Unconventional magnetic behavior of iron-oxide nanoparticles in polymeric matrices

We report the results of magnetization and 57Fe Mössbauer spectroscopy measurements performed in the temperature range 5-300 K on composites containing iron¿oxide nanoparticles encased in polystyrene type resins. After carrying out a suitable field treatment in order to decouple the particles from the matrix, a fraction of the particles freely rotate in response to an applied magnetic field

Bio-based composites from stone groundwood applied to new product development

This paper deals with the product design, engineering, and material selection intended for the manufacturing of an eco-friendly chair. The final product is expected to combine design attributes with technical and legal feasibility with the implementation of new bio-based materials. Considering the industrial design, a range of objectives and trends were determined after setting the market requirements, and the final concept was proposed and modeled. The product geometry, production technology, and legal specifications were the input data for product engineering. The material selection was based on the technical requirements. Polypropylene (PP) composite materials based on coupled-fiberglass, sized-fiberglass, and coupled-stone ground wood reinforcements were prepared and characterized. Final formulations based on these PP composites are proposed and justified

Materials nanocomposits a partir de whiskers de cel•lulosa i matriu polimèrica de cautxú

De acuerdo con los objetivos generales del proyecto y plan de trabajo previsto, para esta anualidad, se obtuvieron fibras y microfibras de celulosa a partir de dos fuentes: celulosa vegetal de pino y eucalipto y celulosa bacterial. Las microfibrillas han sido utilizadas como material de refuerzo para la fabricación de materiales compuestos a partir de caucho natural, policaprolactona y polivinil alcohol. Las muestras se fabricaron mediante la técnica de "casting" en medio acuoso y temperatura ambiente. Las muestras fueron caracterizados en sus propiedades mecánicas, físicas y térmicas. Se observó que, en general, la adición de las microfibrillas de celulosa en las matrices poliméricas provoca una mejora sustancial en las propiedades mecánicas del material en comparación con el polímero sin reforzar. Los resultados pueden resumirse de la siguiente manera: 1.Fabricación de materiales compuestos a base de caucho natural y fibras de celulosa. Se obtuvieron fibras y nanofibras de celulosa que fueron modificadas químicamente y usadas como refuerzo en matriz de caucho. Los resultados mostraron mejora de propiedades mecánicas del material, principalmente en los materiales compuestos reforzados con nanofibras. 2. Obtención de whiskers de celulosa y su utilización como material de refuerzo en una matriz de policaprolactona. Se obtuvieron whiskers de celulosa a partir de pasta blanqueada. La adición en una matriz de policaprolactona produjo materiales compuestos con propiedades mecánicas superiores a la matriz, con buena dispersión de los whiskers. 3. Obtención de fibras de celulosa bacterial y nanofibras de celulosa, aislamiento y utilización sobre una matriz de polivinil alcohol. Se obtuvo celulosa bacterial a partir de la bacteria Gluconacetobacter xylinum. Además se fabricaron nanofibras de celulosa a partir eucalipto blanqueado. La celulosa bacterial como material de refuerzo no produjo importantes mejoras en las propiedades mecánicas de la matriz; en cambio se observaron mejoras destacables con la nanofibra como refuerzo.

Estudis sobre la revalorització de residus de pols de poliuretà rígid : conversió en nous poliols aptes per a l'ús com a matèria primera

L’objecte del present treball fi de carrera es centra en l’estudi de la revalorització de residus de pols de poliuretà a partir de mètodes de glicòlisi. Es pretén comprovar la bondat de dos mètodes bàsics de glicòlisi i la seva aplicació al tractament de residus industrial concrets. Aquesta via química escollida ha de permetre revaloritzar químicament la pols de poliuretà del procés de tall convertint-la novament en matèria primera sota la forma de polímer de poliol, una de les dues matèries primeres claus del procés. L’abast del projecte comprèn l’estudi de les condicions que afecten al procés de glicòlisi, la caracterització dels poliols sintetitzats i la seva idoneïtat per a la formulació de noves escumes de poliuretà

Acoustic properties of polypropylene composites reinforced with stone groundwood

Currently, acoustic isolation is one of the problems raised with building construction in Spain. The publication of the Basic Document for the protection against noise of the Technical Building Code has increased the demand of comfort for citizens. This has created the need to seek new composite materials that meet the new required acoustical building codes. In this paper we report the results of the newly developed composites that are able to improve the acoustic isolation of airborne noise. These composites were prepared from polypropylene (PP) reinforced with mechanical pulp fibers from softwood (Pinus radiata). Mechanical and acoustical properties of the composites from mechanical pulp (MP) and polypropylene (PP) have been investigated and compared to fiberglass (FG) composites. MP composites had lower tensile properties compared with FG composites, although these properties can be improved by incorporation of a coupling agent. The results of acoustical properties of MP composites were reported and compared with the conventional composites based on fiberglass and gypsum plasterboards. Finally, we suggest the application of MP composites as a light-weight building material to reduce acoustic transmitions

Management of corn stalk waste as reinforcement for polypropylene injection moulded composites

The main objective of this study was the management of corn stalk waste as reinforcement for polypropylene (PP) injection moulded composites as an alternative to wood flour and fibers. In the first step, corn stalk waste was subjected to various treatments, and four different corn stalk derivatives (flour and fibers) able to be used as reinforcement of composite materials were prepared and characterized. These derivatives are corn stalk flour, thermo-mechanical, semi-chemical, and chemical fibers. They were characterized in terms of their yield, lignin content, Kappa number, fiber length/diameter ratio, fines, coarseness, viscosity, and the length at the break of a standard sheet of paper. Results showed that the corn stalk derivatives have different physico-chemical properties. In the second step, the prepared flour and fibers were explored as a reinforcing element for PP composites. Coupled and non-coupled PP composites were prepared and tested for tensile properties. For overall trend, with the addition of a coupling agent, tensile properties of composites significantly improved, as compared with non-coupled samples. In addition, a morphological study revealed the positive effect of the coupling agent on the interfacial bonding. The composites prepared with semichemical fiber gave better results in comparison with the rest of the corn stalk derivatives due to its chemical characteristics

Stone-ground wood pulp-reinforced polypropylene composites: water uptake and thermal properties

Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 ºC

Tensile strength characteristics of polypropylene composites reinforced with stone groundwood fibers from softwood

The behavior of stone groundwood / polypropylene injection-molded composites was evaluated with and without coupling agent. Stone groundwood (SGW) is a fibrous material commonly prepared in a high yield process and mainly used for papermaking applications. In this work, the use of SGW fibers was explored as a reinforcing element of polypropylene (PP) composites. The surface charge density of the composite components was evaluated, as well as the fiber’s length and diameter inside the composite material. Two mixing extrusion processes were evaluated, and the use of a kinetic mixer, instead of an internal mixer, resulted in longer mean fiber lengths of the reinforcing fibers. On the other hand, the accessibility of surface hydroxyl groups of stone groundwood fibers was improved by treating the fibers with 5% of sodium hydroxide, resulting in a noticeable increase of the tensile strength of the composites, for a similar percentage of coupling agent. A new parameter called Fiber Tensile Strength Factor is defined and used as a baseline for the comparison of the properties of the different composite materials. Finally the competitiveness of stone groundwood / polypropylene / polypropylene-co-maleic anhydride system, which compared favorably to sized glass-fiber / polypropylene GF/PP and glass-fiber / polypropylene / polypropylene-co-maleic anhydride composite formulations, was quantified by means of the fiber tensile strength factor

Thermoplastic Starch-based Composites Reinforced with Rape Fibers: Water Uptake and Thermomechanical Properties

Fully biodegradable composite materials were obtained through reinforcement of a commercially available thermoplastic starch (TPS) matrix with rapeseed fibers (RSF). The influence of reinforcement content on the water sorption capacity, as well as thermal and thermo-mechanical properties of composites were evaluated. Even though the hydrophilic character of natural fibers tends to favor the absorption of water, results demonstrated that the incorporation of RSF did not have a significant effect on the water uptake of the composites. DSC experiments showed that fibers restricted the mobility of the starch macromolecules from the TPS matrix, hence reducing their capacity to crystallize. The viscoelastic behaviour of TPS was also affected, and reinforced materials presented lower viscous deformation and recovery capacity. In addition, the elasticity of materials was considerably diminished when increasing fiber content, as evidenced in the TMA and DMTA measurements

Gene transfer into the airway epithelium of animals by targeting the polymeric immunoglobulin receptor.

Genes of interest can be targeted specifically to respiratory epithelial cells in intact animals with high efficiency by exploiting the receptor-mediated endocytosis of the polymeric immunoglobulin receptor. A DNA carrier, consisting of the Fab portion of polyclonal antibodies raised against rat secretory component covalently linked to poly-L-lysine, was used to introduce plasmids containing different reporter genes into airway epithelial cells in vivo. We observed significant levels of luciferase enzyme activity in protein extracts from the liver and lung, achieving maximum values of 13,795 +/- 4,431 and 346,954 +/- 199,120 integrated light units (ILU) per milligram of protein extract, respectively. No luciferase activity was detected in spleen or heart, which do not express the receptor. Transfections using complexes consisting of an irrelevant plasmid (pCMV lacZ) bound to the bona fide carrier or the expression plasmid (pGEMluc) bound to a carrier based on an irrelevant Fab fragment resulted in background levels of luciferase activity in all tissues examined. Thus, only tissues that contain cells bearing the polymeric immunoglobulin receptor are transfected, and transfection cannot be attributed to the nonspecific uptake of an irrelevant carrier-DNA complex. Specific mRNA from the luciferase gene was also detected in the lungs of transfected animals. To determine which cells in the lungs are transfected by this method, DNA complexes were prepared containing expression plasmids with genes encoding the bacterial beta-galactosidase or the human interleukin 2 receptor. Expression of these genes was localized to the surface epithelium of the airways and the submucosal glands, and not the bronchioles and alveoli. Receptor-mediated endocytosis can be used to introduce functional genes into the respiratory epithelium of rats, and may be a useful technique for gene therapy targeting the lung.

L'ús de materials compostos en el reforç intern d'estructures de formigó

L’ús de materials compostos de matriu polimèrica (FRP, Fibre Reinforced Polymer) en el reforç intern d'estructures de formigó

Calcium phosphate glasses: silanation process and effect on the bioactivity behavior of Glass-PMMA composites

This article presents the results of a study of the efficiency of silanation process of calcium phosphate glasses particles and its effect on the bioactivity behavior of glasspoly( methyl methacrylate) (PMMA) composites. Two different calcium phosphate glasses: 44.5CaO-44.5P2O5-11Na2O (BV11) and 44.5CaO-44.5P2O5-6Na2O-5TiO2 (G5) were synthesized and treated with silane coupling agent. The glasses obtained were characterized by Microprobe and BET while the efficiency of silanation process was determined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Thermal Analysis (DTA and TG)techniques. The content of coupling agent chemically tightly bond to the silanated glasses ascended to 1.69 6 0.02 wt % for BV11sil glass and 0.93 6 0.01 wt % for G5sil glass. The in vitro bioactivity test carried out in Simulated Body Fluid (SBF) revealed certain bioactive performance with the use of both silanated glasses in a 30% (by weight) as filler of the PMMA composites because of a superficial deposition of an apatite-like layer with low content of CO3 22 and HPO4 22 in its structure after soaking for 30 days occurred. VC 2013 Wiley Periodicals,Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2013.