Studies On Mechanochemical Reinforcement And Toughness Of Polyvinyl-chloride/inorganic Nano-particles Composites

In this paper, mechanochemical modification of inorganic nano-particles was carried out. The effects of mechanochemical modification on interfacial interaction, the morphology, the mechanical properties, the thermal properties, flame retardant properties and the rheological behavior of PVC/nano-particles composites were studied. Concerning the toughness and reinforcement mechanism of mechanochemical modification of nano-particles on PVC, it was also explored.The results of SEM, TEM, Molau test and mechanical properties test indicate that the interfacial interaction between untreated nano-particles is strong and easy to aggregate. The dispersion of untreated nano-particles in the matrix is poor and the interfacial adhesion strength between PVC and nano-particles is weak. As compared with untreated nano-particles, the coupling agents treatment could enhance the interfacial adhesion strength between PVC and nano-particles, but the nano-particles are still dispersed in PVC matrix as aggregated particles. During co-vibromilling of PVC and nano-particles, the macro-radicals formed by the scission of PVC chain can recombine with high-activated fresh surfaces of nano-particles, resulting in the strong interfacial interaction between PVC and nano-particles and excellent dispersion of nano-particles into matrix. Therefore, mechanochemical treatment of nano-particles can greatly increase both tensile strength and impact strength of PVC /nano-particles composites.The mechanical properties of the composites filled with mechanochemically treated nano-particles are higher than those of the composites filled with un-treated and coupling agents treated nano-particles due to the mechanochemical enhancementof interfacial interaction between PVC and nano-particles during vibro-milling. The composites exhibit much better mechanical properties when the contents of mechanochemically treated nano-CaCO3 and nano-SiO2 in the composites reach to 8phr and 3phr. Compared with neat PVC, The impact strength of those composites are increased by 235% and 181% and the tensile strength are improved also. Vibro-milling time has great influence on the mechanical properties of PVC/nano-particles. The mechanical strength of PVC/nano-particles passes through a maximum when nano-CaCO3 and nano-SiO2 are vibro-milled for 4 hours and 6 hours, respectively.SEM micrographs of the impact fractured surfaces of the composites indicate that at high rate of deformation, interfacial debonding between un-treated and coupling agents treated nano-particles and PVC matrix is responsible for the main toughing mechanisms in the composites. For the composites filled with mechanochemically treated nano-particles, the shear yielding of PVC matrix plays a key role in absorbing impact energy. The stronger interfacial adhesion strength is formed and the volume fraction of the interfacial layer between the matrix and the nano-particles increased during vibro-milling process. The interfacial layer can transfer the stress, which improved the tensile strength and the toughness of the composites.Compared with the composites filled with untreated and coupling treated nano-particles, storage modulus, loss modulus, flexural modulus, limited oxygen index, glass transition temperature and thermal stabilities of the composites filled with mechanochemically treated nano-particles are greatly improved. The PVC profiles were manufactured with vibro-milling treated nano-particles in place of elastomer CPE. The tensile strength of the PVC profiles increased by 9 MPa and modulus and the size stabilization get also improved. The above results can provide theoretical foundations for preparing PVC chemical building materials with high strength and toughness.