Papers by Keyword: IPN

Abstract: A series of stable double-terminated UV reactive cationic waterborne polyurethane dispersions was synthesized, while the structure was confirmed by infrared spectroscopy,laser particle size analysis and free NCO root titration; modified by co-monomerhydroxyethyl acrylate with the UV radiation fast curing, the influence of hydroxyethyl acrylate proportion and the polyurethane’s n_NCO/n_OH(R value) to the thermal properties, mechanical properties and yellowing of the product was investigated. The investigation illustrated the UV-curable cationic waterborne polyurethaneacrylate film effectively forming a semi-interpenetrating network system to achieve rapid curing coating.The results showedthe product cured by WPU dispersion of R=1.5 mixed with equimolar HEA obtained lowyellowing, the maximum breaking strength, high elongation at break, high thermal decomposition temperature, high crystallization temperature of hard segment, low glass transition temperature of soft segment, high degree of phase separation, better overall performance.

Abstract: Microwave curing of PU/EP IPN was studied in this paper. Microwave curing IPN was prepared by means of intermittent microwave heating, The results indicates that microwave curing technique can shorten curing time remarkably. The microwave curing and thermal curing IPN have identical structure, tensile property of microwave curing IPN is better than that of thermal curing IPN, Impact strength of thermal curing IPN is slightly higher.

Abstract: Based on the hydrogen bonding between MAA and PDEA, the synthesis of surfactant-free PDEA/PMAA interpenetrating (IPN) nanogels was studied in ultrapure water with N, N-methylene acrylamide (BIS) as a crosslinker, ammonium peroxodisulfate (APS) as an initiator, N,N,N',N'-Tetramethylethylenediamine (TEMED) as an accelerator. First, poly (N, N-diethyl acrylamide) (PDEA) nanogels were synthesized using emulsion precipitation polymerization. As MAA was polymerized in the aqueous dispersion of PDEA nanogels as seeds, PDEA nanogels got interpenetrated with poly (methacrylic acid) (PMAA) due to the effect of the hydrogen bonding between PDEA and PMAA. The chemical structure of the PDEA/PMAA nanogels was studied with Fourier transform infrared (FTIR) spectroscopy. The nanogels morphology was characterized with transmission electron microscopy (TEM) and atomic force microscopy (AFM). And the volume phase transition behaviors and swelling properties were studied with dynamic light scattering (DLS). The experimental results show that the interpenetrating nanogels were very sensitive to temperature. As the amount of MAA increased, the volume of the neutralized PDEA/PMAA nanogels changed less above phase transition temperature and was finally no change. The temperature responsive PDEA/PMAA nanogels will promise to have significant influence on fundamental studies and real applications.

Abstract: Gum tragancanth based organic-inorganic hybrid ion exchanger has been synthesized using a mixture of sodium tungstate, orthophosphoric acid and potassium iodate. The different reaction conditions like reaction temperature, reaction time, pH of reaction medium, solvent volume, monomer concentration and initiator concentration were optimized in order to get the semi-IPN Gt-cl-poly (AA). Onto semi IPN, methylmethacrylate was incorporated using lipase-gluteraldehyde as the initiator-crosslinker system. The IPN finally was converted into ion-exchanger and was studied for its different physico-chemical properties. Ion exchange capacity was studied for Na⁺ and effect of different temperatures on ion exchange capacity was evaluated. Characterization was done using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and EDS techniques.

Abstract: Hyperbranched polymer/HTPB-PU IPNs were prepared, when HTPB (hydroxyl-terminated polybutadiene) and IPDI (isophorone diisocyanate) were cured into polyurethane (HTPB-PU) at the existence of hyperbranched polymer. Differential scanning calorimetry (DSC) was adopted to study the influence of hyperbranched polymer on thermal properties of HTPB-PU, while IPNs were formed. The result shows that the existance of hyperbranched polymer makes glass transition temperature of HTPB-PU reduces by around 2°C and that HTPB-PU lowers the melting point of hyperbranched polymer. Hyperbranched polymer plays a role of internal plasticization on HTPB-PU, and HTPB-PU influences crystallization of hyperbranched polymer in return.

Abstract: Polyurethane/poly (methylacrylate-butylmethacrylate-2-Hydroxyethylmethacrylate) Interpenetrating polymernetworks (IPNs) were prepared by sequential polymerization. Their glass transition performance was measured by using differential scanning calorimetry (DSC). DSC results revealed there are three glass transition temperatures (Tg) for both IPNs samples. Their damping properties were evaluated according to ASTM E756-05. Their loss factor (tan δ>0.3) from 10-1300Hz displays a wide temperature range of 94°C.

Abstract: Novel interpenetrating polymer networks (IPNs) of Polydicyclopentadiene/Polystyrene (PDCPD/PS) were prepared by in-situ polymerization using Ziegler-Natta and peroxide as double catalytic systems. The structure of PDCPD/PS alloy was characterized by Soxhlet extraction, infrared spectrum (IR) and scanning electron microscope (SEM). The results showed that the polymerization of dicyclopentadiene (DCPD) was facilitated in the presence of styrene and the rate of polymerization as well as the conversion of PDCPD was improved with styrene content. The strong IR absorption peaks of PS indicated high penetration of PS within PDCPD networks, and in the process forming IPNs. There were no obvious traces of PS in the alloy brittle fracture, which prepared in liquid nitrogen and was etched by toluene. This result also demonstrated that PS was dispersed in molecular level in the polymer alloy networks and it tangled with PDCPD. The measurements mechanical properties showed that the tensile strength of the polymer alloy was improved with styrene content. This may be due to homogeneous dispersion of PS in the IPNs. The synergistic effect of PS and PDCPD also played a part in enhancing the mechanical properties of polymer alloy.

Abstract: To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.

Abstract: A novel exfoliated polyurethane (PU)/clay Interpenetrating Polymer Networks (IPNs) nanocomposite has been synthesized with polyurethane and organoclay. MTPAC is used as swelling agent to treat Na-montmorillonite for forming organoclay. The results indicate that there is very good compatibility between organoclay and PU. Nanoscale silicate dispersion was analyzed by XRD. The mechanical properties of the nanocomposites have been measured by tensile testing machine. The nanocomposites show obviously improved physical and mechanical properties when compared with the pure polymer. Additionally, PU /MTPAC- clay shows lower water absorption properties than pure PU do. In addition, the reinforcing and intercalating mechanism of silicate layers in polyurethane matrix are discussed.