Macromolecular Design of Aliphatic Polyesters with Maintained Mechanical Properties and a Rapid, Customized Degradation Profile

2011 ◽  
Vol 12 (6) ◽  
pp. 2382-2388 ◽  
Author(s):  
Sofia Målberg ◽  
Anders Höglund ◽  
Ann-Christine Albertsson
Keyword(s):  
Mechanical Properties ◽  
Aliphatic Polyesters

scholarly journals Degradation and Viscoelastic Properties of PLA-PCL, PGA-PCL, PDO and PGA Fibres

2010 ◽  
Vol 636-637 ◽  
pp. 825-832 ◽  
Author(s):  
A.C. Vieira ◽  
J.C. Vieira ◽  
R.M. Guedes ◽  
A.T. Marques
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Polyglycolic Acid ◽  
Aliphatic Polyesters ◽  
First Order Kinetics ◽  
Chain Cleavage ◽  
Degradation Rates ◽  
Different Dimensions ◽  
Hydrolysis Of ◽  
Degradation Time

Aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polydioxone (PDO) and others, have been commonly used in biodegradable products. Hydrolytic and/or enzymatic chain cleavage of these materials leads to α-hydroxyacids, which, in most cases, are ultimately assimilated in human body or in a composting environment. However, each of these has some shortcomings, in terms of mechanical properties and degradation time, which restrict its applications. The combination of these materials, by copolymerization or blending, enables a range of mechanical properties and degradation rates. These are extremely promising approaches which can improve or tune the original properties of the polymers. A composite solution of several materials with different degradation rates also enables tuning the rate of degradation of a device and the mechanical properties. After immersion of an aliphatic polyester device, diffusion occurs very rapidly compared to hydrolysis. Therefore, it is usually considered that hydrolysis of ester bonds starts homogeneously and has traditionally been modelled according to a first order kinetics. In this experimental study, fibres of PLA-PCL, PGA-PCL, PDO and PGA, with two different dimensions, were characterized in terms of their degradation rate under three different environments (water, NaCl and PBS) at constant temperature (37°C). Weights and mechanical properties were measured after six different degradation stages. Stages durations were different depending on materials, according to the predicted degradation times. As other thermoplastics, they are viscoelastic materials. In this experimental study mechanical properties of fibres were compared at different strain rates.

Materials Selection and Scaffold Construction for Liver Tissue Engineering

2005 ◽  
Vol 475-479 ◽  
pp. 2391-2394 ◽  
Author(s):  
Qing Ling Feng
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Porous Scaffold ◽  
Poly Lactic Acid ◽  
Hepatic Tissue ◽  
Aliphatic Polyesters ◽  
Natural Materials ◽  
Liver Tissue Engineering ◽  
Design Selection ◽  
The One

To design the scaffold with suitable properties for the development of tissue engineered livers, materials design, selection and scaffold construct are three dispensable steps to be followed consequently. Firstly, some natural materials such as collagen, chitosan and alignate as well as some prevailing aliphatic polyester such as poly(lactic acid) (PLA), polyglycolide (PGA) and their copolymers poly(lactide-co-glycolide) (PLGA) are selected and characterized by hepatocyte culture. The experimental results reveal that the natural materials with excellent biocompatibility are not suitable as the scaffold alone because of the poor mechanical properties. At same time, aliphatic polyesters with good mechanical properties and biodegrade abilities are also proved inapplicable for hepatocytes for the lack of right cell recognition sites. Among our study scope, the hybrid materials such as collagen/chitosan or collagen/chitosan/heparin are the very promising candidates for hepatic tissue engineering scaffold. Secondly, two novel designs composed of collagen and PLGA, namely, the spindle porous scaffold with separated channels for transportation of nutrient, plasma and the one made by dewaxen-casting method are initiated respectively.

Influence of the Main-Chain Configuration on the Mechanical Properties of Linear Aliphatic Polyesters

2015 ◽  
Vol 48 (16) ◽  
pp. 5845-5854 ◽  
Author(s):  
Mark P. F. Pepels ◽  
Leon E. Govaert ◽  
Rob Duchateau
Keyword(s):  
Mechanical Properties ◽  
Main Chain ◽  
Aliphatic Polyesters ◽  
Chain Configuration

scholarly journals Molecular and Supramolecular Changes in Polybutylene Succinate (PBS) and Polybutylene Succinate Adipate (PBSA) Copolymer during Degradation in Various Environmental Conditions

2018 ◽  
Author(s):  
Michal Puchalski ◽  
Grzegorz Szparaga ◽  
Tadeusz Biela ◽  
Sławomir Sztajnowski ◽  
Agnieszka Gutowska ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Structural Changes ◽  
Physical And Mechanical Properties ◽  
Size Exclusion ◽  
X Ray Diffraction ◽  
Aliphatic Polyesters ◽  
Exclusion Chromatography ◽  
Polybutylene Succinate ◽  
Injection Molded ◽  
Multiangle Laser Light Scattering

In this paper, the influence of the various degradation conditions, on the molecular and supramolecular structure of polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA) copolymer during degradation time is described. Experiment was carried out by the use injection molded samples and normalized conditions of biodegradation in soil, composting and artificial weathering. Materials were studied by using size-exclusion chromatography (SEC) coupled with multiangle laser light scattering (MALLS) detection and wide-angle X-ray diffraction (WAXD). Additionally, the physical and mechanical properties of the samples were determined. The performed experiments clearly show difference impact of selected degradation condition on the macroscopic, supramolecular and molecular parameters of studied aliphatic polyesters. The structural changes in PBS and PBSA explain the observed changes in the physical and mechanical properties of the obtained injection molded samples.

Biobased long-chain aliphatic polyesters of 1,12-dodecanedioic acid with a variety of diols: Odd-even effect and mechanical properties

2019 ◽  
Vol 19 ◽  
pp. 450-458 ◽  
Author(s):  
Changfeng Zhou ◽  
Zhiyong Wei ◽  
Yang Yu ◽  
Shengnan Shao ◽  
Xuefei Leng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aliphatic Polyesters ◽  
Dodecanedioic Acid ◽  
Long Chain

The Thermal Stability and Mechanical Properties of Non-Segregating Blends of Polyimides with Copoly(Urethane-Imide)s

2020 ◽  
Vol 869 ◽  
pp. 280-295
Author(s):  
Andrei Didenko ◽  
Danila Kuznetcov ◽  
Gleb Vaganov ◽  
Valentina Smirnova ◽  
Elena Popova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Differential Scanning Calorimetry ◽  
Mechanical Analysis ◽  
Strength Properties ◽  
Relative Content ◽  
Scanning Calorimetry ◽  
Aliphatic Polyesters ◽  
Polymer Systems ◽  
Aromatic Polyimides

The series of compositions containing thermodynamically incompatible flexible blocks of aliphatic polyesters and rigid blocks of aromatic bis (urethane) imides in the volume of polymers was obtained on the basis of multiblock (segmented) poly (urethane-imides) and related aromatic polyimides. The series includes segmented poly (urethane-imides) with different relative content of flexible and rigid blocks, non-segregating mixtures of poly (urethane-imides) and thermoplastic partially crystalline polyimide, statistical copolymers of poly (urethane-imide) with imide, and non-segregating mixtures of statistical copolymers with thermoplastic polyimide. The derived polymer systems were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The deformation and strength properties of film samples are determined. It is shown that the properties of the studied polymers change as their content of imides blocks increases, and the transition from thermoplastic poly (urethane-imide) elastomers to thermoplastic polyimides is observed.

Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

1974 ◽  
Vol 32 ◽  
pp. 514-515
Author(s):  
S. Fujishiro
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Mechanical Processing ◽  
Ray Method ◽  
X Ray ◽  
Transmission Electron ◽  
Water Quench ◽  
Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

1983 ◽  
Vol 41 ◽  
pp. 220-221
Author(s):  
L.J. Chen ◽  
H.C. Cheng ◽  
J.R. Gong ◽  
J.G. Yang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Automobile Industry ◽  
High Strength ◽  
Weight Percent ◽  
Low Alloy Steels ◽  
Dual Phase ◽  
Resource Requirement ◽  
Alloy Steels ◽  
Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Electron Microscopic Observation of the Longitudinal Organization of Poly (p-Phenylene Terephthalamide) Fibers

1982 ◽  
Vol 40 ◽  
pp. 680-681
Author(s):  
Li Li-Sheng ◽  
L.F. Allard ◽  
W.C. Bigelow
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Microscopic Observation ◽  
Electron Microscopic Observation ◽  
Electron Microscopic ◽  
Aromatic Polyamides ◽  
Radial Arrangement ◽  
Scanning Electron ◽  
Better Than

The aromatic polyamides form a class of fibers having mechanical properties which are much better than those of aliphatic polyamides. Currently, the accepted morphology of these fibers as proposed by M.G. Dobb, et al. is a radial arrangement of pleated sheets, with the plane of the pleats parallel to the axis of the fiber. We have recently obtained evidence which supports a different morphology of this type of fiber, using ultramicrotomy and ion-thinning techniques to prepare specimens for transmission and scanning electron microscopy.

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