Toughening of polypropylene combined with nanosized CaCO3 and styrene-butadiene-styrene

Nanocomposites of nanosized CaCO3/SBS/PP were prepared by using twin-screw and single-screw extruder. By adding nanosized CaCO3 particles into SBS/PP blend, the notched impact strength, flexural modulus, and tensile strength of the composites can be improved, whereas, by adding microsized CaCO3 particles into SBS/PP blend, the notched impact strength of the composite is decreased markedly. At nanosized CaCO3 content of 16 phr (parts per hundred PP resin by weight), the impact strength of nanosized CaCO3/SBS/PP composite reaches 56.55 KJ/m(2), which is 1.27 times that of SBS/PP blend. At nanosized CaCO3 content of 4 phr, the tensile strength of the composites reaches 31.3 MPa, which is 1.23 times that of SBS/PP blend. The maximum and balanced torque of the composites improves significantly by the addition of CaCO3 nanoparticles. The increased shear force during compounding continuously breaks down SBS particles, resulting in the reduction of the SBS particles size, and improving the dispersion of SBS particles in PP matrix. Thus the toughening effect of SBS on matrix was improved. Simultaneously, the existence of SBS provides the matrix with a good intrinsic toughness, satisfying the condition that nanosized inorganic particle of CaCO3 efficiently toughens polymer matrix. The synergistic toughening function of nanosized CaCO3 and SBS on PP matrix was exhibited.