Mara Zeni

Materials produced from plant biomass: Part I: evaluation of thermal stability and pyrolysis of wood

This paper compares the thermal stability of the sawdust of different wood species, an important factor in producing reinforced polymers. The compositions of two wood species, Pinus taeda and Eucalyptus grandis, were determined to evaluate the influence of the main wood components on the thermal stability of this material. The two species were submitted to thermogravimetric analysis at different heating rates to calculate the activation energy (Ea) using the Flynn-Wall-Ozawa (FWO) and Kissinger methods. The results suggest that larger quantities of holocellulose and lignin associated with lower extractive contents give the wood greater thermal stability. The Ea values calculated for the two species were in the range of 146-165 kJ.mol-1. Evaluation of the activation energy values offers a simplified means to better understand the thermal decomposition of the sawdust of different wood species used in developing composites.

Characterization of composites based on expanded polystyrene wastes and wood flour.

This paper aims to evaluate the potential for the use of recycled expanded polystyrene and wood flour as materials for the development of wood plastic composites. The effects of wood flour loading and coupling agent addition on the mechanical properties and morphology of wood thermoplastic composites were examined. In addition, a methodology for the thermo-mechanical recycling of expanded polystyrene waste was developed. The results show that the mechanical properties decreased as the wood flour loading increased. On the other hand, the use of poly(styrene-co-maleic anhydride), SMA, as a coupling agent improved the compatibility between the wood flour and polystyrene matrix and the mechanical properties subsequently improved. A morphological study revealed the positive effect of the coupling agent on the interfacial bonding. The density values obtained for the composites were compared with the theoretical values and showed agreement with the rule of mixtures. Based on the findings of this work, it appears that both recycled materials can be used to manufacture composites with high mechanical properties and low density.

Degradation study of polypropylene (PP) and bioriented polypropylene (BOPP) in the environment

Polymers are vastly employed for numerous purposes in different industrial segments and generate soaring quantities of discarding in the environment. This research analyzed the degradability/biodegradability of polypropylene films (PP) and Bioriented polypropylene (BOPP) polymers after 11 months interred in the Sao Giacomo landfill in Caxias do Sul. Comparing the buried PP film to a sample of virgin PP, two peaks of degrading activity appeared at the TG curve as well as structure modification typified by occurrence of new absorption bands at FTIR, which can be credited to changes in crystallinity. Thermal analysis carried out on the buried PP and BOPP showed decreases in the percentage of crystallinity due to chain scission. The major reduction was observed in the PP, since its crystallinity is a consequence of polymerization instead of chain orientation processes, as in BOPP. Cracks and erosion of the polymer surface were detected in both PP and BOPP, indicating degrading processes by microorganisms.

Effects of wood flour addition and coupling agent content on mechanical properties of recycled polystyrene/wood flour composites

The effect of filler addition and coupling agent content on the mechanical properties and morphology of wood plastic composites was examined. Using wood flour as the reinforcement filler and recycled expanded polystyrene as the thermoplastic matrix polymer, a particle-reinforced composite was prepared using a co-rotating twin-screw extruder. In the sample preparation, four levels of filler loading (10, 20, 30, and 40u2009wt%) and three levels of coupling agent content (1, 2, and 4u2009wt%) were used. The influence of particle size and particle morphology was also evaluated. The results showed that short fibers provide a higher specific surface area, enlarging the contact surface area with the polymer matrix. A wood flour loading of more than 20u2009wt% caused a decrease in the mechanical properties studied. The addition of 2u2009wt% of coupling agent improved the interfacial adhesion between the polymer matrix and wood flour and increased the flexural and impact strengths of the lignocellulosic composites. Addition of a coupling agent content greater than 2u2009wt% caused a reduction in the mechanical properties evaluated. A morphological study revealed that the positive effect of coupling agent on the interfacial adhesion of wood flour reinforced the expanded polystyrene composites.

Study of ion-selective membranes from electrodialysis removal of industrial effluent metals II: Zn and Ni

Electrodialysis (ED) with ion-exchange membranes represents one of the most important membrane methods of treatment of industrial effluents discharged. Attention to the deep ecological aspect of this method implies favourable forecasts for its future. Preparation and analysis of the properties of asymmetric membranes prepared photochemically with one epoxy resin and zeolite are related to the ion-selective transport when compared with Nafion 417 commercial membranes. Excellent results are shown from Ni2+ and Zn2+ recuperation with solution prepared and industrial effluent (90% recovery in 2 h from ED).

Effect of non-solvents used in the coagulation bath on morphology of PVDF membranes

The aim of this paper was to prepare a poly (vinylidene fluoride) (PVDF) membrane using different non-solvents in the coagulation bath for the phase inversion method. In order to increase the mechanical strength of membranes, facing the pressure of work, was used a macro-porous polyester support. The morphology and structure of the resulting membranes were evaluated by scanning electron microscopy, porosity measurements, water and 1-octanol uptake, contact angle, pure water flux, hydraulic permeability and hydraulic resistance. The morphology and pure water flux changed significantly using ethanol (symmetric membrane) and/or water (asymmetric membrane) as the non-solvent. The symmetric membrane presented a high hydrophobic surface (water contact angle ~136o) and a higher pure water flux and porosity than the asymmetric membrane, which presented a lower hydrophobicity surface (water contact angle ~90o). The morphologies obtained suggest different applications.

Thermoplastic polyurethane synthesis using POSS as a chain modifier

In this study, thermoplastic polyurethanes (TPUs) were synthesized using the one-shot process in solution. To obtain the samples n-phenylaminopropyl polyhedric oligomeric silsesquioxane (POSS) was added as a chain modifier during the synthesis in four different amounts. The samples were characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and capillary rheometry. FTIR confirm the TPU attainment due the absence of the band at ~2253 cm-1 suggesting a complete conversion of the isocyanate terminations. The TGA showed that incorporation of POSS decreased the rate of mass loss of TPU under isothermal conditions. The flexible phase showed an enhanced stability to temperature, probably due to increased phase separation between the rigid and flexible domains. The DSC showed that incorporation of 0.4 wt. (%) of POSS increased the glass transition temperature of the flexible phase. Moreover, addition of POSS modified the melting behaviour, providing samples with a higher melting enthalpy compared to neat TPU as a consequence of the formation of larger crystals. The capillary rheometry analysis revels that the POSS addition showed a clear tendency toward higher intrinsic viscosities as the amount of POSS was increased.

Characterization of Polyamide 66 membranes prepared by phase inversion using formic acid and hydrochloric acid such as solvents

The membranes properties prepared from water/formic acid (FA)/ polyamide 66 (PA66) and water/hydrochloric acid (HCl)/polyamide 66 (PA 66) systems has been studied. The different solvents interact distinctly with the polymer, affecting the membrane morphology. The asymmetric structure of the membranes showed a dense top layer and a porous sublayer. The membranes M-HCl prepared from HCl/PA 66 system showed a larger dense layer (around 23 μm) in compared to those prepared from FA/PA 66 system (M-FA) (around 10 μm). The membrane morphology was a determinant factor in results of water absorption, porosity and pure water flux. The lower thickness of dense layer in M-FA membranes resulted in a higher water absorption and, consequently, porosity, approximately 50%, compared with M-HCl membranes, approximately 15%. The same trend was observed to permeate flux, the lower thickness of dense layer higher pure water flux.

Characterization of EVA residues from the shoe industry and post-consumer urban-waste polyethylenes

This paper presents a characterization of a crosslinked EVA residue (EVA-c) from expanded sheets used in the shoe industry and post-consumer urban-waste polyethylenes regarding their molecular (FTIR), mechanical (tensile and impact tests), morphological (SEM), thermal (DSC, TGA) and dynamic-mechanical (DMTA) properties. For comparison, the properties of the EVA-c and recycled polyethylenes are compared to respective virgin polymers. The recycled polyethylenes generally presented similar properties to the virgin ones. On the other hand, some EVA-c properties differed from virgin ones since it has a high degree of crosslinking and it therefore has a higher tensile modulus and lower elongation at break, notched Izod impact strength and hardness. Additionally, crosslinking was also found to modify the thermal properties (TGA and DSC) of EVA-c.

Preparation and Characterization of PA66/Alumina Composite Membrane

In this study, polymer/ceramic composite membranes were prepared and characterized. The polymer used was polyamide 66 (PA66) deposited by dip coating on the inner surface of α-alumina-based (Al2O3) microporous tube. A coating on the ceramic support surface and the formation of the selective layer was analyzed by scanning electron microscopy (SEM) in membranes with one (PA-1) and two layers (PA-2). The results of mercury porosimetry showed that the deposition of the polyamide layers decreases the average pore size. The PA-1 presented an average pore size of 0.35 μm, while the PA-2 presented two peaks of 0.18 and 0.56 μm. Both showed a superior performance than the ceramic support (pore diameter of 0.65 μm). Although, the permeate flux was higher with an impregnation membrane, the number of layers (one or two) just introduced a slight difference in pore statistical analysis. The order of rejection coefficient values for protein molecules is BSA > egg albumin > trypsin. The permeation tests showed that the composite membrane can be applied in ultrafiltration processes with MWCO of 69 kDa.