Search results for "Polyester"
showing 10 items of 221 documents
Preparation of three-layered porous PLA/PEG scaffold: relationship between morphology, mechanical behavior and cell permeability.
2015
Interface tissue engineering (ITE) is used to repair or regenerate interface living tissue such as for instance bone and cartilage. This kind of tissues present natural different properties from a biological and mechanical point of view. With the aim to imitating the natural gradient occurring in the bone-cartilage tissue, several technologies and methods have been proposed over recent years in order to develop polymeric functionally graded scaffolds (FGS). In this study three-layered scaffolds with a pore size gradient were developed by melt mixing polylactic acid (PLA) and two water-soluble porogen agents: sodium chloride (NaCl) and polyethylene glycol (PEG). Pore dimensions were controll…
Characterization and osteogenic activity of a silicatein/biosilica-coated chitosan-graft-polycaprolactone.
2014
Several attempts have been made in the past to fabricate hybrid materials that display the complementary properties of the polyester polycaprolactone (PCL) and the polysaccharide chitosan (CHS) for application in the field of bone regeneration and tissue engineering. However, such composites generally have no osteogenic activity per se. Here we report the synthesis of a chitosan-graft-polycaprolactone (CHS-g-PCL) and its subsequent characterization, including crystallinity, chemical structure and thermal stability. Upon surface-functionalization of CHS-g-PCL with osteogenic biosilica via the surface-immobilized enzyme silicatein, protein adsorption, surface morphology and wettability were a…
Ester-Ester Exchange Reactions of Aliphatic Polyesters
1979
Abstract The kinetics of ester-ester exchange reactions of poly(ethylene adipate) and poly(trimethylene adipate) at 312°C and in the absence of a solvent and catalysts has been reported previously. Independent investigations of the thermal degradation reactions of these polyesters under high vacuum have shown that pyrolysis already starts above 270°C. An ester-ester exchange mechanism via a reversible thermal degradation reaction is proposed.
The Effect of Calcium Carbonate on the Photo-Oxidative Behavior of Poly(butylene adipate-co-terephthalate)
2020
The aim of this work is to evaluate the influence of nanosized CaCO3 on the photo-oxidation of poly(butylene adipate-co-terephthalate) (PBAT)-based nanocomposites. The PBAT/CaCO3 nanocomposites are prepared by using a corotating twin-screw extruder with 0, 2, and 5 wt% of CaCO3. The films are obtained by film blowing process. Specimens of the nanocomposites and that of the pure polymer are subjected to accelerated aging with a cycle of 8 h of light at a temperature of 55 °C followed by 4 h condensation at 45 °C to evaluate the effects of the CaCO3 addition on the photo-oxidation of PBAT. The results indicate that the modulus and tensile strength of the nanocomposites are increased significa…
Mechanical properties of the nanometer scale pre-crystalline order of a poly (ethylene terepthalate) / poly (ethylene naphthalene) blend
2006
A previous study carried out on PET has shown that this polymer undergoes a continuous structural modification over a wide cooling rate interval when solidified from the melt[1] assuming a semi-crystalline structure below 2 K s 1 and a completely amorphous one above 100 K s 1. Most important was the existence of a state of intermediate order between the above cooling rates which was evidenced by the absence of crystalline reflections in the WAXS patterns and the occurrence of SAXS maxima[2] and exothermic peak areas (DSC) in the cooling rate range above 2 K s 1. Microhardness (MH) measurements revealed that this phase affects the mechanical properties[3] plausible if one thinks of crystalli…
Blend scaffolds with polyaspartamide/polyester structure fabricated via TIPS and their RGDC functionalization to promote osteoblast adhesion and prol…
2019
Target of this work was to prepare a RGDC functionalized hybrid biomaterial via TIPS technique to achieve a more efficient control of osteoblast adhesion and diffusion on the three-dimensional (3D) scaffolds. Starting from a crystalline poly(l-lactic acid) (PLLA) and an amorphous alpha,beta-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-d,l-aspartamide-graft-polylactic acid (PHEA-EDA-g-PLA) copolymer, blend scaffolds were characterized by an appropriate porosity and pore interconnection. The PHEA-EDA-PLA interpenetration with PLLA improved hydrolytic susceptibility of hybrid scaffolds. The presence of free amino groups on scaffolds allowed to tether the cyclic RGD peptide (RGDC) via Michael…
Core-shell PLA/Kef hybrid scaffolds for skin tissue engineering applications prepared by direct kefiran coating on PLA electrospun fibers optimized v…
2021
Abstract Over the recent years, there is a growing interest in electrospun hybrid scaffolds composed of synthetic and natural polymers that can support cell attachment and proliferation. In this work, the physical and biological properties of polylactic acid (PLA) electrospun mats coated with kefiran (Kef) were evaluated. Gravimetric, spectroscopic (FTIR-ATR) and morphological investigations via scanning electron microscopy confirmed the effective formation of a thin kefiran layer wrapped on the PLA fibers with an easy-tunable thickness. Air plasma pre-treatment carried out on PLA (P-PLA) affected both the morphology and the crystallinity of Kef coating as confirmed by differential scanning…
Effect of hydroxyapatite concentration and size on morpho-mechanical properties of PLA-based randomly oriented and aligned electrospun nanofibrous ma…
2019
The growing demand for nanofibrous biocomposites able to provide peculiar properties requires systematic investigations of processing-structure-property relationships. Understanding the morpho-mechanical properties of an electrospun scaffold as a function of the filler features and mat microstructure can aid in designing these systems. In this work, the reinforcing effect of micrometric and nanometric hydroxyapatite particles in polylactic acid-based electrospun scaffold presenting random and aligned fibers orientation, was evaluated. The particles incorporation was investigated trough Fourier transform infrared spectroscopy in attenuated total reflectance. The morphology of the nanofibers …
The solidification behavior of a PBT/PET blend over a wide range of cooling rate
2009
In recent years, much attention has been paid to the development of high-performance polyester blends, among which blends of polybutylene terephthalate/polyethylene terephthalate (PBT/PET) are expected to exhibit remarkable properties as far as their crystallization behavior is concerned. Through trial and error, appropriate commercial compositions have been chosen which could not be otherwise explained by a suitable interpretation of the mechanisms determining their solidification behavior. The solidification behavior of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a continuous cooling transformation (CCT) procedure developed previously, aiming …
Influence of small amounts of polyvinylchloride on the recycling of polyethyleneterephthalate
1999
Abstract Polyethylene terephthalate (PET), and polyvinyl chloride (PVC), are commonly encountered in plastics stream coming from separate collections of plastic bottles. The presence of PVC in the recycled PET is very dangerous because of the chain scission provoked by the hydrogen chloride evolved from the macromolecules during degradation of PVC. Recycled PET must be free of PVC; contents of PVC as little as 100 ppm can induce degradation and discoloration of the polyester. PET, in its turn, is degraded when the processing is carried out in the presence of water. In previous work, however, the degradation of PET was eliminated and rather an increase of the molecular weight has been measur…