868 resultados para ELASTOMER BLENDS
Resumo:
The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C PVA) of two types of poly (vinyl alcohol) (PVA) and the effect of the type and the concentration of plasticizers on the phase properties of biodegradable films based on blends of gelatin and PVA, using a response-surface methodology. The films were made by casting and the studied properties were their glass (Tg) and melting (Tm) transition temperatures, which were determined by diferential scanning calorimetry (DSC). For the data obtained on the first scan, the fitting of the linear model was statistically significant and predictive only for the second melting temperature. In this case, the most important effect on the second Tm of the first scan was due to the HD of the PVA. In relation to the second scan, the linear model could be fit to Tg data with only two statistically significant parameters. Both the PVA and plasticizer concentrations had an important effect on Tg. Concerning the second Tm of the second scan, the linear model was fit to data with two statistically significant parameters, namely the HD and the plasticizer concentration. But, the most important effect was provoked by the HD of the PVA.
Resumo:
Blends of fiber from sugar cane bagasse, corn starch, and whey protein concentrate were extruded. A single screw extruder, equipped with a screw at a constant compression ratio of 1:1 and a die diameter of 3 mm, was used. The best processing conditions were determined according to a central composite rotatable design (α = 1.41) with 5 central points, which gives a total of 13 tests. During the extrusion process the content of insoluble fiber decreased and that of soluble fiber increased. An increase in the contents of fiber and in the barrel temperature resulted in a decrease in the expansion index values and an increase in the water absorption index values; whereas in blends with intermediate fiber contents the effects in these parameters were found to be the opposite. High fiber contents increased penetration force but decreased luminosity, water solubility index values and the adhesive force in gels. The extrusion process improved the functional properties of sugarcane fiber bagasse enabling its addition to diverse alimentary systems.
Resumo:
The opportunity to supplement common cassava biscuits with a product of higher nutritional value meets consumer expectations. In this work it was studied the effects of process parameters and flaxseed addition on physical properties of expanded snacks. Extrusion process was carried out using a single screw extruder in a factorial central composite rotatable design with four factors: flaxseed flour percentage (0-20%), moisture (12-20%), extrusion temperature (90-130 °C) and screw speed (190-270). The effect of extrusion variables was investigated in terms of expansion index, specific volume, water absorption index, water solubility index, color parameters (L*, a* ,b*) and hardness. The data analysis showed that variable parameters of the extrusion process and flaxseed flour affected physical properties of puffed snacks. Among the experimental conditions used in the present study, expanded snack products with good physical properties can be obtained under the conditions of 10% flaxseed flour, 230 rpm screw speed, temperature of 90 °C and moisture of 12%.
Resumo:
A cassava-based puffed snack was produced using a single screw extruder to determine the effect of the raw material composition (cassava leaf flour and moisture) and the process parameters (extrusion temperature and screw speed) on the physical characteristics of an extruded-expanded snack. A central composite rotational design, including four factors with 30 treatments, was used with the following as dependent variables: expansion index, specific volume, water solubility index, water absorption index, color (L*, a*, b*), and hardness. Under conditions of low moisture content (12 to 14%), low percentage of cassava leaf flour (2 to 4%), and intermediate conditions of extrusion temperature (100°C) and screw speed (230rpm), it was possible to obtain puffed snack products with desirable characteristics.
Resumo:
The aim of this study was to determine the physical and microbiological characteristics of extruded broken beans flour, in addition to developing mixtures for gluten-free cake with these flours, evaluating their technological and sensory quality. Gluten-free formulations were prepared with 45%, 60% and 75% of extruded broken beans. All analyzes of the flours and mixtures for cakes were performed according to standard techniques found in the literature. Sensory analyzes of cakes applied the 9-point structured hedonic scale. Results were submitted to variance analysis and comparison of means test (Tukey, p<0.05). The use of extruded broken beans improved the water absorbed and water solubility index of the mixtures for gluten-free cake, and for the lower viscosity and retrogradation when compared to the standard formulation. All cakes were accepted (rate ≥ 7) for all the analyzed attributes. From the technological and sensory standpoints, the development of gluten-free cake mixtures is feasible with up to 75% of extruded broken beans.
Resumo:
This thesis aims to develop new toughened systems for epoxy resin via physical and chemical modifications. Initially the synthesis of DGEBA was carried out and the properties compared with that of the commercial sample. Subsequently the modifier resins to be employed were synthesized. The synthesized resin were characterized by spectroscopic method (FTIR and H NMR), epoxide equivalent and gel permeation chromatography. Chemical modification involves the incorporation of thermoset resins such a phenolics, epoxy novolacs, cardanol epoxides and unsaturated polyester into the epoxy resin by reactive belnding. The mechanical and thermal properties of the blends were studied. In the physical modification route, elastomers, maleated elastomers and functional elastomers were dispersed as micro-sized rubber phase into the continuous epoxy phase by a solution blending technique as against the conventional mechanical blending technique. The effect of matrix toughening on the properties of glass reinforced composites and the effect of fillers on the properties of commercial epoxy resin were also investigated. The blends were characterized by thermo gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy and mechanical property measurements. Among the thermoset blends, substantial toughening was observed in the case of epoxy phenolic novolacs especially epoxy para cresol novolac (ECN). In the case of elastomer blending , the toughest blends were obtained in the case of maleic anhydride grafted NBR. Among functional elastomers the best results were obtained with CTBN. Studies on filled and glass reinforced composites employing modified epoxy as matrix revealed an overall improvement in mechanical properties
Resumo:
Zinc butyl xanthate [Zn(bxt)2] was prepared in the laboratory . The effect of this xanthate with zinc diethyl dithiocarbamate (ZDC) on the vulcanization of natural rubber ( NR), polybutadiene rubber (BR), and NR/BR blend has been studied at different temperatures. The amounts of Zn (bxt)2 and ZDC in the compounds were optimized by varying the amount of ZDC from 0 . 75 to 1.5 phr and Zn (bxt)2 from 0 . 75 to 1 .5 phr. The cure characteristics were also studied . HAF filled NR, BR, and NR / BR blend compounds were cured at different temperatures from 60 to 150 C. The sheets were molded and properties such as tensile strength, tear strength, crosslink density and elongation at break, compression set, abrasion resistance, etc. were evaluated. The results show that the mechanical properties of 80NR/20BR blends are closer to that of NR vulcanizates, properties of 60NR/40BR blends are closer to BR vulcanizates, while the 70NR/30BR blends show an intermediate property.
Resumo:
Blends of chlorobutyl rubber (CIIR) with two grades of ethylene-propylene diene monomer rubber (EPDM) were prepared and the effect of blend ratio on the cure characteristics, hot air ageing resistance, steam ageing resistance, and mechanical properties were evaluated. The blend of CIIR with EPDM grade 301 T showed additive behavior and the blend with the other grade of EPDM (NDR 4640) showed synergistic behavior.
Resumo:
The effects of modifying blends of poly(vinyl chloride) (PVC) with linear low density polyethylene (LLDPE) by means of acrylic acid, maleic anhydride, phenolic resins and p-phenylene diamine were investigated. Modification by acrylic acid and maleic anhydride in the presence of dicumyl peroxide was found to be the most useful procedure for improving the mechanical behaviour and adhesion properties of the blend. The improvement was found to be due mainly to the grafting of the carboxylic acid to the polymer chains; grafting was found to be more effective in LLDPE/PVC blends than in pure LLDPE.
Resumo:
Studies conducted on butadiene-acrylonitrile copolymer (NBR)/poly(vinyl chloride) (PVC) blends at different temperatures indicate that an optimum temperature exists for the formation of a particular blend. The mechanical properties of the blends confirm this observation. PVC stabilizer based on, magnesium oxide , zinc oxide, and stearic acid was found to be very useful in NBR/PVC blends.
Resumo:
Blends of polychloroprene rubber and plasticized polyvinylchloride have been prepared in various compositions and their properties evaluated. The properties of the blends show that they can be used to replace polychloroprene in many applications
Resumo:
Ethylene-propylene-diene rubber (EPDM) and isobutylene-isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/ EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined.
Resumo:
Butyl (IIR) tube reclaim (RR) was mixed with carbon black filled natural rubber (NR) compounds at various percentages. The blend containing a low percentage of RR was found to show improved ageing resistance and improved processability with out much reduction in the mechanical properties.
Resumo:
Polymer-solvent interaction parameters for the blends of natural rubber (NR) with styrene-butadiene rubber (SBR) and polybutadiene rubber ( BR) are calculated using the Flory-Rehner equation by equating the network density of the vulcanizates in two solvents.