post Processing ◽  
Multiwalled Carbon ◽  
Content Type ◽  
Conventional Methods ◽  
Projection Stereolithography

Purpose Polymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing. Design/methodology/approach Carbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly. Findings With the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods. Practical implications This allows functional parts to be manufactured using SL. Originality/value In this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

scholarly journals The Effect of UV Exposure on the Service-life of Thermochromic Microcapsules Integrated into the Epoxy Matrix

2021 ◽  
Author(s):  
Olga BULDERBERGA ◽  
Andrey ANISKEVICH
Keyword(s):  
Mechanical Properties ◽  
Service Life ◽  
Epoxy Resin ◽  
Epoxy Matrix ◽  
Uv Light ◽  
Colour Change ◽  
Critical Time ◽  
Tensile Tests ◽  
Uv Exposure ◽  
Exposure Effect

The effect of ultraviolet (UV) exposure on the service-life of thermochromic microcapsules integrated into the epoxy matrix was investigated. The microcapsules of the formaldehyde shell contain the core of thermochromic leuco dye. Seven sets of epoxy resin samples filled with concentrations from 0 to 10 wt.% of microcapsules were investigated. The composite samples were exposed to UV for approximately 1000 h. For the quantitative evaluation of colour change under UV, a fast and simple original procedure based on samples’ image treatment was developed. With the exposure time intervals of 50 h, samples were taken out from the UV light chamber to evaluate the exposure effect on their reversible thermochromic ability and mechanical properties. Periodical evaluation of the UV light effect on mechanical properties during the exposure was performed by microhardness tests. Tensile tests of the samples till the fracture were performed every 200 h. The critical time under the exposure of the UV lamp that destroys the reversible thermochromic reaction of the microcapsules was defined as 200 h. At the same time, it has been found that the mechanical properties of the epoxy resin under the same UV source were not strongly affected after 1000 h of irradiance and changed in the frame of ~ 10 %.

scholarly journals Characterization of a Conjugate between Rose Bengal and Chitosan for Targeted Antibiofilm and Tissue Stabilization Effects as a Potential Treatment of Infected Dentin

2012 ◽  
Vol 56 (9) ◽  
pp. 4876-4884 ◽  
Author(s):  
Annie Shrestha ◽  
Michael R. Hamblin ◽  
Anil Kishen
Keyword(s):  
Mechanical Properties ◽  
Rose Bengal ◽  
Structural Changes ◽  
Structural Integrity ◽  
Green Light ◽  
Cross Linking ◽  
Antibiofilm Activity ◽  
Content Type ◽  
Dentin Collagen

ABSTRACTBacterial biofilms and dentin structural changes are some of the major challenges in the management of infected dentin tissue. This study characterized a photosensitizer-conjugated chitosan with enhanced photodynamic efficacy against dental biofilms, as well as the ability to reinforce the postinfected dentin matrix in order to improve its mechanical and chemical stability. Rose Bengal-conjugated chitosan (CSRB) was synthesized using a chemical cross-linking method and characterized for photophysical, photobiological, and cytotoxicity properties. Its potential as an antibacterial and matrix-reinforcing agent on dentin collagen was also evaluated.Enterococcus faecalisas planktonic andin vitrobiofilms was treated with CSRB and photodynamically activated with 5 to 60 J/cm2green light. Dentin collagen was used for the CSRB cross-linking experiments and evaluated for chemical changes, resistance to enzymatic degradation, and mechanical properties. CSRB was a photosensitizer with efficient singlet oxygen yield.In vitrophotoactivation gave higher fibroblast cell survival than did RB alone. CSRB showed significant antibiofilm photoinactivation (P< 0.01). The CSRB-cross-linked dentin collagen showed higher resistance to collagenase degradation and superior mechanical properties (P< 0.05). In summary, the photoactivated CSRB particles synthesized in this study may be a synergistic multifunctional treatment approach with lower cytotoxicity and effective antibiofilm activity as well as the ability to reinforce the dentin collagen to enhance resistance to degradation and improve mechanical properties. This may be a targeted treatment strategy to deal with infected dentin hard tissues in a clinical scenario, where both disinfection and structural integrity need to be addressed concomitantly.

Study on laser sintering of pine/co-PES composites and the investment casting process

2019 ◽  
Vol 25 (8) ◽  
pp. 1349-1358 ◽  
Author(s):  
Hui Zhang ◽  
David Bourell ◽  
Yanling Guo ◽  
Xiaodong Zhang ◽  
Yu Zhuang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Investment Casting ◽  
Laser Sintering ◽  
Processing Temperature ◽  
Post Processing ◽  
Advanced Technique ◽  
Content Type ◽  
Structural Patterns ◽  
Complex Structural

Purpose A pine/co-PES composite (PCPES composite) was proposed as the feedstock for powder bed fusion (laser sintering, LS). This paper aims to provide some necessary experimental data and the theoretical foundation for LS of pine/co-PES, especially for the application of using the laser-sintered pine/co-PES parts as complex structural patterns in investment casting. Design/methodology/approach The PCPES composites with different pine loadings were mixed mechanically. The composite’s preheating temperature and processing temperature during LS were determined experimentally based on the material’s thermal behavior. The effects of pine powder on the binding mechanism of PCPES composites were discussed through analyzing the microstructure of the laser-sintered parts’. Mechanical properties and dimensional precision of laser-sintered PCPES parts in different pine loadings were tested, and the parts’ mechanical properties were strengthened by wax-infiltration post-processing. The influence extents of process parameters on the mechanical properties of laser-sintered 20 Wt.% pine/co-PES parts were investigated using a 1/2 fractional factorials experiment. Findings 20 Wt.% pine/co-PES is considered to be a promising wood-plastic composite for laser sintering. The relationship between mechanical strength of its laser-sintered parts and process parameters was built up using mathematical formulas. Experimental results show density, tensile strength, flexural strength and surface roughness of laser-sintered 20 Wt.% pine/co-PES parts are improved by 72.7-75.0%, 21.9-111.3%, 26.8-86.2%, 27.0-29.1% after post-process infiltration with a wax. A promising application of the wax-infiltrated laser-sintered parts is for investment casting cores and patterns. Research limitations/implications The proper process parameters and forming properties of laser-sintered parts are limited to the results of laser sintering experiments carried on using AFS 360 rapid prototyping device. Originality/value This investigation not only provides a new feedstock for laser sintering with the advantages of low cost and fabricability but also uses an advanced technique to produce personalized wood-plastic parts efficiently. Mathematical models between mechanical properties of laser-sintered PCPES parts and LS process parameters will guide the further LS experiments using the 20 Wt.% pine/co-PES composite. Besides, the laser-sintered PCPES parts after wax-infiltration post-processing are promising as complex structural patterns for use in investment casting.

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