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Poor Adhesion (poor + adhesion)

Distribution by Scientific Domains

Polymers and Materials Science	80%

Selected Abstracts

Primary Cell Adhesion on RGD-Functionalized and Covalently Crosslinked Thin Polyelectrolyte Multilayer Films,

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005
C. Picart
Abstract Polyelectrolyte multilayers (PEMs) are now widely used for biomedical applications. In this work, we investigated the primary osteoblast adhesion properties of PEMs of poly(L -lysine) (PLL), poly(L -glutamic acid) (PGA), poly(alginic acid) (Palg), and poly(galacturonic acid) (Pgal). In order to compensate for the poor adhesion of the as-synthesized films, two kinds of film modifications were achieved: a purely physical modification by film crosslinking, and a chemical modification by grafting a arginine,glycine,aspartic acid (RGD) peptide to PGA. Crosslinking was performed using a water-soluble carbodiimide in combination with N -hydroxysulfosuccinimide (sulfo-NHS) to induce amide formation. This reaction was followed by Fourier-transform IR spectroscopy. For film functionalization, a 15-amino-acid peptide was grafted to PGA and deposited as the top layer of the film. PLL/PGA, PLL/Palg, and PLL/Pgal films were crosslinked or functionalized. The films were tested for both short-term adhesion properties and long-term proliferation of primary osteoblasts. Whereas the effect of film crosslinking on short-term adhesion was moderate, it was much more important for the RGD-functionalized films. On the other hand, the long-term proliferation was the same or even higher for the crosslinked films as compared with the functionalized films. This effect was particularly enhanced for the PLL/Palg and PLL/Pgal films. Finally, we functionalized PLL/PGA that had been crosslinked prior to PGA-RGD deposition. These architectures exhibited even higher short-term adhesion and proliferation. These results clearly show the important role of the physical properties of the films, besides their chemical properties, for the modulation of primary cell-adhesion behavior. [source]

Effect of EPDM on Morphology, Mechanical Properties, Crystallization Behavior and Viscoelastic Properties of iPP+HDPE Blends

MACROMOLECULAR SYMPOSIA, Issue 1 2007
Nina Vranjes
Abstract Summary: Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE) with and without ethylene-propylene-diene (EPDM) terpolymer as compatibilizer were systematically investigated to determine the influence of the EPDM on blends properties. The morphology was studied by Scanning Electron Microscopy (SEM). Mechanical properties of investigated systems: tensile strength at break, elongation at break, yield stress and Izod impact strength were determined. Crystallization behavior was determined by Differential Scanning Calorimetry (DSC). Dynamic Mechanical Analysis (DMA) was used to determined the storage modulus (E,), loss modulus (E,), and loss tangent (tan ,). The PP+HDPE blend revealed poor adhesion between PP and HDPE phases. Finer morphology was obtained by EPDM addition in PP+HDPE blends and better interfacial adhesion. Addition of HDPE to PP decreased tensile strength at break, elongation and yield stress. Decrease of tensile strength and yield stress is faster with EPDM addition in PP+HDPE blends. Elongation at break and impact strength was significantly increased with EPDM addition. The addition of EPDM in PP+HDPE blends did not significantly change melting points of PP phase, while melting points of HDPE phase was slightly decreased in PP+HDPE+EPDM blends. The EPDM addition increased the percentage of crystallization (Xc) of PP in PP+HDPE blends. The increase of Xc of HDPE was found in the blend with HDPE as matrix. Dynamical mechanical analysis showed glass transitions of PP and HDPE phase, as well as the relaxation transitions of their crystalline phase. By addition of EPDM glass transitions (Tg) of HDPE and PP phases in PP+HDPE blends decreased. Storage modulus (E,) vs. temperatures (T) curves are in the region between E,/T curves of neat PP and HDPE. The decrease of E, values at 25,°C with EPDM addition in PP+HDPE blends is more pronounced. [source]

Mechanical properties of recycled polyethylene ecocomposites filled with natural organic fillers

POLYMER ENGINEERING & SCIENCE, Issue 9 2006
F.P. La Mantia
The use of natural organic fillers in addition to postconsumer recycled polymers is getting a growing interest during the last years; this is due to many advantages they can provide in terms of cost, aesthetic properties, environmental impact. In this work, several types of wood flour (differing each other with regard to production source and particle size) were added to a recycled polyethylene coming from films for greenhouses and the effects of filler type, content, and size were investigated. Investigation was then focused on the improvement of mechanical properties, through the addition of polar copolymers (ethylene- co -acrylic acid, ethylene-vinyl acetate) and a maleic anhydride-grafted-grafted polyethylene (Licocene® PE MA 4351 TP), in order to try to overcome the poor adhesion between polar filler particles and nonpolar polymer chains. Investigation was also based on SEM micrographs. An overall positive influence of these additives was observed. Polym. Eng. Sci. 46:1131,1139, 2006. © 2006 Society of Plastics Engineers. [source]

Processing, properties and stability of biodegradable composites based on Mater-Bi® and cellulose fibres

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003
D. Puglia
Abstract In this work, the behaviour of biocomposites obtained by the addition of flax cellulose pulp to Mater-Bi®, a commercial thermoplastic matrix based on starch, has been studied in comparison with traditional glass fibre composites. The composites were produced by compounding with a twin-screw extruder. Depending on the kind of fibre, reinforcement contents of 10,40% were obtained. The mechanical behaviour, both in normal conditions and after water absorption, was analysed. It has been noted that the addition of cellulose pulp increases the composite modulus more than glass fibre: in fact, a poor adhesion of the interface between the glass fibre and Mater-Bi® has been observed. The thermal degradation behaviour of the composite has been studied by thermogravimetric analysis (TGA). Different degradation peaks have been observed and the activation energies, related to the main peak, have been calculated. The addition of cellulose pulp produces better mechanical properties and higher thermal stability. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Designing a Three-dimensional Expanded Polytetrafluoroethylene,Poly(lactic-co-glycolic acid) Scaffold for Tissue Engineering

ARTIFICIAL ORGANS, Issue 4 2009
Hung-Jen Shao
Abstract:, The purpose of this study was to design a three-dimensional expanded polytetrafluoroethylene (ePTFE),poly(lactic-co-glycolic acid) (PLGA) scaffold for tissue engineering. To test the feasibility of this composite scaffold, a series of two-dimensional culture experiments were performed to investigate the behavior of anterior cruciate ligament (ACL) cells on the ePTFE and PLGA membranes. It was found PLGA provided a cell-favorable substrate for cell adhesion, migration, and growth, indicating PLGA is an ACL cell-conductive material. Conversely, poor adhesion and proliferation of ACL cells were observed on the ePTFE, even on the collagen-coated ePTFE. Therefore, the scaffold was not fabricated by coating PLGA on the ePTFE surface because it is difficult to coat anything on the extremely hydrophobic ePTFE surface. Instead, the ePTFE embedded in the PLGA matrix was prepared by immersing ePTFE scrim yarns into the PLGA solution, and then precipitating PLGA to form a three-dimensional construction with porous morphology. The role of ePTFE is regarded as a reinforcing constituent to improve the mechanical strength of porous PLGA matrix to provide early repair strength for tissue healing. However, porous PLGA matrix acts as a supportive environment for allowing cell adhesion, migration, and growth to guide the repair and regeneration of ligament tissue. To test this assumption, a preliminary animal experiment of rabbit ACL wound healing with this three-dimensional ePTFE,PLGA scaffold was performed. These results are very encouraging because such a new scaffold made of ePTFE scrim yarns embedded in PLGA may serve as ACL prostheses in the ligament tissue engineering. [source]