Polyurethane Epoxy systems

Subsequently, several research teams became interested in studying the damping characteristics of IPN s. Wong and Williams characterized the tan d vs temperature behavior of polyurethane-epoxy semi-IPN s, noting one very broad peak ranging from 273 to 363 K for the 50/50 composition. Klempner and co-workers also studied the polyurethane/epoxy system, but prepared foams by a one-shot method, producing SIN s. Using an impedance tube method of measurement, enhanced sound absorption was found. 

Polyurethane sealant formulations use TDI or MDI prepolymers made from polyether polyols. The sealants contain 30—50% of the prepolymer the remainder consists of pigments, fiUers, plastici2ers, adhesion promoters, and other additives. The curing of the sealant is conducted with atmospheric moisture. One-component windshield sealants utili2e diethyl malonate-blocked MDI prepolymers (46). Several polyurethane hybrid systems, containing epoxies, siUcones, or polysulfide, are also used. 

When metal inserts require hermetic sealing, consider coating them with a flexible elastomer such as an RTV rubber, polyurethane, or epoxy system. A second method is to design an annular space or reservoir at one end of the insert from which to dispense the flexible elastomers to effectively create a hermetic seal. Flexible sealants are also used to compensate for differences in the thermal coefficient of expansion between metal and plastic. 

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). 

This is in agreement with the results of Bennett and Zedler (12) they have pointed out that conventional urethane, vinyl and epoxy systems show widely divergent release rates. Whereas the vinyl system lost TBTO at a rate of 1-2 yg/cm2/day and polyurethane at 25 yg/cm2/day, the epoxy system virtually lost no tin. 

Dict (1961), 221-R (Carbowax) 445 (Epoxy Resins) 4) V. Jamieson, RARDE (Royal-ArmamentResearch DevelopmentEstablish-r tnent) Memo(X)20/63, "Explosive Compositions of Improved Mechanical and Thermal Stability , Part 1, Polyurethane and Epoxy Systems , GreatBritain, Apr 1963(Conf)(Not used as a source of information)(PicArsn C104439) 5) Kirk Othmer, 2nd edit 8( 1965)... 

Crosslinking catalyst Through choice of die appropriate metal (Ti or Zr) and chelating agent reactivity can be controlled Increased reaction rate in silicone, polyurethane, and epoxy systems... 

In SIN formation, both timing and rates of polymerization to form the two networks are important. With an acrylate-epoxy system, it was found that simultaneous gelation produced materials with poorer properties than those formed by slightly mismatched polymerization rates (6). In another instance (7), polyurethane-poly(n-butyl methacrylate) SINs in which the acrylate was initiated photolytically at various times after the onset of polyurethane formation produced a series of materials, presumably with the same chemical composition, with an average particle size that decreased as the delay time to acrylic initiation increased. Damping properties of these materials changed systematically across the series. 

Cracks occur in concrete structures for several reasons (ACTI, 1993a Concrete Society, 1982). The purpose of crack injecting systems is to fill in the cracks. Epoxy systems are a popular choice for non-moving cracks. In cracks where some movement is anticipated, polyurethane systems are used (Table 1.3). 

Fillers. Fillers mentioned for epoxy systems (subsection 2.2.6.4) are used in polyurethanes too. Ground calcium carbonate (coated as well as uncoated) is commonly used. Barium sulphate, silica fumes, wood flour and milled glass fibres are also used. 

Epoxy resins produced by the reaction of bisphenol A and epichloro-hydrin are versatile polymers with several useful properties (subsection 2.2.2.1). However, one significant weakness is their brittle nature. Incorporation of plasticisers is not very useful. Dibutyl phthalate is an exception, showing good compatibility but offering only limited ability to flexibilise the resin. Moreover, plasticisers affect the mechanical properties and chemical resistance of the cured system. With polyurethanes it is possible to complement the flexibility of the epoxy system. Numerous attempts have been made to combine the two types to achieve beneficial modifications (Lee and Nivelle, 1967). These modifications proved successful under high-temperature cure but inferior results were obtained for ambient cures. 

Three-component IPNs prepared from polyurethane, epoxy, and unsaturated polyester resin resulted in even broader tan 5 values when compared to two component (PU/E) IPN elastomers. Furthermore, the tan S values for the three component IPN systems were still high after the transitions were apparently complete, which is of enormous significance in sound energy absorption applications. IPN foams prepared by using PU/E (two-component) showed excellent energy absorbing abilities. This was reflected in rebound, hysteresis, and sound absorption studies. 

Vipiex. [Crowley Chem.] Hasticizer/ex-toider for polyurethane, primer coatings, epoxy systems. 

Organic coatings are used to block the penetration of carbon dioxide or chloride ions. They form a continuous polymeric film on the surface of the concrete, of a thickness ranging from 100 to 300 pm. The binder can already be present in the liquid paint as a polymer, or the polymer can be formed due to chemical reactions between monomeric components that are mixed just before application. Modem coating systems are usually built up of several layers applied consecutively. They are compatible with the alkalinity of the concrete and are based on various types of polymers (e. g. acrylate, polyurethane, epoxy), pigments and additives, and are made suitable for application by the addition of solvents or diluents. 

Uses Defoamer for org. paints incl. nitrocellulose, polyurethane, alkyd-melamine baking enamels, epoxy systems, oil-free polyesters, aikyd paints, acid-curing systems, and inks Properties Colorless Iiq. hydrocarbon-like odor sp.gr. 0.82 g/cc dens. 

Consider the surface tension change in the course of polymerization of the POPT-TDI polyurethane system with added surfactant. As mentioned, compared with epoxy systems this one has a number of peculiarities evidently due to alteration of the structure of the poly-... 

Between 1 and 4 moles of PO can be added per mole of EDA. The monopropoxylated EDA can be used as an intermediate in the synthesis of a polyurethane catalyst. The di- and tri-propoxylates can be used as cross-linkers for epoxy systems. The fully propoxylated molecule is used as a crosslinker in polyurethane systems. 

Fifth Sixth Chlorinated rubber system Chlorinated rubber system paint Vinyl resin or chlorinated rubber system Epoxy or polyurethane resin system paint ... 

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