Surgical gloves were manufactured using the RVNRL process. A fractional factorial design at two levels showed that five parameters of the coagulant dipping process which were studied independent. Coagulant concentration and dwell time in the radiovulcanized latex presented major main effects while the temperature of the former before dipping into the radiovulcanized latex and the flow time of the radiovulcanized latex on the former surface presented opposite main effects. The withdrawal rate of the former from the radiovulcanized latex did not change glove thickness. The mathematical correlation between the estimates of thickness and the significant main effects of coded variables was = 0.212 + 0.025x1 + 0.019x2. This optimized equation allowed reproduction of a surgical glove thickness in the range of 0.157 to 0.291mm, which is considered acceptable by international standard specification
Response surface methodology was utilized to conceive a mathematical relationship between the crosslinking efficiency of natural rubber latex vulcanized by gamma rays, and the process parameters (n-butyl acrylate and KOH). The radiation vulcanization of latex can be optimized at low vulcanization dose (VD) and at high concentration of n-BA. This relationship can be estimated by the following model. See on the magazine.
RESUMEN [2]. El gran interés por los sistemas con arcillas se debe a su estructura laminar con dimensión nanométrica [1,6,10,11]. El resultado de la relación entre el área superficial y el espesor es una gran área interfacial que permite un alto grado de interacción con el polímero, lo que implica un alto índice de refuerzo para poca carga incorporada. La mayor parte de los estudios se realizan utilizándose arcillas sintéticas del tipo Motmorillonita-sódica pero, las motmorillonitas naturales, comúnmente identificadas como bentonitas, son las más importantes [5; 12]. La capacidad de intercambio de cationes de las arcillas permite la rápida formación de un coloide con la adición de agua. Es necesario modificar las arcillas para que presenten superficies organofílicas, ya que ___________________________________________________________________________________________
Natural rubber latex is a dispersion of natural rubber particles in water. These particles are coated with a protein layer which will stabilize the dispersion in water by forming an electric charge in the layer. Any different condition affecting this layer disturbs the stability of dispersion. Microorganism attack disturbs the protein layer and consequently the stability of the dispersion. By adding 1.2% by weight of NH3, the stability of the dispersion can be improved. The fresh latex was irradiated by Co-60 with irradiation dose of 10, 20, 30, 40 and 100 kGy. The results showed a relationship between the volatile fatty acid content (VFA, product from microorganism attack on carbohydrate) and the green strength or the physical properties of vulcanized film. Low VFA number showing a higher physical strength of the film either un-vulcanized or vulcanized. It appeared that the structure was responsible in yielding a good physical property of the film.
Monitor of natural radionuclides in aquatic raw is very important to guaranty the normal control level in the environmental medium and the human. In this report were available the concentration of 226Ra and 228Ra in Cananeia’s underground water, Iguape and Comprida Island into the south region of Sao Paulo state, by gross alpha and beta counting method. The concentration of 226Ra was variety into the interval 0.80 to 23 mBqL-1 in April/2009 (rain period) and into the interval 0.63 to 12 mBqL -1in August/2009 (dried period). The concentration of 228Ra was variety into the interval 18 to 39 mBqL-1 in April/2009 and into the interval 15 to 72 mBqL-1 in August/2009. The Activities ratio of 228Ra/226Ra was variety into the interval 3.3 to 31.7 at rain period and 1.1 to 26.7 at dried period. To compare the yield values of 226Ra and 228Ra these show high activity of the 228Ra isotope. The calculate dose no arising the reference of effective dose level available by WHO.
To improve the parameters of the transesterification process by the basic route for the production of biodiesel, crude fish oil (AP), obtained from the viscera of fish, and residual vegetable oils (AR) blenders were used. Because the AP contains high percentages of long chain polyunsaturated fatty acids that are responsible for its instability is that it was mixed with increasing percentages of AR. This translated into a higher conversion performance to biodiesel by the basic route, also depending on the level of free fatty acids. The index of methyl esters obtained from the blends and the original oils was analyzed. The calculation of the performance of each reaction is made based on the produced esters. The analysis is complemented by measuring the kinematic viscosity of the blends and the pure oils, as well as the biodiesel produced. The results showed yields higher than 90% when using the process of transesterification of the blends by the basic route. The standardization of blends by its acidity index is of great importance reaching a maximum value of 3.5 mg KOH/g. On the other hand, the viscosity of the biodiesel produced, from the blends, is kept within international standards; In addition, the process conditions are improved.
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