Effect of adhesion on the fracture toughness of calcium carbonate–filled polypropylene

Abstract

The effect of adhesion on the strain energy release rate (Gc) and Charpy notched impact strength (NIS) of calcium carbonate (CaCO3)‐filled polypropylene (PP) at room temperature is investigated over a wide interval of particulate filler volume fractions. The concentration dependence of Gc and NIS are discussed in terms of competition between the effects of increasing stiffness, decreasing effective matrix cross section, and the transition from a plane strain to a plane stress mode of failure. In all cases the plane stress and plane strain limits of the critical strain energy release rate for initiation of cracks were not affected by the presence of the filler and are the same as those for neat matrix. In the case of no adhesion between components, the size of the crack tip plastic zone increases with increasing filler volume fraction (vf) because of the reduction of the material yield strength. In the region 0 < vf < 0.12, there is a mixed mode of failure, and the measured value of Gc for crack initiation increases steadily as the sample cross section approaches a fully plane stress state. The reduction in yield strength also results in the increase in Gc for crack propagation as reflected by an increase in NIS. Above vf= 0.12, the specimen cross section is in a fully plane stress state, and further increase in filler volume fraction (decrease in matrix effective cross section) has the net effect of reducing both Gc and NIS. In the case of “perfect” adhesion, the yield strength increases only slightly with vf. In the region 0 < yr < 0.05 there is also a mixed mode of failure, but the increase in Gc is much less than that for the no‐adhesion case since the size of the plastic zone in front of the crack is much smaller. Above vf= 0.05, the combined effects of increasing stiffness, reduction of the size of the plastic zone, and decreasing matrix cross section dominate the behavior, causing a steady reduction in both Gc and NIS. Good agreement was found between experimental data and calculations based on fracture mechanics principles.

The Melt Flow Properties of Poly(propylene)/Glass Bead Composites

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Effect of silane-grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

“…9 Functionalized polyolefins can create strong bonds with the filler surface and form physical entanglements with the matrix in the bulk. The effect of functionalized polyolefins on PP composites filled with mica, 10 -13 CaCO 3 ,9,[14][15][16][17][18] Mg(OH) 2 , 9,14,17,19 and reinforced with glass fiber 20 -23 have been investigated.…”

Effect of in-situ formed core–shell inclusions on the mechanical properties and impact fracture of polypropylene

“…In rubber toughened polymers, the enhanced fracture toughness is usually offset by the reduced elastic modulus, enhanced creep compliance and reduced high temperature properties [5]. The use of rigid particulate fillers with controlled interfacial adhesion can prevent this problem to some degree, though rigid fillers usually increase viscosity and density [3,8,10,11,14]. Simultaneous enhancement of low temperature impact resistance without significant penalty in high temperature properties can be achieved by adding both rigid and soft inclusions with controlled spatial arrangement of the rigid and elastomer component [5].…”

“…Various toughening strategies were used over last 30 years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In rubber toughened polymers, the enhanced fracture toughness is usually offset by the reduced elastic modulus, enhanced creep compliance and reduced high temperature properties [5].…”