Structure And Properties Of Poly(Vinyl Chloride)/Halloysite Nanotubes Nanocomposites

In the present work, naturally occurred halloysite nanotubes (HNTs) are used for PVC/HNTs nanocomposites synthesized via melt blending and in situ polymerization. The preparation, structure and properties of the PVC/HNTs nanocomposites are investigated fully. Surface modifications of the HNTs are achieved, the interfacial interactions between HNTs and PVC and their effect on the structure and properties of the nanocomposites are studied in detail.(1) PVC/HNTs nanocomposites are prepared by melt blending. The results show that HNTs are uniformly dispersed in the PVC matrix. HNTs are effective in toughening and reinforcing PVC nanocomposites simultaneously. Interfacial interaction of hydrogen bonding between (Si-O) of the HNTs and the?-hydrogen from the CHCl groups of PVC matrix is substantiated. The fracture surface of the PVC/HNTs nanocomposite which shows the ductile behavior is different from that of PVC. The toughening mechanism is explained according to the cavitation mechanism.(2) The thermal properties, smoke evolution and fire properties of PVC/HNTs nanocomposites are investigated in detail. The incorporation of HNTs has significant effect on the improvement of the heat distortion temperature and vicat softening temperature of PVC/HNTs nanocomposites. Thermogravimetric analyses results show that the apparent activation energy (Ea) is improved with the increasing of HNTs indicate that the thermal properties of the PVC/HNTs nanocomposites are improved. The results of the cone calorimetry measurements, smoke density and oxygen index tester show that the addition of HNTs leads to a remarkable reduction in the smoke production rate, the total smoke production and the peak heat release rate, also leads to the increase of oxygen index, suggesting promising smoke suppression and flame retardant effect on PVC.(3) To improve the interfacial bonding between the HNTs and PVC matrix, HNTs are modified by methacryloxypropyltrimethoxysilane (MPS). The structure and properties of the nanocomposites are investigated. The interfacial interaction between the modified HNTs(m-HNTs) and PVC is improved and the dispersion of m-HNTs is more uniform than that of HNTs. The m-HNTs are effective in toughening and reinforcing PVC nanocomposites simultaneously. The PVC/m-HNTs nanocomposites have better mechanical properties and modulus compared with PVC/HNTs nanocomposites. The m-HNTs can also improve the thermal stability and rheological property of PVC nanocomposites.(4) Halloysite nanotubes(HNTs) grafted with polymethyl methacrylate(PMMA) are synthesized. Then, PVC/PMMA-grafted HNTs nanocomposites are prepared by melt compounding. The morphology, mechanical properties and thermal properties of the nanocomposites are investigated, the toughening mechanism is explained. The interfacial bonding between the HNTs and the PVC matrix can be enhanced by improving miscibility and entanglement of the grafting polymers with the matrix macromolecules. PMMA-grafted HNTs uniformly dispersed in PVC matrix and effectively improve the toughness, strength and modulus of PVC. The fracture surfaces of the nanocomposites exhibited plastic deformation feature indicating ductile fracture behaviors. Nanotube bridging of HNTs is also observed and proposed as the major energy dissipating events. PMMA-grafted HNTs also increase the thermal stability of PVC. The glass transition temperature (Tg), T5%, T50% and Tmax of PVC/PMMA-grafted HNTs nanocomposites are higher than that of pristine PVC.(5) The PVC/HNTs composite are synthesized via in situ polymerization of vinyl chloride (VC) in the presence of HNTs nanoparticles. The mean particle size, the degree of porosity and the cold plasticizer absorption (CPA) of PVC composite resins decreased with the addition of HNTs, while the apparent density increased. The PVC/HNTs nanocomposites which are prepared by melt compounding exhibit much higher toughness and thermal properties than PVC. The HNTs uniformly dispersed in PVC matrix. The rheological properties of the PVC/HNTs composite resins are also improved.