Sharif Digital Repository

With the environmental concerns and scarce supply of the crude oil, a revival in the development of bio-based and compostable materials is coming. They are in general being called the ''green'' materials, among which poly(lactic acid) (PLA) got the most extensive attention due to its good combined properties, including the renewable feedstock, the compostability, and its good mechanical properties, especially the young's modulus and stiffness. PLA has found numerous applications. It is considered having the highest potential to replace some regular petroleum based plastics. However PLA has its own shortcomings, its brittleness, low heat distortion temperature and relatively high cost witch... 

In the recent years, the enhancing of utilization of polymeric materials, especially in packaging application, became the serious concern because of the problems of their recycling. One of efficient ways for solving this problem is usage of biodegradable polymers. Thermoplastic starch (TPS) is one the alternative materials which is produced in gelatinization process by plasticizers. However, using of TPS because of its low mechanical properties, poor processability and high water absorption is not applicable and it is necessary to improve that. One of the strategy in order to improving the TPS properties is blending with other polymers, such as polylactic acid (PLA) which the biodegradable... 

Polylactic acid (PLA) is a biocompatible polymer that could be used for biomedical applications. Carbon nanotubes (CNT) have excellent mechanical strength and modulus and also are electrically conductive. Inclusion of CNT in PLA could improve mechanical and electrical properties of PLA and find applications as biomaterials in biomedical engineering. The success of the resulted nanocomposites of PLA/CNT depends on uniform dispersion of CNT within PLA and good interfacial adhesion between the nanotubes and the matrix PLA. Chemical modification of CNT surface by grafting maleic anhydride has been reported. However, for biomedical applications chemical agents may prove harmful and should be... 

Polylactic acid (PLA) nanocomposite films reinforced with surface-modified carbon nanotube (CNT) particles were prepared by solution-phase methods. In order to enhance the flexibility of the film, and to improve nanoparticle dispersion throughout the final material, polyvinyl acetate (PVA) was also added to the polymeric backbone during the nanocomposite preparation process. Characteristics of the former nanocomposite films were investigated by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), mechanical testing, and electrical resistance measurement. In this study, our results showed that increasing... 

Composite film PLA/PVDF and nanocomposite films PLA/PVDF/MWCNT with a solution method by solvent Dimethyl formamide was prepared at 65◦c. poly vinylidene fluoride as matrix phase and poly lacticacid was used an amplifier. In the next sextion multiwalled carbon nanotubes were added to the PLA/PVDF composite.Scaning Electron microscope results, showed that the PLA/PVDF composite and PLA/PVDF/MWCNT nanocomposites, non porous structure and carbon nanotubes in the polymer matrix have been well dispersed. The impact of nanoparticles in the polymer matrix by X-Ray Diffraction and Differential Scaning Calorimetry was investigated. With differential scaning calorimeter (DSC) and stress strain test,... 

Nanodiamond (ND)/polylactic acid (PLA) nanocomposites have the potential for biomedical applications and bone tissue engineering. In this research, nanodiamond/poly lactic acid nanocomposites were prepared by mechanical mixing solution method and applying ultrasonication. Also, PLA-based nanofiber scaffold reinforced by nanodiamond were prepared by electrospinning methods. To find the optimum value of parameters to prepare this nanocomposite sample, the effect of nanofiller concentration, mixing rate and duration, the role of solute and ultrasonication, and solvent evaporation conditions were investigated and then it compared to the neat polylactic acid sample. By means of Fourier transform... 

There are so many problems in using of petroleum-based polymers such as their stability in the environment. According to the research carried out on this problem, one of the best ways to overcome this hardship is using of bio-based polymers. The most important bio-based polymer is polylactic acid. The very polymer enjoys the best mechanical properties but it is so expensive that make it impossible to afford. Therefore, in this project, a nano-composite structure of polylactic acid with thermoplastic starch reinforced with nano-particles was produced. After manufacturing, the process of mixture and the best percent for the very mixture for its use in packaging industry were investigated  

One of the great challenges of food industry is the lack of packing materials which can disperse active compositions properly for variety of applications; therefore an antioxidant/antibacterial release system of poly lactic acid in a specific time is a necessity for being used in food packing industry. Most of the researches have been done in the field of drug release system, yet numbers of researches done in the field of food industry are rare. Rate of antibacterial/antioxidant release from polymeric film is relatively fast also calculated based on Fick’s second law of diffusion; therefore primary poly lactic acid is modified by adding ameliorative agents such as poly ethylene glycol and... 

Nowadays, the use of processed conductive polymers for conducting matrix polymers, as well as improving other properties for planting in the body, is very common. In this project, the fabrication and identification of electrically conductive films and fibers from biocompatible poly lactic acid and conductive polyAniline polymer in the form of nano-fibers or nanoparticles was intended. These fibers and films have been made in form of a plate or tube then, have been used as biosensors. These polymeric prostheses should be sterilized before planting in human body. Gamma rays are the best sterilization methods and are used at low doses (25 kGy) to sterilize plastic medical supplies. On the other... 

Oxygen barrier properties of poly (lactic acid) (PLA) films were improved by blending it with hydrolyzed poly (vinyl acetate). Poly (vinyl acetate-co-vinyl alcohol) with vinyl alcohol contents of 0, 5, 10 and 15% was prepared using acid-catalyzed hydrolysis of poly (vinyl acetate). The Blend films of PLA/poly (VAc-co-VA) containing 0, 5, 10 and 15% of the copolymer with various degree of hydrolysis was prepared by solution-casting method. Effect of gamma irradiation on the films was examined by exposing them to radiation doses of 0, 20, 35 and 50 kGy. The films remained colorless and transparent after irradiation. Morphology of the samples characterized by optical microscopy displayed not... 

Poly (vinyl alcohol) (PVA) hydrogel is a biocompatible material, which has been widely applied in drug delivery applications. Microspheres, nanospheres, and other types of particle-based drug delivery vehicles have proven capacity for long-term release. There is growing interest to overcoming the inherent pharmacological limitations of hydrogels by formulating particulate systems into the hydrogel matrix to form new delivery platforms. We here describe a simple composite system based on poly (vinyl alcohol) (PVA) hydrogels containing entrapped drug-loaded poly (lactic acid) (PLA) microspheres for controlled delivery over extended period of time. Gamma-Irradiation and freeze-thawing was... 

In recent years along with time and cost intensive process of developing new and better drugs for diseases like cancer, scientists and researchers are attempting to develop novel drug delivery systems for already existing drugs.The purpose of these novel drug delivery systems such as nanogels is controlling drug release rate as well as delivery to a specific target tissue in order to reduce side effects. One of the most commonly used drugs for cancer treatment is Doxorubicin HCl, commercially known as Adricin. In this project biodegradable and biocompatible polymers PLA and PEG were used to synthesize nanocarriers for Adricin. These nanocarriers were then dispersed in an agar hydrogel. The... 

Fixation devices and implants are the most applied devices in orthopedic operation and dentistry. Interference screw is one of these devices that is made by biodegradable nanocomposite polymeric materials in this project. The purpose of this project is designing interference screw, applicable to body, and doing related tests since in vivo tests. For this purpose, hand injection molding, was designed to prepare screws in laboratory scale, first. For making samples, poly(D,L) lacticacid, nano hydroxyapatite as reinforce and polyethylene glycol as plasticizer were used. These samples were made by combination of solvent casting and melt processing methods. Adding nano hydroxyapatite and... 

Poly (Lacticacid) belongs to the family of aliphatic polyesters. PLA can be made from annually renewable resources to yield articles for use in either the industrial packaging field or the biocompatible /bioabsorbable medical device market. Production of PLA through polycondensation in an industrial way was the aim of this project. In order to have the appropriate reaction conditions a steel reactor was designed and constructed. Feasibilty of PLA production in the constructed reactor was investigated and the product was analyzed, using H-NMR and FT-IR spectrum analysis. The average molecular weight was measured by GPC and ubbelohde viscometery method. Studies have shown that oligomerization... 

Nanocomposites of PLA/Ag, PLA/PEG/Ag and PLA/PEG/Oleic acid were synthesized via chemical reduction of AgNO3.The formation of nano-silver particles (Ag-NPs) started in the aqueous phase (using NaBH4 as a reducing agent) followed by transfer of the silver nanoparticles into the organic phase (PLA solution in chloroform) due to the presence of van der waals interactions between the hydroxyl groups of the PLA and the particles charges surrounded in the surface of the Ag-NPs. The nanocomposites films were prepared by the solution casting method. The XRD patterns and UV-Vis spectra of the nanocomposites demonstrated face–centered cubic (fcc) silver crystals and spherical nanoparticles... 

Polylactic acid (PLA) is considered as a great option to be employed as 3D porous scaffold in tissue engineering applications owing to its excellent biocompatibility and processability. However, relatively weak mechanical properties, low degradation rate and inappropriate biodegradability limit its extensive usage. In order to overcome the mentioned challenges, micrometric magnesium (Mg) particles were incorporated into the PLA matrix by the fused deposition modeling (FDM) technique. The effects of various Mg contents (i.e., 2, 4, 6, 8 and 10 wt%) on the mechanical, thermal, structural, wettability, rheological, biodegradability characteristics and cellular behavior of the 3D porous PLA-Mg... 

In this work, magnetite (Fe3O4) nanoparticles with an average siz21.9nm
modified by oleic acid were prepared by the coprecipitation method, which can linked well with organic molecules because of the presence of C-O-C on their surface. Then magnetic poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) microspheres were prepared by the single emulsion solvent evaporation technology. The incorporation of magnetit nanoparticles and dox into the PLA matrix was confirmed by FTIR. XRD and VSM confirmed the existence of MNPs in the microspheres which maintained superparamagnetic behavior with a saturation magnetization of 50.69 emu/g.Electron microscopy SEM showed that the magnetic microspheres... 

One of the most important concerns in food industry is decreasing the contamination of food and increasing their shelf life. Antimicrobial/antioxidant packaging, an active packaging concept, can be considered an extremely challenging technology that could have a significant impact on shelf-life extension and food safety of meat and meat products. Due to harmfulness of chemical preservatives, their use has been limited and therefore natural antimicrobial/antioxidant agents have become more popular. Propolis is a natural resinous substance, with a high polyphenol content, produced by honeybees and characterized by antimicrobial, anti-inflammatory and antioxidant properties, which make it... 

The purpose of this project was to produce and examine the Poly(lactic acid)/poly(ethylene-co-vinyl acetate)/ nano-clay nanocomposite by solution casting that can be used for food packaging. In this study, it was observed that solvent evaporation at 4°C gives uniform films, without phase separation and free of voids, in a certain composition of polymers related to the rate of solvent evaporation.According to DMTA results Poly(lactic acid) and poly(ethylene-co-vinyl acetate) with 28% vinyl acetate, were compatible in less than 10% poly(ethylene-co-vinyl acetate) content in blend of them. Also, results of SEM tests showed that ethylene-co-vinyl acetate particle size in blends with 3 and 5...