Papers by Keyword: Biodegradable

Abstract: In this study various compositions in the phosphate based glass (PBG) system of (50-x)P₂O₅-40Ca-(5+x)Na-5TiO₂ and (50-x)P₂O₅-40Ca-(5+x)Na-5Fe₂O₃, where x= 5 and 10 were investigated for glass transition temperature (T_g) via thermo mechanical analyser (TMA) and differential scanning calorimetry (DSC). The amorphous nature of the glasses was confirmed via XRD. The T_g measured via DSC was consistently higher by 19°C-29°C compared to TMA and was due to the thermal history and the heating rate of the samples. The T_g increased with increasing phosphate content in both glass systems. The T_g for Ti containing PBG was found to be in the range of 453°C-500°C whilst T_g for Fe containing PBG was in the range of 449°C-494°C. Consistently higher T_g for the Ti containing glass series compared to the Fe containing glasses may be attributed to the smaller ionic radius and therefore higher field strength of Ti⁴⁺.

Abstract: Mg-1.6 Gd alloy ingot were prepared by hot extrusion. The extruded alloy exhibits the recrystallised grain size and excellent mechanical properties. The aim of this study is to explore the microstructure and mechanical properties of extruded Mg-1.6 Gd to be used as implant. Extrusion was performed at temperatures of 400°C, 450 °C, 500°C and 550°C with a speed of 1mm/s and extrusion ratio of 30%. Tension and hardness testing were carried out on samples taken from extruded rod of Mg-Gd alloy. Microstructure observation revealed that all extruded alloy specimens constitued of finer grain size (~14 um) compared to that of the as-cast alloy (> 500 um) as the result of full recrystallization occured at 400 °C. The grain size increased larger with an increase temperature and the peak value is 25mm at temperature of 550 °C. Hardness of the alloy decreased as the extrusion temperature increased from 48.7 HV at 400 °C to 42 HV at 550 °C which is associated with the change in the grain size. Tensile strengths were not apparently affected by the temperature change, however, it was observed that the tensile and yield strengths dropped at 500 °C. Meanwhile, the elongation decreased with increasing temperature which reached 24 % at the lowest temperature. Detailed explaination of the relationship of microstructure and mechanical properties is discussed in this paper.

Abstract: The effect of thermoplastic starch (TPS) and banana fiber contents on thermal characteristics of linear low-density polyethylene (LLDPE) matrix were investigated. The measurements from differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA), proved the effectiveness of TPS and banana fiber in improving the blend degradation. On the other hand the LLDPE/TPS/banana fiber composites showed better thermal stability than the LLDPE/TPS blend, which is reflected to the LLDPE chains movement restriction. The incorporation of banana fiber into the LLDPE/TPS blends was found to interfere with the chains movement and resulting in more thermally stable and improving the blends stiffness.

Abstract: Due to ecological and sustainability constraints, in late years we see great achievements in green technology in the field of materials science. The development of high-performance biocomposites (made from natural resources) is increasing worldwide. The challenge in working with natural fiber reinforced composites is the large spectrum of possibilities for making them.Biocomposites properties are influenced by a number of variables, including the fiber type, environmental conditions (where the plant fibers are sourced), processing methods, and any modification of the fiber. It is well known that recently exists a large interest in the industrial applications of composites containing biofibers reinforced with biopolymers. The characteristics of reinforcing fibers used in biocomposites, including source, type, structure, composition, as well as mechanical properties, will be reviewed. The variety of biocomposite processing techniques as well as the factors (moisture content, fiber type and content, coupling agents and their influence on composites properties) affecting these processes will be discussed.Techniques for processing the natural fiber reinforced composites will be discussed based on thermoplastic matrices (compression molding, extrusion, injection molding, and thermoforming), and thermosets (resin transfermolding, sheet molding compound). Their influence on mechanical performance (tensile, flexural and impact properties) will be evaluated. Finally, the work will conclude with recent developments and future trends of biocomposites.

Abstract: Novel biodegradable cellulose-based hydrogels were synthesized using a non-toxic crosslinker, polyethylene glycol diglycidyl ether (PEGDE). The effects of the crosslinker concentration and the ratio of sodium carboxymethyl cellulose (CMC) to cellulose were investigated. The results indicate that decreasing the amount of PEGDE and increasing the CMC to cellulose ratio resulted in better swelling. The 9:1 CMC/cellulose hydrogel with incorporating 3g of PEGDE had a swelling ratio of 230g/g. The synthesized hydrogels exhibited less swelling in NaCl solution due to a decrease in the osmotic pressure between the interior of the hydrogel network and the external immersion medium.

Abstract: New biodegradable Fe-Zn alloys with different concentration of zinc were prepared by electroforming in this paper. The composition, phase and microstructure of the Fe-Zn alloys were investigated by EDX, XRD and SEM, respectively. The potentiodynamic polarization and static immersion test were used to evaluate the in vitro biodegradation properties of these alloys. The results revealed that the alloys consist of single-phase Fe-Zn solid solution and have a better degradation property than pure iron, which make it a potential material used for bioabsorbable endovascular stent.

Abstract: The need for structural materials in temporary implant applications has grown in the recent years; materials that provide short – term structural support and which can be reabsorbed into the body after healing are being sought. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg shows great promise as a potential biocompatible and biodegradable material in biomedical applications where it has gained the interest of researchers in the field. Biodegradable and bioabsorbable magnesium – based alloys provide a number of benefits over traditional permanent implants. There are however some disadvantages to the use of Mg alloys, one of the most critical being the release of hydrogen and alkalinization resulted from the corrosion of Mg. In connection to these drawbacks, a possible solution could be finding alloying elements which would contribute to the reduction of the corrosion rate in the human body. Studies show that a promising alloy for Mg, could be Calcium - a major component of the human bone and also an essential element in the chemical composition of cells. The present paper shall focus on the elaboration of Mg-Ca alloys, respectively Mg0,63Ca to Mg0,8 5 Ca, in the form of bars. These bars were obtained by cast in an inert atmosphere in the presence of argon, in order to be analyzed as biodegradable orthopedic implants. The structure of the alloy has been studied through SEM analyses, X-Ray diffraction, and EDAX to determine the chemical composition, as well as the distribution of elements in the structure. The main desiderate is finding an alloy which would have a minimum healing period postsurgery, pathophysiology and toxicology and a promising degradation behavior.

Abstract: Implants based on titanium alloys, stainless steel and cobalt –chromium have been the primary biomaterials used for load bearing applications and they have been remarkably successful throughout time, but on the long term, there appear a series of inconveniences regarding these metallic implants. Thus, there have been cases of aseptic osteolysis around the implant, with pain and high degree of loosening of the prosthesis which constitutes a limitation of the long term benefits of metallic implants. Therefore, researchers have found new materials for implants, more competitive and efficient. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg is an essential mineral for human metabolism and its deficiency has been linked to various pathological conditions. The main advantages of Mg alloys are its superior mechanical and biocorrosive properties and its biocompatibility. Mg is a very light-weight metal with a lower density than that of biocompatible Ti alloys, which is closer to that of the human bone. In the present paper we shall focus on presenting some biological testing studies of several Mg alloys from the system Mg-Ca, with different percentages of Ca. Three methods have been use for this: determining the ph at different sample incubation times in culture environment; citotoxicity tests made in vitro which: evaluate the contact toxicity by putting the samples in the buckets of cellular culture plates; evaluate the cellular proliferation at the surface of the tested materials by fluorescence microscopy and deflection microscopy; evaluation of toxicity by testing the effect of the extraction liquid resulting from the incubation of the material with testing cell specific culture environment.

Abstract: China has been the country which is suffering serious coastal erosion that primarily caused by the increase of hydrodynamic force and the unbalance between input and output sediment. Comparing with the traditional revetment, most of which were made of reinforced concrete, the ecological shoreline protection can prevent coastal erosion in an ecological method. In this article, a biodegradable coastline protection mat (BCP-mat) was proposed and different arrangement methods direct to various areas was presented to solve the problems such as high cost, complicated construction caused by existing ecological method. In the end, the existing technology problems and promotion difficulties was discussed in the perspective of design and management.

Abstract: Biodegradable polyurethane foam (PUF) was prepared by using tung oil and starch as the modifiers, they were mixed with polyether polyol and some other reaction auxiliary agents, and then reacted with toluene diisocyanate (TDI). The structure and thermal stability of products were analyzed based on SEM and TG, and the soil burial method was used to investigate the biodegradability of products. The results indicated that polyurethane foam modified by tung oil and starch has good thermal stability, good mechanical properties and good biodegradability. The degradation rate of PUF modified by 5: 2 of starch/ tung oil was 38% after 120 d.