Maria Madalena de Camargo Forte

Thermal decomposition of wood: influence of wood components and cellulose crystallite size.

The influence of wood components and cellulose crystallinity on the thermal degradation behavior of different wood species has been investigated using thermogravimetry, chemical analysis and X-ray diffraction. Four wood samples, Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP) were used in this study. The results showed that higher extractives contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the wood thermal stability. On the other hand, the thermal decomposition of wood shifted to higher temperatures with increasing wood cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of wood species.

Rheological evaluation of polymer-modified asphalt binders

)) using two oil shale contents (2 and 4%) and petroleum aromatic oil to evaluate comparatively the effect of the compatibilizer agent on the SBS PMB properties. The rheological characteristics of the SBS PMBs were analyzed in a dynamic shear rheometer (DSR) and the morphology accessed by fluorescence optical microscopy. The viscoelastic behavior of the samples corroborated the results for the classical properties and varied according to the sample morphology and composition. The results indicate that the aromatic and shale oils have similar effects on the microstructure, storage stability and viscoelastic behavior of the PMBs. Thus, shale oil could be successfully used as a compatibilizer agent without loss of properties or could even replace the aromatic oil. Following the Superpave methodology it was observed that the linear- and radial-SBS PMBs and linear-SBS PMB with 2% of shale oil can be used up to 70 °C, and the linear-SBS PMBs with 4% of shale oil or 2% of aromatic oil can be used only up to 64 °C.

Ethylene and 1-butene copolymerization catalyzed by a Ziegler–Natta/Metallocene hybrid catalyst through a 23 factorial experimental design

In this work, a 2 3 factorial experimental design for the evaluation of ethylene– 1-butene copolymerization was employed. The following reaction parameters were used as independent variables: catalyst type, Al/Ti molar ratio and 1-butene concentration. The copolymerization was carried out using hybrid Ziegler – Natta/Metallocene catalysts with different titanium molar ratios. The catalyst activity and polymer characteristics were statistically analyzed through response surface methods. It was found that the catalyst type has a significant effect on activity, melt flow index and 1-butene content. Copolymers presented crystallinity values ranging from 46 to 58% and melt temperature in the 128– 131 8C range. Copolymer comonomer content varied from 2 to 6% in weight. q 2002 Published by Elsevier Science Ltd.

Aspectos Morfológicos e Relação Estrutura - Propriedades de Poliestireno de Alto Impacto

Toughening of glassy polystyrene (PS) matrix by polybutadiene rubber addition mainly increases its impact resistance. The rubber modified polymer, known as High Impact Polystyrene (HIPS), has unique features. During the in situ styrene polymerization in a rubber solution grafting of polystyrene chains occurs onto polybutadiene molecules and magnifies the interaction at the rubber-PS interface. The HIPS is a mate- rial that has a large application in the packaging industry and refrigerator cabinets. The aim of this paper is to point out and discuss some of the structural and morphological characteristics of HIPS and its correlation with general properties. The standard techniques applied in the characterization of the structure and morphology of HIPS were revised.

Study of castor oil polyurethane - poly(methyl methacrylate) semi-interpenetrating polymer network (SIPN) reaction parameters using a 2³ factorial experimental design

3factorial experiment design to evaluate the castor oil polyurethane-poly(methyl methacrylate) semi-IPN synthesis. The reaction parameters used as independent variables were NCO/OH molar ratio, polyurethane polymerization time and methyl methacrylate (MMA) content. The semi-IPNs were cured over 28 h using two thermal treatments. The polymers were characterized by infrared and Raman spectroscopy, thermal analysis and swelling profiles in n-hexane. The glass transition temperature (Tg) and the swelling were more affect by the NCO/OH molar ratio variation. The semi-IPNs showed Tg from - 27 to - 6 °C and the swelling range was from 3 to 22%, according to the crosslink density. The IPN mechanical properties were dependent on the cure temperature and MMA content in it. Lower elastic modulus values were observed in IPNs cured at room temperature.

Characterization and evaluation of the nature of chemical species generated in hybrid Ziegler–Natta/metallocene catalyst

In the present work CpTiCl3 pretreated with tri-iso-butylaluminium was immobilized on MgCl2 supported Ziegler–Natta catalyst. The resulting catalysts were characterized by a series of techniques, namely thermal analysis (TGA/DTA), X-ray photoelectron spectroscopy (XPS), 27 Al magic angle spin nuclear magnetic resonance ( 27 Al MAS–NMR), UV–VIS spectroscopic analysis, inductively-coupled plasma–atomic emission spectroscopy (ICP–AES) and elemental analysis. The catalysts UV–VIS spectrum showed a broad absorption band at 390 nm indicating the presence of metallocene cyclopentadienyl ring. According to XPS analysis, only hybrid catalysts showed two peaks in the Ti (2p 3/2 ) region after the spectrum deconvolution, a lower binding energy peak at 455 eV and another one at 457 eV (Ti 4+ ). These appear to be due to difference of electronegativity in the coordination sphere of the Ti due to the TiCl4 and the Cp(i-Bu)TiCl2 fixed on the hybrid Ziegler–Natta catalyst. All catalyst systems were active in ethylene-1-butene copolymerization. The resulting polymers obtained with the hybrid catalyst showed a shoulder in the DSC thermogramme fusion peak. It might be caused by a polymer fraction produced by the additional Ti center in the catalyst due to the Cp(i-Bu)TiCl2. Microscopic analysis showed that the polymer replicated the spherical morphology of the catalyst grain.

Linear Low Density Polyethylene Thermal Fractionation by DSC Technique

Abstract Crystallization of linear low density polyethylene was studied through DSC analyses. Melting peak resolution was determined in order to establish the effect of crystallization conditions on polymer thermal fractionation. The isothermal number, fractionation window, and annealing time were varied, and suitable crystallization conditions were evaluated based on the sharpness of the DSC endothermic curve. The results confirmed that the selection of the thermal fractionation conditions is very important to control the multiple melting peaks number. The polyethylene endothermic curve profile changed significantly according to the crystallization conditions.

Esferas (beads) de alginato como agente encapsulante de óleo de croton zehntneri Pax et Hoffm

Alginate beads (ALG) crosslinked with calcium and coated with cashew gum (GC) were prepared and loaded with an essential oil from Croton zehntneri Pax et Hoffm (Cz). The beads were characterized by FTIR, thermal properties, with respect to their size, shape, larvicide loading, swelling, and in vitro and in vivo release kinetics. Results showed that beads with ALG:Cz =1:1 relative ratio showed higher loading and encapsulation efficiency, although presenting a faster release kinetics. On the other hand, ALG beads coated with GC showed Q values from 10 to 12, representing a significant increase in the hydrophilic character of the matrix. Infrared spectroscopy and thermal analysis confirmed the presence of essential oil encapsulated in beads. Morphologic investigation by SEM revealed a highly spherical and porous surface. The in vitro profile showed that the Cz oil encapsulated had a prolonged release in ALG-GC beads, probably due to the crosslinking. In vivo tests showed that the mortality degree was related to the mass of the beads, where beads having oil content from 1.81 to 4.25 mg caused larvae mortalities from 72 to 100% after 24 h. The control release system was found to be effective up to 70 days. These results showed that ALG-GC beads loaded with Cz are promising candidate for the control of Stegomyia aegypti larvae.

Synthesis of hydrocarbon polymers by cationic polymerization and their thermal properties

Cationic homo- and co-polymerization of indene (Ind), styrene (St), limonene (Lim), and 5-ethylidene-2-norbornene (ENB) was performed with AlCl3 in dichloroethane at −20 °C under inert N2. The aim of this work is to investigate the effect of the reaction conditions on the molecular weight of polyindene (PInd) obtained by cationic polymerization with AlCl3 without an electron donor, and also to determine the effect of the use of cyclic diolefin comonomers on the polymer properties. The polymers were synthesized at a monomer/catalyst molar ratio (MR) of 100; St and Lim showed the highest and lowest reactivity, respectively. The polymers were characterized by 13C and 1H NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, size exclusion chromatography, differential scanning calorimetry, and thermogravimetric analysis. PInd with a number average molecular weight (M n) of 45 × 103 g/mol and a glass transition temperature (T g) of 207 °C was obtained, whereas only oligomeric polylimonenes were obtained. Cyclic diolefins depressed both the M n and T g values of the Ind-copolymers. There was a dramatic decrease in the M n of the polymers: those obtained at a MR of 1:1 in the feed presented M n values lower than 104 g/mol, with the exception of poly(Ind-co-ENB), which is cross-linked. Poly(Ind-co-Lim) with lateral double bonds, a comonomer content of 1 to 20 mol%, and T g values in the range of 140–200 °C were obtained.

Evaluation of the effect of organic pro-degradant concentration in polypropylene exposed to the natural ageing

The production and consumption of plastics in the last decade has recorded a remarkable increase in the scientific and industrial interest in environmentally degradable polymer (EDPs). Polymers wastes are deposited improperly, such as dumps, landfills, rivers and seas, causing a serious problem by the accumulation in the environment. The abiotic processes, like the photodegradation, are the most efficient occurring in the open environmental, where the polymers undergo degradation from the action of sunlight that result from direct exposure to solar radiation, however depend of the type of chemical ageing, which is the principal component of climatic ageing. The subject of this work is to study the influence of concentration of organic pro-degradant (1, 2 and 3 % w/w) in the polypropylene (PP) exposed in natural ageing. PP samples with and without the additive were processed in plates square form, obtained by thermal compression molding (TCM) using a press at 200°C under 2 tons for 5 min, and then were exposed at natural ageing during 120 days. The presence of organic additive influenced on PP degradability, this fact was assessed by changes in the thermal and morphology properties of the samples after 120 days of natural ageing. Scanning Electronic Microscopy (SEM) results of the morphological surface of the modified PP samples showed greater degradation photochemical oxidative when compared to neat PP, due to increase of rugosity and formation of microvoids. PP samples with different pro-degradant concentration under natural ageing presented a degree of crystallinity, obtained by Differential Scanning Calorimeter (DSC) increases in comparing the neat PP.The production and consumption of plastics in the last decade has recorded a remarkable increase in the scientific and industrial interest in environmentally degradable polymer (EDPs). Polymers wastes are deposited improperly, such as dumps, landfills, rivers and seas, causing a serious problem by the accumulation in the environment. The abiotic processes, like the photodegradation, are the most efficient occurring in the open environmental, where the polymers undergo degradation from the action of sunlight that result from direct exposure to solar radiation, however depend of the type of chemical ageing, which is the principal component of climatic ageing. The subject of this work is to study the influence of concentration of organic pro-degradant (1, 2 and 3 % w/w) in the polypropylene (PP) exposed in natural ageing. PP samples with and without the additive were processed in plates square form, obtained by thermal compression molding (TCM) using a press at 200°C under 2 tons for 5 min, and then were exp...