Polyurethane Epoxy networks

Other reports on the morphology and mechanical behavior of organosiloxane containing copolymeric systems include polyurethanes 201 202), aliphatic 185, 86) and aromatic117,195> polyesters, polycarbonates 233 236>, polyhydroxyethers69,311, siloxane zwitterionomers 294 295) and epoxy networks 115>. All of these systems display two phase morphologies and composition dependent mechanical properties, as expected. 

For imperfect epoxy-amine or polyoxypropylene-urethane networks (Mc=103-10 ), the front factor, A, in the rubber elasticity theories was always higher than the phantom value which may be due to a contribution by trapped entanglements. The crosslinking density of the networks was controlled by excess amine or hydroxyl groups, respectively, or by addition of monoepoxide. The reduced equilibrium moduli (equal to the concentration of elastically active network chains) of epoxy networks were the same in dry and swollen states and fitted equally well the theory with chemical contribution and A 1 or the phantom network value of A and a trapped entanglement contribution due to the similar shape of both contributions. For polyurethane networks from polyoxypro-pylene triol (M=2700), A 2 if only the chemical contribution was considered which could be explained by a trapped entanglement contribution. 

In the foregoing considerations, formation of elastically inactive cycles and their effect have not been considered. For epoxy networks, the formation of EIC was very low due to the stiffness of units and could not been detected experimentally the gel point conversion did not depend on dilution in the range 0-60% solvent therefore, the wastage of bonds in EIC was neglected. For polyurethanes, the extent of cyclization was determined from the dependence on dilution of the critical molar ratio [OH] /[NCO] necessary for gelation (25) and this value was used for the statistical calculation of the fraction of EIC and its effect on Ve as described in (16). The calculation has shown that the fraction of bonds wasted in EIC was 2-2.5% and 1.5-2% for network from LHT-240 and LG-56 triols, respectively. 

Cristea, M., Ibanescu, S., Cascaval, C.N., Rosu, D. Dynamic mechanic analysis of polyurethane-epoxy interpenetrating polymer networks. High Perform. Polym. 21, 608-621 (2009)... 

Jla, Q.M., Zheng, M.S., Chen, H.X., Shen, R.J. Morphologies and properties of polyurethane/ epoxy resin Interpenetrating network nanocomposites modified with organoclay. Mater. Lett. 60, 1306-1309 (2006)... 

Chen, S., Wang, Q., Wang, T., Pei, X. Preparation, damping and thermal properties of potassium tltanate whiskers filled castor oil-based polyurethane/epoxy Interpenetrating polymer network composites. Mater. Des. 32, 803-807 (2011)... 

Lei Z, Yang Q, Wu S, Song X (2009) Reinforcement of polyurethane/epoxy interpenetrating network nanocomposites with an organically modified palygorskite. J Appl Polym Sci 111 3150-3162... 

Figure 7.17. Lap-shear (psi) vs. network composition for polyurethane/epoxy SINs SIN-I (open circles) SIN-II (triangles semi-SIN (filled circles) SIN-III (crosses).

A. Christou, Reliability Aspects of Moisture and Ionic Contamination Diffusion Through Hybrid Encapsulants, in Proceedings of the Technical Program—International Microelectronics Conference (1978) p. 237, Industrial Scientific Conference Management, Inc., New York. Electric insulators and dielectrics Silicone/epoxy-polyurethane interpenetrating networks, moisture, and ion diffusion through potting compounds. 

H. L. Frisch, R. Foreman, R. Schwartz, H. Yoon, D. Klempner, and K. C. Frisch, Barrier and Surface Properties of Polyurethane-Epoxy Interpenetrating Polymer Networks. II, Polym. Eng. Sci. 19(4), 294 (1979). Polyurethane/epoxy SINs. Contact angles of drops of methanol mixtures on polyurethane/epoxy interpenetrating network films. Transmission of vapors in polyurethane/epoxy SINs. 

H. L. Frisch and K. C. Frisch, Polyurethane-Epoxy Interpenetrating Polymer Networks— Barrier and Surface Properties, Prog. Org. Coat. 7, 107 (1979). Epoxy/Polyurethane SINs. Lap Shear, critical surface tension, and permeability studies. 

K. C. Frisch, D. Klempner, S. K. Mukherjee, and H. L. Frisch, Stress-Strain Properties and Thermal Resistance of Polyurethane-Polyepoxide, Interpenetrating Polymer Networks, J. Appl. Polym. Sci. 18(3), 689 (1974). Polyurethane/Epoxy SIN. Tensile strength. Heat resistance. 

Linear Elastic and Rubber Elastic Behavior. Although stiffening is quite noticeable in the glassy regime of the amorphous phase, the most spectacular effect is seen in the rubber elastic regime phase, as already evoked in the case of reinforcement by cellulose whiskers (2). The PA6-clay hybrids example presented in Table 3 is quite representative of the situation encoimtered with semi crystalline thermoplastics, but elastomeric networks benefit as well of clay layer dispersion with a two- to threefold increase in modulus for polyurethane or epoxy networks... 

In this case, an apparent activation energy is determined, and it has higher values than secondary relaxations 100-300 kJ/mol for urethane-soybean oil networks (Cristea et al. 2013), 200-300 kJ/mol for polyurethane-epoxy interpenetrating polymer networks (Cristea et al. 2009), more than 400 kJ/mol for semicrystalline poly(ethylene terephtalate) (Cristea et al. 2010), and more than 600 kJ/mol for polyimides (Cristea et al. 2008, 2011). The glass transition temperature is the most appropriate reference temperature when applying the time-temperature correspondence in a multifrequency experiment. The procedure allows estimation of the viscoelastic behavior of a polymer in time, in certain conditions, and is based on the fact that the viscoelastic properties at a certain tanperature can be shifted along the frequency scale to obtain the variation on an extended time scale (Brostow 2007 Williams et al. 1955). The shift factor is described by the Williams-Landell-Ferry (WLF) equation ... 

Mahesh K.P.O., Alagar Muthukaruppan, and Jothibasu S. A comparative study on the preparation and characterization of aromatic and aliphatic bismaleimides-modified polyurethane-epoxy interpenetrating polymer network matrices. J. Appl. Polym. Sci. 99 no. 6 (2006) 3592-3602. 

This project is oriented to prepare nanocomposites based on interpenetrated polymer network (IPN), such as polyurethanes, epoxies and acrylate by way of creating nanoparticles of SiO TiO and other metal... 

Texter and Ziemer created polyurethanes via FP in microemulsions. Chen et created epoxy-polyurethane hybrid networks frontally. Pot lives were on the order of hours. Hu et frontally prepared urethane-acrylate copolymers in... 

In general, research on classes of materials is connected with that on materials with specific properties but includes somewhat more general research on composites, polyurethanes, epoxies, fluoropolymers, ferroelectric liquid crystals (especially those with fast switching times), polymer-polymer miscibility, double network elastomers, crystallization in polymers, polymeric Langmuir-Blodgett and other multilayer films, and polymer-stabilized synthetic membranes. 

Siloxane containing interpenetrating networks (IPN) have also been synthesized and some properties were reported 59,354 356>. However, they have not received much attention. Preparation and characterization of IPNs based on PDMS-polystyrene 354), PDMS-poly(methyl methacrylate) 354), polysiloxane-epoxy systems 355) and PDMS-polyurethane 356) were described. These materials all displayed two-phase morphologies, but only minor improvements were obtained over the physical and mechanical properties of the parent materials. This may be due to the difficulties encountered in controlling the structure and morphology of these IPN systems. Siloxane modified polyamide, polyester, polyolefin and various polyurethane based IPN materials are commercially available 59). Incorporation of siloxanes into these systems was reported to increase the hydrolytic stability, surface release, electrical properties of the base polymers and also to reduce the surface wear and friction due to the lubricating action of PDMS chains 59). 

Since this pioneering work a number of IPNs have been prepared. Poly(styrene) has been used as the second network polymer in conjunction with several other polymers, including poly(ethyl acrylate), poly(n-butyl acrylate), styrene-butadiene, and castor oil. Polyurethanes have been used to form IPNs with poly(methyl methacrylate), other acrylic polymers, and with epoxy resins. 

Thermosets consist of a network of interconnected chains whose positions are fixed relative to their neighbors. Such polymers do not flow when heated. Instead, when exposed to high temperatures, thermosets degrade into char. Examples of thermosets include some polyurethanes and epoxy resins. 

In this contribution, we report equilibrium modulus and sol fraction measurements on diepoxidet-monoepoxide-diamine networks and polyoxypropylene triol-diisocyanate networks and a comparison with calculated values. A practically zero (epoxides) or low (polyurethanes) Mooney-Rivlin constant C and a low and accounted for wastage of bonds in elastically inactive cycles are the advantages of the systems. Plots of reduced modulus against the gel fraction have been used, because they have been found to minimize the effect of EIC, incompleteness of the reaction, or possible errors in analytical characteristics (16-20). A full account of the work on epoxy and polyurethane networks including the statistical derivation of various structural parameters will be published separately elsewhere. 

In addition, from thermal and thermomechanical measurements, it is found that typical epoxy-amine networks exhibit one glass transition temperature, Tg, and one sharp well-defined relaxation peak. The same techniques were used for crosslinked polyurethanes based on triol and diisocyanate or diol and triisocyanate (Andrady and Sefcik, 1983). Similar conclusions to those found for epoxy-amine networks were attained. 

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