Crystallization fracture resistance

Studies dealing with the influence of MWD on the toughness of P-PP are sparse. A metallocene P-PP, the archetype of a material with a narrow polydispersity (PI 2-3), was recently shown to exhibit a lower relative increase of the fracture resistance (between its non-nucleated and / -modified versions) than its Ziegler-Natta (ZN) homologue (PI 5-6) [117]. This result was attributed to the worse crystallization ability of a single-site grade—resulting in... 

Fig. 8 Evolution of the amount of /3-phase (DSC), the crystallization temperature, Tc, and the mechanical performances (fracture resistance at 23 °C and stiffness) as a function of the amount of calcium pimelate...

Glass beads PET Epoxy APES silane increases interfacial adhesion but hinders crystallization of PET by reducing nucleating activity of filler fracture resistance increased but no improvement of HjO resistance 23 33... 

Figure 7.18 shows schematic crack paths through (a) water ice and (b) ice cream. The weakest part of the water ice microstructure is the ice-matrix interface, so the crack follows a path along the edges of the ice crystals as far as possible. In the ice cream, the air bubbles are the weakest links so the crack passes through them. The ice crystals are the most fracture-resistant components so in both cases the crack passes around them. Ice cream is effectively a particulate-reinforced composite material, i. e. a material in which tough particles are embedded in a relatively soft continuous phase in order to increase the overall fracture resistance. Since the microstructure is heterogeneous, it is not possible to predict exactly where the crack will form or precisely what path it... 

Addition of sorbitol derivative induces PP to crystallize into smaller spherulites. The small spherulites have advantages (exeellent fracture resistance and optical performance) because of the high surface energy and bourrdary strength between spherulites. The formation of the transcrystals is affected by rrrarty factors, inclnding epitaxy, topography of the fiber, surface energy of the fiber, and rrrarty other. ... 

Yuan Q, Deshinane C, Pesacreta T C and Misra R D K (2008) Nanoparticle effects on spherulitic structure and phase formation in polypropylene crystallized at moderately elevated pressures The influence on fracture resistance. Mater Sci Eng A480 181-188. 

The measurement of mechanical properties is a major part of the domain of characterisation. The tensile test is the key procedure, and this in turn is linked with the various tests to measure fracture toughness... crudely speaking, the capacity to withstand the weakening effects of defects. Elaborate test procedures have been developed to examine resistance to high-speed impact of projectiles, a property of civil (birdstrike on aircraft) as well as military importance. Another kind of lest is needed to measure the elastic moduli in different directions of an anisotropic crystal this is, for instance, vital for the proper exploitation of quartz crystal slices in quartz watches. 

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