scholarly journals Post-process optimization of 3D printed poly(lactic-co-glycolic acid) dental implant scaffold for enhanced structure and mechanical properties: effects of sonication duration and power

2021 ◽  
Vol 32 (8) ◽  
Author(s):  
R. N. V. C. Virinthorn ◽  
M. Chandrasekaran ◽  
K. Wang ◽  
K. L. Goh
Keyword(s):  
Structural Damage ◽  
Glycolic Acid ◽  
Solvent Mixture ◽  
Ultrasonic Waves ◽  
Poly Vinyl Alcohol ◽  
Covalent Bonds ◽  
Process Stage ◽  
Post Process ◽  
3D Printed ◽  
Ft Ir

AbstractWe described a technique of a post-process stage to partially remove the poly(vinyl alcohol) (PVA) binder in Poly(lactic-co-glycolic acid) (PLGA) dental scaffolds. The scaffolds were exposed to ultrasonic waves while immersed in an ethanol/acetone solvent mixture that possessed both polar and nonpolar properties. A factorial experiment was conducted in which the scaffolds were treated to three levels of sonication power (pW): 0, 20% (22 W) and 40% (44 W), and soaking duration (t): 5, 15, and 30 min. The treated scaffolds were characterized by FT-IR, optical microscopy, and mechanical (compressive) testing. FT-IR revealed that the amount of PVA decreased with increasing pW and t. Two-way ANOVA revealed that increasing pW and t, respectively, resulted in increasing scaffold surface area to volume (SVR). Sonication and solvent caused structural damage (i.e., unevenness) on the scaffold surface, but the damage was minimal at 20% pW and 30 min. The optimal values of pW and t resulting in enhanced fracture strength, strain and toughness were 20% and 30 min, respectively, which corroborated the findings of minimal structural damage. However, sonication had no significant effects on the scaffold stiffness. Mechanistic analysis of the effects of sonication predicted that the ultrasonic energy absorbed by the scaffold was sufficient to disrupt the van Der Waals bonds between the PVA and PLGA but not high enough to disrupt the covalent bonds within the PLGA. This technique is promising as it can partially remove the PVA from the scaffold, and mitigate problematic issues down the line, such as thermal degradation during sterilization, and undue delay/variability in biodegradation.

Temperature Dependence of the Critical Electron Dose for Fatty Acid Monolayers

1982 ◽  
Vol 40 ◽  
pp. 78-79
Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser
Keyword(s):  
Electron Beam ◽  
Fatty Acid ◽  
Inelastic Scattering ◽  
Temperature Dependence ◽  
Structural Damage ◽  
Direct Result ◽  
Second Step ◽  
Strong Temperature Dependence ◽  
Electron Dose ◽  
Covalent Bonds

The structural damage of molecules irradiated by electrons is generally considered to occur in two steps. The direct result of inelastic scattering events is the disruption of covalent bonds. Following changes in bond structure, movement of the constituent atoms produces permanent distortions of the molecules. Since at least the second step should show a strong temperature dependence, it was to be expected that cooling a specimen should extend its lifetime in the electron beam. This result has been found in a large number of experiments, but the degree to which cooling the specimen enhances its resistance to radiation damage has been found to vary widely with specimen types.

scholarly journals Multifunctional application of PVA-aided Zn–Fe–Mn coupled oxide nanocomposite

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Buzuayehu Abebe ◽  
H. C. Ananda Murthy ◽  
Enyew Amare Zereffa
Keyword(s):  
Charge Transfer ◽  
Analytical Techniques ◽  
Antibacterial Activities ◽  
Poly Vinyl Alcohol ◽  
Blue Dye ◽  
Ternary Oxide ◽  
Gram Positive Bacteria ◽  
Transfer Capability ◽  
Ft Ir ◽  
Synthesized Materials

AbstractZinc oxide (ZnO) is a fascinating semiconductor material with many applications such as adsorption, photocatalysis, sensor, and antibacterial activities. By using a poly (vinyl alcohol) (PVA) polymer as a capping agent and metal oxides (iron and manganese) as a couple, the porous PVA-aided Zn/Fe/Mn ternary oxide nanocomposite material (PTMO-NCM) was synthesized. The thermal, optical, crystallinity, chemical bonding, porosity, morphological, charge transfer properties of the synthesized materials were confirmed by DTG/DSC, UV–Vis-DRS, XRD, FT-IR, BET, SEM-EDAX/TEM-HRTEM-SAED, and CV/EIS/amperometric analytical techniques, respectively. The PTMO-NCM showed an enhanced surface area and charge transfer capability, compared to ZnO. Using the XRD pattern and TEM image analysis, the crystalline size of the materials was confirmed to be in the nanometer range. The porosity and superior charge transfer capabilities of the PTMO-NCM were confirmed from the BET, HRTEM (IFFT)/SAED, and CV/EIS analysis. The adsorption kinetics (adsorption reaction/adsorption diffusion) and adsorption isotherm test confirmed the presence of a chemisorption type of adsorbate/methylene blue dye-adsorbent/PTMO-NCM interaction. The photocatalytic performance was tested on the Congo red and Acid Orange-8 dyes. The superior ascorbic acid sensing capability of the material was understood from CV and amperometric analysis. The noble antibacterial activities of the material were also confirmed on both gram-negative and gram-positive bacteria.

Novel pH-Sensitive Poly(Vinyl Alcohol) Based Polyampholyte as Pervaporation Membrane

2016 ◽  
Vol 852 ◽  
pp. 979-983
Author(s):  
Ping Rui Meng ◽  
Liang Bo Li
Keyword(s):  
Aqueous Solution ◽  
Vinyl Alcohol ◽  
Water Resistance ◽  
Graft Copolymerization ◽  
Sodium Acrylate ◽  
Poly Vinyl Alcohol ◽  
Permeate Flux ◽  
Ft Ir ◽  
Ethanol Aqueous Solution ◽  
Poly Acrylamide

Sodium acrylate (NaAA) and acrylamide (AM) were grafted onto poly (vinyl alcohol) (PVA) using potassium persulfate as an initiator, Graft copolymerization namely poly (vinyl alcohol)-g-poly (acrylamide/sodium acrylate) (PVA-g-PAM/SAC). The poly (vinyl alcohol)-g-poly (vinylamine/sodium acrylate) (PVAMC) was prepraed by Hofmann rearrangement.The PVAMC homogeneous membrane was characterized by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM).The water resistance of the PVAMC membranes is the best when pH of the PVAMC solutions was 4, at that time the numbers of-NH3+ and-COO- groups trended to be equal, so the isoelectric point was pH=4. At 90 °C the pervaporation of PVAMC composite membrane was tested and showed that the separation factor and the permeate flux were about 1001 and 1341 g/(m2·h) for 90wt% ethanol aqueous solution, and they were about 1297 and 1040 g/(m2·h) for 90wt% isopropanol aqueous solution.

scholarly journals Evaluation of Synthesized Cross Linked Polyvinyl Alcohol as Potential Disintegrant

2010 ◽  
Vol 13 (2) ◽  
pp. 114 ◽  
Author(s):  
Ashok Patel ◽  
Pradeep Vavia
Keyword(s):  
Acute Toxicity ◽  
Poly Vinyl Alcohol ◽  
Physical Parameters ◽  
Crosslinking Reaction ◽  
Tap Density ◽  
Ft Ir ◽  
Sedimentation Volume ◽  
Acidic Conditions ◽  
Formed Product ◽  
Good Flow

PURPOSE: The present study deals with evaluation of crosslinked poly vinyl alcohol (PVA) as a potential disintegrant. METHODS: Crosslinking of PVA was carried out using glutaraldehyde as a crosslinker, in presence of acidic conditions. The crosslinking reaction was optimized for a) polymer: crosslinker ratio; b) temperature requirement and c) reaction duration. Certain physical parameters of the disintegrant (including sedimentation volume, hydration capacity, specific surface area and bulk and tap density) were determined and compared to the known disintegrants. Characterization was carried out using FT-IR, DSC, XRD, SEM and Photo microscopy studies. The developed excipient was also studied for acute toxicity in rats and found to be safe for oral use. RESULTS: Disintegration property of formed product was compared to known disintegrant (Ac-Di-Sol) and it was found to give better results. The disintegration mechanism of developed disintegrant was postulated based on results obtained from various physical evaluations including: Study of effect of disintegrant concentration, fillers, and hardness, mode of incorporation and method of granulation on disintegration activity. CONCLUSIONS: By changing the condition parameters of well known crosslinking reaction of PVA, we obtained a crosslinked product which had excellent disintegration activity, good flow and optimal tableting properties.

scholarly journals Development of poly(vinyl alcohol)-based membranes by the response surface methodology for environmental applications

2020 ◽  
Vol 24 ◽  
pp. e5
Author(s):  
Juliana Zanol Merck ◽  
Camila Suliani Raota ◽  
Jocelei Duarte ◽  
Camila Baldasso ◽  
Janaina Da Silva Crespo ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Citric Acid ◽  
Response Surface ◽  
Acid Concentration ◽  
Vinyl Alcohol ◽  
Membrane Preparation ◽  
Poly Vinyl Alcohol ◽  
Esterification Reaction ◽  
Citric Acid Concentration ◽  
Ft Ir

The pollution of hydric sources by pharmaceuticals is an issue in many countries, particularly in Brazil. The presence of these substances causes deleterious effects on the environment and human health. One of the main sources of this contamination is domestic sewage, due to the expressive amount of medicines released in their unaltered form. Unfortunately, traditional wastewater treatment is not effective for the removal of pharmaceuticals and, for this reason, membrane technology is an attractive alternative to overcome this issue. In this regard, hydrophilic polymers, such as poly(vinyl alcohol) (PVA), are the most suitable. However, their high affinity with water causes intense swelling, leading to severe modifications in the membrane properties. In view of all these facts, the present work evaluated the swelling of PVA-based membranes, with the aim of finding the membrane preparation method that has the lowest swelling, thereby providing the most suitable characteristics for pharmaceutical removal from wastewater. The membranes were prepared by the casting of a polymeric solution, with PVA as a basis polymer, citric acid as a crosslink agent and glycerol and silver nanoparticles as performance additives. The process optimization was performed using a design of experiments with posterior analysis by the response surface methodology (RSM). The RSM assessed the effect on the membrane swelling of the factors, including citric acid concentration and the time and temperature of crosslinking. The membrane characterization was performed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy coupled with a field emission gun (SEM-FEG) and water contact angle (WCA) measurements. Overall, the condition that showed the lowest swelling was obtained with 10% of citric acid and crosslinking for 4 h at 130 °C. Under these conditions, the membrane had a mass swelling of 42% and a dimensional swelling of 24%. Additionally, our statistical analysis revealed that the factors with the dominant effects were the citric acid concentration and the temperature of crosslinking. The FT-IR analysis suggested that the crosslinking occurred by an esterification reaction, as showed by the stretching frequencies of C=O at 1710 cm-1 and ester C-O at 1230 cm-1. Moreover, the SEM-FEG images revealed a smooth and flat surface and a dense cross section with a thickness of ~113 μm. Concerning the WCA, the angle was at ~80°, which is characteristic of hydrophilic materials. Finally, the data suggested that it is possible to optimize the membrane preparation process with adequate properties so that it can be subsequently applied to the removal of pharmaceuticals from hospital wastewater.

The Effect of Hydrostatic Pressure on Physical Properties and Microstructure of Spruce and Cherry

Holzforschung ◽  
2000 ◽  
Vol 54 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Voichita Bucur ◽  
Simone Garros ◽  
Claire Y. Barlow
Keyword(s):  
Hydrostatic Pressure ◽  
Structural Damage ◽  
Untreated Wood ◽  
Average Density ◽  
Ultrasonic Waves ◽  
Ultrasonic Velocities ◽  
Main Effect ◽  
Natural Wood ◽  
Effect Of Hydrostatic Pressure ◽  
Longitudinal Ultrasonic Waves

Summary The effect of hydrostatic pressure on the density, the ultrasonic velocities and the microstructure of spruce and cherry wood has been studied. Generally speaking, under hydrostatic pressure wood becomes less heterogeneous and less anisotropic than natural wood. In spruce, crushing and buckling of the thin-walled cells in the earlywood takes place. This also has the effect of disrupting the medullary rays, which assume a zig-zag path through the structure. Cherry has a much more homogeneous structure, and the main effect of the hydrostatic pressure is compaction of the vessels by buckling of the walls. The fibres are scarcely affected by the treatment. The width of the earlywood zone decreased after the application of pressure by 26% in spruce, and by 11% in cherry. The average density was increased by the hydrostatic pressure by 26% for spruce and by 46% for cherry. The densitometric profile of spruce demonstrates significant changes following the pressure treatment, with the minimum density DMin increasing and the maximum density DMax decreasing. For cherry, the densitometric profile is shifted rather uniformly towards higher densities, and the annual ring profile is spatially slightly compacted but otherwise similar to that of untreated wood. The anisotropy of wood (expressed by the ratio of acoustic invariants) decreased by 56% for spruce and by 33% for cherry. The structural damage in spruce is predominantly found in the radial (R) direction, and this corresponds to a reduction of 73% in the velocity of the longitudinal ultrasonic waves in the radial direction, VRR. In cherry, the structural damage is mainly in the transverse, T direction. The velocity of the longitudinal ultrasonic waves in the transverse direction, VTT is reduced by 44%. The medullary rays in cherry seem to be the most important anatomical feature influencing the propagation of ultrasonic waves.

Dual-Charge Nanofiber Mats Made of Chitosan(CS)/Poly(Vinyl Alcohol) (PVA) and Poly-(Acrylic Acid-Co-Maleic Acid) (PAMA)/PVA

2019 ◽  
Vol 819 ◽  
pp. 145-150
Author(s):  
Thapakorn Chareonying ◽  
Junnasir M. Sakilan ◽  
Theerasak Rojanarata ◽  
Prasopchai Patrojanasophon ◽  
Prasert Akkaramongkolporn ◽  
...  
Keyword(s):  
Acrylic Acid ◽  
Maleic Acid ◽  
Vinyl Alcohol ◽  
Electrospinning Process ◽  
Poly Vinyl Alcohol ◽  
Water Capacity ◽  
Ft Ir ◽  
Nanofiber Mats ◽  
Positively Charged ◽  
Poly Acrylic Acid

Nanofibers have been widely used for tissue engineering. Using charged polymers for the preparation of nanofibers can be useful for the loading of substances or macromolecules. Dual charge nanofiber mats are expected to be able to immobilize both positively charged and negatively charged substances in one versatile nanofiber mat. The purpose of this study was to prepare and characterize dual-charge nanofibers generated from poly (vinyl alcohol) (PVA)/poly-(acrylic acid-co-maleic acid) (PAMA) and chitosan (CS)/PVA. The polymer solutions of PAMA/PVA (1:1.63 w/w) and CS/PVA (1:2.33 w/w) were electrospun to form the nanofibers using dual-jet electrospinning process. The obtained dual-charge nanofibers were thermally crosslinked by leaving the nanofibers in the oven at 110-130 °C for 0.5, 1, 3, 5 h. The appearance of the nanofiber mat was characterized by a scanning electron microscope (SEM), and the diameter of nanofibers were determined by an image analysis software (J-micro vision®). The percentage water insolubilization and FT-IR spectra were also determined. The dual-size nanofiber mats with smooth and bead-free fibers were obtained. The diameter of the PAMA/PVA and CS/PVA fibers was 574.54 ± 142.98 nm and 225.69 ± 41.92 nm, respectively. The desirable temperature and time for the crosslink of the dual-charge nanofiber mats was 130 °C for 1 h which could provide a high insolubilization with water capacity of 93.22 ± 2.23%.

Promoting bone regeneration by 3D-printed poly(glycolic acid)/hydroxyapatite composite scaffolds

2020 ◽  
Author(s):  
Taegyun Yeo ◽  
Young-Gwang Ko ◽  
Eun Jin Kim ◽  
Oh Kyoung Kwon ◽  
Ho Yun Chung ◽  
...  
Keyword(s):  
Bone Regeneration ◽  
Glycolic Acid ◽  
Composite Scaffolds ◽  
Hydroxyapatite Composite ◽  
3D Printed

scholarly journals Surface Modification of Poly(lactic-co-glycolic acid) Microspheres with Enhanced Hydrophilicity and Dispersibility for Arterial Embolization

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1959
Author(s):  
Jiao Wang ◽  
Jianbo Li ◽  
Jie Ren
Keyword(s):  
Glycolic Acid ◽  
Arterial Embolization ◽  
Contact Angles ◽  
In Vitro Cytotoxicity ◽  
Plga Microspheres ◽  
Sem Images ◽  
Water Contact ◽  
Prospective Application ◽  
Ft Ir

In this study, a series of poly(lactic-co-glycolic acid) (PLGA) microspheres with different particle sizes for arterial embolization surgery were prepared. The polydopamine (PDA) and polydopamine/polyethyleneimine (PDA/PEI) were respectively coated on the PLGA microspheres as shells, in order to improve the hydrophilicity and dispersibility of PLGA embolization microspheres. After modification, with the introduction of PDA and PEI, many hydrophilic hydroxyl and amine groups appeared on the surface of the PLGA@PDA and PLGA@PDA/PEI microspheres. SEM images showed the morphologies, sizes, and changes of the as-prepared microspheres. Meanwhile, the XPS and FT-IR spectra demonstrated the successful modification of the PDA and PEI. Water contact angles (WCAs) of the PLGA@PDA and PLGA@PDA/PEI microspheres became smaller, indicating a certain improvement in surface hydrophilicity. In addition, the results of in vitro cytotoxicity showed that modification had little effect on the biosafety of the microspheres. The modified PLGA microspheres suggest a promising prospective application in biomedical field, as the modified microspheres can reduce difficulties in embolization surgery.

Sign in / Sign up

Export Citation Format

Share Document