Effect of the Size of Particles on Their Adhesion in Composite Polypropylene/SiO2

The effect of particle size on the mechanical characteristics of biaxially oriented composite polypropylene/SiO2 is studied. The material is oriented in plane by squeezing two lead-tin alloy plates with the composite film being placed between them. Deformation is defined by the composition of the plates. This makes it possible to obtain the material with low degrees of orientation. The oriented composite preserves plasticity typical of the polypropylene matrix. After biaxial orientation of the unfilled PP, the yield point decreases by approximately 40% upon subsequent stretching. A reduction in the size of particles changes their adhesion behavior during stretching. Coarse particles with a size of about 20 µm separate from PP during stretching. On the contrary, nanoparticles with sizes of 200 and 500 nm do not separate even under plastic deformation of the composite. As a result, nanoparticles reinforce the thermoplastic the same way as carbon black nanoparticles reinforce rubber. The energy detachment criterion explaining an increase in the detachment stress with decreasing particle size is derived.