Flexible Epoxy Resins

Chem. Descrip. Branched polymer with ether and urethane groups, contg. crosslinking, blocked isocyanate groups Uses Raw material, flexibilizer for epoxy resins, flexible coatings and sealing compds., PU systems Features Solv.-free... 

Uses Flame retardant for thermoplastics (ABS, HIPS), thermosets (unsat. polyester, epoxy resins, flexible urethane foam), adhesives, coafings, and textiles... 

MMM-A-260 Water-resistant Liquid Adhesive. MMM-B-00350 Binder Adhesive, Epoxy Resin-Flexible. SS-S-1996 Sealer, Water and Weather Resistant. TT-C-00598 Caulking Compound. 

Casting resin Thermoplastic elastomer Cast resin, flexible Mineral- and/or glass-filled Epoxy molding and encapsulating compound Polystyrene... 

Shipment, Stora.ge, ndPrice. Tank cars and tank trailers, selected to prevent color formation, are of aluminum or stainless steel, or lined with epoxy or phenoHc resins dmms are lined with phenoHc resins. Flexible stainless steel hose is used for transfer. Because of butanediol s high freezing point (about 20°C) tank car coil heaters are provided. The U.S. Hst price for bulk quantities in 1991 was about 2.18/kg, but heavy discounting was prevalent for large contracts. 

A second type of uv curing chemistry is used, employing cationic curing as opposed to free-radical polymerization. This technology uses vinyl ethers and epoxy resins for the oligomers, reactive resins, and monomers. The initiators form Lewis acids upon absorption of the uv energy and the acid causes cationic polymerization. Although this chemistry has improved adhesion and flexibility and offers lower viscosity compared to the typical acrylate system, the cationic chemistry is very sensitive to humidity conditions and amine contamination. Both chemistries are used commercially. 

The alkyd resins are of value because of their comparatively low cost, durability, flexibility, gloss retention and reasonable heat resistance. Alkyd resins modified with rosin, phenolic resin, epoxy resins and monomers such as styrene are of current commercial importance. 

Network properties and microscopic structures of various epoxy resins cross-linked by phenolic novolacs were investigated by Suzuki et al.97 Positron annihilation spectroscopy (PAS) was utilized to characterize intermolecular spacing of networks and the results were compared to bulk polymer properties. The lifetimes (t3) and intensities (/3) of the active species (positronium ions) correspond to volume and number of holes which constitute the free volume in the network. Networks cured with flexible epoxies had more holes throughout the temperature range, and the space increased with temperature increases. Glass transition temperatures and thermal expansion coefficients (a) were calculated from plots of t3 versus temperature. The Tgs and thermal expansion coefficients obtained from PAS were lower titan those obtained from thermomechanical analysis. These differences were attributed to micro-Brownian motions determined by PAS versus macroscopic polymer properties determined by thermomechanical analysis. 

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Polymeric materials are commonly used for bonding materials. Impact or contact adhesives are mainly based on highly crystalline polychloroprene (Neoprene), NR latex is used as a flexible adhesive very suitable for use with fabrics. Rigid adhesives based on materials such as polystyrene cement, epoxy resin or cyanoacrylates are suitable for bonding of rigid materials. The bond is provided by intramolecular forces between the adhesive and the adherend. Adiabatic... 

Microgels have been prepared from epoxy resins which were intramolecular-ly crosslinked by a polyalkylene polyamine/polycarboxylic acid for flexible, corrosion resistant coatings [354]. 

Thermosensitive hydrogels, 13 743 THERMOSET Thermoset recycling pyramid, 13 780-781 Thermoset elastomers, 20 71 Thermoset epoxy resins, curing of, 10 421 Thermoset flexible polyurethane foams properties of, 25 461 Thermoset matrix composites, 21 456 Thermo set molding properties of diallyl isophthalate, 2 262t Thermoset polymers, 25 455 cured, 10 425... 

In India, flexible sheet explosives are generally made from indigenously available unsaturated polyester resins, epoxy resins and natural rubber etc. and common... 

This structure has superior water-resistant properties in comparison to conventional polyols used for PU synthesis. Room temperature cures are easily obtained with typical urethane catalysts. Short chain diols, fillers and plasticizers may also be used in their formulations in order to vary physical properties. Formulations usually with NCO/OH ratio of 1.05 are used for this purpose. Such urethanes are reported to be flexible down to about -70 °C. HTPB is regarded as a work horse binder for composite propellants and PBXs. HTPB also successfully competes with widely used room temperature vulcanizing (RTV) silicones and special epoxy resins for the encapsulation of electronic components. HTPB-based PUs are superior in this respect as epoxy resins change their mechanical properties widely with temperature. 

Epoxy-Liquid Polysulfide Blends Epoxy resins in combination with liquid PSs appear to possess many added advantages as the elastomeric PS segments in epoxy chains impart permanent flexibility [18]. Epoxy-liquid PS blends have been reported as binders for Army illuminating formulations [8]. Similarly, novolac epoxy-liquid PS blends have been reported for inhibition of composite propellants [19]. 

A very wide range of curing times and temperatures exists for epoxy resin systems. Therefore, they offer a great deal of design flexibility for use both as structural bonding adhesives and protective surface coatings. 

Figure 3. Effect of EME 58 (58 wt% mercaptoester units co-polymer) coupling agent concentration on the peel strength of flexible epoxy (amine-cured)/AD = acetone-degreased steel test panels following (a) I day and (b) 3 day exposure to 57°C condensing humidity. See Appendix 4 for epoxy resin and cure description.

To improve the weatherabihty of epoxies, which normally chalk and yellow, epoxy—polyester alloys or hybrids are used. These powders with improved overbake resistance cure at temperatures as low as 130°C. They have film flexibility similar to epoxy resins, but their hardness is slightly decreased. Corrosion resistance is equivalent to epoxy powders in most cases, although solvent and alkali resistance is inferior. 

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