Rubber blends dynamic modulus

Gupta et al. (39) has studied the effect of dynamic cross-linking on tensile yield behavior of PP/EPDM rubber blends. They prepared blends of PP/EPDM in internal mixer by simultaneous blending and dynamic vulcanization. Dimethyl phenolic resin vulcanized PP/EPDM blends showed higher yield stress and modulus than unvulcanized PP/EPDM blend (Fig. 14.17 and Table 14.1). They found the increase in... 

Reinforcing effect by CNT was studied also in rubber blends. Blended latex of NR and SBR at dry wt ratio of 80/20 was reinforced with CNT in the range 0.1-0.4 phr and it was observed the increase of tensile strength, modulus at 300% strain and dynamic-mechanical properties, although in the presence of a reduction of elongation at break." ... 

Paheme emulsion model failed to describe the dynamic modulus of the PP/EPDM blends after radiation, because the viscosity ratio increased significantly and the rubber phase changed from deformed droplets to hard domains after radiation (Cao et al. 2007). Intercoimections among inclusions of the dispersed phase (Shi et al. 2006) and the existence of multiple emulsion (emulsion-in-emulsion) structure exhibiting different relaxation domains in compatibilized systems are other factors contributing to the failure of Palieme s model (Friedrich and Antonov 2007 Pal 2007). 

Abstract This chapter deals with the non-linear viscoelastic behaviour of rubber-rubber blend composites and nanocomposites with fillers of different particle size. The dynamic viscoelastic behaviour of the composites has been discussed with reference to the filler geometry, distribution, size and loading. The filler characteristics such as particle size, geometry, specific surface area and the surface structural features are found to be the key parameters influencing the Payne effect. Non-Unear decrease of storage modulus with increasing strain has been observed for the unfilled vulcanizates. The addition of spherical or near-spherical filler particles always increase the level of both the linear and the non-linear viscoelastic properties. However, the addition of high-aspect-ratio, fiber-like fillers increase the elasticity as well as the viscosity. 

Blends comprised of amorphous, low Tg polymers are of primary interest for elastomeric type applications, of which the large tire market commands considerable interest. This section will consider blends of elastomeric polymers, generally low Tg, amorphous blends. In specific cases, low modulus, crystalline polymer blends (such as ethylene copolymers) with other elastomeric materials will be included. Also blends containing crystalline polymer, where the primary component of the blend is the elastomeric component and the blend is considered an elastomeric material, will be discussed. Specifically, dynamic vulcanized blends such as polypropylene/ethylene-propylene rubber blends will be included in this section. 

Tackifying resins enhance the adhesion of non-polar elastomers by improving wettability, increasing polarity and altering the viscoelastic properties. Dahlquist [31 ] established the first evidence of the modification of the viscoelastic properties of an elastomer by adding resins, and demonstrated that the performance of pressure-sensitive adhesives was related to the creep compliance. Later, Aubrey and Sherriff [32] demonstrated that a relationship between peel strength and viscoelasticity in natural rubber-low molecular resins blends existed. Class and Chu [33] used the dynamic mechanical measurements to demonstrate that compatible resins with an elastomer produced a decrease in the elastic modulus at room temperature and an increase in the tan <5 peak (which indicated the glass transition temperature of the resin-elastomer blend). Resins which are incompatible with an elastomer caused an increase in the elastic modulus at room temperature and showed two distinct maxima in the tan <5 curve. 

The B-series of silica samples were also blended with rubber and the compound formulation is shown in Table 17.6. The uncured gums were then tested according to ISO 5794-2 1998. The uncured samples were tested using a Mooney viscometer and an RPA, which measures the dynamic mechanical properties as the samples cure. Figure 17.7 shows the results of these two tests for the Mooney viscosity at 100°C, storage modulus, loss modulus, and tan 8. 

In contrast to the rigid TPOs described above, low-modulus/flexible grades of TPO blends are also produced commercially. In flexible TPOs, the rubber content can be as high as 60 %, and in some cases, the dispersed rubber may also be partially cross-linked during the mixing without losing the thermoplastic character of the matrix. However, the latter type of dynamically vulcanized elastomeric alloys or thermoplastic vulcanizate rubbers (TPVs) are considered as a separate class of elastomeric materials and hence will be discussed under elastomer blends. On the other hand, the soft TPO blends discussed here contain a low-modulus olefln copolymer elastomer as the major component with some polypropylene added to impart melt processability. 

The EB treatment of the GTR containing LDPE and EVA matrix blends showed significant benefits. The 200 kGy EB absorbed dose (in air) resulted in a better tensile strength and increased elongation at break, without changing the tensile modulus, which provides more rubber-Uke properties [142]. The modest change in hardness proves the cross-linking effect caused by the EB treatment in all cases. The dynamic mechanical analysis confirmed the compatibilization effect of EVA and... 

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