ABSTRACT:Interpenetrating polymer networks (IPNs) were prepared from polyurethane (PU)-modified epoxy with different molecular weight of polyol and polyurethanes based on the mixture of polydiol and polytriol by a one-shot method. Two types of PU-modified epoxy: PU-crosslinked epoxy and PU-dangled epoxy were synthesized, and the effects of the different molecular weights of polyol in the PU-modified epoxy/PU IPNs on the dynamic mechanical properties, morphology, and damping behavior were investigated. The results show that the damping ability is enhanced through the introduction of PU-modified epoxy into the PU matrix to form the IPN structure. As the molecular weight of polyol in PU-modified epoxy increases, the loss area (LA) of the two types of the IPNs increases. PU-dangled epoxy/PU IPNs exhibit much higher damping property than that of the PU-crosslinked epoxy/PU IPNs with 20 wt % of PUcrosslinked epoxy.
ABSTRACT:This study prepared an interpenetrating polymer network of bismaleimide and polybutylene adipate-based polyurethane-crosslinked epoxy (BMI/PU-EP IPN) using the simultaneous bulk polymerization technique. Infrared spectra analysis was also performed to identify the polyurethane-crosslinked epoxy (PU-EP). Also investigated herein were the mechanical properties including tensile strength, fracture energy, and Izod impact strength of various bismaleimide content in PU-EP matrix. In addition, differential scanning calorimetry and thermogravimetric analyses of the BMI/PU-EP IPN were conducted as well. Analyses results demonstrate that the bismaleimide was dissolved primarily in the polyurethane domains of the epoxy matrix to form a compatible system, thereby increasing the mechanical strength of the BMI/PU-EP IPNs.
SYNOPSISA seeded soapless emulsion polymerization was carried out with poly(methy1 methacrylate) (PMMA) as seeds, styrene as monomers, and potassium persulfate (K2S2O8) as the initiator to synthesize the PMMA/polystyrene (PS) composite latex. The morphology of the latex particles was observed by transmission electron microscopy (TEM). It showed a core-shell structure. A core-shell kinetic model was proposed for the seeded emusion polymerization, in which the thickness of the shell was not constant. An increase of the conversion would increase the thickness of the shell. The entire course of polymerization could be divided into three regions: In the first region, the propagation rate constant (K,) and termination rate constant (K,) were kept constant at constant temperature. The kinetic data showed that the square root of polymer yield (Wi") was proportional to the reaction time. In the second region, the gel effect was considered and the termination rate constant (K,) was empirically modified. The K , would decrease with increasing the conversion. In the third region, both the gel effect and the glassy effect were considered the propagation rate constant was also empirically modified. The prediction on the conversion and the number-average molecular weight of polymers during the seeded emusion of polymerization on the basis of our core-shell kinetic model fitted well with the experimental data. 0 1995
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