Bio-material polylactic acid/poly(butylene adipate-co-terephthalate) blend developed for extrusion- based additive manufacturing

Bio-material polylactic acid and poly(butylene adipate-co-terephthalate) were blended to achieve increased ductility of the blend. Cloisite was added to improve the stiffness of the blend. The blends were made into filament suitable for extrusion-based additive manufacturing. Melt flow index of the filament and mechanical properties of the printed bars were tested. Preliminary results showed that the melt flow index increases significantly with cloisite and the modulus of polylactic acid/poly(butylene adipate-co-terephthalate) improved slightly. The notched impact strength of the blend increased with increasing content of cloisite, and it increased significantly after annealing, especially for blends without cloisite

Mechanical evaluation of polylactic acid (PLA) with nominal Hydroxyapatite filler for use in biomedical implants

Abstract only availableAn active area of research in the biomedical implant field is poly lactic acid (PLA). Polylactic acid is very interesting material for this field because it is a biocompatible and biodegradable material. One downside to using Polylactic acid PLA in biomedical implants is that it mechanical strength is much lower than that of its metal counterparts. However polylactic acid's many material attributes such as being biocompatibility and biodegradability make it a very promising and useful material if the mechanical properties were increased. In attempt to increase the bending strength of the Polylactic acid a Hydroxappatite filler was used. A mold was fabricated and samples were made using the heating press method. The samples were then test under three point bending to determines there bending strength using ASTM standard D5023-07. Pol lactic acid (PLA) was tested ranging from zero percent Hydroxyappattie filler to five percent Hydroxyappatite filler. Pure polylactic acid PLA was used as a base for comparisons. From these test to date the polylactic acid has shown a significant improvement in bending strength. This is a very promising result for polylactic acid's future in the biomedical field. Furthermore if it can be demonstrate that similar increases in bending strength in our polylactic acid samples can be demonstrated in actual bone screws or plates the increase in mechanical properties would have numerous implications for poly lactic acid in the biomedical field.MU Undergraduate Research Scholars Progra

Study on flame retardant properties of poly(lactic acid) fibre fabrics

Polylactic acid  and its blended yarns with various fibres have been converted in to woven fabrics. These fabric samples have been scoured and then tested for mechanical and flame retardant properties. The results indicate that the high alkaline scouring severely damages polylactic acid fibre. Therefore, mild alkaline scouring is done for further studies. The scoured fabric samples are tested for various flame retardant properties and compared with polyester blended fabrics. Results indicate that polylactic acid fibre is not suitable for upholstery, apparel and work wear in terms of flame retardant properties

Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration

The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre absorbed with the growth factor. nHA–PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA–PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules

Crystallinity and impact strength improvement of wood-polylactic acid biocomposites produced by rotational and compression molding

Polylactic acid is one of the most used biopolymers due to its overall properties and biodegradability. Nevertheless, polylactic acid  has important drawbacks such as brittleness, low thermal stability, and higher cost than most commodity polymers. In order to overcome those disadvantages without compromising biodegradability, the addition of wood particles and thermal annealing on the crystallinity and impact strength of wood-polylactic acid  biocomposites were studied. The samples were prepared by compression and rotational molding using two different wood particles: white ash and tzalam. The results showed that thermal annealing at 100 °C, 40 minutes, increased the crystallinity up to 60 % and also improved the thermal stability of polylactic acid  and its biocomposites as determined via dynamic mechanical analysis. The specimens not exposed to thermal annealing exhibited important storage modulus loss above 60 °C, which mostly disappeared with the thermal treatment. Furthermore, the impact strength was substantially increased by the thermal treatment. Additionally, accelerated weathering tests showed that the thermally annealed samples had better dimensional stability growing their potential applications over a wider range of conditions

Kinetics and the Theoretical Aspects of Drug Release from PLA/HAp Thin Films

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The theory of dissolution kinetics of gentamicin from polylactic acid-hydroxyapatite thin film composites is spotlighted with the combination of diffusion and polymer degradation modeling. The use of various mathematical models, characterizing diffusion, dissolution or/and erosion prevalence as well as a mix of dissolution-diffusion rate processes were employed in order to compare theory with experimental data. A number of factors influence the release kinetics of gentamicin from medical drug release systems and devices. It is difficult to have a single mathematical model that takes all these factors into account. It is shown that the degradation of the polymer matrix plays the biggest role in the release kinetics of polymer-ceramics thin film composites. It was also observed that multistage drug release form these devices depends also on the degradation kinetics of the polymer matrix. The effect of pH and device sizes were not studied but could also be of interest in future studies

Biodegradable Polylactic Acid (PLA) Microstructures for Scaffold Applications

In this research, we present a simple and cost effective soft lithographic process to fabricate PLA scaffolds for tissue engineering. In which, the negative photoresist JSR THB-120N was spun on a glass subtract followed by conventional UV lithographic processes to fabricate the master to cast the PDMS elastomeric mold. A thin poly(vinyl alcohol) (PVA) layer was used as a mode release such that the PLA scaffold can be easily peeled off. The PLA precursor solution was then cast onto the PDMS mold to form the PLA microstructures. After evaporating the solvent, the PLA microstructures can be easily peeled off from the PDMS mold. Experimental results show that the desired microvessels scaffold can be successfully transferred to the biodegradable polymer PLA.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Modification of biodegradable polyesters with inorganic fillers

In attempts to address the growing need of materials with controlled degradation characteristics and good mechanical properties for tissue engineering applications, composites based on biodegradable polymers and a potentially bioactive novel inorganic synthetic filler were produced and characterized. Composites were produced by solution mixing of a commercial polylactic acid, as well as a biodegradable thermoplastic polyester based on butylene adipate/succinate, with synthetic magnesium/aluminum carbonate minerals, known as hydrotalcites. Two types of hydrotalcites, at 30 wto/o filler level, were used: surface coated and uncoated. Composites were also melt-mixed in a twin-screw extruder for comparison. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Melt Rheology were used to characterize the unfilled polymers and their composites. Results of long-term degradation data in vitro in a PBS solution are also presented. The polylactic acid composites showed significant differences compared to the unfilled polymers and the copolyester composites. The copolyester composites showed only slight thermal and hydrolytic short and long-term degradation. By contrast, hydrotalcites appear to promote in all cases degradation of the matrix in the polylactic acid composites. During the course of long-term degradation of the polylactic acid and its composites, Elemental Analysis for released Mg and Al ions was performed, as well as measurement of pH changes. Scanning Electron Microscopy was also used to study morphological changes of the composites. Further investigation is needed involving degradation experiments in vivo for the most promising polylactic acid/hydrotalcite composites

Production, by co-grinding in a media mill, of porous biodegradable polylactic acid-apatite composite materials for bone tissue engineering

This paper presents the results of a study of the production of porous biodegradable composite materials by co-grinding, followed by scaffolding. Dry powders of polylactic acid and nanocrystalline carbonated apatite, analogous to bone mineral were co-ground in a tumbling ball mill in order to disperse the mineral filler within the polymer. Porous scaffolds were then made by hot moulding the mixture of the two components along with a pore-forming agent which was subsequently eliminated by washing. The mechanical resistance of the scaffolds was evaluated in order to determine the best operating conditions to produce implants offering optimised properties for use as bone substitutes. It was shown that 30 wt.% of filler and 70 wt.% of pore-forming agent produce scaffolds which are sufficiently porous and resistan