Síntese de poliuretanos modificados por óleo de mamona empregados em materiais energéticos

The aim of this work was to synthesize a polyurethane polymer matrix using castor oil as a polymer chain modifier, whose characteristics can be adjusted for use as a binder in the manufacture of energetic materials such as propellant and pyrotechnics for aerospace use. We attempted the partial substitution of hydroxyl-terminated polybutadiene (HTPB), a pre-polymer commonly used as a starting polyol in obtaining energetic matrix composites. Thermoanalytical techniques were employed to characterize the material based on castor oil and the unmodified HTPB. The results showed similar behaviors, confirming the possibility of their use as polymer matrix composites through the proposed adaptations.

Acúmulo de cargas elétricas em propelente sólido compósito com matriz de polibutadieno líquido hidroxilado

Composite solid propellants prepared with HTPB prepolymer - Hydroxyl Terminated Polybutadiene, AP - Ammonium Perchlorate as oxidizer and aluminum particles as an additive metal, have characteristics of high electrical resistivity. The loading process of the polymer matrix did not obtain homogeneity, resulting in clusters, mainly of metal particles. The effect of clustering in the composite was studied and observed experimentally, and this effect was one of the factors explaining the phenomenon of electrical charging of the composite. This electrical potential, when discharged abruptly, can generate an electric spark with sufficient energy for sustained ignition of a solid rocket motor.

Desenvolvimento de tecnologia de pré-polímeros na síntese de poliuretanos empregados em combustíveis sólidos

The aim of this work was to synthesize a polyurethane polymer matrix using polyols as a raw material to obtain a binder such as the hydroxyl terminated polybutadiene (HTPB) pre-polymer in energetic material formulation. The soybean-based polyol was the best starting raw material for producing a binder for solid fuel formulation in rocket motor applications. Characterization of the obtained soybean-based polyurethane binder was carried out by employing FT-IR analysis and thermo analytical techniques that showed similar HTPB binder thermo decomposition behaviors, confirming their potential for use as polymer matrix composites.

HYDROLYTIC DEGRADATION BEHAVIOR OF PLLA NANOCOMPOSITES REINFORCED WITH MODIFIED CELLULOSE NANOCRYSTALS

Bionanocomposites derived from poly(L-Lactide) (PLLA) were reinforced with chemically modified cellulose nanocrystals (m-CNCs). The effects of these modified cellulose nanoparticles on the mechanical and hydrolytic degradation behavior of polylactide were studied. The m-CNCs were prepared by a method in which hydrolysis of cellulose chains is performed simultaneously with the esterification of hydroxyl groups to produce modified nanocrystals with ester groups. FTIR, elemental analysis, TEM, XRD and contact angle measurements were used to confirm and characterize the chemical modifications of the m-CNCs. These bionanocomposites gave considerably better mechanical properties than neat PLLA based on an approximately 100% increase in tensile strength. Due to the hydrophobic properties of the esterified nanocrystals incorporated into a polymer matrix, it was also demonstrated that a small amount of m-CNCs could lead to a remarkable decrease in the hydrolytic degradation rate of the biopolymer. In addition, the m-CNCs considerably delay the degradation of the nanocomposite by providing a physical barrier that prevents the permeation of water, which thus hinders the overall absorption of water into the matrix. The results obtained in this study show the nanocrystals can be used to reinforce polylactides and fine-tune their degradation rates in moist or physiological environments.

Experimental Studies on Non-Metallic Composite Bone Implants With a Special Reference to Staphylococcal Biofilm Infection

Non-metallic implants made of bioresorbable or biostable synthetic polymers are attractive options in many surgical procedures, ranging from bioresorbable suture anchors of arthroscopic surgery to reconstructive skull implants made of biostable fiber-reinforced composites. Among other benefits, non-metallic implants produce less interference in imaging. Bioresorbable polymer implants may be true multifunctional, serving as osteoconductive scaffolds and as matrices for simultaneous delivery of bone enhancement agents. As a major advantage for loading conditions, mechanical properties of biostable fiber-reinforced composites can be matched with those of the bone. Unsolved problems of these biomaterials are related to the risk of staphylococcal biofilm infections and to the low osteoconductivity of contemporary bioresorbable composite implants. This thesis was focused on the research and development of a multifunctional implant model with enhanced osteoconductivity and low susceptibility to infection. In addition, the experimental models for assessment, diagnostics and prophylaxis of biomaterial-related infections were established. The first experiment (Study I) established an in vitro method for simultaneous evaluation of calcium phosphate and biofilm formation on bisphenol-Aglycidyldimethacrylate and triethylenglycoldimethacrylate (BisGMA-TEGDMA) thermosets with different content of bioactive glass 45S5. The second experiment (Study II) showed no significant difference in osteointegration of nanostructured and microsized polylactide-co-glycolide/β-tricalcium phosphate (PLGA /β-TCP) composites in a minipig model. The third experiment (Study III) demonstrated that positron emission tomography (PET) imaging with the novel 68Ga labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) CD33 related sialic-acid immunoglobulin like lectins (Siglec-9) tracer was able to detect inflammatory response to S. epidermidis and S. aureus peri-implant infections in an intraosseous polytetrafluoroethylene catheter model. In the fourth experiment (Study IV), BisGMATEGDMA thermosets coated with lactose-modified chitosan (Chitlac) and silver nanoparticles exhibited antibacterial activity against S. aureus and P. aeruginosa strains in an in vitro biofilm model and showed in vivo biocompatibility in a minipig model. In the last experiment (Study V), a selective androgen modulator (SARM) released from a poly(lactide)-co-ε-caprolactone (PLCL) polymer matrix failed to produce a dose-dependent enhancement of peri-implant osteogenesis in a bone marrow ablation model.

Utilization of recycled mineral wool as filler in wood plastic composites

The impact of a recycled mineral wool filler on the various properties of wood plastic composites was studied and the critical factors affecting the formation of the properties were determined. An estimation of the volume of mineral wool fiber waste generated in the European Union between the years 2010-2020 was presented. Furthermore, the effect of fiber pre-treatment on the properties of the wood plastic composites were studied, and the environmental performance of a wood plastic composite containing recycled mineral fibers was assessed. The results showed that the volumes of construction and demolition waste and new mineral wool produced in the European Union are growing annually, and therefore also the volumes of recycled mineral wool waste generated are increasing. The study showed that the addition of recycled mineral wool into composites can enhance some of the mechanical properties and increase the moisture resistance properties of the composites notably. Recycled mineral wool as a filler in wood plastic composites can also improve the fire resistance properties of composites, but it does not protect the polymer matrix from pyrolysis. Fiber pre-treatment with silane solution improved some of the mechanical properties, but generally the use of maleated polypropylene as the coupling agent led to better mechanical and moisture resistance properties. The environmental performance of recycled mineral wool as the filler in wood plastic composites was superior compared to glass fibers. According to the findings, recycled mineral wool fibers can provide a technically and environmentally viable alternative to the traditional inorganic filler materials used in wood plastic composites.

Optimisation de la concentration en électrolytes au sein des matrices à base de HASCA pour la libération prolongée

Le sel sodique du carboxyméthylamidon à haute teneur en amylose, HASCA (Amylose 60%-amylopectine 40%), est un polymère hydrophile ionique utilisé pour obtenir des comprimés matriciels à libération prolongée. Il est caractérisé par la formation d'un hydrogel lors de la mise en contact avec le milieu de dissolution. La libération du principe actif (PA) à travers ce polymère est principalement contrôlée par la diffusion fickienne et la relaxation du réseau polymérique. De plus, la solubilité du PA est un facteur qui permet de moduler la libération, cependant, la solubilité d’un médicament dépend de la forme utilisée et du pH. Les bases ou les acides libres présentent une solubilité moins élevée que leurs sels. Nous proposons d’étudier l’effet d’une combinaison entre le sel et la forme acide ou le sel et la forme alcaline dans le même comprimé matriciel d’HASCA. Comme objectif de ce travail, nous étudions l’influence de la nature du polymère sur le profil de libération de PA dans un milieu aqueux en gradient de pH à cause de la nature des matrices à base d’HASCA caractérisées par la présence de groupement carboxyliques, ionisés ou non selon l’acidité du milieu de dissolution. Nous étudions également l’influence de la nature du PA (base libre ou son sel vs acide libre ou son sel) sur le profil de libération, ceci en sélectionnant des PAs modèles représentatifs de chaque catégorie. L’influence de changement de proportions entre la forme libre (acide ou base) et son sel sur le profil de libération est aussi investiguée. Pour ce, des comprimés à base de HASCA avec des proportions différentes de, soit le naproxène acide et le naproxène de sodium (PA acide et son sel), soit la tétracycline et le chlorhydrate de tétracycline (PA alcalin et son sel) ont été utilisés. Ceux-ci sont évalués lors des tests de dissolution dans un milieu simulant le milieu gastro-intestinal, selon les normes de l’USP (spectrophotométrie UV). Nous avons également menés des études de vitesse de dissolution intrinsèque sur les PAs purs, afin de déterminer leur solubilité et vitesse de libération dans les même pH de dissolution étudiés. Nous avons réussit d’obtenir des comprimés matriciels à base de HASCA convenables à être administrés une fois par jour en utilisant une combinaison du naproxène acide et son sel comme PA. Tandis que les résultats ont montré qu’en utilisant la tétracycline et son sel, les temps de libération étaient trop élevés pour permettre la réalisation d’une formulation convenable pour une administration quotidienne unique

PET-SWNT nanocomposites through ultrasound assisted dissolution-evaporation

Poly(ethylene terephthalate) (PET) based nanocomposites have been prepared with single walled carbon nanotubes (SWNTs) through an ultrasound assisted dissolution-evaporation method. Differential scanning calorimetry studies showed that SWNTs nucleate crystallization in PET at weight fractions as low as 0.3%, as the nanocomposite melt crystallized during cooling at temperature 24 °C higher than neat PET of identical molecular weight. Isothermal crystallization studies also revealed that SWNTs significantly accelerate the crystallization process. Mechanical properties of the PETSWNT nanocomposites improved as compared to neat PET indicating the effective reinforcement provided by nanotubes in the polymer matrix. Electrical conductivity measurements on the nanocomposite films showed that SWNTs at concentrations exceeding 1 wt% in the PET matrix result in electrical percolation. Comparison of crystallization, conductivity and transmission electron microscopy studies revealed that ultrasound assisted dissolution-evaporation method enables more effective dispersion of SWNTs in the PET matrix as compared to the melt compounding method

Modification of Polypropylene and Polystyrene Using Nanosilica

The present work focuses on the modification of the commonly used thermoplastics, polypropylene and polystyrene using nanosilica preparcd from a cheap source of sodium silicate. Melt compounding technique has been used for nanocomposite preparation as it is simple and suited to injection moulding. Nanosilica in a polymer matrix provide significant enhancement in strength, stiffness and impact strength. Incorporation of silica particles in a polymer also improves its thennal stability. To achieve better dispersion of fillers in polymer matrices the mixing was done at different shear rates. The enhancement in material properties indicates that at higher shear rates there is greater interaction between particles and the matrix and it depends on filler concentration and type of polymer used. N anosilica is a useful filler in thennoplastic polymers and has been applied in automotive applications, electronic appliances and consumer goods.This thesis is divided into six chapters. General introduction to the topic is described in chapter 1. Salient features of polymer nanocomposites, their synthesis, properties and applications are presented. A review of relevant literature and the scope and objectives are also mentioned in this chapter.The materials used and the vanous experimental method and techniques employed in the study are described in chapter 2. Preparation of nanocomposites by melt blending using Thenno Haake Rheocord, preparation of samples, evaluation of mechanical and thennal properties using UTM, Impact testing and characterization using DMA, TGA and DSC and morphology by SEM are described.The preparation of nanosilica from a laboratory scale to a pilot plant scale is described in chapter 3. Generation of surface modified silica, evaluation of kinetic parameters of the synthesis reaction, scale up of the reactor and modeling of the reactor are also dealt with in this chapter.The modification of the commodity thennoplastic, Polypropylene using nanosilica is described in chapter 4. Preparation of PP/silica nanocomposites, evaluation of mechanical properties, thermal and crystallization characteristics, water absorption and ageing resistance studies are also presented.The modification of Polystyrene using synthesized nanosilica IS described in chapter 5. The method of preparation of PS/silica nanocomposites, evaluation of mechanical properties (static and dynamic), thermal properties melt flow characteristics using Haake Rheocord, water absorption and ageing resistance of these nanocomposites are studied.

Studies on the structural, electrical and magnetic properties of composites based on spinel ferrites

This thesis mainly deals with the preparation and studies on magnetic composites based on spinel ferrites prepared both chemically and mechanically. Rubber ferrite composites (RFC) are chosen because of their mouldability and flexibility and the ease with which the dielectric and magnetic properties can be manipulated to make them as useful devices. Natural rubber is chosen as the Matrix because of its local availability and possible value addition. Moreover, NR represents a typical unsaturated nonpolar matrix. The work can be thought of as two parts. Part l concentrates on the preparation and characterization of nanocomposites based on y-Fe203. Part 2 deals with the preparation and characterization of RFCs containing Nickel zinc ferrit In the present study magnetic nanocomposites have been prepared by ionexchange method and the preparation conditions have been optimized. The insitu incorporation of the magnetic component is carried out chemically. This method is selected as it is the easiest and simplest method for preparation of nanocomposite. Nanocomposite samples thus prepared were studied using VSM, Mossbauer spectroscopy, Iron content estimation, and ESR spectroscopy. For the preparation of RFCs, the filler material namely nickel zinc ferrite having the general formula Ni)_xZnxFez04, where x varies from 0 to 1 in steps of 0.2 have been prepared by the conventional ceramic techniques. The system of Nil_xZn"Fe204 is chosen because of their excellent high frequency characteristics. After characterization they are incorporated into the polymer matrix of natural rubber by mechanical method. The incorporation is done according to a specific recipe and for various Loadings of magnetic fillers and also for all compositions. The cure characteristics, magnetic properties and dielectric properties of these composites are evaluated. The ac electrical conductivity of both ceramic nickel zinc ferrites and rubber ferrite composites are also calculated using a simple relation. The results are correlated.

Ethylene-Propylene-Diene Terpolymer/Hexafluoropropylene-Vinylidinefluoride Elastomeric Composites: Thermal, Mechanical and Microwave Properties

In the present study, an attempt has been made to prepare composites by incorporating expanded graphite fillers in insulating elastomer matrices and to study its DC electrical conductivity, dielectric properties and electromagnetic shielding characteristics, in addition to evaluating the mechanical properties. Recently, electronic devices and components have been rapidly developing and advancing. Thus, with increased usage of electronic devices, electromagnetic waves generated by electronic systems can potentially create serious problems such as malfunctions of medical apparatus and industry robots and can even cause harm to the human body. Therefore, in this work the applicable utility of the prepared composites as electromagnetic interference (EMI) shielding material are also investigated. The dissertation includes nine chapters

Effect of cycling on the magnetization of ion exchanged magnetic nanocomposite based on polystyrene

Magnetic nanocomposites containing iron oxide particles embedded in a polymer matrix have been synthesized using the method of ion exchange. They have been characterized by using low temperature and room temperature magnetic measurements and Mo¨ ssbauer spectroscopy. The iron content in these samples has also been determined. The results have been analysed and explained. The physical and chemical properties of these nanocomposite materials are different from those of the bulk. Some of the unique properties of these materials find application in information storage, color imaging, ferrofluids and magnetic refrigeration

Low temperature Mössbauer studies on magnetic nanocomposites

Nanocomposites with magnetic components possessing nanometric dimensions, lying in the range 1–10 nm, are found to be exhibiting superior physical properties with respect to their coarser sized counterparts. Magnetic nanocomposites based on gamma iron oxide embedded in a polymer matrix have been prepared and characterized. The behaviour of these samples at low temperatures have been studied using Mössbauer spectroscopy. Mössbauer studies indicate that the composites consist of very fine particles of g-Fe2O3 of which some amount exists in the superparamagnetic phase. The cycling of the preparative conditions were found to increase the amount of g-Fe2O3 in the matrix

A microwave absorber based on strontium ferrite–carbon black–nitrile rubber for S and X-band applications

Flexible and thin single layer microwave absorbers based on strontium ferrite–carbon black–nitrile rubber composites have been fabricated employing a specific recipe and their reflection loss characteristics were studied in the S (2–4 GHz) and X-bands (8–12 GHz). The incorporation of carbon black not only reinforces the rubber by improving the mechanical properties of the composite but also modifies the dielectric permittivity of the composite. Strontium ferrite when impregnated into a rubber matrix imparts the required magnetic permeability to the composite. The combination of strontium ferrite and carbon black can then be employed to tune the microwave absorption characteristics of the resulting composite. The complex dielectric permittivity and permeability were measured by employing a cavity perturbation technique. The microwave absorption characteristics of composites were modelled in that an electromagnetic wave incident normally on the metal terminated single layer absorber. The influence of filler volume fraction, frequency, absorber thickness on the bandwidth of absorption are discussed and correlated

Modification of Polypropylene/High Density Polyethylene Blend Using Nanokaolinite Clay and E-Glass Fibre: Preparation, Characterization and Micromechanical Modelling

Upgrading two widely used standard plastics, polypropylene (PP) and high density polyethylene (HDPE), and generating a variety of useful engineering materials based on these blends have been the main objective of this study. Upgradation was effected by using nanomodifiers and/or fibrous modifiers. PP and HDPE were selected for modification due to their attractive inherent properties and wide spectrum of use. Blending is the engineered method of producing new materials with tailor made properties. It has the advantages of both the materials. PP has high tensile and flexural strength and the HDPE acts as an impact modifier in the resultant blend. Hence an optimized blend of PP and HDPE was selected as the matrix material for upgradation. Nanokaolinite clay and E-glass fibre were chosen for modifying PP/HDPE blend. As the first stage of the work, the mechanical, thermal, morphological, rheological, dynamic mechanical and crystallization characteristics of the polymer nanocomposites prepared with PP/HDPE blend and different surface modified nanokaolinite clay were analyzed. As the second stage of the work, the effect of simultaneous inclusion of nanokaolinite clay (both N100A and N100) and short glass fibres are investigated. The presence of nanofiller has increased the properties of hybrid composites to a greater extent than micro composites. As the last stage, micromechanical modeling of both nano and hybrid A composite is carried out to analyze the behavior of the composite under load bearing conditions. These theoretical analyses indicate that the polymer-nanoclay interfacial characteristics partially converge to a state of perfect interfacial bonding (Takayanagi model) with an iso-stress (Reuss IROM) response. In the case of hybrid composites the experimental data follows the trend of Halpin-Tsai model. This implies that matrix and filler experience varying amount of strain and interfacial adhesion between filler and matrix and also between the two fillers which play a vital role in determining the modulus of the hybrid composites.A significant observation from this study is that the requirement of higher fibre loading for efficient reinforcement of polymers can be substantially reduced by the presence of nanofiller together with much lower fibre content in the composite. Hybrid composites with both nanokaolinite clay and micron sized E-glass fibre as reinforcements in PP/HDPE matrix will generate a novel class of high performance, cost effective engineering material.