Sílvia Helena Prado Bettini

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.

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.

Effect of lubricant on mechanical and rheological properties of compatibilized PP/sawdust composites

An investigation was performed regarding the effect of compatibilizer and lubricant concentrations on the mechanical and rheological properties of polypropylene/sawdust composites using two-level factorial central composite design. Maleic anhydride grafted PP (PP-g-MA) was used as compatibilizer and the lubricant used was Struktol TPW 113. Composites without these additives were also prepared. Processing was carried out in a co-rotating twin-screw extruder coupled to a Haake rheometer. Mechanical properties were assessed from tensile tests and rheological properties were evaluated by oscillatory measurements and melt flow index (MFI) test. Tensile strength improved with increasing compatibilizer concentration in the composites and reached a maximum value in the absence of lubricant. When both additives were present tensile strength decreased, suggesting a possible interaction between lubricant and compatibilizer, reducing efficiency of the latter. The general trend observed for rheological results was a decrease in complex viscosity, storage modulus and MFI when both additives were present.

In situ sonochemical synthesis of ZnO particles embedded in a thermoplastic matrix for biomedical applications.

Zinc oxide particles were synthesized and dispersed in situ in a polystyrene (PS) matrix using ultrasound. PS ultrasonic degradation was investigated at different polymer concentrations in organic solvent in contact with aqueous media prior to the particle synthesis. Decrease in weight-average molecular weight (Mw) was strongly dependent on polymer concentration in organic solvent and sonication time: degradation occurred less at higher polymer concentration, yet increased with longer times of more than 30min. The ZnO particles with a 800nm flower-like morphology were dispersed in the polystyrene matrix in situ; the composite presented both a lower average molecular weight (Mw) and lower number average molecular weight Mn when compared to pristine polystyrene, however thermal degradation temperature and Youngs modulus were similar to the pristine polystyrene. The composite prepared in situ presented lower particle aggregation in comparison with ZnO commercially dispersed with ultrasound under the same conditions. Antibacterial activity of the ZnO/PS coating was tested against Escherichia coli (Gram-negative bacteria; DMS No. 10290) by evaluating bacterial growth inhibition after 20h on contact with the film surface. The results indicated that bacterial growth was inhibited in the medium in contact with the composite prepared in situ compared to the film of composite prepared by mixing and the pristine PS. This study showed the potential use of ZnO/PS composite prepared in situ as antibacterial coatings.

Avaliação de sistemas pró-degradantes na degradação termooxidativa do PEAD

The evaluation of pro-degradant systems based on iron and manganese in the form of metallic stearate, and d2wTM commercial additive, based on organic salt of manganese, was carried out on films of high density polyethylene (HDPE) in thermal oxidative conditions (80 °C oven and absence of light). The thermo oxidative degradation was monitored by mechanical properties, by infrared spectroscopy and by size exclusion cromatography. The results show that both metals accelerate thermal oxidative degradation of HDPE. However, the pro-degrading performance of manganese is significantly higher than iron. Considering iron, the degradation increases with increasing concentration of the metal, while manganese presents the maximum value of degradation depending on the concentration. The oxidation state of iron does not interfere with pro-degrading performance. The commercial additive d2wTM significantly accelerates HDPE thermo-oxidation, but its performance is lower than manganese stearate as a function of the set of stabilizing additives to be added to the commercial product.

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