José Augusto Marcondes Agnelli

Preparation and characterization of thermoplastic starch/zein blends

Blends of starch and zein plasticized with glycerol were prepared by melting processing in an intensive batch mixer connected to a torque rheometer at 160 °C. The resulting mixtures were compression molded and then characterized by scanning electron microscopy, differential scanning calorimetry, wide-angle X ray diffraction and water-absorption experiments. The blends were immiscible, showing two distinct phases of starch and zein. The water uptake at equilibrium and its diffusion coefficient were determined. The water uptake at equilibrium decreased with increasing zein content. The diffusion coefficient fell sharply on addition of 20% zein and remained constant as zein content was increased. No appreciable effect of zein on starch crystallization was observed by X ray diffraction. The use of zein in thermoplastic starch compositions causes a decrease in the water sensitivity of these materials and lower its melt viscosity during processing making zein a suitable and very promising component in TPS compositions.

Wood pulp reinforced thermoplastic starch composites

Thermoplastic starch is potentially a low cost alternative biodegradable plastic that is readily available material, but owing to its poor mechanical properties and high susceptibility to water, its actual replacement of the polymers currently in use is limited. In this study we investigated the employment of wood pulp as fiber reinforcement for thermoplastic starch. The composites were prepared with regular cornstarch plasticized with glycerol in the presence of fiber. The matrix compositions were starch/glycerol 70/30, 80/20 and 90/10 (w/w). The wood pulp fiber content was varied from 5 to 15% by weight. The composites were characterized by mechanical tests, scanning electron microscope and water absorption experiments at 97% relative humidity. It was found that the addition of fiber led to a large increase in the elastic modulus and tensile strength and that these effects are very dependent on the glycerol content. The water absorbed by the composites was sharply reduced by the addition of pulp, and seems to be independent of the amount of glycerol and pulp content. Scanning electron microscopy of fracture surfaces revealed that fibers were well dispersed in the matrix and were strongly bonded to it.

Grafting of maleic anhydride onto polypropylene by reactive processing. I. Effect of maleic anhydride and peroxide concentrations on the reaction

Grafting reactions were performed in a Haake torque rheometer, according to a central composite experimental design, where the maleic anhydride and peroxide concentrations, rotor speed, and reaction time were varied. The 27 formulations were analyzed by Fourier transformed infrared spectroscopy and melt-flow index measurements (MFI). An increase in peroxide concentration caused an increase in the percentage of reacted maleic anhydride and in MFI. The effect of initial maleic anhydride concentration presented different types of behavior, depending on the peroxide level.

Evaluation of methods used for analysing maleic anhydride grafted onto polypropylene by reactive processing

Grafting of maleic anhydride onto polypropylene, in the presence of peroxides, was performed through reactive processing. The samples obtained were submitted to several analyses in order to check for conversion of the acid groups to anhydrides and whether purification was necessary. Quantification of reacted maleic anhydride was tested by titration of acid groups and Fourier transform infrared spectroscopy (FTIR). It was concluded that each type of processing requires verification of the necessity to purify the samples for removal of residual maleic anhydride. Spectroscopy was shown to be better for the quantification of reacted maleic anhydride, as long as the samples are submitted to thermal treatment at 130°C for at least 24 h.

Thermal, mechanical and morphological properties of poly (hydroxybutyrate) and polypropylene blends after processing

The ever increasing accumulation of plastic waste in the environment has motivated research on polymers that degrade rapidly after being discarded as possible substitutes for conventional inert plastics. Biodegradable polymers can be an alternative, since they have non-toxic residual products and low environmental permanence. Poly (hydroxybutyrate) is a biodegradable polymer with a strong potential for industrial purposes, but its thermal instability and fragility limit its applications. Thus, an alternative to improve the processability and properties of poly (hydroxybutyrate) is to mix it with another polymer, not necessarily a biodegradable one. In this work, different mixtures of poly(hydroxybutyrate) or PHB and polypropylene or PP were extruded and injected. After processing, the blends were studied and their miscibility, mechanical properties and degradability in different soils were analyzed. The main results indicated that the PHB/PP blends had better mechanical properties than pure PHB, as well as improved immiscibility and higher degradation in alkaline soil. The poly-hydroxybutyrate/polypropylene blends showed a tendency for lower crystallinity and stiffness of the polymer matrix, proportional to the amount of polypropylene in the blends, rendering them less stiff and fragile. The degradation tests showed that both pure PHB and blends with 90% PHB and 10% PP were degraded, with loss of their mechanical properties and weight.

Evaluation of PHB, PHB-V and PCL biodegradation in composted soil

In contemporary society, a solution or a minimally satisfying approach to the serious environmental problems stemming from the widespread use of polymers has been one of the great challenges the scientific community has had to cope with. The studies around these compounds, including their biodegradability, have acquired fundamental importance. In this work, we present the results from an evaluation of the biodegradation of poly-b-(hydroxybutyrate) (PHB), poly-b-(hydroxybutyrate-co-valerate) (PHB-V) and poly-(e-caprolactone) (PCL), with products obtained from composting of municipal solid wastes, using the technique of aerobic biodegradation characterization known as Sturm Test. The thermal analysis of these polymers was done using differential scanning calorimeter (DSC). The melting temperature and crystallinity were also determined. The biodegradation test showed that PHB degraded faster than the other two polymers, probably because the chemical structure of this polymer made the attack by microorganisms easier.

Grafting of maleic anhydride onto polypropylene by reactive processing. II. Effect of rotor speed and reaction time

Grafting of maleic anhydride onto polypropylene was performed in a Haake torque rheometer, according to a central composite experimental design, in which four factors were varied: the maleic anhydride and peroxide concentrations, rotor speed, and reaction time. The current article investigates the effect of rotor speed and reaction time on the level of reacted maleic anhydride, obtained by infrared spectroscopy, and on the extent of degradation, by means of melt-flow index (MFI) measurements. The behavior of the variables studied depends on the levels of maleic anhydride and peroxide concentrations. The increase in rotor speed results in an increase in the percentage of reacted maleic anhydride and a reduction in MFI when the initial maleic anhydride concentration is high, and in a reduction in the percentage of reacted maleic anhydride and increase in MFI when the initial maleic anhydride concentration is low (for the central levels of peroxide concentration and reaction time). The effect of the variable reaction time depends on the remaining parameters.

Elaboration and Characterization of Nano-Biocomposites Based on Plasticized Poly(Hydroxybutyrate-Co-Hydroxyvalerate) with Organo-Modified Montmorillonite

Nano-biocomposites based on a biodegradable bacterial copolyester, poly(hydroxybutyrate-co-hydroxyvalerate), have been elaborated with an organo-modified montmorillonite (OMMT) clay as nanofiller, and acetyl tributyl citrate as plasticizer. The corresponding (nano)structures, thermal and mechanical properties, permeability, and biodegradability have been determined. Polyhydroxyalkanoates are very thermal sensitive then to follow the degradation the corresponding matrices have been analyzed by size exclusion chromatography. The results indicate that the addition of the plasticizer decreases the thermo-mechanical degradation, during the extrusion. These nano-biocomposites show an intercalated/exfoliated structure with good mechanical and barrier properties, and an appropriated biodegradation kinetic. Intending to understand the changes in the thermal properties, the nano-biocomposites were characterized by thermal gravimetric analysis and differential scanning calorimetry. The presence of the OMMT clay did not influence significantly the transition temperatures. However, the filler not only acted as a nucleating agent which enhanced the crystallization, but also as a thermal barrier, improving the thermal stability of the biopolymer. The results indicated that the addition of the plasticizer reduces the glass transition temperature and the crystalline melting temperature. The plasticizer acts as a processing aid and increases the processing temperature range (lower melting temperature).

The influence of the industrial processing on the degradation of poly(hidroxybutyrate) - PHB

PHB was characterized after different industrial processes by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Melt Flow Index (MFI), Complex Dielectric Relaxation (CDR) and Size Exclusion Chromatography (SEC). Some properties of PHB were investigated before and after processing, in order to understand how temperature and other extrusion or injection conditions affect the polymer degradation. All the processed samples showed an increasing in the melt flow index, a decreasing of the dynamic crystallization temperature, and a reduction in the molar mass, suggesting some degradation. The molar mass reduction after processing, predicted when only thermal degradation is considered, was calculated in function of the kinetic parameters, such as constant thermal degradation and residence time during the industrial processing. It was found that the real molar mass reduction was higher than the theoretical value, indicating an important contribution of the shearing of polymeric chains during processing in the PHB degradation.

Accelerated artificial aging of particleboards from residues of CCB treated Pinus sp. and castor oil resin

Tests simulating exposure to severe weather conditions have been relevant in seeking new applications for particleboard. This study aimed to produce particleboards with residues of CCB (chromium-copper-boron oxides) impregnated Pinus sp. and castor oil-based polyurethane resin, and to evaluate their performance before and after artificial accelerated aging. Panels were produced with different particle mass, resin content and pressing time, resulting eight treatments. Particles moisture and size distribution were determined, beyond panel physical and mechanical properties, according to NBR14810-3: 2006. After characterization, treatments B and G (small adhesive consumption and better mechanical performance, respectively) were chosen to artificial aging tests. Statistical results analysis showed best performances were achieved for waterproof aged samples, of both B and G treatments. As example, in treatment B, MOR and MOE values were 23 MPa and 2,297 MPa, samples before exposure; 26 MPa and 3,185 MPa, 32 MPa and 3,982 MPa for samples after exposure (non-sealed and sealed), respectively.