Rheological behaviour rubber blends

The influence of dichlorocarbene modified natural rubber (DCNR) on the rheological behaviour of blends based on NR and hydrogenated nitrile rubber (HNBR) was studied.The NR used in this study was ISNR 5 grade from India. The HNBR used was a Zetpol 2010 grade (Nippon Zeon, Japan) with... 

The influence of electron beam irradiation on rheological properties and morphology of polypropylene and polypropylene/ethylene-propylene rubber blends was studied. Electron beam irradiation of isotactic PP causes pronounced chain scission (degradation) at dosis < 100 kGy. Melt viscosity can be controlled easily up to this dose for pure PP. For the blende however, an anomalous rheological behaviour is observed. 

Irradiation of PP/EPDM blends causes pronounced differences in rheological behaviour compared with irradiated PP, which cannot be explained only by crosslinking of the EPDM phase. A possible explanation is the formation of grafted copolymers from PP onto the EPDM rubber particles. In blends a higher crosslinked fraction (based on 100% EPDM) is found than in irradiated EPDM (Table 1). The authors, however, are well aware that this is not an absolute prove of the presence of a graft copolymer and certainly is not a quantitative method to measure the amount of grafting. In order to get more evidence IR and NMR experiments will be performed in the future. 

The rheological performance of rubber blends manifests the ease or diiSculty of their fabrication. Mooney viscosity measurement is usually used to determine the rheological behaviour of an uncured batch at a specific temperature. Other rheometers like plate-plate or capillary may be used for rheological characterization. 

Rheological Behaviour of Natural Rubber Based Blends... 

For the NR based blends, therefore, the rheological behaviour must be considered case by case such as blending with thermoplastics and blending with other rubbers. In the case of the chemically modified NR based-blends, it was not only the type of polymer used to blend with NR, but also the variation of the chemical modification of NR would control the different rheological property of the blends. Special-property NR based blends obtained from the... 

Oommen et al. had studied melt rheological behaviour of the blends between NR and poly(methyl methacrylate) based on the effect of blend ratio, processing conditions and graft copolymer concentration as a function of shear stress and temperature. It was clarified that the viscosity of the blends increased with the increase of the amount of NR. On the other hand, the flow behaviour of the blends was found to be influenced by dynamic vulcanization of the rubber phase. 

The adhesion of rubbers is further complicated by the rheology of rubber and its added compounding constituents. Blending two or more rubbers will give more complexity to the flow and adhesion behaviour of the system. The ability of the rubber compound to flow and establish intimate contact with the substrate is of paramount importance, to enable the forces discussed previously to establish the conditions required for optimal adhesion. Any material which interferes with the establishment of the interface must be avoided. The establishment of a stable, strong interface between the two materials is the foremost requirement for successful adhesion. 

High molar mass epoxy prepolymers containing rabber dispersions based on carboxyl-terminated butadiene-acrylonitrile copolymer were prepared from initially miscible solution of low molar mass epoxy prepolymers, bisphenol A and carboxyl-terminated NBR. During chain extension inside a twin screw extruder due to epoxy-phenoxy and epoxy-carboxy reactions, a phase separation process occurs. Epoxy-phenoxy and epoxy-carboxy reactions were catalysed by triphenylphosphine. The effect of reaction parameters (temperature, catalyst, reactant stoichiometry) on the reactive extrasion process were analysed. The structure of the prepolymers showed low branching reactions (2-5%). Low molar mass prepolymers had a Newtonian rheological behaviour. Cloud-point temperatures of different reactive liquid butadiene aciylonitrile random copolymer/epoxy resin blends were measured for different rubber concentrations. Rubber... 

Utracki, L., and Sammut. P.. Rheological response of polyamide pp blends Part 3 Solid state behaviour. Plastics, Rubber Composite. Proc. <6. Applications, lb. 4. 221 229 (1991). 

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