Kinetics And Damping Property Of Polyurethane/Poly(Methyl Methacrylate)Interpenetrating Polymer Networks

Semi-compatible polyurethane (PU) and poly(methyl methacylate)(PMMA) were chosen as the matrix of the simultaneous interpenetrating polymer networks (SIPNs) in this thesis. SIPNs of linear PU and linear PMMA were synthesized and their damping property were studied.The methods of SIPNs formation kinetic were firstly carried out by means of titration of the-NCO functional group for PU and using gas chromatography for methyl methacylate (MMA). Factors that influenced the kinetics of the SIPN formation, such as the composition ratio, temperature, initiator concentration, catalyst concentration, time at which initiator was added, and presence of chain extender1,4-butanediol, were investigated. It was found that all factors that influenced the system viscosity would affect the kinetics of the SIPN formation. Increasing the system viscosity would not only restrain the movement of PU oligomer but also affect the auto-acceleration effect of MMA free radical polymerization. The stepwise polymerization of PU and the free radical polymerization of MMA were interactional. If too much of the dibutyltin dilaurate catalyst was added to the system, MMA would not totally polymerize, thus the SIPN would not completely form. Therefore, it is necessary to control relative polymerization rate between the two polymers. Furthermore, the kinetics of polyurethane formation obeyed the principles of a second-order function during the early period of the reaction. Also a third-order function at high conversion of the-NCO functional group was reliable.According to the kinetics investigated above, approapriate concentrations of initiator and catalyst were selected to synthesize a series of semi-and full-PU/PMMA SIPNs in bulk polymerization. Functional monomer (FM) was firstly used in this thesis. Dynamic mechanical analysis was carried out to determine the damping property of the system. Factors influenced the damping property of the system including composition ratio, crosslinking densities, nano-SiO2content, content of FM, and internetwork grafting agent (IGA) content were investigated. The morphology of SIPN was characterized by transmission electron microscope. Furthermore, relationship between the damping property and the morphology was studied. The obtained results showed that changing the system crosslinking densities could only expand the peak width; the peak intensity however would not change distinctly. When moderate nano-SiO2was uniformly distribute in the SIPN, the tanδ value between the PU phase and the PMMA would increase apparently. The system would possess a continuously wide damping area when20%FM was added. The system would be optically transparent when only3%IGA was added. Inter-grafting method was an effective way to synthesize material that has great peak intensity of damping.