A comparative study was conducted for three natural rubber (NR) composites: one containing raw jute fibers, one containing bleached jute fibers, and one containing cellulose nanocrystals (CNCs). The composites were prepared by adding each filler at 5 or 10 phr to the latex before chemical coagulation, and the composites were processed in a two-roll mixing mill. The mechanical, thermal, and vulcanization properties of the prepared composites were then determined. The NR stiffness increased with increasing fiber content, particularly when bleached fibers were added, as evidenced by the increased elastic moduli, maximum torques, glass transition temperature, and crosslinking density. Scanning electron microscopy showed agglomerates in the composite with 10 phr CNCs, which led to poorer mechanical performance compared to that of the bleached fiber-reinforced composite (10 phr). On the other hand, the addition of CNCs to the NR increased the cure rate index, thereby significantly advancing the optimum vulcanization time.

There is growing interest in replacing the synthetic reinforcements used for natural rubber (NR) composites with natural fibers from renewable, environmentally sustainable sources. Jute fibers may be suitable reinforcements for NR because they have a high tensile strength, which is comparable to other fillers such as glass fibers. Thus, we studied the incorporation of bleached jute fibers into NR, characterizing the mechanical, dynamic mechanical, and morphological properties of the composites. The addition of fibers to the NR latex was achieved by chemical coagulation, followed by vulcanization in a laboratory two-roll mixing mill. The elastic modulus at 100 and 300% elongation of the NR doubled after the addition of 10 phr of fibers without significant loss in the tensile strength or the elongation at break. The hardness was increased by 47%, and the storage modulus also increased, indicating the excellent interactions between the surfaces of the fibers and the NR matrix.

AbstractThe main objective of this work is to study the influence of clay addition on dynamically revulcanized blends of Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). GTR was previously devulcanized in a system comprised of a conventional microwave oven adapted with a motorized stirring, with a fixed microwave power and at various exposure times. The influence of clay addition on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties, with morphology being also analyzed. The results depict that the clay can modify the rheological behavior of the GTR phase, in addition to the thermal and mechanical properties of some blends.

<title>Abstract</title><p>The main objective of this work is the study of the influence of microwaves devulcanization of the elastomeric phase on dynamically revulcanized blends based on Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). The devulcanization of the GTR was performed in a system comprised of a conventional microwave oven adapted with a motorized stirring at a constant microwaves power and at various exposure times. The influence of the devulcanization process on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties. The morphology was also studied.</p>

Este trabalho visa estudar e caracterizar o desempenho de aditivos retardantes de chama não bromados em copolímero de ABS. Foram estudadas combinações de retardantes de chama, como: o polifosfato de amônio (APP), a melamina, nanopartículas de dióxido de titânio e argila organicamente modificada com sal quaternário de fosfônio. Os materiais obtidos foram caracterizados por ensaios mecânicos (resistência ao impacto Izod e resistência à tração), análise termogravimétrica (TG), avaliação da morfologia e ensaio de retardância à chama. Os resultados obtidos indicaram uma redução de cerca de 48% na velocidade de propagação da chama dos compósitos com APP/melamina/TiO2/argila organofílica, em relação ao copolímero de ABS puro.

This work presents a study on alternative systems to substitute brominated flame retardants used in ABS. Combinations of flame retardants without bromine were studied: Ammonium polyphosphate, Melamine, Titanium dioxide Nanoparticles and phosphonium salt modified Organoclay. The composites obtained were characterized by mechanical tests (Izod Impact and Tensile strength), thermal analyses, scanning electron microscopy and Flame Retardancy tests. The results indicated that the Linear Burning Rate of ABS was reduced ca. 48% when the APP/MEL/OMMT/TiO2 system was used.