Synthesis And Characterization Of Soybean Oil-based Polyurethane/epoxy Resin Interpenetrating Polymer Network (IPN)and Its Nanocomposites

On account of the limitation of petroleum-based resources and demands on the development of environment friendly products, the studies on preparation of green and biodegradable polymer materials from renewable resources have gradually attracted increasing attention. Among these resources vegetable oil-based polymers are promising as a result of their outstanding performance and excellent environment sustainability because of their unique structure. Vegetable oil-based polyurethane (PU) materials are one kind of the most widely used and studied polymers since they have comparable properties to petroleum-based polyurethane, such as excellent flexibility, abrasion resistance, corrosion resistance, etc.Epoxy resin (EP) has good chemical compatibility, extensive practicability and reasonable cost which make it available to numerous industrial fields. However, epoxy resin is associated with low impact strength, and brittleness due to its inherent structure which brings the limitation of epoxy resin application. Therefore, toughening epoxy resin is needed to improve the toughness of epoxy resin and make epoxy resin have better mechanical properties.As a kind of natural nanofillers, attapulgite (ATT) can be used to enchance polymer materials to increase the strength of the polymer materials directly or after modification owing to its special structure and properties.In this thesis, soybean oil-based polyol with good biological characteristics was used to prepare polyurethane prepolymer. PU prepolymer and epoxy resin were mixed together to form interpenetrating polymer network (IPN) which aimed to toughen epoxy resin of high brittleness and low impact strength with flexible polyurethane. The effects of soybean oil-based PU prepolymers on toughening epoxy resin were studied. Finally, silane coupling agent (KH570)-modified attapulgite was used as a nanofiller to prepare PU/EP IPN/KH570-ATT nanocomposites. The effect of KH570-ATT on the structure and properties of IPN was investigated.FT-IR spectra of epoxied soybean oil and polyol showed that epoxied soybean oil had been synthesized by ring-opening reaction with methanol. Then soybean oil-based polyurethane prepolymer was prepared with these polyols. For soybean oil-based polyurethane/EP IPN, FT-IR spectra showed that the characteristic absorption of the-NCO groups at2252cm-1was disappeared in IPNs, implying that IPN was formed between PU and EP. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results indicated that glass transition temperatures (Tg) decreased with PU prepolymer contents in IPN increasing. Furthermore, DMA results showed IPN had a better damping property than EP. Tensile tests showed that PU significantly improved the toughness of EP. SEM observations indicated that IPN presented a phase separation structure that spherical PU particles dispersed in EP matrix which spread and absorb external stress to improve the system’s toughness.The results showed that KH570had a high grafting rate to the surface of ATT and did not affect crystalline structure of ATT with the surface structure of Si-O-Si. As can be seen from the SEM diagrams, on the surface of KH570-ATT it can be seen that ATT was wrapped by silane coupling agent and the diameter of KH57O-ATT became longer than that of ATT. For IPN/KH570-ATT nanocomposites, DMA results showed that the addition of KH570-ATT increased the Tg of IPN. Furthermore, the Tg of IPN nanocomposites increased with the rise of KH570-ATT contents. The addition of modified ATT improved the damping properties of IPN nanomcomposites. IPN nanocomposites with0.5wt%KH570-ATT showed the best damping properties. Mechanical tests showed that KH570-ATT improved the mechanical properties of IPN. A small amount of KH570-ATT increased both the tensile strength and elongation at break. However, with the increase of KH570-ATT contents, the tensile strength and elongation at break of the IPN presented a downward trend. Young’s modulus of IPN/KH570-ATT nanocomposites increased with the increase of KH570-ATT contents. SEM observations suggested that higher KH570-ATT content led to aggregation of KH570-ATT in the nanocomposited, which caused a decline in mechanical properties of IPN.