Resumo: Este artigo tem a intenção de divulgar e apresentar a inserção da área ou da cadeia produtiva de Compósitos Poliméricos com Fibras Vegetais Naturais dentro do contexto do Projeto Fênix Amazônico. Duas frentes de pesquisa e desenvolvimento na área de compósitos de polímeros com fibras naturais vegetais são propostas: uma que trabalharia com sistemas de produção com maquinário relativamente barato e simples, para que as comunidades rurais da Amazônia pudessem absorver tal tecnologia; uma outra frente para desenvolver materiais compósitos com tecnologia de fabricação mais avançada. Deste modo esperamos despertar o interesse da comunidade científica e tecnológica das mais diversas áreas em colaborar com o desenvolvimento de novas tecnologias que possam ser utilizadas para a recuperação de áreas degradadas da Amazônia. Palavras-chave: Compósitos poliméricos, fibras vegetais naturais, termoplástico/madeira, biodiversidade, Floresta Amazônica, parceria. Development of Polymeric Composites with Natural Fibers: A Contribution to the Sustainability of AmazonAbstract: 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.
ABSTRACT:The isothermal crystallization kinetics of blends of different polypropylene (PP) resins and a liquid crystalline polymer (LCP) after two different melting conditions (200 and 290°C) were studied by DSC and polarized light optical microscopy. The resins were a homopolymer (hPP), a random copolymer with ethylene (cPP), and a maleic anhydride grafted PP (gPP). The LCP was Vectra A950, a random copolymer made of 75 mol % of 4-hydroxybenzoic acid and 25 mol % of 2-hydroxy,6-naphthoic acid. It was observed that the overall crystallization rates of all the blends after melting at 200°C were higher than those after melting at 290°C. The LCP acted as a nucleating agent for all the PP resins; however, its nucleating effect was stronger for the hPP than for the cPP and gPP resins. After both melting conditions, an increase was observed in the overall crystallization rate of the hPP and gPP resins with the increase in the amount of LCP, but not in the cPP crystallization rate. The fold surface free energy e of hPP and cPP in the blends decreased, but increased in the gPP blends. Finally, all the PP resins formed transcrystallites on the LCP domain surfaces.
An optical fiber sensor similar to the one developed by Thomas and Bur 1 was constructed for the monitoring of the crystallization of three polyesters during the injection molding process. The polyesters studied were: polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene terephthalate (PET). With this optical system it was possible to obtain, in real time, some essential parameters of the polyester crystallization kinetics at different processing conditions. Thus, a study of the influence of injection molding variables on the nonisothermal crystallization kinetics of these polyesters was done. The processing variables were: mold wall and injection temperatures, T w and T i , respectively; flow rate, Q; and holding pressure, P h . The experiments were done following a first order central composite design statistical analysis. The morphology of the samples was analyzed by polarized light optical microscopy, PLOM. The signal of the laser beam during the filling and the crystallization stages of the injection molding of these materials was found to be reproducible. The measurements showed that this system was sensitive to variations of the crystallization of different types of polymers under different processing conditions. The system was not able, however, to monitor the crystallization process when the crystallinity degree developed by the sample was very low, as in the PET resin. It was also observed that T w and T i were the most influential variables on the crystallization kinetics of PBT and PTT. Due to its slower crystallization kinetics, PTT was found to be more sensitive to changes in these parameters than the PBT.
The nonisothermal crystallization of polypropylene resins, i-PP, during injection molding, using an optical device inserted in the injection mold cavity was monitored. The device detected the change of optical properties which occurs in polymers during their crystallization process; thus the intensity of a laser beam after it passed through the crystallizing polymer was measured during an injection molding cycle. The collected light intensity after the end of the cycle was correlated with the morphologies and final crystallinity degree of the samples. The influence of nucleating agents and the change of the parameters of the injection molding process on the morphology and optical signals were also investigated. The morphologies were analyzed by polarized light optical microscopy, PLOM. The % of crystallinity of the samples was measured by wide angle X-rays diffraction, WAXS. It was concluded that the optical device was sensible to different polymer crystallization kinetics, morphology type, and changes in the injection molding parameters. It was also found that the mold temperature and packing pressure and time were the factors that affected most the kinetics of crystallization of these polymers in this particular disk geometry. The WAXS results showed that the lower the final light intensity the higher the % of crystallinity in the samples. POLYM. ENG. SCI.,
Abstract:The Amazon Rain Forest has attracted worldwide attention due its large scale services to climate and also due to the green house gas emissions arising from deforestation. Contributing to the later and detrimental to the former, timber logging in the region has very low efficiency (only 16% in the production chain). Such timber extraction, often referred to as selective logging, has been claimed as a sustainable extractive industry, because the forest is said to restore itself through regenerative growth. But forest regeneration in the Amazon occurs naturally only in a very limited scale, resulting that large scale, low efficiency logging poses a big treat to the functional integrity of the biome, supplying to the market only a fraction of what it could if done differently. So, instead of extracting big centennial logs from the forests, the Amazonian Phoenix project proposes that large expanses of degraded lands be reforested using pioneer plants species from the forest itself. These plants have the capacity to heal gaps in the canopy, being able to grow and produce woody biomass in very extreme conditions. The idea is to mimic the OPEN ACCESSSustainability 2009, 1 1432 regenerative dynamics of the natural ecosystem in short cycle agrosilvicultural production areas, utilizing a variety of technologies to transform raw fibers from these fast growth native plants into a variety of materials with high aggregated value. This communication presents the research on natural fibers by the Polymeric Composites Group within the Amazonian Phoenix Project. Sustainable technologies employing materials with good and responsible ecological footprints are important and necessary stimulus for a change in the destructive economical activities present in the Amazon frontiers. The relatively well established wood polymer composites technology, for example, is a good candidate solution. Two research and development fields are proposed: the first one considers production systems with simple and cheap machinery, to facilitate technology assimilation by rural communities in the Amazon. The second one aims at developing composite materials with advanced production technology, like profile and sheet extrusion and injection molding. The source of the fibers would be both the short cycle agrosilviculture with softwood species, on already deforested lands, and the hardwood residues from operating sawmills. Preliminary results show that softwood fibers act as potentially important reinforcement for synthetic plastics.
In this work the thermal and transport properties of dichloromethane in blends of a bottle‐grade polyethylene terephthalate copolymer, PET, and a liquid crystalline polymer, LCP, were measured. Thermal characterizations of the blends were made by modulated differential scanning calorimetry and dynamic mechanical thermal analyses. An approximated LCP “bulk orientation” was also calculated by wide angle X‐ray diffraction. The morphology was analyzed by scanning electron microscopy. The resulting sorption curves of pure PET, and the B20, B40 and B60 blends were sigmoid type curves, while the sorption curve of the B80 blend was a two‐stage type curve. The diffusion coefficients of the B20 and B40 blends were found to be the lowest of all the blends. These low diffusivities were attributed to the occurrence of strong long‐range and short‐range interactions between the PET and the LCP in the B20 and B40 blends, and also to the perfection of the PET crystals in the B20 blend.
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