Fast Curing Of Epoxy Resin Nanocomposites Via Frontal Polymerization

Frontal polymerization is a kind of polymerization process, which takes the self reaction heat as the driving force, and moves continuously through the reaction area. Frontal polymer has the advantages of simple, fast, energy saving and environmental protection. It is a new technology which can be used in the preparation of materials for rapid prototyping, and has been widely used in the preparation of vinyl polymer materials. Although there have been some preliminary research on front polymerization technique in the field of thermosetting resins, majority of them were concentrated in the basic research of the descending front polymerization(d FP). Taking into account that horizontal frontal polymerization(h FP) method has more practical significance, in this paper, comparative study of UV-initiated d FP and h FP techniques of epoxy resin was performed on its front polymerization behavior. Especially, the applications of h FP technique on preparation of epoxy-base organic-inorganic nanocomposites were studied. The specific contents are as follows:Frontal behavior of UV initiated d FP and h FP approach was comparatively studied. The results show that the frontal velocity and maximum temperature of both approaches increase with the increase of the loading of thermal curing agent; frontal velocity of h FP approach is greater than that of d FP approach, but maximum temperature is smaller than that of d FP approach. FTIR, DSC, TG and DMA tests show that, condensates cured by frontal polymerization have a very high degree of cure and excellent thermal stability. For the first time a set propagating angle was observed in the h FP approach, and its value increases with the increase of the concentration of the thermal initiator concentration.By frontal polymerization method, for rapid preparation of Si O2/EP nano composite were fabricated rapidly. The effect of addition of nano fillers on the frontal behavior including initiating time, maximum temperature and frontal velocity was studied. And the structure and properties of the cured composites were characterized by means of Fourier infrared spectroscopy, TG and SEM. The results show that, for modified nano-Si O2 by surface grafting and unmodified gas phase Si O2, the trigger time of the frontal polymerization increases with the increase of nano filler content, while frontal velocity and the maximum temperature decrease when using either photo initiation or thermal frontal polymerization. At the same filler content, photoinitiated frontal polymerization exhibits a shorter trigger time, faster velocity and higher maximum when compared to thermal initiated frontal polymerization. Analysis of FTIR and TG shows that the nano Si O2/EP composite materials prepared by frontal polymerization technology has a very high degree of curing and good thermal stability. Impact test and SEM analysis show that the addition of modified Si O2 into epoxy resin has an obvious toughening effect, and the impact strength of the composite increases when the filler content increases; while adding unmodified gas-phase Si O2 shows little effect on EP toughing, and even will reduce the impact strength. The results of comparative analysis show that the modified Si O2 has better toughening effect on epoxy resin than the gas phase Si O2.Ba Ti O3/EP nano composites were prepared by using photo-triggerd d FP/h FP approach, and the effect of Ba Ti O3 content on the frontal behavior was studied. The cured products were characterized by means of FTIR, TG and SEM, and impact performance of the composites prepared by photo initiation and traditional thermal curing was comparatively studied.The results show that Ba Ti O3 content shows equal effect on the frontal behavior to photo-triggered d FP/h FP process, namely, with increasing the content of the nano fillers, the trigger time increases, frontal velocity decreases, and maximum temperature decreasesThe results of FTIR test showed that the epoxy groups were completely involved in the curing reaction. TG showed that the addition of nano Ba Ti O3 improved the thermal stability of the cured epoxy resin. The impact strength of nano Ba Ti O3/EP composites increases with the increase of Ba Ti O3 content, and the impact strength of the composite obtained by FP is larger than that of the composite cured by thermal curing method. The morphology of the impact fracture surface show that nanoparticles disperses evenly in the composite materials obtained by photoinitiated frontal polymerization, while aggreagation exists in the composite materials cured by traditional curing process, indicating that photo-triggered frontal polymerization is a kind of energy-saving and rapid method for new materials preparation. It not only effectively solves the agglomeration phenomenon of nanoparticles, but also has important theoretical significance and practical application value.