Using a 3-Steps Supercritical Fluids Assisted Process for the Generation of Nanostructured Biopolymeric Scaffolds

2019 ◽  
Vol 12 (1) ◽  
pp. 7-14
Author(s):  
Stefano Cardea
Keyword(s):  
Mechanical Properties ◽  
Extracellular Matrix ◽  
Lactic Acid ◽  
Supercritical Fluids ◽  
Supercritical Co2 ◽  
Cellular Structure ◽  
High Porosity ◽  
Polymeric Gel ◽  
Very High

Background: Scaffolds can be used to substitute the extracellular matrix and to favour the generation of tissues and organs. Until now, various processes have been implemented for scaffolds generation, but they are characterized by several limits. Methods: In this work, we tested a supercritical fluids assisted process for the generation of nano-structured biopolymeric scaffolds; it is characterized by three steps: generation of a polymeric gel (loaded with a porogen), drying of the gel using supercritical CO2, waterwashing to remove the porogen. Results: 3D Poly(D,L-lactic acid) scaffolds have been obtained, characterized by very high porosity (> 90%) and surface are (> 200 m2/g), and by a fibrous nanostructure (fibres ranging between 60 and 400 nm) superimposed to a micrometric cellular structure. Conclusion: Moreover, suitable mechanical properties (up to 125 KPa) and very low solvents residue (< 5 ppm) have been obtained.

Misestimation of the ITZ Thickness around Non-Spherical Aggregates

2021 ◽  
Vol 1036 ◽  
pp. 432-441
Author(s):  
Ming Qi Li ◽  
Hui Su Chen
Keyword(s):  
Mechanical Properties ◽  
Cross Section ◽  
Linear Analysis ◽  
Interfacial Transition Zone ◽  
High Porosity ◽  
Two Dimensional ◽  
One Dimensional ◽  
3D Microstructure ◽  
Porosity And Permeability ◽  
Very High

The ITZ (interfacial transition zone) in concrete has very high porosity and permeability, which affects concrete’s macroscopic mechanical properties and transport properties. Two-dimensional (2D) areal analysis and one-dimensional (1D) linear analysis are usually used to study ITZ’s microstructure. However, 3D microstructure is difficult to be characterized by 1D and 2D information. For example, 2D cross-section planes do not always intercept both the ITZ and the corresponding aggregate, which causes some ITZ regions are ignored by researchers. Therefore, ITZ’s volume and thickness will be misestimated, and leads to the misestimation of the diffusivity. In this paper, the effect of aggregate’s shape on the misestimation of ITZ thickness t is studied. The results reveal that the misestimation increases with the increasing sphericity s of aggregates.

Individual construction of freeform-fabricated polycaprolactone scaffolds for osteogenesis

2017 ◽  
Vol 62 (5) ◽  
Author(s):  
Lu Liu ◽  
Guixin Shi ◽  
Ying Cui ◽  
Hui Li ◽  
Zhengchao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Extracellular Matrix ◽  
Biological Activity ◽  
Individual Differences ◽  
Disease Status ◽  
High Porosity ◽  
Mechanical Parameters ◽  
Freeform Fabrication ◽  
Natural Bone ◽  
Rabbit Femur

AbstractThe construction of engineered bone mostly focuses on simulating the extracellular matrix (ECM) for proper biological activity. However, the complexity of architecture and the variability of the mechanical properties of natural bones are related to individual differences in age, nutritional state, mechanical loading and disease status. Defect substitutions should be normed with the host natural bone, balancing architectural and mechanical adaption, as well as biological activity. Using a freeform fabrication (FFF) method, we prepared polycaprolactone (PCL) scaffolds with different architectures. With simulation of structural and mechanical parameters of rabbit femur cancellous bone, individual defect substitution with the characteristics of the rabbit femur was obtained with high porosity and connectivity. Biological adaption

Compounding and Melt Strengthening of Poly(Lactic Acid): Shear and Elongation Rheological Investigations for Forming Process

2013 ◽  
Vol 554-557 ◽  
pp. 1751-1756 ◽  
Author(s):  
Benoit Mallet ◽  
Khalid Lamnawar ◽  
Abderrahim Maazouz
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Supercritical Co2 ◽  
Food Packaging ◽  
Blow Up ◽  
Good Alternative ◽  
Chain Extension ◽  
Poly Lactic Acid ◽  
Forming Process ◽  
Batch Foaming

The poly (lactic acid) (PLA), through its organic origin and its biodegradation properties, can be a good alternative to petroleum-based polymers. To this end, the forming process as well blown extrusion and foaming of PLA was investigated in this study as an alternative for the production of food packaging. Through this work, we present some promising routes to enhance its processing ability which presents several challenges mainly due to the poor shear and elongation properties of this biopolymer. To our knowledge, there is no paper dedicated to the investigation of foaming and/or blown extrusion of PLA that involves structural, rheological and thermo-mechanical properties. To achieve this objective, various formulations of PLA with multifunctionalized epoxy, nucleants and plasticizer were prepared and characterized on the basis of their linear viscoelasticity and extensional properties. The balance of chain extension and branching has been also investigated using solution viscosimetry, Steric exclusion chromatography (SEC) and rheology (relaxation spectrum, Van Gurp Palmen curves….). We pushed further by characterizing both the structure and thermo-mechanical properties of PLA formulations. On one hand, a batch foaming assisted with supercritical CO2 was achieved following a full characterization in physicochemical, rheological and thermal domain, The influence of the foaming parameters, the extent of chain modification as well as the contribution of crystallization on cell morphology was evaluated. Based on these parameters, structures ranging from micro to macro-cellular-cell were obtained. On the other hand, the stability maps of blown processing for neat and modified PLA were established at different die temperatures. We have achieved a great enhancement of the blown processing windows of PLA with high BUR (Blow Up Ratio) and TUR (Take Up Ratio) attained. We were able to demonstrate that a higher kinetic of crystallization can also be reached for chain-extended and branched PLA formulated with adequate amounts of nucleants and plasticizers. Induced crystallization during process was also demonstrated. Through this work, blown films with interesting thermo-mechanical and mechanical properties have been produced using an optimal formulation for PLA. References [1] A. Maazouz, K. Lamnawar, B. Mallet, Patent: C08L67/00; C08J5/10. FR2941702 (A1). (2010) [2] Y.-M. Corre, A. Maazouz, J. Duchet, J. Reignier, Batch foaming of chain extended PLA with supercritical CO2: Influence of the rheological properties and the process parameters on the cellular structure. J. of Supercritical Fluids,58 (2011) 177-188 [3] B. Mallet, K. Lamnawar, A. Maazouz, Compounding and processing of biodegradable materials based on PLA for packaging applications: In greening the 21st century material’s world, Frontiers in Science and Engineering, 1-2(2011) 1-44 [4] B. Mallet, K. Lamnawar, A. Maazouz, Improvement of blown extrusion processing of PLA: structure-processing-properties relashionships. Polymer engineering and Science (To appear in 2013).

scholarly journals Correlation Between the Structure and Compressive Property of PMMA Microcellular Foams Fabricated by Supercritical CO2 Foaming Method

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 315 ◽  
Author(s):  
Ruizhi Zhang ◽  
Ju Chen ◽  
Yuxuan Zhu ◽  
Jian Zhang ◽  
Guoqiang Luo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Size ◽  
Supercritical Co2 ◽  
Cellular Structure ◽  
Experimental Testing ◽  
Element Model ◽  
Cellular Structures ◽  
Compressive Property ◽  
Compressive Properties ◽  
Microcellular Foams

In this study, we fabricated poly (methyl methacrylate) (PMMA) microcellular foams featuring tunable cellular structures and porosity, through adjusting the supercritical CO2 foaming conditions. Experimental testing and finite element model (FEM) simulations were conducted to systematically elucidate the influence of the foaming parameters and structure on compressive properties of the foam. The correlation between the cellular structure and mechanical properties was acquired by separating the effects of the cell size and foam porosity. It was found that cell size reduction contributes to improved mechanical properties, which can be attributed to the dispersion of stress and decreasing stress concentration.

Preparation and properties of flexible poly(lactic acid) blend foams

2018 ◽  
Vol 37 (4-6) ◽  
pp. 189-205 ◽  
Author(s):  
Liu Wei ◽  
He Shicheng ◽  
Zhou Hongfu
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Constitutive Model ◽  
Rheological Behavior ◽  
Cellular Structure ◽  
High Performance ◽  
Poly Lactic Acid ◽  
Compression Property ◽  
Rigid Particles ◽  
Foaming Behavior

High-performance poly(lactic acid) (PLA) foam has been recognized as a promising material because of its biodegradability. However, low flexibility and foamability of PLAs has limited its use in different fields. In this study, a blend-toughening technology was used to toughen PLA and prepare flexible foams. The mechanical properties of PLA blends were evaluated, and the cellular structure of these foaming blends was characterized. The results show that the blending components significantly affected the overall mechanical properties and foaming behavior of PLA. The toughness of PLA was enhanced by adding poly(butylene adipate- co-terephthalate) (PBAT) and rigid particles. The rheological behavior of PLA was also affected by adding PBAT. Therefore, the cellular structure of the PLA foams was affected. A constitutive model was also used to fit the experimental results of the compression property of the PLA foam.

UNS A97075

Alloy Digest ◽  
1986 ◽  
Vol 35 (7) ◽  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aluminum Alloy ◽  
High Strength ◽  
Heat Treating ◽  
Good Resistance ◽  
Temperature Performance ◽  
Structural Applications ◽  
Structural Parts ◽  
Very High

Abstract UNS No. A97075 is a wrought precipitation-hardenable aluminum alloy. It has excellent mechanical properties, workability and response to heat treatment and refrigeration. Its typical uses comprise aircraft structural parts and other highly stressed structural applications where very high strength and good resistance to corrosion are required. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fatigue. It also includes information on low temperature performance as well as forming, heat treating, and machining. Filing Code: Al-269. Producer or source: Various aluminum companies.

KAISER ALUMINUM ALLOY 7050

Alloy Digest ◽  
2000 ◽  
Vol 49 (1) ◽  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tensile Strength ◽  
Aluminum Alloy ◽  
Heat Treating ◽  
High Fracture Toughness ◽  
High Fracture ◽  
Kaiser Aluminum ◽  
Structural Parts ◽  
Very High

Abstract Kaiser Aluminum Alloy 7050 has very high mechanical properties including tensile strength, high fracture toughness, and a high resistance to exfoliation and stress-corrosion cracking. The alloy is typically used in aircraft structural parts. This datasheet provides information on composition, physical properties, hardness, tensile properties, and shear strength as well as fracture toughness and fatigue. It also includes information on forming, heat treating, machining, and joining. Filing Code: AL-366. Producer or source: Tennalum, A Division of Kaiser Aluminum.

TIMKEN 16-15-6

Alloy Digest ◽  
1963 ◽  
Vol 12 (12) ◽  
Keyword(s):  
Mechanical Properties ◽  
Creep Resistance ◽  
Elevated Temperatures ◽  
Roller Bearing ◽  
Heat Treating ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Corrosion And Oxidation ◽  
Very High ◽  
High Creep Resistance

Abstract Timken 16-15-6 is a non-magnetic, austenitic, corrosion and heat resistant steel having high creep resistance at elevated temperatures and good corrosion and oxidation resistance. It age-hardens at elevated temperatures after solution quenching, and possesses very high mechanical properties. This datasheet provides information on composition, microstructure, hardness, and tensile properties as well as creep. It also includes information on forming, heat treating, machining, and joining. Filing Code: SS-150. Producer or source: Timken Roller Bearing Company.

scholarly journals Fabrication of Hybrid Nanofibers from Biopolymers and Poly (Vinyl Alcohol)/Poly (ε-Caprolactone) for Wound Dressing Applications

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2104
Author(s):  
Sibusiso Alven ◽  
Blessing Atim Aderibigbe
Keyword(s):  
Mechanical Properties ◽  
Wound Healing ◽  
Vinyl Alcohol ◽  
Wound Dressing ◽  
Chronic Wounds ◽  
Cellular Adhesion ◽  
Wound Dressings ◽  
Poly Vinyl Alcohol ◽  
High Porosity ◽  
Hybrid Nanofibers

The management of chronic wounds is challenging. The factors that impede wound healing include malnutrition, diseases (such as diabetes, cancer), and bacterial infection. Most of the presently utilized wound dressing materials suffer from severe limitations, including poor antibacterial and mechanical properties. Wound dressings formulated from the combination of biopolymers and synthetic polymers (i.e., poly (vinyl alcohol) or poly (ε-caprolactone) display interesting properties, including good biocompatibility, improved biodegradation, good mechanical properties and antimicrobial effects, promote tissue regeneration, etc. Formulation of these wound dressings via electrospinning technique is cost-effective, useful for uniform and continuous nanofibers with controllable pore structure, high porosity, excellent swelling capacity, good gaseous exchange, excellent cellular adhesion, and show a good capability to provide moisture and warmth environment for the accelerated wound healing process. Based on the above-mentioned outstanding properties of nanofibers and the unique properties of hybrid wound dressings prepared from poly (vinyl alcohol) and poly (ε-caprolactone), this review reports the in vitro and in vivo outcomes of the reported hybrid nanofibers.

Sign in / Sign up

Export Citation Format

Share Document