scholarly journals EFFECT OF TEMPERATURE AND TIME ON THE HOMOGENEITY OF POLYLACTIC ACID /HYDROXYAPATITE COMPOSITES FOR BONE SCAFFOLDS

2021 ◽  
Vol 40 (3) ◽  
Keyword(s):  
Polylactic Acid ◽  
Effect Of Temperature ◽  
Bone Scaffolds

scholarly journals Additive manufacturing of PLA-based scaffolds intended for bone regeneration and strategies to improve their biological properties

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 571-599
Author(s):  
Ricardo Donate ◽  
Mario Monzón ◽  
María Elena Alemán-Domínguez
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Additive Manufacturing ◽  
Bone Regeneration ◽  
Polylactic Acid ◽  
State Of The Art ◽  
Biological Properties ◽  
Design Stage ◽  
Bone Scaffolds ◽  
Regeneration Of Bone

AbstractPolylactic acid (PLA) is one of the most commonly used materials in the biomedical sector because of its processability, mechanical properties and biocompatibility. Among the different techniques that are feasible to process this biomaterial, additive manufacturing (AM) has gained attention recently, as it provides the possibility of tuning the design of the structures. This flexibility in the design stage allows the customization of the parts in order to optimize their use in the tissue engineering field. In the recent years, the application of PLA for the manufacture of bone scaffolds has been especially relevant, since numerous studies have proven the potential of this biomaterial for bone regeneration. This review contains a description of the specific requirements in the regeneration of bone and how the state of the art have tried to address them with different strategies to develop PLA-based scaffolds by AM techniques and with improved biofunctionality.

Polylactic Acid Bone Scaffolds Made by Heat Treatment

2012 ◽  
Vol 627 ◽  
pp. 751-755 ◽  
Author(s):  
Jia Horng Lin ◽  
Hsiu Ying Chung ◽  
Kun Da Wu ◽  
Shih Peng Wen ◽  
Chao Tsang Lu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Polylactic Acid ◽  
Hollow Structure ◽  
Test Results ◽  
Widespread Application ◽  
Bone Scaffolds ◽  
Lower Porosity ◽  
Plied Yarn ◽  
Thermally Treated

Polylactic acid (PLA) has a widespread application, such as bone scaffolds, in biomedical field. This study creates PLA bone scaffolds, which has a structural stability, by using 150 denier (D) PLA plied yarn. 75 D PLA filaments are combined and then twisted into plied yarn. During the twisting process, the twists per inch (TPI) are varied. The resulting plied yarn undergoes heat treatment, and then is evaluated with mechanical property tests, determining an optimal TPI of 9. The plied yarn is then braided into PLA bone scaffolds. PLA bone scaffolds, thermally treated or not, are observed by a stereomicroscope and tested for porosity and tensile strength. According to test results, the optimal TPI is 9, which results from the optimal tensile strength. However, the variation in elongation of various 150 D plied yarn is not significant. When observed by a stereomicroscope, PLA bone scaffolds, which are thermally treated, have a compact filament arrangement. This is due to thermal bonding between filaments; in addition, the heat treatment duration is short, so the PLA filaments are not melted completely, resulting in a stable, hollow structure. According to porosity and tensile strength test, PLA bone scaffolds that are thermally treated exhibit a lower porosity and tensile strength due to the compact arrangement and tender phenomenon of the filaments. As a result, the optimal PLA bone scaffolds are made of 150 D plied with a TPI of 9, followed by a heat treatment at 165 °C for ten minutes.

Property Evaluation of Polylactic Acid Multilayer Braids Used as Bone Scaffolds

2012 ◽  
Vol 627 ◽  
pp. 844-848
Author(s):  
Jia Horng Lin ◽  
Hsiu Ying Chung ◽  
Shih Peng Wen ◽  
Wen Cheng Chen ◽  
Yueh Sheng Chen ◽  
...  
Keyword(s):  
Contact Angle ◽  
Tensile Strength ◽  
Optimal Condition ◽  
Polylactic Acid ◽  
Water Contact Angle ◽  
Tissue Scaffolds ◽  
Water Contact ◽  
Bone Scaffolds ◽  
Property Evaluation ◽  
Plied Yarn

Polylactic acid (PLA), which is biodegradable, is largely used as biomaterial such as bone scaffolds. This study twists PLA filaments into PLA plied yarn, during which twist per inch (TPI) varies as 9, 10, 11, 12, and 13. Tensile strength and elongation of the resulting plied yarn are then evaluated. The optimal TPI is 10, which results from an optimal tensile strength of 3.3 g/den and elongation of 42 %. The optimal plied yarn is made into PLA braids on a 16-spindle braiding machine, with a ratio of take-up gear to braid gear of 60:60, 70:60, 80:60, 90:60, or 100:60. The braids with various gear ratios are then made into multilayer braids with a diameter of 4 mm. The resulting multilayer braids are evaluated for surface observation, porosity and water contact angle. The optimal porosity is 55-65% and the optimal water contact angle is below 30°. This optimal condition indicates that the multilayer braid exhibit good hydrophilicity and a good candidate for bone tissue scaffolds.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

The effect of temperature on high-resolution TEM image contrast

1995 ◽  
Vol 53 ◽  
pp. 640-641
Author(s):  
T. Geipel ◽  
W. Mader ◽  
P. Pirouz
Keyword(s):  
Form Factor ◽  
Inelastic Scattering ◽  
Accurate Method ◽  
Waller Factor ◽  
Effect Of Temperature ◽  
Specimen Thickness ◽  
Influence Of Temperature ◽  
Debye Waller Factor ◽  
Influence Of Temperature On ◽  
Atomic Form Factor

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).

The development of dormancy in bulblets of Lilium speciosum generated in vitro. II. The effect of temperature

1990 ◽  
Vol 80 (3) ◽  
pp. 431-436 ◽  
Author(s):  
Isabelle Delvallee ◽  
Annie Paffen ◽  
Geert-Jan De Klerk
Keyword(s):  
Effect Of Temperature ◽  
Lilium Speciosum

Effect of Temperature on ADP-Induced Platelet Aggregation

1973 ◽  
Vol 29 (01) ◽  
pp. 183-189
Author(s):  
C. A Praga ◽  
E. M Pogliani
Keyword(s):  
Platelet Aggregation ◽  
Incubation Period ◽  
Room Temperature ◽  
Important Variable ◽  
Practical Significance ◽  
Effect Of Temperature ◽  
Induce Platelet Aggregation ◽  
Cuvette Holder ◽  
Exact Temperature

SummaryTemperature represents a very important variable in ADP-induced platelet aggregation.When low doses of ADP ( < 1 (μM) are used to induce platelet aggregation, the length of the incubation period of PRP in the cuvette holder of the aggregometer, thermostatted at 37° C, is very critical. Samples of the same PRP previously kept at room temperature, were incubated for increasing periods of time in the cuvette of the aggregometer before adding ADP, and a significant decrease of aggregation, proportional to the length of incubation, was observed. Stirring of the PRP during the incubation period made these changes more evident.To measure the exact temperature of the PRP during incubation in the aggre- gometer, a thermocouple device was used. While the temperature of the cuvette holder was stable at 37° C, the PRP temperature itself increased exponentially, taking about ten minutes from the beginning of the incubation to reach the value of 37° C. The above results have a practical significance in the reproducibility of the platelet aggregation test in vitro and acquire particular value when the effect of inhibitors of ADP induced platelet aggregation is studied.Experiments carried out with three anti-aggregating agents (acetyl salicyclic acid, dipyridamole and metergoline) have shown that the incubation conditions which influence both the effect of the drugs on platelets and the ADP breakdown in plasma must be strictly controlled.

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