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Natural rubber is an indispensable raw material that supplies about half of the world's rubber consumption. The latex that is extracted from the trees is composed of polyisoprene rubber, proteins, sugars, amino acids, lipids, and minerals. When the liquid latex emanates from the trees, it comes into contact with bacteria that cause it to decompose and coagulate. To hinder the decomposition and destabilization process, ammonia and other environmental and health hazard chemicals are added to the latex. The addition of these chemicals affects the health of plantation and rubber industry workers and results in residues that are contaminated with these chemicals, which require that processing facility effluents undergo costly treatment processes. Here, we present two novel liquid latex preservation and stabilization methods in an acid medium free of ammonia or other dangerous chemicals. The first method uses dodecyl benzene sulfonic acid to both stabilise and preserve the liquid latex, and the second uses ethoxylated tridecyl alcohol to stabilise and hydrofluoric acid to preserve the colloidal suspension. Both formulations result in rubber with superior mechanical properties, that is safe for the rubber plantation and industry workers, and with residues that no longer adversely affect the environment. [ABSTRACT FROM AUTHOR]

In the last decades, numerous large forest fires have been recorded in Portugal. On 15 and 16 October 2017, seven extreme wildfires events (EWEs) took place in the central region of Portugal. Aiming to contribute to the assessment of the smoke impact of these EWEs, this study estimates their atmospheric emissions using a bottom-up approach with high spatial and temporal resolution. To this end, fire data were used, such as ignition location and time, propagation, burned area, and fuel load and emission factors according to forest species. A particular fire – EWE in Lousã with a high fuel load – emitted ~50% of the sum of the emissions of the six other case studies. The spatial distribution of the EWE emissions indicates that fuel load is an important component of emissions estimation. The obtained results were compared with remote sensing data, showing good agreement in terms of total values. During these EWEs, particulate matter and carbon monoxide emissions were higher than Portuguese anthropogenic emissions in 2017. This approach contributes to the state of the art on forest fire emissions, reducing uncertainty and obtaining the best possible and detailed quantification of the temporal and spatial variability of EWE emissions. This study estimates the smoke emissions from Portuguese extreme wildfires events using a bottom-up approach with high spatial and temporal resolution. Fire data were used, such as ignition location and time, propagation, burned area, and fuel load and emission factors according to forest species. [ABSTRACT FROM AUTHOR]

Polymer foams have wide application area due to their light weight, resistance to impact, ability of insulation, and damping properties for specific applications. In this study, two different thermoplastic materials, polylactic acid (PLA) and polypropylene (PP), were used to compare their foaming ability in foam injection molding. Chemical foaming agent, azodicarbonamide, was used in foam injection molding and tensile test samples were obtained. Mechanical strength of the polymer foam samples were investigated by tensile test. Scanning electron microscopy was applied in order to observe the differences in cell morphologies of PLA and PP foams. It has been seen that 23.4% higher cell density and 151.2% higher cell size have been seen in the PLA foam when the results were compared with PP foam. This induced sharp reductions in mechanical strength of PLA foam while PP foams gave smooth decreases in the mechanical strength. Weight reduction in PLA was also 366.6% higher than that of PP foam due to its higher cell density. [ABSTRACT FROM AUTHOR]

The article presents a study on the characterization of the vulcanization process of silicon rubber through the modeling of dynamic Differential Scanning Calorimetry (DSC) tests. It states that Kissinger equation and the Kamal-Sourour model were used to determine kinetic parameters that fit the experimental data. The said technique allows the determination of the activation energy through Kissinger's model, which is used to determine the parameters for the Kamal-Sourour model.

This research included the modeling and simulation of the flow of epoxy resin during manufacturing of copper-clad laminates. Three conceptual models were proposed, based on the three resin flow mechanisms during processing: squeezing flow in thin fluid channels, seepage though a permeable medium, and a combination of squeezing and seepage flow. The similarity between the governing equations of each of the models was illustrated using dimensional analysis. The viscosity effect caused by the resin curing process was taken into consideration in the flow models. The results from the simulations provided deep insight into the dependence of the models on the respective geometric and empirical parameters. [ABSTRACT FROM AUTHOR]