Antonio J. F. Carvalho

Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides

Oils, and Polysaccharides Alessandro Gandini,*,†,‡ Talita M. Lacerda,†,‡ Antonio J. F. Carvalho,‡ and Eliane Trovatti†,‡ †Saõ Carlos Institute of Chemistry, University of Saõ Paulo, Avenida Trabalhador Saõ-carlense 400, CEP 13566-590, Saõ Carlos, Saõ Paulo, Brazil ‡Department of Materials Engineering, Saõ Carlos School of Engineering, University of Saõ Paulo, Avenida Joaõ Dagnone 1100, CEP 13563-120, Saõ Carlos, Saõ Paulo, Brazil

Thermoplastic starch/natural rubber blends

Thermoplastic starch/natural rubber polymer blends were prepared using directly natural latex and cornstarch. The blends were prepared in an intensive batch mixer at 150 °C, with natural rubber content varying from 2.5 to 20%. The blends were characterised by mechanical analysis (stress-strain) and by scanning electron microscopy. The results revealed a reduction in the modulus and in tensile strength, becoming the blends less brittle than thermoplastic starch alone. Phase separation was observed in some compositions and was dependent on rubber and on plasticiser content (glycerol). Increasing plasticiser content made possible the addition of higher amounts of rubber. The addition of rubber was, however, limited by phase separation the appearance of which depended on the glycerol content. Scanning electron microscopy showed a good dispersion of the natural rubber in the continuos phase of thermoplastic starch matrix.

Recycling Tires? Reversible Crosslinking of Poly(butadiene)

Furan-modified poly(butadiene) prepared by the thiol-ene click reaction is crosslinked with bismaleimides through the Diels-Alder reaction, giving rise to a novel recyclable elastomer. This is possible because of the thermal reversibility of the adducts responsible for the formation of the network. The use of this strategy provides the possibility to produce recyclable tires.

Compatible ternary blends of chitosan/poly(vinyl alcohol)/poly(lactic acid) produced by oil-in-water emulsion processing.

Ternary compatible blends of chitosan, poly(vinyl alcohol), and poly(lactic acid) were prepared by an oil-in-water (O/W) emulsion process. Solutions of chitosan in aqueous acetic acid, poly(vinyl alcohol) (PVA) in water, and poly(lactic acid) (PLA) in chloroform were blended with a high-shear mixer. PVA was used as an emulsifier to stabilize the emulsion and to reduce the interfacial tension between the solid polymers in the blends produced. It proved to work very well because the emulsions were stable for periods of days or weeks and compatible blends were obtained when PVA was added. This effect was attributed to a synergistic effect of PVA and chitosan because the binary blends PVA/PLA and chitosan/PLA were completely incompatible. The blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), stress-strain tests, and Fourier transform infrared spectroscopy (FTIR). The results indicated that despite the fact that the system contained distinct phases some degree of molecular miscibility occurred when the three components were present in the blend.

Estudo comparativo de amidos termoplásticos derivados do milho com diferentes teores de amilose

Corn starches with approximately 72% and 100 % of amylopectin were processed in an intensive mixer connected to a torque rheometer in the presence of glycerol (plasticizer) at 160oC. The thermoplastic starches were conditioned at 53 ± 2% of relative humidity for two weeks and characterized by X-ray diffraction, tensile test and dynamical mechanical analysis (DMA). The starch with lower amylopectin content presented higher viscosity during the processing which was attributed to linear amylose chains. The thermoplastic starches TPS1 (72% of amylopectin) and TPS2 (100% of amylopectin) did not display significant differences in water absorption. After two weeks of aging, TPS1 exhibited semicrystalline structure, whereas TPS2 presented a amorphous structure. After six weeks, the crystallinity of TPS1 increased and some crystalline behavior could be detected in TPS2. The mechanical and dynamical mechanical properties were affected by starch crystallinity, which is a function of amylose/amylopectin ratio.

Simple Green Approach to Reinforce Natural Rubber with Bacterial Cellulose Nanofibers

Natural rubber (NR) is a renewable polymer with a wide range of applications, which is constantly tailored, further increasing its utilizations. The tensile strength is one of its most important properties susceptible of being enhanced by the simple incorporation of nanofibers. The preparation and characterization of natural-rubber based nanocomposites reinforced with bacterial cellulose (BC) and bacterial cellulose coated with polystyrene (BCPS), yielded high performance materials. The nanocomposites were prepared by a simple and green process, and characterized by tensile tests, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM), and swelling experiments. The effect of the nanofiber content on morphology, static, and dynamic mechanical properties was also investigated. The results showed an increase in the mechanical properties, such as Youngs modulus and tensile strength, even with modest nanofiber loadings.

Thermal properties of nylon6/ABS polymer blends: Compatibilizer effect

Nylon6/ABS binary blends are incompatible and need to be compatibilized to achieve better performance under impact tests. Poly(methyl methacrylate/maleic anhydride) (MMA-MA) is used in this work to compatibilize in situ nylon6/ABS immiscible blends. The MA functional groups, from MMA-MA copolymers, react with NH2 groups giving as products nylon molecules grafted to MMA-MA molecules. Those molecular species locate in the nylon6/ABS blend interfacial region increasing the local adhesion. MMA-MA segments are completely miscible with the SAN rich phase from the ABS. The aim of this work is to study the effects of ABS and compatibilizing agent on the melting and crystallization of nylon6/ABS blends. This effect has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Incorporation of this compatibilizer and ABS showed little effect on the melting behavior of the PA6 crystalline phase, in general. DMTA analysis confirmed the system immiscibility and showed evidence of compatibility between the two phases, nylon6 and ABS, produced by MMA-MA copolymer presence. The nylon6/ABS blend morphology, observed by transmission electron microscopy (TEM), changes significantly by the addition of the MMA-MA compatibilizer. A better dispersion of ABS in the nylon6 phase is observed.

Compatible blends of thermoplastic starch and hydrolyzed ethylene-vinyl acetate copolymers

Ethylene-vinyl acetate copolymer (EVA) with 19% of vinyl acetate and its derivatives modified by hydrolysis of 50 and 100% of the initial vinyl acetate groups were used to produce blends with thermoplastic starch (TPS) plasticized with 30 wt% glycerol. The blends were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, water absorption, stress-strain mechanical tests, dynamic mechanical analysis and thermogravimetric analysis. In contrast to the blends with unmodified EVA, those made with hydrolyzed EVA were compatible, as demonstrated by the brittle fracture surface analysis and the results of thermal and mechanical tests. The mechanical characteristics and water absorption of the TPS were improved even with a small addition (2.5 wt%) of hydrolyzed EVA. The glass transition temperature rose with the degree of hydrolysis of EVA by 40 and 50°, for the EVA with 50 and 100% hydrolysis, respectively. The addition of hydrolyzed EVA proved to be an interesting approach to improving TPS properties, even when very small quantities were used, such as 2.5 wt%.

A straightforward double coupling of furan moieties onto epoxidized triglycerides: synthesis of monomers based on two renewable resources

The bulk reaction of 2-furfuryl amine with epoxidized linseed oil took place at both its ester moieties (aminolysis) and oxirane groups (ring opening) producing three fatty acid furan amides incorporating further furan heterocycles along their chains. These reactions were followed spectroscopically and the ensuing monomers used in Diels–Alder reversible polycondensations.

Blendas compatíveis de amido termoplástico e polietileno de baixa densidade compatibilizadas com ácido cítrico

Blends of citric acid-modified thermoplastic starch (TPS) and low density polyethylene (LDPE) were prepared by reactive extrusion (REX) and characterized by scanning electron microscopy (SEM) of the fragile fracture surfaces, Fourier-transform infrared spectroscopy (FTIR), water absorption in 53% relative humidity environment and by X-ray diffraction. The modified TPS was prepared by the reactive extrusion of a mixture of corn starch, citric acid and glycerol (30%). TPS-LDPE blends were then prepared by the processing of TPS and PEBD both in pellets in a single screw extruder. It was observed an important compatibilization effect, attributed to the reduction of TPS melt viscosity and consequently the reduction of the interfacial tension between TPS and PEBD phases. The FTIR spectra showed shifting of starch bands confirming the compatibilization effect of citric acid. Important change on blend morphology as function of the TPS modification were observed, in particular for the blends prepared with the addition of 1,0 - 1,5% AC which showed a more homogeneous and finer dispersed phase.