Leila L. Y. Visconte

Flame retardancy in thermoplastic polyurethane elastomers (TPU) with mica and aluminum trihydrate (ATH)

Abstract Two types of aluminum trihydrate (ATH), with or without surface treatment, and mica were incorporated into TPU composites. The quantity of mica that should be used has been previously evaluated from mechanical properties. In the present work, different mixtures of TPU/ATH/mica were prepared and those compositions presenting fire retardancy were identified through the two principal tests in this area: vertical burning (UL94) and oxygen index (ASTM D2863). The influence of mica on fire resistance was also evaluated. The objective of this work was to obtain good flame retardancy in TPU–mica composites and an optimum cost-performance balance as a consequence of mica addition.

Mechanical properties of thermoplastic polyurethane elastomers with mica and aluminum trihydrate

Abstract In the present work two types of fillers were incorporated into thermoplastic polyurethane elastomers (TPU): mica and aluminum trihydrate (ATH). In the first stage, mixtures were prepared with TPU and 5, 10, 20, 25 and 30 phr of mica. The optimum amount of filler was evaluated for mechanical properties. In the second stage, ATH was used in mixtures with TPU and mica in the preparation of compositions with good flame retardant. All mixtures were obtained by extrusion and after compression molding they were evaluated through mechanical properties of tensile resistance, Shore A hardness and abrasion resistance. The objective of this work is to obtain good mechanical properties from TPU composites with mica–ATH as fillers and optimum cost-performance balance, in addition to flame retardant characteristics.

Caracterização mecânica e morfológica de compósitos de polipropileno e fibras de coco verde: influência do teor de fibra e das condições de mistura

Polypropylene composites containing 10, 20 and 30% in volume of green coconut fiber were prepared in a Haake chamber at various processing temperatures and shear rates. The flexural modulus and morphological characteristics of the composites were evaluated and compared with pure polypropylene. Optimization experiments indicated that a temperature of 170 °C, shear rate of 60rpm and green coconut fiber content of 30% showed the best properties by flexural modulus. These observations were confirmed by a morphology analysis.

Dielectric properties of flame resistant EPDM composites

Formulations of ethylene-propylene-diene rubber containing mixtures of aluminum hydroxide (ATH) and carbon black (HAF) as fillers were developed, aiming to achieve a synergism in properties, to fit national and international standards for application as insulation in electric wires and cables, yet keeping the fire resistance. After flammability determination, the developed compositions were analyzed for dielectric constant, dissipation factor, dielectric strength, and volumetric and surface resistivity. It was found that for flame resistance, a minimum amount of 160 phr of ATH must be present. However, this composition contains 15 phr of HAF, which is harmful to the electric properties. Only the composition with 170/7.5 (ATH/HAF) exhibited the desired performance.

Aspectos Históricos da Vulcanização

Rubbers, to be turned into useful materials from the commercial applications point of view, need the addition of a few other ingredients which, upon vulcanization, will impart the desired characteristics to the material. In this paper, historical aspects of vulcanization are revised as well as the evolution of the additives used in most of the formulations.

Aluminum hydroxide and carbon black filled NBR/PVC composites: vulcanization and processability studies

The influence of aluminum hydroxide (ATH) and carbon black (CB) was investigated in vulcanizable compositions of the physical mixture NBR/PVC (butadiene-acrylonitrile copolymer/polyvinyl chloride) by varying the ATH:CB ratio. The results were compared to those for pure gum type (no filler added) NBR/PVC formulation. Two types of ATH, with and without a coupling agent, were used in an attempt to improve ATH:polymer interaction. The developed compositions were analysed for rheometric and processing properties.

Revisão dos tratamentos químicos da fibra natural para mistura com poliolefinas

The use of natural fibers as reinforcement in polymer composites has been a focus of interest. However, these composites exhibit lower mechanical properties than those of pure polymers because of the low interfacial interactions between the hydrophobic polymer matrix and the hydrophilic fiber. To overcome this problem, different chemical treatments applied to the fibers have been reported. One of the most used treatments is mercerization, which can improve adhesion between the fiber and polymeric matrix. Another chemical treatment involves the use of acids (stearic and oleic acids). The chemically treated fibers used in composite materials showed improved mechanical properties.

Mechanical and Flammability Properties of ATH‐Filled EPDM Compositions

Poly(ethylene-co-propylene-co-diene) (EPDM) compositions filled with mixtures of aluminium hydroxide (ATH) and carbon black (HAF) were evaluated for electrical applications. Mechanical and flammability tests were carried out in order to find out the relative amounts of the two fillers which would give the best balance of properties, mainly to meet the Brazilian Society for Technical Standards-ABNT. For good flame resistance, amounts as high as 160 phr ATH, at least, must be used.

Curing Characteristics and Aging Properties of Natural Rubber/Epoxidized Natural Rubber and Cellulose II

In this work, natural rubber (NR) and regenerated cellulose (cel II) latexes were co-coagulated and to the mixture epoxidized natural rubber (ENR) was added on a two-roll mill. The cellulose content was fixed at 20 phr while ENR content varied from 0 to 75 phr. The influence of ENR was studied through the cure characteristics, aging and dynamic-mechanical properties. The aging provides nanocomposites with better solvent resistance and increased tensile strength at ENR content of 25 phr. The results suggest that a new type of light-colored nanocomposites were obtained, which presented high mechanical performance and resistance to solvents.

UV‐light induced crosslinking reaction of cinnamate natural rubbers: Effect of the spacer length, counter‐ion nature, and content

Maleated natural rubber was modified by introducing different contents of cinnamate groups, separated from the main chain by —(CH2)n— spacers (n = 2 to 6). Residual carboxylic acid groups were neutralized as Li, Na, and K-salts. The kinetic behavior of these materials towards ultraviolet-induced crosslinking reaction was investigated and correlated with Tg.