José Donato Ambrósio

Desenvolvimento de compósitos poliméricos com fibras vegetais naturais da biodiversidade: uma contribuição para a sustentabilidade amazônica

This paper presents the research on Polymeric Composites with Natural Fibers in the Amazon Fenix Project. Two research and development fields based on polymeric composites with natural vegetable fibers are proposed: the first one considers production systems with simple, cheap machinery to facilitate technology assimilation by rural communities in the Amazon; the second one aims at developing composite materials with advanced production technology. It is hoped to raise awareness for scientific and technological development for the recovery of degraded areas in Amazon.

The effect of extrusion conditions and the use of a compatibilizer in the crystallization of PBT/ABS blends

Poly(butylene terephthalate) (PBT)/ acrylonitrile-butadiene-styrene (ABS) terpolymer blends were prepared in a twin screw extruder and the use of methyl methacrylate-glycidyl methacrylate-ethyl acrylate (MGE) terpolymer as compatibilization additive was evaluated. The effect of different screw profiles and mixing conditions were evaluated on the crystallization of the blends. Differential scanning calorimetry (DSC) was used to evaluate melting and crystallization behaviors of the PBT/ABS blends. The binary PBT/ABS blend has shown a double melting peak when cooled at lower cooling rates, mainly due to its melt-recrystallization during the heating up step. ABS has not affected the melting characteristics of neat PBT. The presence of MGE, as a reactive compatibilizer, in the PBT/ABS blends has reduced its heat of fusion and has partially inhibited its melt-recrystallization under heating. As result, it has prevented the occurrence of double melting peak. The epoxy functional groups of the MGE may react in situ to the carbonyls and hydroxyls end groups of the PBT molecules, thereby hindering the mobility of PBT molecules during the crystallization process due to its grafting to the compatibilizer molecules. The melt mixed blends prepared at lower feeding rate have shown a higher degree of crystallinity for the PBT/ABS blend, probably due to degradation of PBT caused by longer residence time in the extruder. The highest shear stress imposed to the blends at higher screw speed increased the degree of crystallinity of PBT, also due to its degradation.

Flexible thermoplastic composite of Polyvinyl Butyral (PVB) and waste of rigid Polyurethane foam

This study reports the preparation and characterization of composites with recycled poly(vinyl butyral) (PVB) and residue of rigid polyurethane foam (PUr), with PUr contents of 20, 35 and 50 wt %, using an extruder equipped with a Maillefer single screw and injection molding. The components of the composites were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetry. The composites were evaluated by melt flow index (MFI), tensile and hardness mechanical tests and scanning electron microscopy (SEM). Tg determined by DSC of PVB sample (53 °C) indicated the presence of plasticizer (Tg of pure PVB is 70 °C). MFI of the composites indicated a viscosity increase with the PUr content and, as the shear rate was held constant during injection molding, higher viscosities promoted higher shear stresses in the composites, thereby causing breaking or tearing of the PUr particles. The SEM micrographs showed low adhesion between PVB and PUr and the presence of voids, both inherent in the rigid foam and in the interphase PVB-PUr. The SEM micrographs also showed that PVB/PUr (50/50) composite exhibited the smallest particle size and a more homogeneous and compact structure with fewer voids in the interface. The stiffness of the composites increases with addition of the PUr particles, as evidenced in the mechanical tests.

Influência das condições de processamento na obtenção de blendas PBT/ABS

In order to correlate processing conditions in intermeshing co-rotational twin-screw extrusion (ICTSE) and properties of PBT/ABS blends, devices have been developed to obtain extruded strips from PBT/ABS blends. The PBT/ABS blend compatibilized with reactive copolymer methyl methacrylate- glycidyl methacrylate (MGE) has shown higher viscosity, lower heat of fusion and lower ductile-brittle transition temperature (DBTT) when compared to the non compatibilized PBT/ABS blend, possibly due to chemical reactions between MGE epoxy groups and the molecule end groups from PBT. Concerning the screw rotation, the compatibilized blend processed with 120 rpm has shown higher viscosity, lower heat of fusion and better impact strength properties than the one processed with 240 rpm. This could be a consequence of degradation of the blend components, caused by higher screw rotation. The feeding rate has presented itself as the processing parameter with the greater influence on blend properties. A feeding rate of 3.5 kg/h has severely compromised impact strength properties, reduced the viscosity and increased the heat of fusion, in contrast to a feeding rate of 7.0 kg/h. These observations can be attributed to a higher residence time, with the blend being submitted to higher temperature and shear for a long time, leading to the degradation of blend constituents.

Evaluation of Vulcanized Elastomeric Composites after Ageing in Biodiesel

The incorporation of biodiesel in the worldwide energetic matrix has an increasing tendency to use in the world. However, there are many technological challenges to consolidate this biofuel as an alternative to fossil fuels. The evaluation of the materials compatibilities used in the automotive industry and biodiesel production chain has been configured as an important area of research in finding appropriate materials that comes into contact with diesel biodiesel/blends. The present work aims to evaluate the physical properties for elastomeric composites prepared with polymeric matrix of ethylene propylene diene monomer (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber (NR) and styrene-butadiene rubber (SBR). The composites were prepared under controlled conditions of mixing and vulcanization. The elastomeric composites were aged in a blend containing 95 vol% of diesel and 5 vol% of biodiesel (B5 blend). The static total immersion tests were carried out at controlled temperature (50°C) for 7, 14, 21 and 28 days, substituting the B5 blend every 7 days. The results showed that the properties of NBR are less affected than other elastomers. It showed better mechanical performance and less influence on the glass transition temperature, indicating less degradation of this rubber in contact with B5 blend used in immersion tests.

Characterization of waste tire rubber devulcanized in twin-screw extruder with thermoplastics

Waste tire rubber (WTR) supplied by a truck tire retreader were processed in an intermeshing co-rotating twin-screw extruder (ICTSE). The extrusion process evaluated the efficiency of the thermomechanical recycling in the devulcanization of WTR rubbers. Samples were prepared by varying the process parameters, the particles sizes and thermoplastics, and the latter was used as devulcanization auxiliary agents. After extrusion, samples were subjected to solvent extraction to determine the soluble fraction (SF). Subsequently, these SF were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The highest SF (29 wt%) was obtained with higher screw rotating speed and with smaller particle size. Higher SF indicated a higher degree of devulcanization. The FTIR and DSC analyses showed that natural rubber was the main rubber extracted from extruded samples. In addition, polypropylene was more effective than low-density polyethylene in the devulcanization process, promoting higher SF.

Effects of 3-APTMS-Modified Nano-SiO2 on the Mechanical Properties and Crystallization Behavior of Polyamide-6

Nanocomposites of polyamide-6 with nanoSiO2 surface modified by 3-aminopropyltrimethoxysilane (3-APTMS) were prepared by melt blending in torque rheometer. Chemical modification of nanoparticles surface with 3-APTMS were observed by FTIR. Prior to nanocomposites processing, neat polyamide-6 (PA-6) was processed in a torque rheometer with varying processing parameters: polymer residence time in the chamber, rollers rotational speed, and polymer filling volume in the chamber. Two levels for each parameter were fixed. The influence of these parameters on degradation of PA-6 was determined by dilute solution viscosity and capillary rheometry. Results indicate that the best condition was achieved with the higher polymer residence time in the chamber, the higher rollers rotational speed, and the higher polymer filling volume in the chamber. With this information, PA-6 pellets were mixed with nanosilica particles unmodified and surface-capped by 3-APTMS via melt blending in torque rheometer, obtaining PA-6 composites with 1 wt.% of nanofillers. Mechanical and thermal properties of nanocomposites were evaluated by means of tensile test and differential scanning calorimetry (DSC).

Influence of Poly(Vinyl Butyral) on the Dynamic-Mechanical and Mechanical Properties of Polypropylene/Wood Flour Composites

This study reports the influence of recycled poly (vinyl butyral) (PVB) in dynamic mechanical and mechanical properties of polypropylene (PP)/wood flour composites prepared in a twin screw extruder. After extrusion, the PP/wood flour composites were injection molded to obtain specimens for tensile, flexural, impact and dynamic mechanical (DMA) tests. The morphology of the composites was analyzed by scanning electron microscopy (SEM). The addition 10 wt% of PVB in PP/wood flour composite reduced from 5°C to-10°C the β transition (glass transition) peak temperature of the loss modulus. In a temperature range between 40°C and 100°C the composites containing PVB presented the highest peak in the loss modulus. The most intense tan delta peaks between 50°C and 100°C for composites containing PVB were attributed to the combined effects of PP α transition with the PVB glass transition temperature. The PP/wood flour composites with PVB presented a tendency to increase the absorbed energy by impact.

Natural Fiber Polymer Composites Technology Applied to the Recovery and Protection of Tropical Forests Allied to the Recycling of Industrial and Urban Residues

“Often when pursuing research into green composites we say we are protecting the environment, that we are working for nature. We may as well stop kidding ourselves – nature will be fine; nature will work out OK and adapt to changes. It s humans that will cease to exist if we continue the way we are at present. Some scientists and engineers have realized that they need to take responsibility for the outcome of their work. Researching ways of creating faster machines and bigger toys, without due consideration of the effects on the environment or on people, is irresponsible... We need to consider the impact that our material choice and design will have on the society and the environment”* Generation of residues is inherent to human activities. After the Industrialization Period, with modernization of the society, the amount of industrial and postconsumer residues, together with the associated environmental problems, has been increasing at alarming levels. Residue management has become a major problem in modern society. The search for innovative solutions for the reuse of solid residues increased in the late 20th century and has intensified with growing urgency for environmental preservation. Many residue management solutions aim to add value to residue through the development of new materials and processes. Natural fiber polymer composites basic technologies are already relatively well established. Excellent textbooks can be found on this theme (Klyosov, 2007; Niska & Sain, 2008; Mohanty et al., 2005). Its concepts can be extended to the reuse of solid industrial and urban residues. In these composites the matrix is a polymer, and wood, vegetable or animal fibers are used as fillers or reinforcements. Both polymer and fiber may have been generated as an industrial or postconsumer residue. Another environmental problem that must be accounted for is the huge amount of deforested areas worldwide, also a consequence of human activities. Important research has