摘要:

The melt Theological behavior of nitrile rubber (NBR)/ethylene-vinyl acetate (EVA) copolymer blends was studied with special reference to the effect of the blend ratio, cross-linking systems, and shear rate using a capillary rheometer. At a given shear stress at 90°C, the viscosities of the blends vary slightly with composition. The effect of cross-linking systems [viz., sulfur (S), peroxide (DCP) and mixed (S+DCP) systems] on the viscosity of NBR/EVA blends is negligible. The melt viscosity of the blends decreases with increasing shear rate, showing pseudoplastic behavior. The flow behavior index values also support the pseudoplastic nature of these blends. Various theoretical models were used to predict the melt viscosity of the blends. Parameters such as die swell, principal normal stress difference, recoverable shear strain, and shear modulus were calculated to characterize the melt elasticity of these blends. The melt elasticity of the system was increased by the addition of NBR to EVA. The extrudate deformation at different shear rates was also studied. It was observed that as the shear rate increases, the extrudate surface exhibits a higher degree of deformation. The morphology of the extrudates of the blends at different shear rates has been examined by a scanning electron microscope. The morphology was found to be dependent on the blend ratio and shear rate.

ISSN:0360-2559    

DOI:10.1080/03602559909351581

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The abrasion resistance of two grades of epoxidized natural rubber (ENR 25 and ENR 50) and one grade of styrene-butadiene rubber (SBR) were studied using an Akron abrasion tester. An accelerated sulfur vulcanization system with 2-mercaptobenzothiazole (MBT) as the accelerator is used throughout the study. Carbon black (N 330), precipitated silica, and calcium carbonate were chosen as the fillers. The range of sulfur and filler loadings was from 1 to 5 phr and 10 to 50 phr, respectively. Mixing was done on a two-roll mill. Results obtained show that for all the rubbers studied, the volume loss due to abrasion decreases with increasing sulfur loading and passes through a minimum at about 3 phr of sulfur. This observation is attributed to the changes of cross-link types from monosulfidic to polysulfidic crosslink as sulfur concentration is increased. However, further sulfur loading would cause a “tight” cure, thus increasing the abrasion loss. For sulfur loading less than 3 phr, ENR 25 indicates the highest abrasion loss, followed by SBR and ENR 50. For the filled stock, minimum loss is observed at about 35–40 phr of filler. Reinforcing filler such as carbon black exhibits better abrasion resistance than calcium carbonate, a nonreinforcing filler. The abrasion loss increases at higher filler loading due to the dilution effect of fillers. Ozone plays an important role in the abrasion property of unsaturated rubbers, as reflected by the higher abrasion loss in the presence of ozone.

ISSN:0360-2559    

DOI:10.1080/03602559909351582

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The influence of unsaturated polyester resin to sand ratios as well as γ-irradiation on the physico-mechanical properties of the sand-polyester composite has been investigated. The samples were prepared at different ratios ranging from 5% to 30% of unsaturated polyester to sand, then subjected to γ-irradiated between 10 and 100 kGy. The effect on the compressive strength, total porosity, and water absorption, in addition to infrared spectroscopy and thermogravimetric analysis (TGA) were studied. The results indicate that the compressive strength increases with the increase of unsaturated polyester resin and the γ-irradiated dose, whereas the total porosity and water absorption values were decreased. These are attributed to adhesion between the sand and unsaturated polyester under the effect of γ-irradiation. Infrared spectra showed the appearance of new bands as a result of the formation of the Si=C bond. Also, TGA showed that the thermal stability of the composite increases with the increase of exposure dose.

ISSN:0360-2559    

DOI:10.1080/03602559909351583

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Properties of a polymer depend not only on its composition and molecular mass but also on the method of its preparation and on subsequent treatment of the polymer sample. To understand this phenomenon, the authors studied the effect of the rate of sedimentation of isotactic polypropylene from solution on its sorption capacity toward the low-molecular compound phenyl-ß-naphthylamine and on the antioxidant effectivity of this compound at polypropylene melt. The data obtained may be explained by taking into account the topological disorder in the arrangement of the polymer chains.

ISSN:0360-2559    

DOI:10.1080/03602559909351584

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this study, the sorption enthalpy (δHS1), sorption free energy (δG1), sorption entropy (δS1), enthalpy, and free energy at infinite dilution (δH1 and δG1) values were calculated for selected probes such as alcohols, ketones, acetates, cyclic ethers, aromatics, and alkanes in the temperature range 403-433 K for poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) homopolymers, and the PVC-PMMA blend system. The values of the Flory-Huggins interaction parameters χ1(23) have been calculated in this temperature range and show the importance of specific interactions between the polymers and the solvents. The values of the polymer-polymer interaction parameters χ23(for the temperature range 403–433 K) were found to change from +3.57 to +1.16 for alcohols, from +2.99 to +0.52 for ketones, from + 1.60 to −0.48 for acetates, from +0.96 to −1.46 for cyclic ethers, from +2.66 to +0.12 for aromatics, and from +8.73 to +1.06 for alkanes.

ISSN:0360-2559    

DOI:10.1080/03602559909351585

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0360-2559    

DOI:10.1080/03602559909351586

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0360-2559    

DOI:10.1080/03602559909351570

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor