Toughened PPS

The preferred average particle size 1n HIPS was believed to be 0.8 ijm (J.). However, our current data indicate that a number average particle diameter of 1.05 urn and 0.5 -urn appear to be a preferred size for HIPS and rubber-toughened polypropylene (PP), respectively. The morphology of the rubbery phase in a toughened PP appears to be less complex, as evidenced in Figure 2 where the dark, also osmium-stained, phase is the styrene-butadiene rubber (SBR) particles. No PP occlusions were found in this material since it is a physical blend of SBR and PP. 

Fig. 23 Flexural impact strengths of /S-modified rubber toughened PP plotted versus the amount of rubber content of the blends and the testing temperature. The arrows indicate samples that did not break. Data taken from Varga [165]...

Fig. 24 Stiffness (ISO R527 with ASTM D638 type I samples) of a- and -nucleated rubber toughened PP plotted versus their puncture impact resistance (ISO 6603-2) measured at 4ms-1 and room temperature. Data adapted from Lambla [124]...

Fig. 36 Typical evolution of the yield stress, ay, of a non-nucleated and -modified PP and their b 15 wt% toughened PP/EPR blends as a function of the strain rate, As/At. Tensile tests performed at room temperature on a base resin exhibiting an MFR of 12 dgmhr1...

Electron Microscopic Results. Electron micrographs were obtained from deformation tests of toughened PP and PA. The micrographs of toughened PP shown in Figure 13 reveal ruptured particles and plastically deformed matrix material between these voids. The cavitation step inside the particles, with the subsequent deformation and fibrillation of the adjacent material, can also be clearly seen in Figure 14. 

Figure 14. Deformation of toughened PP, showing an increasing number of cavi-tated particles with increasing elongation (SEM image produced in an in situ deformation test). The deformation direction is horizontal.

This classification is valid for a given temperature. With variation in temperature there can be a transition from one mechanism to another. For instance, decreasing the temperature of toughened PP shifts a shear yielding mech-... 

Figure 3. Impact strength of EPR-toughened PP-PA6 (70/30) blends containing 2.5, 5.0, and 10 vol% PP-g-MA compared with EPR-toughened PP, as a function of EPR volume fraction.

Polypropylene (PP) is often blended with ethylene/propylene (BP) rubbers to improve the impact resistance. This so-called toughened PP (TPP) can be a mechanically blended PP/C2C3 rubber system or an in-situ polymerised PP/C2C3 rubber system. A number of rubber parameters (like concentration, particle size, particle size distribution, crystallinity, molecular weight etc.) determine the ultimate effect of the rubber addition on the impact resistance. DMA is one of the analytical techniques often used to investigate blends of polymers with an impact improver. The determination of the relation between the area of the rubber relaxation maximum as measured by DMA and the rubber concentration is usually a first step in such an investigation. The method to determine this area and the results measured on a series of PP/C2C3 rubber blends are reported below. 

Reactive compatibilization of CORES Toughened PP had crosslinked De Loor et al. 1996... 

Kim, C. M., Michler, C. H., Rosch, J., and Miilhaupt, R. 1998. Micromechanical deformation processes in toughened PP/PA/SEBS-g-MA blends prepared by reactive processing. Acta Polymerica 49 88-95. 

Reactive compatibilization of EVAc/EMAc/PP blends CORI Toughened PP had cross-linked EVAc/EMAc phase De Loor et aL 1996... 

PP nanocomposite toughened with poly (ethylene-co-octene) using PP-g-MAH (6 wt%) as compatibilizer Thermal stability of the rubber-toughened PP nanocomposites was studied Thermal stability was improved significantly with the addition of small amount of organoclay Lim et al. 2006... 

Propathene Polypropylene, PP, toughened PP/EPR blends ICI Materials - Plast. 

More realistic interpretation of DBT, based on an idea of mechanical nature of this transition, was proposed based on studies of PC, PMMA, PE, rubber-toughened PP, and nylons (77). The concept of mixed mode of fracture has been used to analyze experimental data on temperature dependence of G/. 

Furthermore, the crazes in PP show other similar characteristics to those of amorphous polymers. They grow apparently normal to the direction of major tensile stress which somewhat deviates from the tensile direction because of spherulitic structure. There are similar environmental effects on craze initiation (see also Environmental stress cracking of polypropylene in this book). Crazing is also an important source of toughness in toughened PP alloy systems such as propylene-ethylene block copolymers. 

Figure 7 Deformation structures in rubber toughened PP at -40 C ultrathin section, deformed and investigated in a 200 kV TEM,...

It is interesting to note that there is a similarity of the deformation mechanisms in toughened PP and particle-filled PP. By the effect of locally increased deformability such particle-filled polymers show not only a better stiffness, but also a relatively good toughness. 

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