Xi Zhu

Bio: Xi Zhu is an academic researcher from Naval University of Engineering. The author has contributed to research in topics: Bead & Fourier transform infrared spectroscopy. The author has an hindex of 3, co-authored 3 publications receiving 36 citations.

Dynamic mechanical and underwater acoustic properties of the polyurethane/epoxy resin blend elastomers filled with macroporous poly(vinyl acetate-co-triallyl isocyanurate) resin beads

Abstract: Macroporous poly(vinyl acetate-co-triallyl isocyanurate) resin beads were prepared by suspension polymerization and used as acoustic particles for polyurethane (PU)/epoxy resin (EP) intercrosslinked elastomer matrices. The influences of the beads on the dynamic mechanical and underwater acoustic properties of the matrices were investigated. The results show that the underwater acoustic absorption properties of the matrices were improved by the beads, and this depended on the amount of the beads, the composition ratios of PU to EP, the bead diameters, the matrix thickness, and the water temperature. A comparison of the matrix with a 70/30 composition ratio of PU to EP to one without the beads showed that the average acoustic absorption coefficient of the composite with 5% beads increased from 0.38 to 0.55, and the peak value increased from 0.42 to 0.65, but the composites with 10 and 15% of the beads had lower acoustic absorption coefficients at low frequency and a much higher acoustic absorption coefficient at high frequency. The results also indicate that the beads with smaller diameters had a better enhancing effect on the underwater acoustic properties of the matrices. The results of the dynamic mechanical measurements showed that the damping properties of the composites depended on the composition ratios of PU to EP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

The synthetic kinetics and underwater acoustic absorption properties of novel epoxyurethanes and their blends with epoxy resin

Abstract: Reaction kinetics between isocyanate-terminated prepolyurethane (PPU) and glycidol using dibutyltin dilaurate (DBTDL) as a catalyst was investigated by monitoring the change in the intensity of the absorbance peak of NCO stretching band at 2,270 cm−1 on Fourier transform infrared spectrum at different temperatures. The results indicated that the reactions of TDI- and IPDI-type PPU with glycidol followed second-order kinetics, and their activation energies could be efficiently reduced by DBTDL. For TDI-type PPU, the reaction activation energies were 80.37 kJ mol−1 without catalyst, 49.86 kJ mol−1 with 0.1 % of DBTDLs, and 37.85 kJ mol−1 with 0.2 % of DBTDLs, respectively. For IPDI-type PPU, the reaction activation energies were 69.16 kJ mol−1 without catalyst, 63.05 kJ mol−1 with 0.1 % of DBTDLs, and 55.57 kJ mol−1 with 0.2 % of DBTDLs, respectively. This corresponding TDI- and IPDI-type epoxyurethane (EPU) were blended with epoxy resins (EPs) and cured by the Michael adduct of ethlylenediamine with butyl acrylate (molar ratio = 1:1) curing agent, to prepare EPU/EP blend elastomers for underwater acoustic absorption materials. The TDI-type EPUs had good acoustic absorption properties and the average acoustic absorption coefficient of TDI-type EPU was 0.75, the maximum acoustic absorption coefficient was 0.94; the EPUs blended with E-51 EP had better acoustic absorption properties than those from E-44; and the EPU from PPG-2000 had better underwater acoustic absorption properties than that from PPG-1000.

Synthesis, porous structure, and underwater acoustic properties of macroporous cross-linked copolymer beads

Abstract: The macroporous and elastomeric beads from polyurethane acrylate (PUA), ethyl methacrylate (EMA), and styrene (St) are prepared by suspension polymerization using n-heptane as porogen and 1,2-divinylbenzene (DVB) as cross-linking agent. The scanning electronic microscope results show that the beads of PUA–EMA–St cross-linked copolymers have many large pores on their surfaces and interiors, and the macroporous sizes are dependent of the copolymer composition and the dosages of cross-linking agents and porogen. Average porous diameters decrease as the dosages of DVB increase and the contents of PUA and porogen decrease. The cross-linked copolymers have two kinds of beads (one with many larger holes on the surface and another with much smaller pores or without pore), when the ratio of PUA to EMA and St is from 6/4 to 4/6. The macroporous and elastomeric beads can improve the underwater acoustic absorption properties of the polyurethane/epoxy (PU/EP) blend elastomer, and the underwater acoustic properties of the composites based on PU/EP blend elastomer and the beads depend mainly on the amounts of the beads and the dosages of porogen.

A Review on Acrylate-Terminated Urethane Oligomers and Polymers: Synthesis and Applications

Abstract: Polyurethane-acrylate oligomers are a new class of polyurethane which are produced by the reaction of polyols with diisocyanate and capped by acrylate. There is a growing demand for modification with improved properties of the polyurethane-acrylate. This review covers the following topic: structure, modification of polyurethane-acrylate backbone, reactive diluents, curing, mechanical, optical, thermal behavior, and applications presented herein. The basic understanding of the chemistry and mechanistic aspects of these oligomers has reached a level was tailor-made formulations suitable for a particular application may be selected.