Preparation of low protein latex : Effect of different cure systems and fillers on its properties

Natural rubber latex, an aqueous colloidal dispersion of polyisoprene is widely used in production of gloves, catherers, rubber bands etc. The natural rubber latex content present in products such as gloves causes allergic problems. Of the different types of allergies reported, latex is known to produce Type I and Type IV allergies. Type I is called immediate hypersensitivity and type IV is called delayed hypersensitivity. It has been reported that some of the proteins present in the latex are mainly responsible for the allergic reactions type I. Significant reduction in the allergic response (type I) of natural rubber latex can be achieved by the reduction in its protein content, however out of the total proteins present in the latex or latex film only a fraction is extractable. The major techniques employed to reduce protein content of latex include leaching, autoclaving, chlorination, use of proteolytic enzymes and use of non ionic surfactants. Sulphur vulcanization of dipped products is responsible for Type IV allergy. N-nitrosamine, a carcinogenic substance is produced as a result of sulphur vulcanization. Radiation vulcanization can be used as an alternative for sulphur vulcanization. The current research deals with techniques to reduce the allergy associated with latex products. To reduce the type I allergy, low protein latex is developed using polyethylene glycol, a non- ionic surfactant. The present study employs radiation vulcanization to eliminate type IV allergy. The effect of different cure systems and fillers on the properties of low protein latex is also investigated as a part of the study.

Radiopacity and Chemical resistance of Elastomer-Barium sulphate nanocomposites

The Human race of our century is in gluttonous search for novel engineering products which led to a skyrocketed progress in research and fabrication of filled polymers. Recently, a big window has been opened up for speciality polymers especially elastomers with promising properties. Among the many reasons why rubbers are widely used in the process industries, three are considered as important. Firstly, rubbers operate in a variety of environments and possess usable ranges of deformity and durability and can be exploited through suitable and more or less conventional equipment design principles. Secondly, rubber is an eminently suitable construction material for protection against corrosion in the chemical plant and equipment against various corrosive chemicals as, acids and alkalies and if property tailored, can shield ionising radiations as X-rays and gamma rays in medical industry, with minimum maintenance lower down time, negligible corrosion and a preferred choice for aggressive corroding and ionising environment. Thirdly, rubber can readily and hastily, and at a relatively lower cost, be converted into serviceable products, having intricate shapes and dimensions. In a century’s gap, large employment of flexible polymer materials in the different segments of industry has stimulated the development of new materials with special properties, which paved its way to the synthesis of various nanoscale materials. At nano scale, one makes an entry into a world where multidisciplinary sciences meet and utilises the previously unapproached infinitesimal length scale, having dimension which measure upto one billionth of a meter, to create novel properties. The nano fillers augment the elastomers properties in an astonishing fashion due to their multifunctional nature and unprecedented properties have been exhibited by these polymer-nanocomposites just to beat the shortcomings of traditional micro composites. The current research aims to investigate the possibility of using synthesised nano barium sulphate for fabricating elastomer-based nanocomposites and thereby imparting several properties to the rubber. In this thesis, nano materials, their synthesis, structure, properties and applications are studied. The properties of barium sulphate like chemical resistance and radiopacity have been utilized in the present study and is imparted to the elastomers by preparing composites.

Occupational contact urticaria: lessons from the French National Network for Occupational Disease Vigilance and Prevention (RNV3P)

International audience

Avaliação da sensibilidade ao latex em profissionais de saúde num hospital do norte alentejano

Nos profissionais de saúde a alergia ao látex representa um importante problema de saúde ocupacional. Em contexto hospitalar, a principal fonte de exposição alergénica é a utilização de luvas látex empoadas e a inalação dos bioaerossóis que se formam pela manipulação das mesmas. Mediante consentimento informado, os participantes preencheram um inquérito de resposta fechada e realizaram os testes cutâneos (TC). Aqueles que apresentaram reacção foram encaminhados para a consulta de imunoalergologia e realizaram TC para alimentos, doseamentos séricos de imunoglobulinas (lgE total e específica). Foram incluídos no estudo 44 dos 48 participantes (a=0.1). A sensibilidade ao látex foi posta em evidência em 15 dos elementos da amostra, seis dos quais reagem ao extracto de látex utilizado nos TC. A alergia ao látex foi diagnosticada em duas pessoas. A aplicação de questionários na avaliação sensibilização ocupacional ao látex pode vir a constituir ferramenta válida de auscultação deste problema nas instituições prestadoras de cuidados de saúde. ABSTRACT: Latex allergy is a major occupational disease among health care workers. ln hospitals, the main source of allergen exposure is the powdered latex gloves latex and the inhalation of the aerosols formed by its direct manipulation. By means of informed assent, the participants filled an inquiry and carried out the SPT. Those with cutaneous reaction to the latex extract went to an immunoallergology appointment. SPT for fruit and pollen with cross reactivity to latex allergens where performed, and blood levels of total and specific lgE where determined. The study group included 44 of the 48 participants (a=0.1). Fifteen elements showed latex sensitization and six of them had cutaneous reaction to the latex extract used in the SPT. Latex allergy was found in two health care professionals. Questionnaires may provide a reliability tool to access the sensitization due to natural rubber products and the symptoms more commonly associated with it, in health care facilities.

Increased Vascular Permeability, Angiogenesis and Wound Healing Induced by the Serum of Natural Latex of the Rubber Tree Hevea brasiliensis

Increases in vascular permeability and angiogenesis are crucial events to wound repair, tumoral growth and revascularization of tissues submitted to ischemia. An increased vascular permeability allows a variety of cytokines and growth factors to reach the damaged tissue. Nevertheless, the angiogenesis supply tissues with a wide variety of nutrients and is also important to metabolites clearance. It has been suggested that the natural latex from Hevea brasiliensis showed wound healing properties and angiogenic activity. Thus, the purpose of this work was to characterize its angiogenic activity and its effects on vascular permeability and wound healing. The serum fraction of the latex was separated from the rubber with reduction of the pH. The activity of the dialyzed serum fraction on the vascular permeability injected in subcutaneous tissue was assayed according Mile`s method. The angiogenic activity was determined using a chick embryo chorioallantoic membrane assay and its effects on the wound-healing process was determined by the rabbit ear dermal ulcer model. The serum fraction showed evident angiogenic effect and it was effective in enhancing vascular permeability. In dermal ulcers, this material significantly accelerated wound healing. Moreover, the serum fraction boiled and treated with proteases lost these activities. These results are in accordance with the enhancement of wound healing observed in clinical trials carried out with a biomembrane prepared with the same natural latex. Copyright (C) 2009 John Wiley & Sons, Ltd.

Natural hydraulic lime (nhl3.5) mortars with scrap tire rubber

The use of wastes and industrial by-products as building materials is an important issue in order to decrease costs with waste management and the embodied energy of building products. In this study scrap tire rubber was used as additional aggregate of mortars based on natural hydraulic lime NHL 3.5 and natural sand. Different particle size fractions and proportions of scrap tire rubber were used: a mix obtained directly from industry and separated fine, medium and coarse fractions; 0 %, 18 %, 36 % and 54 % of the weight of binder, corresponding to 2.5 %, 5 % and 7.5 % of the weight of sand. As mortars based on NHL specifications became stricter with the current version of EN 459–1:2015, the influence of the rubber’s additions on the mortars’ fresh state, mechanical and physical performance is presented in this work: flow table consistency, water retention, dynamic elasticity modulus, flexural and compressive strength, open porosity and bulk density, capillary absorption, drying and thermal conductivity are studied. The use of the rubber mix coming from the waste tire industry seems advantageous and may open possibilities for use as raw material by the mortars industry.

Attenuation of foot pressure during running on four different surfaces: asphalt, concrete, rubber, and natural grass

The practice of running has consistently increased worldwide, and with it, related lower limb injuries. The type of running surface has been associated with running injury etiology, in addition other factors, such as the relationship between the amount and intensity of training. There is still controversy in the literature regarding the biomechanical effects of different types of running surfaces on foot-floor interaction. The aim of this study was to investigate the influence of running on asphalt, concrete, natural grass, and rubber on in-shoe pressure patterns in adult recreational runners. Forty-seven adult recreational runners ran twice for 40 m on all four different surfaces at 12 +/- 5% km . h(-1). Peak pressure, pressure-time integral, and contact time were recorded by Pedar X insoles. Asphalt and concrete were similar for all plantar variables and pressure zones. Running on grass produced peak pressures 9.3% to 16.6% lower (P < 0.001) than the other surfaces in the rearfoot and 4.7% to 12.3% (P < 0.05) lower in the forefoot. The contact time on rubber was greater than on concrete for the rearfoot and midfoot. The behaviour of rubber was similar to that obtained for the rigid surfaces - concrete and asphalt - possibly because of its time of usage (five years). Running on natural grass attenuates in-shoe plantar pressures in recreational runners. If a runner controls the amount and intensity of practice, running on grass may reduce the total stress on the musculoskeletal system compared with the total musculoskeletal stress when running on more rigid surfaces, such as asphalt and concrete.

Anatomical and functional evaluation of tympanoplasty using a transitory natural latex biomembrane implant from the rubber tree Hevea brasiliensis

PURPOSE: To compare the role of transitory latex and sylastic (R) implants in tympanoplasty on the closure of tympanic perforations. METHODS: A randomized double-blind prospective study was conducted on 107 patients with chronic otitis media submitted to underlay tympanoplasty and divided at random into three groups: control with no transitory implant, latex membrane group, and sylastic (R) membrane group. RESULTS: Greater graft vascularization occurred in the latex membrane group (p<0.05). Good biocompatibility was obtained with the use of the latex and silicone implants, with no effect on the occurrence of infection, otorrhea or otorragy. CONCLUSION: The use of a transitory latex implant induced greater graft vascularization, with a biocompatible interaction with the tissue of the human tympanic membrane.

NHL 3.5 mortars with scrap tire rubber

The use of wastes and industrial by-products as building materials is an important issue in order to decrease costs with waste management and the embodied energy of building products. Scrap tire rubber has been studied as aggregate for cementitious materials. Natural hydraulic limes are natural binders with particular characteristics of both air and hydraulic binders. Their specifications became stricter with the last version of EN 459-1:2010. In this study scrap tire rubber was used as additional aggregate of mortars, based on NHL3.5 and natural sand. Different particle size fractions and proportions of scrap tire rubber were used: a mix obtained almost directly from industry (only after sieving for preparation of particle sizes similar to mortar aggregate) and separated fine, medium and coarse fractions; 0%, 18%, 36% and 54% weight of binder, corresponding to 2.5%, 5% and 7.5% weight of sand. The influence of the rubbers´ additions on the mortars´ fresh state, mechanical and physical performance is presented, namely by flow table consistency, water retention, fresh bulk density, dynamic elasticity modulus, flexural and compressive strength, open porosity and bulk density, capillary absorption, drying and thermal conductivity. The use of the rubber mix coming from the waste tire industry seems advantageous and may open possibilities for use as raw material by the mortars industry.

Biological cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets of three rubber tree clones

Life cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets from three rubber tree clones. The biological cycle of Tenuipalpus heveae Baker, 1945 (Tenuipalpidae), a potential rubber tree pest mite, was studied by the observation of individuals reared on leaflets of the clones GT 1, PB 235 and RRIM 600, in controlled environmental conditions. Three daily observations were done of 60 eggs on leaflets from each clone in order to verify the development of immature stages and the female oviposition. The fertility life table was constructed based in the collected data. Mites reared on PB 235 had faster rate of development, requiring less time in days, to double its population in number (TD), and had the highest values for egg production, female longevity, net reproductive rate (Ro), intrinsic rate of natural increase (r m) and finite rate of increase (λ). Lower reproductive values and the longest time necessary to reach adult stage were recorded for the mites on GT 1. In all studied clones, the deutonymphal phase had the highest viability, while the larval phase had the lowest, highlighted by the survivorship curve that indicated high mortality during this life stage. The clone PB 235 allowed the most suitable conditions for the development of T. heveae, followed by RRIM 600, while GT 1 was the less suitable substratum to rear this mite species.

Evaluation of Magnetic,Dielectric and Mechanical Properties of Rubber Ferrite Composites

In the present study the preparation and characterisation of rubber ferrite composites (RFC) containing barium ferrite (BaF) and strontium ferrite (SrF) have been dealt with. The incorporation of the hard ferrites into natural and nitrile rubber was carried out according to a specific recipe for various loadings of magnetic fillers. For this, the ferrite materials namely barium ferrite and strontium ferrite having the general formula MO6Fe2O3 have been prepared by the conventional ceramic techniques. After characterisation they were incorporated into the natural and nitrile rubber matrix by mechanical method. Carbon black was also incorporated at different loading into the rubber ferrite composites to study its effect on various properties. The cure characteristics, mechanical, dielectric and magnetic properties of these composites were evaluated. The ac electrical conductivity of both the ceramic ferrites and rubber ferrite composites were also calculated using a simple relation. The investigations revealed that the rubber ferrite composites with the required dielectric and magnetic properties can be obtained by the incorporation of ferrite fillers into the rubber matrix, without compromising much on the processability and mechanical properties.

Marine bacterial prodigiosin as dye for rubber latex, polymethyl methacrylate sheets and paper

Prodigiosin is known for its immunomodulatory, antibacterial, antimycotic, antimalarial, algicidal and anticancer activities. Here, we reported the evaluation of prodigiosin pigment as a dyeing agent in rubber latex, paper and polymethyl methacrylate (PMMA) so that it can be considered as an alternative to synthetic pigments. Maximum color shade was obtained in rubber sheet prepared with 0.5 parts per hundred gram of rubber (phr) pigment and PMMA sheet incorporated with 0.08 μg pigment. Results indicate scope for utilization of prodigiosin as dye for PMMA and rubber and also prodigiosin dyed paper as a pH indicator. Further, being a natural and water insoluble pigment, it is ecofriendly

Análise da volatilidade de preço do mercado da borracha natural

O foco central deste estudo foi desenvolver uma análise da trajetória dos prsços da borracha natural bensflciada ao longo do século XX, através da utilização dos testes econométricos da dasse - ARCH: GARCH, E-GARCH e TARCH para o da Malásia, principal entidade de formação do preço intemacional da commodity. Como resultado dos testes estatísticos dos dados disponíveis no mercado, observouse uma forte incidência de ciclos de sazonalidade no preço intemacional da borracha impactando diretamente na produção mundial. Observa se ainda a baixa capacidade de resposta da produção a choques de demanda devido ao longo prazo de maturação das pfantações

Biological cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets of three rubber tree clones

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Seasonality of pathogenic fungi in mites of rubber tree plantations adjacent to fragments of Cerrado

Fungos são os patógenos mais freqüentemente observados em populações de ácaros, auxiliando o controle destes em diferentes culturas. Vinte e cinco amostras de folhas foram coletadas de cultivos de seringueiras vizinhas a dois fragmentos de vegetação de Cerrado. em cada seringal, 25 plantas foram selecionadas para coletas e sete folhas ao redor da copa foram coletadas até a altura de sete a oito metros do solo. Aproximadamente 250 indivíduos de Calacarus heveae Feres, Phyllocoptruta seringueirae Feres e Tenuipalpus heveae Baker, coletados aleatoriamente, foram montados. Hirsutella thompsonii Fisher foi observado nas três espécies de ácaros e T. heveae foi a espécie mais infectada. Os maiores níveis de infecção ocorreram de novembro a fevereiro (estação chuvosa). Na estação seca, os níveis de infecção ficaram abaixo dos 5%. H. thompsonii tem potencial para ser usado como micoacaricida na estação chuvosa.