Regina C. Reis Nunes

• Federal University of Rio de Janeiro

Sandwich composites are materials that have superior properties including low weight, high impact energy absorption and high thermal insulation features, compared to conventional materials. In this study, four different sandwich samples were explored for use in cold storage chambers. The composites were created using an injection molding process wi...

This work aims at studying not only the rheological behavior of natural rubber-based compositions by making use of different contents of fluoromica or ME 100 synthetic mica in a natural rubber (NR) matrix, but also the different filler.filler and matrix-filler interactions before and after curing. The ME 100 content in NR varied from 0 to 10 phr (p...

This article reports the production of electrospun fibers from blends of poly(lactic acid) (PLA) and epoxidized natural rubber (ENR) solutions. The produced fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dy...

This chapter discusses three kinds of composites with natural rubber (NR) and cellulose. The properties and features of several kinds of short fibers used as fillers of NR are discussed. The chapter also discusses the preparation and importance of nanocomposites with cellulose and presents a review of NR/regenerated cellulose nanocomposites. NR/cel...

Resumo– Este trabalho tem como objetivo analisar a melhor combinação de aceleradores em sistemas de cura eficiente, com base na Reologia, em composições vulcanizadas e não vulcanizadas da borracha natural (NR). Sistemas de cura eficiente apresentam predominância em ligações cruzadas do tipo mossulfídicas, devido ao uso somente de aceleradores, prop...

Neste trabalho foi estudado o efeito Payne como uma medida das interações carga-carga e polímero-carga em nanocompósitos de montmorilonitaorganofílica (MMTorg) e borracha nitrílica (NBR), usando o Analisador de Processamento de Borracha - RPA 2000. Os nanocompósitos de NBR e MMTorg foram preparados em um misturador de rolos e o efeito Payne foi ava...

Hybrid nanocomposites of natural rubber (NR), clay (MMT) and cellulose II (CEL II) were obtained with elastomeric latex, cellulose xanthate and aqueous suspension of the clay. The content of MMT varied from 1 to 5 phr (per hundred resin) while cellulose II was kept as 15 phr. The formation of nanocomposites from co-coagulation of natural rubber lat...

Composites of recycled poly(ethylene terephthalate) (PET) and short glass fibers (GFs) in different compositions (0, 20, 30, and 40 wt% of GFs) with optimized microstructures and high mechanical performance were obtained through melt processing. Composites showed appropriate dispersion and distribution and suitable bonding of the GF throughout the...

The focus of this paper is to establish a characterisation method for seven polyamide (PA) grades to determine the major material to manufacture an automotive worm gear. The composite properties were measured according to the worm gear loadings: tensile strength, Young's modulus, abrasion and impact resistance. They were also correlated to the PA m...

The swelling of styrene–butadiene rubber (SBR) when exposed to organic solvents was measured and mathematically cor-related to the toluene concentration in a complex mixture such as gasoline. This relation enables inferences to be made regarding the composition and quality criteria of the fuel and represents a new method to detect adulterations. Ch...

In this work, nanocomposites of styrene butadiene rubber (SBR), cellulose II, and clay were prepared by cocoagulation of SBR latex, cellulose xanthate, and clay aqueous suspension mixtures. The incorporated amount of cellulose II was 15 phr, and the clay varied from 0 to 7 phr. The influence of cellulose II and clay was investigated by rheometric,...

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-mec...

Most condom manufacturers claim a 5 year shelf-life for their products; however, condoms can decay much more rapidly than the reported shelf-life would suggest, because of the uncontrolled storage conditions. For this reason, development of mathematical model to predict condom shelf-life as a function of storage conditions can be very useful. In th...

In this work, sodium montmorillonite clay was added, as filler, to nanocomposites of natural rubber (NR) and cellulose II (regenerated cellulose) in amounts varying from 0 to 5 phr (per hundred resin). Natural rubber (NR)/cellulose II/montmorillonite nanocomposites were prepared by co-coagulating NR latex, montmorillonite aqueous suspension and cel...

Nanocomposite materials obtained from natural rubber (NR) reinforced with different amounts of cellulose II nanoparticles (in the range of 0 to 30phr) are studied by dielectric spectroscopy (DS). For comparative purposes the pure materials, NR and cellulose, are also investigated. The dielectric spectra of the nanocomposites exhibit: (a) two overla...

This work is aimed at incorporating mica to the matrix of a polyether type thermoplastic polyurethane elastomer (TPU), for the development of new materials in which the inherent properties of mica could be combined to those of TPU. This thermoplastic elastomer has high cost, unlike mica, which is inexpensive and abundant in Brazil. The different co...

In this work a new non-structural adhesive based on a high styrene content SBRcopolymer(SBR-53) was developed. This new product is intended to be used in the furniture segment, to replace the chloroprene rubber(CR-M) adhesive, whose base polymer is imported. Different adhesive formulations were developed specifically for the furniture industry, and...

In this work, mixtures of natural rubber (NR) and styrene-butadiene copolymer (SBR) were prepared in 1/1 ratio. The sequence with which the additives were incorporated and the influence of fillers, such as mica and carbon black, were evaluated regarding the physical-mechanical properties. The mixtures were prepared in a two-roll mill, according to...

The recycling of waste rubber has very important significances, such as protection of the environment and conservation of energy. Considering that most of published works concerning this subject are about tire recycling, the objective of this work was to develop and characterize formulations containing a type of industrial waste, from the manufactu...

The curing behavior of commercial phenol-formaldehyde novolac resins with hexamethylenetetramine (HMTA) under non-isothermal and isothermal conditions was followed by dynamic rheological measurements. Changes in parameters of the viscoelastic material such as storage modulus (G′) and complex viscosity (η*) during the cure process were evaluated acc...

White rice husk ash (WRHA) and black rice husk ash (BRHA) were incorporated as filler in natural rubber (NR) compounds. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 Curometer at 150, 160, 170 and 180°C. From the rheometric data obtained at 150°C, a specific constant related to the filler structur...

Natural rubber (NR) isolated from Hevea Brasiliensis was investigated by differential scanning calorimetry, dielectric spectroscopy, and high-pressure dielectric spectroscopy. In the range of frequencies (5 × 10−2 to 3 × 106 Hz), temperatures (−120 to 120 °C), and pressures (0.1 to 240 MPa) studied, the dielectric spectra exhibit two overlapped α-p...

Epoxidized natural rubber (ENR) samples of various epoxidation degrees were synthesized from natural rubber (NR) latex, and 25 mole% epoxide of ENR was used to prepare ENR room temperature-curable films for coating applications. The films were prepared from rubber solutions. Trimethylolpropane tris(2-mercaptoacetate) (TMP-SH) was used as a curing a...

In this work mica or carbon black were used as filler in composites of acrylic rubber (ACM). The fillers differ not only in nature, mica being a mineral material and carbon black being organic, but also in form and particle size. The content of filler varied from 0 to 50 phr and its influence on ACM was evaluated based on cure parameters, mechanica...

Frequently a set of properties required for a given application cannot be accomplished by one elastomer only and, thus, mixtures of two or more polymers must be employed. In these cases, the other ingredients added are normally dispersed in a non homogeneous way, depending on their affinity to each polymer. The degree of dispersion each additive ex...

The recycling of waste rubber has considerable significance in terms of environmental protection and energy conservation. Considering that most of the relevant literature is concerned with tire recycling, the objective of this study is to develop and characterize styrene-butadiene rubber composites containing only industrial rubber scraps devulcani...

The processing characteristic of blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA), in different compositions, were studied by torque rheometry. The polymers were mixed in a batch mixer in proportions of 20, 40, 60 and 80% by weight of PVDF, at 190 °C using rotor speeds of 30, 60 and 100 rpm. The results have shown tha...

Mechanical recycling of vulcanized rubber scraps is a low-cost alternative in the search for the recovery of this kind of industrial solid waste. The aim of this study is to incorporate styrene–butadiene rubber (SBR) industrial scraps into a base formulation of SBR used in the fabrication process of extruded profiles. Rheometric, mechanical and mor...

Thin solid copper films were evaporated on polymer surfaces by ion plating process. The polymers chosen as substrates in this work were polyamide - PA (polar) and polypropylene PP (non polar), and the adhesion measurement was done by pull strength. The film thickness was found to dictate the adhesion strength of surface films, with thick films bein...

Neste trabalho é apresentado o estudo da formação de reticulações na temperatura ambiente, de borracha natural epoxidada (ENR) de 25% de grau de epoxidação, com um agente de cura contendo o tiol trimetilolpropano tris(2-mercaptoacetato) (TMP-SH). As composições foram realizadas a partir de solubilização da ENR e, posterior reação com o TMP-SH. Fora...

This paper presents the crosslinking study at room temperature of epoxidised natural rubber (ENR), of 25% of epoxidation level, with a curing agent containing thiol trimethylolpropane tris(2-mercaptoacetate) (TMP-SH). The compositions were made from solubilization of ENR, and subsequent reaction with TMP-SH. Compositions with 5, 10 and 20 phr of TM...

Composites of recycled poly(ethylene terephthalate) (PET) reinforced with short glass fiber (GF) (0, 20, 30, and 40 wt %) were compounded in a single-screw extruder (SSE) and in a intermeshing corotating twin-screw extruder (TSE). An SSE fitted with a barrier double-flight screw melting section in between two single-flight sections and a TSE with a...

The problem of vulcanized rubber scraps is of high importance nowadays, and the revulcanization of these scraps is an alternative to reutilize them. This work concerns the investigation of the processability of new compositions made from revulcanizable rubber scraps, through data from the Haake torque rheometer and the Rubber Process Analyzer (RPA)...

Poly(ethylene terephthalate) (PET) composites containing muscovite mica as reinforcing filler were prepared by melt mixing, and their molecular dynamics were investigated by low-field NMR. Spin-lattice and proton spin–spin relaxation times of composites containing different amounts of the filler from 2 to 15 wt% were evaluated and the results compa...

This work is concerned with the influence of mica in natural rubber compounds on properties such as Mooney viscosity, processability and rheological behavior. The amount of this filler was varied from 0 to 40 phr and the stabilized and totalized torques, specific and mechanical energies were determined in a HAAKE torque rheometer. The elastic torqu...

SBR and EPDM extruded profile scraps are ground under ambient conditions for further utilization in recycling and reclaiming processes. The obtained powders (SBR-r and EPDM-r, respectively) are physically, thermally, and chemically characterized and the results are analyzed as for its suitability for reuse methods. It is possible to obtain powdered...

Nanocomposites of butadiene-acrylonitrile copolymer (NBR) and cellulose II were obtained from mixtures of nitrile rubber latex and cellulose xanthate by using a co-coagulation system. The influences of low and medium acrylonitrile content in NBR and the cellulose II content, varying from 0 to 30 phr, were investigated by means of rheometric and equ...

A reciclagem de elastômeros vulcanizados tem sido um problema para as empresas geradoras de resíduos elastoméricos, e ao mesmo tempo um amplo campo de estudo para pesquisadores da área. Diante da possibilidade de recuperação desses resíduos, deu-se início a este trabalho, relacionado à incorporação de pó de pneu de automóvel (STR-r) como uma carga,...

The influences of elastomer ratio and preparation mode on the degradation behavior of NR/BR Natural rubber and polybutadiene rubber blends were investigated by using non-isothermal thermogravimetric analysis (TGA). The activation energy for the degradation process was determined by using both the Ozawa and the Kissiger methods, none of them requiri...

The recycling of vulcanized elastomers represents a problem for companies generating elastomeric residues and has become a wide field of study for researchers in this area. This study addresses the possible use of these residues and investigates an alternative for their recovery through incorporation of tread powder of cars tires (STR-r) as a fille...

Most condom manufacturers claim a 5-year shelf life. A predictive test for condom shelf life is needed, because products shipped to tropical climates have decayed much more rapidly than the stated shelf life would suggest. In this work, five brands of condoms were aged under ambient conditions for 5 years, and in an oven at 50 and 70 °C for various...

Misturas de elastômeros vêm sendo largamente utilizadas na indústria de borracha com a finalidade de se conseguir propriedades específicas, sem a necessidade de sintetizar novos polímeros. O polibutadieno puro (BR) não apresenta boas características de processamento e de resistência à tração e ao rasgamento sendo, por essa razão, normalmente utiliz...

Uma alternativa para as empresas geradoras de resíduos elastoméricos é a incorporação dos mesmos em suas formulações. Esse trabalho tem como objetivo preparar compósitos a partir da incorporação de resíduos industriais de SBR (copolímero de butadieno-estireno) e de EPDM (terpolímero de etileno-propileno-dieno), em formulação ASTM específica para ca...

Blends of polypropylene (PP) and acrylonitrile rubber (NBR) were prepared in a Haake 9000 Rheocord System. Two different phenolic resins were introduced into these blends and the effect of this third component on the mechanical properties was evaluated, as well as the relationship between the crystallization of the polypropylene matrix and the prop...

Nanocomposites of nitrile rubber (NBR) and cellulose II (Cel II) were prepared by co-coagulation of nitrile rubber latex and cellulose xanthate mixtures. The effect of the addition of increasing amounts of Cell II, varying from 0 to 30phr, on the mechanical behavior of a NBR was analyzed. The fracture mechanisms of the nitrile rubber-cellulose II (...

One alternative for elastomeric scraps generation is its incorporation in conventional formulations in the industry itself. In this work, compositions with incorporation of SBR (styrene butadiene rubber) and EPDM (ethylene propylene diene rubber) industrial scraps, in specific ASTM formulation for each elastomer, were prepared. Rheometric character...

Elastomer Blends have been widely used in the rubber industry with the purpose of reaching specific properties without the need of synthesizing new polymers. Polybutadiene rubber (BR) presents poor stress and tear strengths, which is the main reason why BR is usually blended with NR and SBR. These blends are extensively used in the manufacture of t...

Condoms play an important role in the prevention of human immunodeficiency virus transmission. The prediction of condom shelf life became a high priority for the international and national committees responsible for the standardization of the quality of the product. In this work, two sets of batches of natural rubber condoms from three manufactures...

The materials properties of NBR-Cell 2 nanocomposites processed via dynamical cocoagulation process show an enhancement in comparison to conventional filled materials. Experiments with the variation of cellulose content, acid concentration and pressure demonstrate an optimum in the materials properties for a given combination of process parameters....

The blends of acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) prepared on a Haake Torque Rheometer System 9000 were studied in order to investigate the effect of ABS addition on the flow properties of PC. The recorded data obtained from the rheometer were converted, into values of shear rate, shear stress, and viscosity, following the...

The dispersion of carbon black (CB) and carbonyl iron (CI) in polychlorophene (CR) matrices was studied by scanning electron microscopy (SEM). The aim was to determine which of the two is more suited as a radar absorbing material (RAM). Microwave measurements were based on the transmission/reflection method (T/R) using a rectangular waveguide, as t...

An alternative approach for the reuse of waste textiles fabric (WTF) of cotton and polyacrylonitrile was investigated with the purpose of to reinforce high density polyethylene (HDPE) and in addition, a new methodology for obtaining the composites was also developed. It was found that the resulting mechanical properties tested were function of the...

The manufacture of natural rubber goods from the latex has significant commercial interest. The processes to obtain these artifacts, the type and amounts of the vulcanization systems used are of utmost importance in determining their quality and suitability. A number of techniques can be used to verify the efficiency of both the processing and the...

In this work three types of equipments were used, namely, rubber process analyzer (RPA 2000), Mooney viscometer, and dynamic mechanical thermal analyzer, to characterize natural rubber mixtures containing different amounts of regenerated celulose (Cel II) as filler. The RPA 2000 is a new dynamic rheological tester that can analyze raw polymers and...

This work reports sorption processes of oxygen, carbon dioxide, methane, ethylene, and propylene in films of both vulcanized natural rubber and vulcanized rubber–regenerated cellulose composites. The curves representing the pressure dependence of the concentration of carbon dioxide in the composites clearly exhibit a slight concavity with respect t...

É descrito um processo de obtenção de composições de celulose e emulsões poliméricas através da co-precipitação de uma solução de celulose e uma emulsão de polímero e/ou suas misturas, a co-precipitação sendo efetuada adicionando a mistura de solução de celulose e emulsão polimérica a uma solução coagulante sob agitação e vazão constantes, o co-pre...

As fibras de raion são industrialmente obtidas por fiação a úmido, num processo que data de 1904 e que se baseia na coagulação de xantato de celulose em meio ácido. Neste trabalho novas fibras foram desenvolvidas usando o mesmo processo de fiação, porem ao xantato de celulose foi adicionada uma composição vulcanizável de látex de borracha natural (...

Elastomeric compositions of natural rubber (NR) and polybutadiene rubber (BR) in a 1 : 1 ratio (w/w), with mica in the range 0–30 phr, were investigated. For all compositions the same formulation was used but two different additives incorporation sequences were followed. The results of the tests showed that the mechanical performance is sequence-de...

The influence of ageing caused by heating on nanocomposites prepared by co-coagulation of natural rubber latex and Cel xanthate mixtures was studied in this work. For comparison purposes, carbon black natural rubber vulcanizates were also prepared. The amount of Cel II (Cel II) varied from 0 to 30 phr, while carbon black from 0 to 35 phr. The diffe...

Vulcanized composites of chloroprene rubber (CR) with cellulose II (Cel II) as a filler were investigated. Cel II, obtained by the coagulation of cellulose xanthate, was incorporated in the rubber by the traditional method. The filler content varied from 0 to 30 phr. For comparison purposes, carbon black (CB)–CR composites were also studied. The CB...

Rubber goods usually require a combination of properties that cannot be provided by one elastomer only and then two or more polymer components have to be mixed to meet specific requirements. In such cases, the additives normally employed in rubber formulations are unevenly distributed, depending on the affinity of each compound to each polymeric ph...

The effects from ageing of materials is important in terms of cost and quality, particularly if the products are to be used under severe weather conditions. In this work, the effect of accelerated ageing in vulcanizable compositions of natural rubber and mica was studied. The amount of the mineral filler employed varied from 0 to 40 phr. The mechan...

The possible use of castor oil fatty acid as an activator for the vulcanization reaction in silica-filled natural rubber (NR) compounds was investigated. The design and analysis of the experiments were carried out by keeping constant the concentration of silica and the other ingredients while the amounts of stearic acid, castor oil and poly(ethylen...

O estudo do efeito do envelhecimento em artefatos é principalmente importante quanto ao custo e qualidade, tornando o material atrativo ou não para produtos expostos a condições climáticas mais exigentes. Neste trabalho foi estudado o efeito do envelhecimento acelerado em composições vulcanizáveis de borracha natural com mica. O teor da carga miner...

O potencial do óleo de mamona como um ativador para a vulcanização de composições de borracha natural (NR) contendo sílica foi investigado. Utilizando-se um planejamento de experimentos adequado, manteve-se a concentração de sílica e outros aditivos constantes enquanto as quantidades de ácido esteárico, óleo de mamona e poli(etileno-glicol) foram v...

In a previous work, two methods using rheometric parameters to calculate the kinetic constant were compared, and the results showed that the higher significative variables could be accurately determinated in opposition to the lower significative ones. Thus, a modification is suggested in this article, by limiting the conversion of the cure reaction...

The complex permeability (µ r *) and permittivity (ε r *) of radar absorbing materials (RAMs) play a key role in determining the reflection and attenuation properties of incident microwaves. Their real (µ′ and ε ′) and imaginary (µ′′ and ε ′ ′) components and relationship with microwave absorbing properties have been investigated in the frequency r...

Rubber blends are frequently prepared to give a balance of the desired properties and, in some cases, reduction of cost as well. Elastomeric mixtures are usually multiphase systems and the dispersion of the additives may not be uniform throughout the phases. In this work, polybutadiene rubber (BR) was mixed with polybutadiene-styrene rubber (SBR) i...

O objetivo deste trabalho foi o desenvolvimento de compósitos claros com propriedades de interesse tecnológico utilizando elastômeros com diferentes polaridades. Para que este objetivo fosse atingido, celulose II em pó foi usada como carga, em borracha natural (NR) ou policloropreno (CR). A celulose II foi obtida por coagulação da solução de xantat...

The rheometric, mechanical, and dynamic mechanical properties as well as fracture surfaces of natural rubber–mica and polybutadiene rubber–mica vulcanizates were studied. Mica was used in the range of 0–30 phr and the rheometric study was carried out at 160°C. The results indicate that the mechanical properties are improved as filler addition incre...

Obtention Process of Nanocomposites with Carboxylated Nitrile Rubber (XNBR) and Cellulose II. Two process for incorporation of cellulose II as filler in carboxylated nitrile rubber elastomers (XNBR), namely S1 and S2, were developed, with the purpose to obtain nanocomposites. The nanocomposites either with 15 phr of cellulose or without filler, pre...

Ageing Resistance of NBR Compounds -Comparison between curing systems The ageing resistance of NBR compounds cured with phenolic resin and sulphur-donor system (TMTD) was investigated. In general, the composition cured with phenolic resin showed better mechanical properties than the one with TMTD. Degradation onset was detected through infrared spe...

In preceding investigations the overall rate and apparent activation energy for the vulcanization process were calculated for natural rubber compounds, assuming that vulcanization follows first-order kinetics. It was observed that the addition of white rice husk ash (WRHA) increased the rate of crosslinking and lowered the apparent activation energ...

The preparation of polymethylvinylsiloxane rubbers with silica (SC) and black rice husk ash (BRHA) as fillers is reported. We conducted stress–strain experiments on these vulcanized rubbers to study the reinforcement properties of the fillers. Curves showing the dependence of the stress on the reciprocal of the elongation ratio displayed, in most c...

The potential of castor oil fatty acid as an activator for the vulcanization reaction in silica filled natural rubber (NR) compounds was investigated. Design and analysis of experiments were carried out by keeping constant the concentrations of silica and the other ingredients while the amounts of stearic acid, castor oil and poly(ethylene glycol)...

Composites of natural rubber (NR) and cellulose II (Cel II) were prepared by co-coagulation of natural latex and cellulose xanthate mixtures. The influence of increasing amounts of Cel II, varying from 0 to 30 phr, on the mechanical properties was investigated. The topography of the fracture surfaces of tensile, tear and abrasion specimens after te...

Rice husk ash was incorporated into natural rubber (NR) using a laboratory size two-roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 Curometer. The torque curves were obtained at 150, 160, 170, and 180°C. The overall rate and the apparent activation energy for the vulcanization process wer...

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 form...

In this work the influence of mica on the mechanical and dynamic mechanical properties of vulcanized natural rubber compositions was studied. The crosslinking density of the compositions was also determined. The data were compared to those of the unfilled composition. The results indicate an increase in modulus, hardness, crosslinking density and c...

Cinza da casca de arroz foi incorporada em borracha natural (NR) utilizando-se um misturador de cilindros. O sistema de vulcanização convencional (CV) foi escolhido e os estudos sobre a cura das composições foram conduzidos em um Curômetro TI-100. As curvas de torque foram obtidas em 150, 160, 170 e 180 degreesC. A velocidade global e a energia de...

As borrachas, para serem convertidas em materiais úteis do ponto de vista de aplicações, precisam ser misturadas a alguns ingredientes, os quais vão lhes dar as características desejadas para, então, serem vulcanizadas. Neste artigo, os aspectos históricos da vulcanização são abordados bem como a evolução dos aditivos essenciais à maioria das formu...

Neste trabalho foi estudada a influência da adição de mica em composições vulcanizáveis de borracha natural quanto às propriedades mecânicas e dinâmico-mecânicas. As diversas composições também foram avaliadas quanto à densidade de ligações cruzadas. Todos os dados foram comparados aos da composição sem carga. Os resultados mostraram que a adição d...

The preparation of elastomeric compositions based on poly(methylvinyl siloxane) using silica and rice husk ash as fillers is reported. Permeation of oxygen, nitrogen, carbon dioxide and methane across the compositions was measured in the temperature interval 30–60° C under upstream pressures lying in the range 15–76 cm Hg. Permeation and diffusion...

Black rice husk ash (BRHA) and white rice husk ash (WRHA) were incorporated into natural rubber (NR) using a laboratory-size two-roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI-100 Curometer. The torque curves were obtained at 150, 160, 170, and 180°C. The overall rate and the apparent activa...

NR/BR blends (50/50) were prepared by using four different sequences to incorporate the additives. After curing under constant conditions the vulcanizates demonstrate sequence-dependent mechanical properties. Based on dynamic mechanical thermal analysis and scanning electron microscopy a correlation between the mechanical performance and the blend...

The corrosive effect from the exposure to salt spray was studied on chloroprene rubber (CR) matrices containing a particulate ferromagnetic filler, viz. carbonyl-iron powder (CIP). The experiments in salt spray chamber are able to create an aggressive condition of sodium chloride atmosphere (NaCl), being important to minimize the time of exposure o...

Este trabalho tem por objetivo avaliar a resistência à corrosão de composições elastoméricas à base de policloropreno (CR) contendo uma carga ferromagnética, após exposição à câmara de névoa salina. O material utilizado no carregamento foi o ferrocarbonila (CI). Este ensaio foi importante, pois evidenciou o processo corrosivo em curto espaço de tem...

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 witho...

Rubber reinforcement increases if the domain size becomes less than 1 μm. Compositions of natural rubber and cellulose II were prepared by co-coagulation of natural latex and cellulose xanthate mixtures. The influence of increasing amount of Cel II, varying from 0 to 30 phr, on processing, curing and mechanical properties were studied. The use of c...

In this work, samples consisting of an elastomeric matrix containing different kinds of active materials in particulate form were prepared for reflectivity measurements. The materials individually used in weight contents of 80% in polychloroprene matrix were: carbonyl-iron (CI) and doped ferrite powders. The microwave reflectivity levels were deter...