Rubber phase volume fraction

Rubber particle size (/i.m) Large particles in blends (%) Rubber phase volume fraction Notched Izod impact strength ft. Ibs/in. Gloss... 

Rubber Particle Size and Shape. If rubber particles act as crack or craze branch points along an advancing crack in matrix polymer, impact strength should depend on the frequency with which branch points are encountered. If C = rubber phase volume fraction, N = number of dispersed particles, and d = average particle diameter, N C -r (P, N is maximized as C increases or d decreases. The probability of an advancing crack hitting a particle as it advances an incremental distance is proportional to cross sectional area Nd2, which equals C/d. Again, C... 

In contrast (Fig, 2E), when the oil was prepolymerized (but not to the point of gelation) prior to addition of the styrene, such PS domains were evident, as found previously for a castor-oil-based SIN (9) and high-impact polystyrene (HIPS) (16). It is evident from Figs. 2A and 2B that when the oil is not prepolymerized prior to adding the styrene-DVB the resulting elastomer phase exhibits a lower rubber-phase volume fraction (RPVF) than is the case when the oil is prepolymerized. 

As mentioned in the section on morphology, the extent of elastomer prepolymerization prior to styrene addition affects the rubber-phase volume fraction (RPVF) and the phase continuity of the SINs. As shown in Table 4 and 5, the behavior of SINs also depends on the acid value. 

Fig. 5.67 Dependence of upon rubber phase volume fraction for a rubber-toughened epoxy resin (after Bucknall and Yoshi (1978) Brit. Polym. J. 10, 53).

Figure 19 Relationship between the fracture energy and rubber phase volume fraction in a rubber-toughened epoxy...

Unfortunately, the distinction betw n nominal rubber ccmtent and rubber phase volume (i.e. volume fraction of rubber particles, including sub-inclusions) has not generally been recognised in the past, so that much of putdished information on the relationship between moduli and compositicm is of little value. The rubber phase volume is considerably higher than the nominal rubber ccmtent in most rubber-touj ened jdastics, especially HIPS and ABS. Only in the ca of melt-blended polymers are the two quantities likely to be equal. In blends of pdy-propylene with ethylene-propylene rubber, for examfde, the rubber particles show no sign of sub-inclusions . ... 

Fig. 7. Yield stress of HIPS, expressed as a fraction of the yield stress of PS, as a function of rubber phase volume. E)ata obtained by Oxboroiigh and Bowden (SS) in tensile (o) and compressive ( ) tests are compared with Eq. 9 (solid line)...

The program can be used in several ways to model the geometry of real materials. In the modeling of a blend of two rubber-toughened plastic components, the discrete-phase volume and rubber particle-size distribution of each blend component would have to be known. Files containing the actual diameters of discrete-phase spheres would also be required. Finally, the rubber-phase volume in each blend component would have to be multiplied by the components weight fraction in the blend. This assumes that both components have the same continuous phase and, therefore, no volume change when blended. 

It has been reported (5) that the elastic modulus of ABS resins prepared by either mass or emulsion polymerization can be represented by a single relationship with the dispersed phase volume fraction. This is in agreement with the theory that the modulus of a blend with dispersed spherical particles depends only on the volume fraction and the modulus ratio of particles to matrix phase. Since the modulus of rubber is almost 1000 times smaller than the modulus of the matrix SAN, the rubber particle volume fraction alone is the most important parameter controlling modulus values of ABS resins. Even for rubber particles containing a high occlusion level, as in ABS produced by mass polymerization, the modulus of the composite particle still remains imchanged from pure rubber, suggesting a unique relationship between modulus and dispersed phase volume fraction. Also, the modulus of a material is a small strain elastic property and is independent of particle size in ABS. The effects of rubber content on modulus and on tensile... 

The important yet unexpected result is that in NR-s-SBR (solution) blends, carbon black preferably locates in the interphase, especially when the rubber-filler interaction is similar for both polymers. In this case, the carbon black volume fraction is 0.6 for the interphase, 0.24 for s-SBR phase, and only 0.09 in the NR phase. The higher amount in SBR phase could be due to the presence of aromatic structure both in the black and the rubber. Further, carbon black is less compatible with NR-cE-1,4 BR blend than NR-s-SBR blend because of the crystallization tendency of the former blend. There is a preferential partition of carbon black in favor of cis-1,4 BR, a significant lower partition coefficient compared to NR-s-SBR. Further, it was observed that the partition coefficient decreases with increased filler loading. In the EPDM-BR blend, the partition coefficient is as large as 3 in favor of BR. 

In comparison to the results obtained for the samples prepared with hexane, it can be concluded that the mean pore size and volume fraction do not depend on the initial concentration of the solvent, ( )o, but mainly on the difference between ( )o and (Fig. 25). Similar qualitative results are also reported for rubber-modified epoxies prepared via reaction induced phase separation [103]. 

Fracture energy is roughly proportional to rubber volume fraction up to phase inversion. 

As in the case of rubber particles it was demonstrated that the fracture energy is roughly proportional to the volume fraction of TP rich phase, both in the case of epoxy/PEI networks (Bucknall and Gilbert, 1989) and bismaleimide networks toughened with various TPs (Stenzenberger et al., 1988). This improvement was evidenced in the range of volume fractions below [Pg.415]

Figure 10.11 The structure of an EPDM/N550 (phr=100) vulcanisate according to the results of NMR and extraction studies - (A) and mechanical data for the case of pure hydrodynamic reinforcement - (B) [62], The volume fraction of microphases/ components is given in vol.%. According to the NMR data, the total network density in the rubber phase, l/2Mc+e+ad, equals 425 mmol/kg, where subscripts c, e and ad stand for chemical crosslinks, chain entanglements and adsorption rubber-filler junctions. The density of the adsorption junctions in the loosely bound rubber, 1/...

From the pure component data it is possible to calculate the expected a behavior as a function of temperature for a blend of the two polymers using the equation ah = sas + < rar, where the subscripts b, s, and r refer to the blend, polystyrene, and rubber, respectively, and the < s represent the volume fractions of the two components in the blend. The calculated curves (Figure 7) are reasonably smooth and exhibit only the polystyrene Tg. The calculated curve for TR-41-2445 is in good agreement with that found experimentally for the solution-blended material. The only significant difference is that below the polystyrene Tg the calculated values of a are about 0.5 X 10 4 deg1 lower than the experimentally determined data points. This may be attributable to the density differences in the samples, particularly for the blended material where density variations and void formation can occur at the interfaces between the polymer phases. 

Fig. 13 is a TTT cure diagram of three systems a neat epoxy resin and the same epoxy modified with two reactive rubbers at the same concentration level. The times to the cloud point, gelation and vitrification are shown for each system. The cloud point is the point of incipient phase separation, as detected by light transmission. The modified system with the longer times to the cloud point and gelation, and the greater depression of Tg, contains the more compatible of the two rubbers. The difference in compatibility could then be used to account for differences in the volume fractions of the phase separated rubber-rich domains and in the mechanical properties of the neat and the two rubber-modified systems. 

For high temperature and rubber-modified epoxy resins, thermal degradation events and the cloud point curve are included on the diagrams, respectively. Two degradation events have been assigned devitrification, or a glass-to-rubber event and revitrification, which is associated with char formation. The cloud points and depressions of Tg for different rubber-modified epoxies can be compared and related to volume fractions of the second phase and to the mechanical properties of the cured materials. 

When applying this method according to micrograms one can calculate volume fraction of HIPS rubber phase Vf in per centage Intermediate surface of rubber and polystyrene phases Sy in mm2/mm3 Mean cord spheres C which is proportioned to diameter of rubber peirticles C in / - Mean free distance among the particles MPD in yu., ... 

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