Processing induced segregation in PLA/TPS blends: Factors and consequences

Poly(lactic acid) (PLA) and thermoplastic starch (TPS) blends with two different glycerol contents were prepared by injection molding. Mechanical properties were characterized by tensile and impact testing, structure by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) as well as Raman spectroscopy, and water absorption was determined as a function of time. Compression-molded specimens were used as reference. The properties of the blends cover a wide range, stiffness changes from 3.3 to around 1.0 GPa, while strength from 54 to 22 MPa as TPS content increases from 0 to 50 wt%. Heterogeneous structure forms in the blends because of the weak interaction of the components. Processing conditions do not change bulk properties. Weak interactions and the large difference in the viscosity of the components lead to the formation of a skin on the surface of the specimens. The skin consists mainly of PLA, while the core contains a larger amount of TPS. The thickness of the skin depends on processing technology and conditions; it is about 18 mu m for the injectionmolded, while 4.5 mu m for the compression-molded parts at 50 wt% TPS content. The development of the skin layer can be advantageous in some applications because it slows down water absorption considerably

Optimal distribution of phosphorus compounds in multi-layered natural fabric reinforced biocomposites

Flame retardancy and mechanical performance of multi-layered biocomposites, consisting of polylactic acid (PLA) matrix films and plain-woven flax fabrics as reinforcement, were investigated. Full factorial design (32) was applied to evaluate the effects of the distribution of P and N containing compounds between the matrix and the fibrous carrier. Composition property correlations of the composite constituents (i.e. flax fabrics treated in aqueous solutions of diammonium phosphate and urea with differing ratio and concentrations and matrix films with 0 to 20 wt% ammonium polyphosphate based intumescent flame retardant content) were determined by thermogravimetric analyses and open flame tests. Positive interaction between the composite constituents was revealed for green composites consisting of various combinations of treated fabrics and intumescent PLA systems. The biocomposites flame retarded with a combined approach, i.e. with a balanced distribution of P containing additives between the phases, were found to gain improved mechanical performance and fire retardancy. It was confirmed by tensile testing and electron microscopy as well as by UL-94, limiting oxygen index and cone calorimeter tests. As a conclusion, interpretation is given for the optimum found

Human disturbances and predation on artificial ground nests across an urban gradient

Perturbaciones antropogénicas y depredación en nidos artificiales en el suelo en un gradiente urbano En nuestro estudio con nidos artificiales observamos que la ausencia de especies de aves que nidifican en el suelo en el centro urbano y en barrios residenciales se debía a las molestias causadas por personas y animales domésticos (perros y gatos) y no a la depredación. Además, la presión por depredación fue superior en la periferia de la ciudad debido al mayor número de depredadores naturales. Nuestros resultados sugieren que la planificación y creación de zonas protegidas podrían aumentar la posibilidad de que las aves que nidifican en el suelo se establecieran y se reprodujeran en paisajes dominados por los humanos.Perturbaciones antropogénicas y depredación en nidos artificiales en el suelo en un gradiente urbano En nuestro estudio con nidos artificiales observamos que la ausencia de especies de aves que nidifican en el suelo en el centro urbano y en barrios residenciales se debía a las molestias causadas por personas y animales domésticos (perros y gatos) y no a la depredación. Además, la presión por depredación fue superior en la periferia de la ciudad debido al mayor número de depredadores naturales. Nuestros resultados sugieren que la planificación y creación de zonas protegidas podrían aumentar la posibilidad de que las aves que nidifican en el suelo se establecieran y se reprodujeran en paisajes dominados por los humanos.In our study with artificial nests we observed that the absence of ground nesting bird species in the city centre and in residential districts was due to disturbance by humans and domestic animals (dogs and cats) rather than to predation. Furthermore, predation pressure was higher in the outskirts of the city due to the greater number of natural predators. Our results suggest that planning and creating undisturbed areas could increase the chances of ground nesting birds settling and breeding in human–dominated landscapes

Characterisation of natural fibre reinforced PLA foams prepared by supercritical CO2 assisted extrusion

Natural fibre reinforced polylactic acid (PLA) foams, as potential green replacements for petroleum-based polymer foams, were investigated. Highly porous (ε > 95%) microcellular PLA foams were manufactured by supercritical CO2 assisted extrusion process. To overcome the inherently low melt strength of PLA, epoxy-functionalized chain extender was applied, while talc was added to improve its crystallization kinetics. The combined application of chain extender and talc effectively promoted the formation of uniform cell structures. The effect of cellulose and basalt fibre reinforcement on the foamability, morphology, structure and mechanical properties of the PLA foams were investigated as well. The addition of 5 wt% natural fibres promoted the cell nucleation, but caused non-uniform distribution of cell size due to the microholes induced by local fibre-matrix debonding. The compression strength of the manufactured basalt fibre reinforced PLA foams reached 40 kPa

Composite foams made from biodegradable polymers for food packaging applications

Polymeric foams are cell structures (porous microstructures) that have been frequently made from synthetic polymers for use in the development of food packaging. Due to the problems concerning the environmental impact caused by polymers from the petrochemical industry, the foams have been more recently studied from biodegradable polymers. However, the polymer materials obtained are usually susceptible to moisture, thus conditioning the collapse of the porous structure of the material. As an alternative, the composite foams have been investigated from nanofillers such as clays, cellulose, nanoparticles, among others. This chapter aims to analyze the recent advances in the studies of composite foams.Fil: Araque Moreno, Luis Miguel. Federal University Of Piauí; BrasilFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Gutiérrez Carmona, Tomy José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Pharmaceutical and Macromolecular Technologies in the Spirit of Industry 4.0

Well designed (multilayer, adaptive, reactive) interphases, being a key element of multicomponent structures, could be tailored to different requirements through controlled technologies. This is the link connecting various green, safe, healthy materials and innovative pharmaceuticals. Upgraded recycling could be performed by interfacial consolidation of self-reinforced composites, the flame retardancy of which is feasible with surprisingly low amount of flame retardant. Examples are shown how the reinforced and foamed forms of thermosetting and thermoplastic biopolymers can play a significant role (after flame retardant modification) in the development of airplanes and electric cars. Biopolymer nanofibres, such as polycaprolactone and polyhydroxybutyrate, could be formed with increased productivity for various medical uses. Raman-based control of the units of integrated continuous technologies has been elaborated including controlled formation of crystals with polymer interlayer for direct tableting

Upgrading of recycled polypropylene by preparing flame retarded layered composite

Upgrading of polypropylene waste was performed by different composite technologies, in order to improve the flame retardancy combined with preserved or improved mechanical properties. The polymer waste of density below 900 kg/m3 is originated from end-of-life vehicles (ELV) after comminution, density separation and comprehensive analysis. Intumescent flame retardant system was used for reducing the flammability; while chopped glass fibre reinforcement was used to compensate the deterioration of mechanical properties caused by flame retardant additives. In mixed composite beside of flame retardants, the reinforcement effect of glass fibre can not be realized; therefore with modification of composite structure (but maintaining the composition) a multilayer composite was developed, which contains 65.5% of recycled polymer, where the core is reinforced with glass fibre covered by flame retarded shell layers. Enhanced flame retardancy (4 min longer time to escape) was achieved by using this layered composite compared to the mixed composite, thus the time to escape could be extended only with modification of composite structure

Human disturbances and predation on artificial ground nests across an urban gradient

In our study with artificial nests we observed that the absence of ground nesting bird species in the city centre and in residential districts was due to disturbance by humans and domestic animals (dogs and cats) rather than to predation. Furthermore, predation pressure was higher in the outskirts of the city due to the greater number of natural predators. Our results suggest that planning and creating undisturbed areas could increase the chances of ground nesting birds settling and breeding in human–dominated landscapes