Effect of rigid particle size on the toughness of filled polypropylene

Abstract

The role of rigid particle size in the deformation and fracture behavior of filled semicrystalline polymer was investigated with systems based on polypropylene (PP) and model rigid fillers [glass beads, Al(OH) 3 ]. The regularities of the influence of particle content and size on the microdeformation mechanisms and fracture toughness of the composites at low and high loading rates were found. The existence of the optimal particle size for fixed filler content promoting both maximum ultimate elongation of the composite at the tensile and maximum toughness at impact test was shown. The decrease of the toughening effect with both decreasing and increasing particle size regarding the optimal one was explained by dual role of particle size, correspondingly as either "adhesive" or "geometric" factors of fracture. The adhesive factor is due by the increase of debonding stress with the particle size decrease and the voiding difficulty resulting in the restriction of plastic flow. The geometric factor consists in the dramatic decrease of the composite strength at break if the void size exceeds the critical size of defect (for a given matrix) at which the crack initiation occurs. The analysis of the filled polymer toughness dependencies upon the particle size revealed that a capacity of rigid particles for the energy dissipation at the high loading rate depends on two factors: (i) ability of the dispersed particles to detach from matrix and to initiate the matrix local shear yielding at the vicinity of the voids and (ii) the size of the voids forming. Based on the findings it was concluded that the optimal minimal rigid particle size for the polymer toughening should answer the two main requirements: (i) to be smaller than the size of defect dangerous for polymer fracture and (ii) to have low debonding stress (essentially lower compared to the polymer matrix yield stress).

Effect of Particle Size on Mechanical Properties of Sawdust-High Density Polyethylene Composites under Various Strain Rates

“…Theoretically, an increase in debonding stress as the particle size decreases would create an adhesive agent that will eventually decrease the toughening effect (Dubnikova et al 2004). Moreover, according to Kitey and Tippur (2005), filler particle size influences the fracture and cracking behavior when particles are weakly bonded to the matrix.…”

Study on Mechanical, Thermal and Electrical Characterizations of Nano-SiC/Epoxy Composites

“…Evidently, particle debonding and the small size of void formed cause the extensive yielding of the surrounding matrix during loading. 12 For the nanocomposites, shear failure propagated across Figure 3b. Smaller limitation of the plastic deformation on the crack initiation stage and less brittle fracture of the material cause higher shear strength as demonstrated above.…”

Solvent‐assisted extrusion of polypropylene/clay nanocomposites

“…The most effective dissipative processes in PP are multiple crazing and shear yielding, with a major contribution from the latter. 20 However, additional processes take place when a rigid particle is added to the polymeric matrix. According to microvoiding theory, 21 when the stress applied exceeds the interfacial adhesion strength between the clay and the polymer matrix, debonding at the interface will occur first; this leads to the formation of microvoids.…”